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Continental J. Earth Sciences 3: 1 - 7, 2008 ©Wilolud Online Journals, 2008.

THE NIGERIAN FUEL ENERGY SUPPLY CRISIS AND THE PROPOSED PRIVATE REFINERIES – PROSPECTS AND PROBLEMS

Adubok, Agwom Sani – Zandi Geology Dept., Gombe State Univeristy, P.M.B.127, Gombe.

sanizandi@yahoo.com

ABSTRACT Dynamism of the world economy has compelled Nigerians to accept the liberalization of its economy to encourage private sector participation and induce managerial efficiency. This has become very imperative most especially, in the downstream sub-sector of the Nigerian oil and gas industry by the establishment and management of private refineries in view of the persistent fuel energy crisis. An attempt is made here at analyzing the prospects and problems of such refineries that are expected to end the fuel energy crisis which started in the 1970s due to increased demand for petroleum products for rehabilitation and reconstruction after the civil war but later metamorphosed into a hydra-headed monster in the 1980s to date. Efforts towards arresting this crisis by the government through the establishment of more refineries, storage depots and network of distribution pipelines etc achieved a short-term solution due to the abysmal low performance of the refineries and facilities in contrast to increasing demand for petroleum products. It is deduced that the low performance resulted from bad and corrupt management by indigenous technocrats and political leaders as well as vandalization of facilities. Prospects for such investments were identified, as well as some of the problems to content with. This is in order to understand the pros and cons of such investments in view of their capital intensiveness and the need to achieve economic goals that must incorporate environmental and social objectives.

KEY WORDS: Fuel Energy, Refinery, Crisis, Prospects, Investment and Market

INTRODUCTION Obadan (2004) placed Nigeria as the sixth largest member of the Oganisation of Oil Exporting Countries (OPEC). The country’s total reserve of this very important and strategic resource is put at about 35billion barrels and the capability for daily production of 3million barrels per day (Kukpolukun, 2005), actual production is however constrained by OPEC quota allocation to about 2.5 million barrels per day. Tinubu (2004) revealed that the Nigerian petroleum products market requires about 50 million litres of products per day, with PMS accounting for about 20million litres. Of this, only about 37.5million litres is made available - a short fall of 25%. Braide (2005), estimated the crisis free demand for petroleum product in Nigeria as 20 million litres for PMS, 12 million litres for AGO and 18million litres for DPK. Whatever the actual daily consumption figure are, the fact remains that this demand is continuously growing. The Nigeria National Petroleum Corporation (NNPC), through its down stream sub-sector has however, steadily failed to meet the fuel energy demand of the country, necessitating the review of the country’s economic regulations, especially as regards government’s participation in the oil and gas industry business with special reference to the down stream sector. This led to its deregulation to pave way for private sector participation in order to induce managerial efficiency and market control of demand and supply at competitive prices. Scarcity according to Enomoh (2001) started in 1976 and grew into a hydra-headed monster in the 1980s to 1990s following deterioration and gradual break down of existing refineries and the associated distribution chain. Ali-Munguno (2001) opined that the persistent energy supply crisis resulted from gross mismanagement, inefficiency and government’s inability to manage the refineries. This complex interplay between demand and supply of petroleum products and their timely supply to the Nigerian consumer is constrained by the following reasons

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Adubok, Agwom Sani – Zandi: Continental J. Earth Sciences 3: 1 - 7, 2008 according to Braide (2005) - Inadequacy of the quantum of crude oil allowed by the federal government for domestic refining; the deficit of available petroleum product needed to satisfy national demand at any given time; the recurrent low capacity utilization of the refineries; epileptic performance of the pipeline distribution network and adverse impact of price regulation in the country. To understand the seriousness of this problem, it is important to note that the petroleum industry accounts for more than 90 % of the nation’s total foreign exchange earnings coupled with its diverse linkages to the other sectors of the economy. It is therefore, necessary that there is continuous uninterrupted supply of the product, most especially the light products – PMS, AGO & DPK that have direct impact on the lives of the citizenry because of their constant usage in daily production activities. The estimated amount of crude required daily for domestic refining that could satisfy the pent-up demand for petroleum products adequately is put at about 530,000bbl/d, about 85,000bbl/d above the combined refining capacity of the state owned and state run refineries (table 1). This is also some 230,000bbl/d above the quantum allowed by the federal government for domestic refining and consumption. Table 1. Existing (Government owned) Refineries in Nigeria

Refinery Name Year established Capacity Old Portharcourt Refinery (by SPDC, Nigerianised 1977)

1965 Later expanded

35,000bl/d 60,000bl/d

Warri Ref. and Petrochem. Company (WRPC)

1978 1986 (Expanded)

100,000bl/d 125,000bl/d

Kaduna Ref. and Petrochem. Company (KRPC)

1980 110,000bl/d

New Porthacourt Refinery 1989 150,000bl/d Total 445,000bl/d

Though the four refineries have the capacity to meet 80% of domestic demand for products, they have, however, undergone significant depreciation due to old age, neglect and idleness. There is therefore, the need to restore Nigeria from the untold hardship of petroleum products scarcity. For these and other reasons therefore, Nigeria adopted a deregulation policy to liberalize the downstream sector of the oil and gas industry to allow for private sector participation thereby encouraging the establishment of private refineries and avoid the complete degeneration of the fuel energy crisis. This paper attempts an analysis of the prospects and problems envisaged in the course of trying to make petroleum product readily available for both domestic and foreign markets by such private refineries, considering our investment policies and business ethics coupled with the economic, social, political and cultural environment. This has become necessary in view of the huge capital investment; skilled manpower, sophisticated and automated equipment, safety operations and complex marketing network required by such refineries Table 2. The Nigerian crude types

Crude type Specific Gravity / A.P.I Sulphur content (%) Forcados Bonnylight (sweet)

0.8708 / 37 0.8398 / 37

0.2 0.14

Qua – Iboe 0.8398 / 37

0.14

Excravos Blend 0.8448 / 36

0.14

Brass River 0.8063 / 44

0.28

(source; www.nigeriabusinessinfor.com, 2005)

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Adubok, Agwom Sani – Zandi: Continental J. Earth Sciences 3: 1 - 7, 2008 The Nigerian Oil and Gas Industry The activities of the oil and gas industry world over are categorized into two sub-sectors, the upstream and the down stream. The earlier, comprises activities ranging from the design of business plans, acquisition of acreages, exploration, drilling and production. Crude oil sales also belong to the first category. Refining, storage (depots and tanks), distribution (pipeline network) and products marketing falls within the downstream sub-sector which is synonymous with the oil and gas industry to the citizenry because of its direct impact on their lives. Refinery strategically links petroleum that is almost useless in its crude form and its conversion process (refining) into products of great importance to the daily survival of individuals as well as corporate organizations. The first successful investment in the Nigerian oil and gas industry was by Shell D’arcy (now SPDC) in1956 when oil on land was stroke at Oloibiri in the present Rivers state, after 18 years of unsuccessful operation (Edmand, 1995). This spurred other oil companies, notably, Agip, Gulf (Chevron), Mobil, Amosea (Texaco), Setrap (Elf), etc to search for oil in the various parts of the Niger Delta region. The establishment of the Nigerian National Oil Company (NNOC) in 1971 and the joining of OPEC by Nigeria, as its 11th member, culminated government’s direct involvement in the oil and gas business. Nigeria has an estimated total crude oil reserve in the neighborhood of 35billion barrels. Government’s target is 40billion barrels by the year 2010 (Kukpolukun 2005). Current daily production however varies due to quota fluctuation as controlled by the world oil and gas demand and supply through OPEC, the global oil Cartel. Nigeria however has the capacity to produce about 3 mbl/d. www.nigeraoilandgasonline (2005) revealed that numerous (606) oil fields have been established, located in the swamps of the Niger Delta region. In addition to these, the marginal fields and the deep offshore accreages have become the toast of the day. Table 2, gives the crude oil types and grades that exist in Nigeria while the country’s marker crude in the international market are the Bonny light and Forcados. Natural gas reserve is put at about 104t3 feet. Despite these efforts in the upstream sub-sector, however, the country has to content with a number of recurrent issues that must be addressed in order to sustain such growth, these include, host community and environmental issues; infrastructural development; youth restiveness; technical expertise, etc. The focus here however, is the downstream sector. Product marketing started in the form of agency representation that was followed by the establishment of branch offices and retail outlets all over the country by the major oil marketing companies - mentioned above (Osibanjo, 1999). By 1960, Shell, Mobil, Texaco, Esso and Total had well established branch offices with adequate storage depots. These depots were largely deregulated with price disparity all over the country and companies operated on healthy competitive basis. Oil produced was refined overseas and imported for sales in the country. Government’s involvement began by the construction of the Porthacourt Refinery, commissioned in 1965 with a capacity for 35,000bl/d. This was beginning to satisfy the gasoline requirements of the nation until the internal crisis (civil war) started in 1967. The post-war reconstruction and rehabilitation programme increased the demand for petroleum products and exposed the inability of the major marketers and the NNPC to meet such increased product demand, hence importation that was also limited by storage capacity at the marketers’ depots. This is supported by Adigun (1993) who posits that the widespread scarcity that culminated in 1975 resulted from high demand for products after the war for rehabilitation and reconstruction; price equalization all over the country (establishment of Price Equilisation Board) and lack of adequate storage facilities. It became necessary therefore, that the NNPC be rehabilitated and restructured by planning for and the construction of more depots, pipeline network and more refineries to facilitate effective distribution. Local companies and individuals were licensed to market products in order to curb scarcity while prices were fixed by the government of the day. The sequences of refinery establishment that followed and their capacities are contained in table 1. Bridging by trucks was also introduced when the refineries and pipelines started having persistent problems and due to lack of interconnectivity between the four refineries (Abubakar, 2001). The refining, petrochemical and the transportation sub sector of the oil and gas industry still have high government investment but beset by lack of commercial pricing environment and resources to properly manage infrastructure. Government, through NNPC has found it almost impossible to maintain the four refineries and provide adequate products nation wide. In addition, a large segment of the distribution system is in dear need for maintenance and

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Adubok, Agwom Sani – Zandi: Continental J. Earth Sciences 3: 1 - 7, 2008 upgrade. To therefore ensure self-sufficiency in refining and adequate uninterrupted domestic supply of all petroleum products at reasonable prices and for export, there is need to liberalize the sub-sector for private participation Need for Private Refineries The need to remove NNPC’s monopoly in refining and distribution of petroleum product in Nigeria has been established. Adubok (2001) revealed that NNPC’s performance in this regard has been unimpressive, mainly due to the dual problems of ill-maintained refineries and improper monitoring of products distribution and marketing arising from corrupt management. Alexander oil and gas connection (1998) also observed that, Nigeria, the best African oil producer has in recent years been forced to import refined products due to the inability of the refineries to meet the nation’s demand. In its 9th volume 2005, it observed that Nigeria, the 8th largest oil producer in the world with large untapped deposits, has become a curse to the nation’s populace as the country today depends largely on importation resulting to ceaseless scarcity, fuel price hikes and attendant effect on prices of other goods and services (Nigeria being a monolithic economy). Finding from www.nigerianbusinessinfor.com (2005) revealed that the break down of refineries and lack of Turn Around Maintenance (TAM) as at when due, between 1966-1988, reduced the total crude processed to 75,000bl/d or 16% efficiency (comparable to other public enterprises). It is imperative therefore, that such public enterprises be privatized to improve management efficiency in view of the huge financial losses and consistent contributions to fiscal deficit with total liabilities for 39 of such enterprises in excess of #81.1trillion as at December 2000 (El-Rufai, 2005). The importation of petroleum products has become a drain pipe to the economy, though it may look cheap now considering the business environment in Nigeria, it is necessary that petroleum refining is locally carried out in view of its spiraling effect on the other sectors of the economy. Doing so, will drastically reduce product prices that are presently highly manipulated (Aluko, 2003). Such costs arise from high landing cost, demurrage financing, distribution margin, highway maintenance cost, cost of insurance and freight (CI%F), etc. Local refining will reduce these and other costs including importation tax and port charges imposed by and payable to the government. Prospects To appraise the investment potentials in the Nigerian oil and gas industry, most especially for the proposed private refineries, it is important to reemphasize that the country is naturally endowed with a lot of mineral resources of economic significance, amongst these is oil and gas. Nigerian oil and gas account for about 80% of the country’s total federal revenues, more than 90% of its export earnings and constituting about 30% of the nation’s GDP. It also finances all other aspects of the economy. As earlier stated, a total crude reserve of 40billion barrels and daily production rate of 4million bbl/d is targeted by the year 2010. To achieve this, marginal fields and deep offshore acreages are being developed. Tar sands from which crude can be extracted are also known to abound in the country. The Nigerian crude oil is known to be of very good quality, American Petroleum Institute (A.P.I) values ranges between, 25 to 45, sulphur, which reduces the quality of petroleum is also very low in content (table 2). Nigerian oil and gas reserves are also known to be very prolific - found in geologically favorable environment (shallow environment with cheap production cost) as compared to other geologically complex areas. This will continue to attract long-term investment in the sector. Crude availability, which is a major investment factor for the proposed private refineries is guaranteed over a long period of time. This is coupled with the high product demand both locally and internationally which is not being met by the existing refineries. Nigeria’s large population - presently put at about 140million and an annual growth rate of about 2.3% as announced by the Nigerian Population Commission (2007), can economically sustain the establishment of numerous private refineries. More so, the country is known to be strategically located for the oil and gas international trade, sea and land routes exist to service both the local and international markets, especially the African sub region where large products demand exist. Storage, distribution and marketing facilities belonging to both the federal government and major marketers exist, however, at different functional stages. The NNPC is known to have numerous depots scattered all over the country, 11,000km of pipeline network, two jetties, one export terminal, a single point mooring buoy, etc. These facilities are essential for the convenient and effective operations of the private refineries without which the products, even when refined cannot reach the consumers. The efficiency and convenience of these facilities need to be ascertained, when proved adequate, it shall go a long way to reducing their initial capital investment

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Adubok, Agwom Sani – Zandi: Continental J. Earth Sciences 3: 1 - 7, 2008 cost of making products available to end-users. Products can also be moved through bridging by trucks and / or the rail, if and when rehabilitated. Refineries may either directly dispense their products by establishing retail outlets or by the utilization of existing ones belonging to the major and independent marketers that control the dispensing outlets. www.nigerianoilandgasonline (2005), observed that in addition to the above, the following incentives also exist for the private refineries, the federal government’s encouragement of foreign investors in the oil and gas industry; a five-year tax holiday (exemption) for all new plants from start of production; foreign investors can now own 100% equity share in any venture incorporated in the country; guaranteed export earning- earnings from the export of any local production is permitted to be retained in an approved export account in any country of choice nominated by the investor and a lot more . Envisaged Problems The liberalization of the downstream sector of the oil and gas industry to allow for private participation has been accepted as the only solution to the fuel scarcity problem because no option has been preferred in its place (Enomoh, 2001). However, the private refineries must operate, balancing government’s interest and management interest, surviving the turbulent investment climate in the country and thereby solving the perennial fuel scarcity problem. Though no private refinery is yet operational in the country, this study however reveals that the following problems are envisaged and must be considered despite the prospects and incentives mentioned above. These include amongst other things the following: unstable policies and government procedures; complex technology requirement and expertise to establish and manage refineries; high capital requirement; the unwillingness on the part of marketers to change from the status quo that greatly benefits them and the abysmal low level of infrastructural development. These will definitely add to the total operational costs that will eventually be paid for by the consumers and hence ending up not addressing the price issue, etc. This ‘climate” according to Tinubu (2004), will not allow foreign investors in the oil sector. Business is undertaken in very unconventional way in Nigeria, all known international laws of doing such has been torn to shreds thereby allowing investors to exploit and extort the consumers who are hardly protected by the policy implementers and the law enforcement agents (Soeze, 2005). Instability in policies and the haphazard nature of their implementation constitute great problems. With this situation, investors face high risks of success. There is therefore the need for remediation of this problem, most especially, policy reviews and implementation as regards international business. Another major problem that might confront the private refineries and militate against stable products price, is the continuous fluctuation in the international market prices of crude oil coupled with the fact that strategic reserves that will guarantee availability for a long time and thereby absorb short-term price increases are lacking. Local sourcing of technology and human inputs are also lacking, more so, sourcing them overseas implies repatriation of revenue with very little positive impact on the domestic economy. The enforcement of local content policy must be encouraged to train Nigerians in refinery operation and management. It is also identified that though, it is easier and convenient to move products by pipelines, the safety of such pipelines network in Nigeria is presently not guaranteed. Its monitoring and surveillance is weak and cases of sabotage through vandalization abounds. To curb this menace, investors must be willing to strive for sustainability rather than profit maximization through community partnering and youth empowerment. In addition, competent monitoring and surveillance teams should be established to ensure safety of such facilities that have become target of the aggrieved. Security agents should institute rapid response initiatives in the pipeline areas, putting in place technical devices that, alerts a command and control center as in other oil producing countries. Other problems that would be encountered by such refineries are high interest rates, unstable exchange rate, inflation and bureaucracy, etc CONCLUSION The failure of the existing state owned refineries to meet the Nigerian petroleum products demand has given credence to the liberalization of the downstream sector of the oil and gas industry and thereby encouraging the establishment of private refineries. It is believed that such private refineries’ operation would be a lucrative investment that will lead to satisfying domestic as well as external demand for petroleum products at appropriate and affordable prices, earn foreign exchange, eliminate import and thereby reducing cost and also improving on local capacity utilization. The petrochemical units of the refineries are particularly figured out as potential source

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Adubok, Agwom Sani – Zandi: Continental J. Earth Sciences 3: 1 - 7, 2008 of massive employment to Nigerians, this is due to the numerous small-scale industries that can emerge using their by-products as raw materials. They are therefore encouraged. Great prospects exist for such refineries in view of the country’s high and fast growing population and large and different grades of hydrocarbon reserves that can sustain such investments for along time exist (40 billion barrels reserve is being targeted by the year 2010). More so, advances in technology for alternative energy sources are low. Nigeria is also strategically located and can be accessed by neighboring African countries for petroleum products, product market is therefore guaranteed. Despite these prospects, however, certain problems exist that may still hinder the smooth take off and operations of these refineries, Nigerians neither posses the expertise nor the local capacity to fully accommodate such ventures. The success of the refineries is much dependent on the activities of the multinational who posses the requisite expertise (Avuru 2004, Ewuga 2004 and Olaleye 2004). They are however skeptical and unenthusiastic embarking on this investments in view of the complexities of doing business in the country. Care, must therefore, be taken to avoid this heavy dependence on foreign market for inputs – expertise, parts and machinery as well as routine maintenance services due to the death of local technology and infrastructure. Approval for refinery licenses must incorporate the local content policy for the continuous involvement and training of local indigenous operators because sole reliance on foreign investors might be a risky decision. They are likely to pull out at the slightest unfavorable business conditions. This may however not apply to Multinationals with businesses in the upstream sector of the Nigerian oil and gas industry, they should be enticed if not mandated to individually or jointly set up refineries and process part of their crude allocation locally as recommended by Adubok (2001) and presently being supported by the National Assembly. These oil companies have huge investment interest in the upstream to protect and not likely to leave in a hurry. More so, their resources availability and managerial efficiency will be brought to bear in the management of such refineries. It is also identified that the government on the one hand must show political will to transform the Niger Delta. Violence and other community related problems this could be achieved by fully involving the people of the area in making policies that affects them and participate in resource allocation (Nwosu, 2004). While Investors on the other hand must be transparent in all their activities to reduce anxiety and suspense that have woven the Nigeria oil and gas industry into a cult (Avuru, 2004). Considering all the above therefore, it is necessary that intending investors critically analyze all plans and steps necessary for the establishment of private refineries and the production of different petroleum by-products at maximum benefit. Such plans must accommodate changes in consumption pattern, crude supply, political risks, growing energy conservation policies, future market prices and the continuous search for alternative energy sources. Refineries once built has very little possibility for adaptation, flexibility for those on the drawing board is however, infinite. REFERENCES Abubakar, A. (2001), How to end fuel shortage by ex-PPMC Boss, edited by Nwora, C; “ Guardian” Newspaper, 3/06/01, pp1-2 Adigun, B.A. (1993): Averting oil shortage in Nigeria – The efficiency and adequacy of supply and distribution facilities in Nigeria, Energy policy agenda, Lagos. Edited By Fawibe, O., pp197 Adubok, A.S-Z. (2001): An appraisal of deregulation as a strategic policy to end Nigeria’s Fuel Energy Crisis, M.B.A (mgt) project, Imo State University, unpublished, pp 47-55 Alexander Oil and Gas Connection (1988), vol.3, pp 1-3

Alexander Oil and Gas Connection (2005), Ogel’s special study, vol.4, ed. Othman and Bunter, pp1 Ali-monguno, S. (2001): Fuel deregulation: a symphony of discord Guardian Features, 20/02/01 Aluko, M.E. (2003): On the fuel price hike and why we are where we are, view point in Lagosforum.com, 2/3/03, pp1-16

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Adubok, Agwom Sani – Zandi: Continental J. Earth Sciences 3: 1 - 7, 2008 Avuru, A. (2004): Ensuring Transparency in Nigerian oil industry, Thisday Perspective, 17/03/04, Pp26 Braide, A.M. (2005): The mechanics and dynamics of fuel scarcity in Nigeria part 1, www.onelga.com, 19/01/2005, pp1-5 Edmand, W.D. (1995): Promoting Investment in Nigerian upstream oil and gas resources, Keynote address, Re-channelling Nigeria’s Energy Resources for Economic.Revival, Ed. Fawibe, O. International Energy Forum, pp 43-54 El-Rufai, N.A (2005): Why Nigerian refineries can’t be sold, ed. Othman and Bunter, in Alexander Oil and Gas, vol. 9, no. 6, pp1-9 Enomoh, G. (2001): Deregulate the entire petroleum sector not just price alone, Guardian Executive brief, 5/3/01, pp46 Ewuga, S. (2004) Our Business attitude, Thisday Perspective, 09/05/04, pg18 Kukpolukun, F. (2005): NNPC’s silent revolution, Tell Magazine Special Edition, no.8, 21/02/05 Pp1-10 Nigerian Population Commission (NPC) - Population census results released 2007 Nwosu, G.F. (2004): NDDC and the burden of developing the Niger Delta, the Guardian Forum, Ed. Aderinbibe Y. pp15 Obadan, M. (2004): the Nigerian business environment, Thisday Newspaper, 14/06/04 Olaleye, Y. (2004): Fuel price hike will discourage foreign investment inflow. Thisday business World, Thisday Newspaper, 9/3/04 Osibanjo, O (1999): Petroleum products distribution and marketing and the scarcity problem M.Sc Thesis in energy and petroleum economics, Delta state university, Unpublished Soeze, C. (2005): Deregulation of the downstream sector of the Nigerian economy, Vanguard Newspaper, 15/02/05 Tinubu, W. (2004): Highly Inflamable – 1, Verdict according to Olusegun Adeniyi, thisday Newspaper, 10/06/04, pp64 www.nigeriaoilandgasonline (2005), The Nigerian Crude Oil Types and Qulity, 19/01/05 www.nigerianbusinessinfor.com (2005), The Nigerian Oil and Gas Industry, 19/01/05 Received for Publication: 24/06/2008 Accepted for Publication: 03/07/2008

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Continental J. Earth Sciences 3:8 - 21, 2008 ©Wilolud Online Journals, 2008. SEDIMENTOLOGICAL CHARACTERISTICS OF THE NIGERIAN TAR SAND DEPOSITS IN PARTS OF

SOUTHWESTERN NIGERIA.

Akinmosin, A1; Osinowo, O.O2

1Department of Earth Sciences, Olabisi Onabanjo University, Ago-Iwoye. 2Department of Geology, University of Ibadan, Ibadan..

ABSTRACT Particle size distribution of some Afowo tar sands as well as mineralogical and bitumen saturation analyses were carried out with the aim of elucidating the sedimentological properties of the deposits. Fifty samples of tar sands of the Afowo Formation in parts of south western Nigeria were subjected to granulometric and petrological analyses to determine the particle size distribution as well as other textural characteristics. Three of the samples were analyzed for phase identification using Phillips PW 1050 diffractometer equipped with Cu X-ray source and operated at 40kV and 30Ma. The results of sedimentological and particle size distribution studies showed that the sands are medium grained, moderately sorted and mesokurtic. The grain morphology can be described as having low to high sphericity, with shapes generally sub-angular to sub-rounded indicating a fairly long period of transportation. Result of x- ray diffraction analysis of the sediments showed that silica is the dominant mineral with traces of hematite and other minerals such as staurolite. Result of the bitumen analyses indicate that the tar sand deposits have an average bitumen saturation of 22.1%.

KEY WORDS- Petrological, Granulometrical, Tar-sands, Sedimentological, Sortingl and Grain-size

INTRODUCTION

The Dahomey basin (Fig. 1) is a marginal pull- apart basin (Klemme, 1975) or Margin sag basin (Kingston et al., 1983), which was initiated during the Early Cretaceous separation of African and South American lithospheric plates. Occurrence of seepage and tar sand deposits over the Okitipupa ridge in the Dahomey basin provided the initial impetus for oil exploration in Nigeria. From the turn of 19th century up till date, no less than over twenty groups comprising public and private ventures have shown degrees of interest in the exploration and exploitation of the deposits. The occurrence of these deposits has been known since early last century, however, intense investigations only commenced from mid 70’s till now. The pioneering efforts were initiated by the Geological Consultancy Unit of the University of Ife (now Obafemi Awolowo University). The geology of these deposits, oil saturation and reserve estimates as well as textural characteristics of the associated sands have been described (Adegoke et al., 1980, and 1981; Enu, 1987). The physicochemical properties of the bitumen in relation to production and processing have been studied (Oshinowo et al., 1982; Ekweozor, 1985; Oluwole et al., 1985). The origin of the bitumen has been discussed (Coker, 1990; Ekweozor, 1986). Other relevant studies on the deposit and geology of the basin include works done by Ako et. al (1983); Ekweozor (1986 and 1990); Ekweozor and Nwachukwu (1989); Enu (1987, 1990); Enu and Adegoke (1984); Elueze and Nton, (2004) and Akinmosin, (2005). These works have highlighted relevant aspects of the geochemical and sedimentological characteristic of the deposit. This paper is however based on detailed studies of 50 surface tar sand samples which is aimed at updating the sedimentological characteristics of the deposits.

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008

FIG. 1: East-West geological section showing the Dahomey Basin and upper part of the Niger Delta (After Whiteman, 1982).

A

A B

River

N

Footpath

Road

Settlement

0 1km

4 37E0

6 40N06 40N0

4 37E0

6 38N0 6 38N0

4 34E0

4 34E0

IDIOBILAYO

IDIOPOPO

Fig. 2: Location Map of the Study Area Showing Tar Sands Outcrop Points. STRATIGRAPHY OF THE DAHOMEY BASIN The study area lies between latitudes 60301 to 60351 N and longitudes 40301 to 60451 E and falls within the eastern Dahomey Basin (Fig. 2).The work of Omatsola and Adegoke (1981) on the Cretaceous stratigraphy of the Dahomey basin has recognized three formations belonging to the Abeokuta Group. These are: the Ise Formation, consisting essentially of continental sands, grits and siltstones, overlying the basement complex uncomformably. Neocomian to Albian age has been assigned to this formation. Overlying the Ise Formation is the Afowo Formation, which consists of coarse to medium-grained sandstones with variable interbeds of shales, siltstones and clay. The sediments of this formation were deposited in a transitional to marginal marine environment. Turonian to Maastritchtian age has been assigned to this formation. The Araromi Formation consists essentially of sand, overlain by dark-grey shales and

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008 interbedded limestone and marls with occasional lignite bands. The formation conformably overlies the Afowo Formation and Maastrichtian to Paleocene age has been assigned (Omatsola and Adegoke, 1981).

Table 1: Summary of grain size analysis. Sample No

Grain Size (mean) Sorting/Standard Deviation

Skewness

Kurtosis

Result Interpretation Result Interpretation Result Interpretation Result Interpretation A1 0.76 Coarse sand 0.78 Moderately

Sorted -0.11 Near

symmetrical 1.04 Mesokurtic

A2 0.25 Medium grained 1.83 Poorly Sorted

-0.13 Near symmetrical

0.90 Mesokurtic

A3 1.53 Medium grained 1.15 Poorly Sorted

-0.09 Near symmetrical

1.16 Leptokurtic

B1 1.83 Medium grained 0.94 Moderately Sorted

-0.02 Near symmetrical

0.99 Mesokurtic

E1 1.43 Medium grained 1.03 Moderately Sorted

-0.03 Near symmetrical

1.05 Mesokurtic

E2 0.82 Coarse sand 0.79 Moderately Sorted

0.00 Near symmetrical

1.04 Mesokurtic

E3 1.26 Medium grained 0.96 Moderately Sorted

0.31 Strongly Fine skewed

1.08 Mesokurtic

E5 1.00 Medium grained 0.73 Moderately Sorted

-0.02 Near symmetrical

1.03 Mesokurtic

E4 0.27 Medium grained 0.71 Moderately Well Sorted

0.05 Near symmetrical

1.02 Mesokurtic

F3 1.44 Medium grained 0.62 Moderately Well Sorted

0.04 Near symmetrical

0.74 Mesokurtic

F4 1.48 Medium grained 0.54 Moderately Well Sorted

-0.09 Near symmetrical

1.2 Leptokurtic

G1 0.82 Coarse sand 1.05 Poorly sorted 0.19 Fine skewed 1.16 Leptokurtic G2 0.46 Coarse sand 0.80 Moderately

Sorted 0.14 Fine skewed 1.07 Mesokurtic

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008

Table 2: Summary of percentage composition of minerals

Sample Quartz Biotite Muscovite Accessory A1 99 - - 1 A3 99.5 - - 0.5 A6 98 - 1 1 A11 99 - - 1 A13 98 - - 2 A17 97 - - 3 A20 95 1 1 3 A22 99 - - 1 A23 99.5 - - 0.5 B2 99.2 - - 0.8 B3 98 - 1.5 0.5 B4 99.2 - - 0.8 B5 98.5 - - 1.5 B9 96 - - 4 B12 98.5 - 1 0.5 B13 98 - - 2 B24 96 - - 4 B25 95 1 3 1 Overlying the Abeokuta Group conformably is the Imo Group, which comprises of shale, limestone and marls. The two-lithosratigraphic units under this group are: Ewekoro and Akinbo Formations. Ewekoro Formation consists of thick fossiliferous limestone. Adegoke (1977) described the Ewekoro Formation as consisting of shaly limestone 12.5m thick which tends to be sandy and was divided into three microfacies. Ogbe (1972) however, further modified this and proposed a fourth unit. The four microfacies making up this formation are described as follows: sandy biomicrite, shelly biomicrite, algal biosparite, and red phosphatic biomicrite. Ewekoro Formation is Paleocene in age and is associated with shallow marine environment due to abundance of coralline algae, gastropods, pelecypods, echinoid fragments and other skeletal debris. Akinbo Formation lies on the Ewekoro Formation and it comprises of shale, glauconitic rock bank, and gritty sand which is pure grey in colour and shows little clay. Lenses of limestone from Ewekoro Formation grades laterally into the Akinbo shale very close to the base. The base is characterized by the presence of a glauconitic band. The age of the formation is Paleocene to Eocene. Table 3: XRD Identified Compounds

Samples Identified Compound Remarks D1 Quartz SiO2

Hematite Fe2O3 Predominant Traces

P3 Quartz SiO2 Staurolite Fe3.546(Al17.99Si8O45)(OH)3

Predominant Possibly present, traces.

P5 Quartz SiO2 Hematite Fe2O3

Predominant Traces

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008 Table 4: Bitumen Saturation Result

Sample No Bitumen Saturation Facies A1 22.3 Medium grained sandstone A3 21.0 Medium grained sandstone A6 29.5 Fine grained sandstone A11 16.2 Medium grained sandstone B2 25.0 Fine grained sandstone B6 20.6 Medium grained sandstone B11 19.8 Medium grained sandstone

Overlying the Imo Group is the Oshoshun Formation. It is a sequence of mostly pale greenish-grey laminated, phosphatic marls, light grey to white-purple clay with interbeds of sandstones. It also consists of claystone underlain by argillaceous limestones with light grey shale at the bottom. There are inclusions of phosphatic and glauconitic materials in the lower part of the formation and the upper part is made up of medium to coarse-grained silty sandstone (Adegoke, 1969). The formation is Eocene in age (Agagu, 1985). The sedimentation of the Oshoshun Formation was followed by a regression, which deposited the sandstone unit of Ilaro Formation (Kogbe, 1976). The sequence represents mainly coarse sandy estuarine deltaic and continental beds, which show rapid lateral facies change. The coastal plain sands are the youngest sedimentary unit in the eastern Dahomey basin. It probably overlies the Ilaro Formation unconformably, but convincing evidence as to this is lacking (Jones and Hockey, 1964). It consists of soft, poorly sorted clayey sand and pebbly sands. The age is from Oligocene to Recent.

METHODOLOGY The outcrops which are located around stream heads and channels were defined based on the nature of the exposure, e.g. springs, channel band, etc and their extent noted. The outcrops were subsequently studied based on facies change and bed thickness measured with measuring tapes. Outcrops co-ordinates and elevation were taken using a GPS. Sampling of tar sands was done with the use of a geologic hammer, cutlass, shovel and digger to chip out samples into sample bags made of polythene material. Lithologic logs of the exposed surfaces were drawn to depict the sedimentological characteristics of the outcrops. The various outcrops were equally captured in photographs with a digital camera. Each sample was properly examined and quality checked. Thereafter, 100g of each sample was weighed using a top loading balance (Fischer brand PF-4001) and soaked in toluene for about 24hours to free the sediment, after which it was washed, dried and re –weighed. The liberated sediments were subsequently taken for the following analyses:

a. Granulometric analysis, b. Petrographic analysis (Mineralogical composition and Provenance study). Other sedimentological analyses carried out include (Lithofacies Identification, Bitumen saturation and .Mineral identification using X-Ray Diffractometric (XRD) technique).

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008

0

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Fig.3: Histograms showing grain size distribution of the sediments Fifty air dried samples each weighing 100 g were run through a set of mechanical sieves of the following mesh sizes, 1.40mm, 1.0mm, 0.70mm, 0.50mm, 0.35mm, 0.25mm, 0.18mm, 0.13mm, 0.09mm, 0.062mm and Pan which are equivalent of – 0.5, 0.0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 phi values respectively arranged in order of the coarsest sieve on top and the finest below. This analysis was done with a mechanical shaker agitating for 15 minutes for each sample. The amount, retained on each sieve was then weighed using a sensitive weighing balance. The bottom of the sieve was then cleaned thoroughly but gently with a brush to dislodge the grains partially stacked in the mesh holes to avoid contamination of subsequent samples. GreenSmith (1978) and Oronsaye (1980) have discussed some constraints of this method, which include errors introduced as a result of sieve apertures not being of constant size and/or grains adhering to the sieves. Inadequate or over sieving and non- standardization of the quantity of sample being sieved are other sources of error inherent in

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008 the sieving method. However, the adoption of 100g of sample and fixed sieving period of about 15 minutes for all samples analyzed are considered effective checks on some of these constraints.

Plate 1: Textural and mineralogical characteristics of the sediments (mag x100)

Plate 2: Textural and mineralogical characteristics of the sediments (mag. X 100)

Plate 3: Quartz varieties showing (quartz with vacuole and re-entrance angle-mag x 100 )

The individual weight, cumulative weight as well as individual and cumulative weight percentages were determined to construct histogram, and cumulative frequency curve for each sample on arithmetic graphs and semi log graphs. The necessary phi values i.e. φ5, φ16, φ25, φ50, φ75, φ84 and φ95 used for calculation of statistical parameters were obtained from the cumulative frequency curves. Mineralogical analysis was carried out by preparing slides of 30 selected samples. These slides were viewed under plane polarized and crossed nicols. Minerals present in each of the samples were identified by comparing them with standard mineralogical charts, and their percentage composition estimated. In addition to such minerals like quartz,

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008 feldspars and micas, sands may also contain other detrital minerals which can be referred to as accessory or heavy minerals. This method was adopted because of quartz abundance in the sediments, and its characteristics of high mechanical and chemical stability under any surface condition when subjected to prolong period of sedimentation without loosing its form. The two petrographic approaches were employed for provenance studies are: Quartz varieties determination and heavy mineral assemblage analyses. Based on Krynine genetic classification of quartz types (Krynine 1940), origin of a particular quartz variety can be determined. His classification was based on the following: i. Extinction (Straight, wavy or undulose extinction)

Plate 4: Photomicrographs of heavy minerals (Mag. x100) ii. Inclusion (minerals or vacuoles). iii. Grain shape and contact or boundary relationship iv. Number of quartz crystal in a sand grain (single or composite grain) Thirty slides of the prepared samples were examined under petrographic research microscope for quartz varieties determination based on Krynine criteria of classification. Inclusions in quartz crystals may be in form of minerals e.g. feldspar, biotite, trace elements etc. or in form of vacuoles which mostly are trapped in air during crystallization. Space may be left in form of re-entrance angle formed as a result of leaching away of labile or unstable mineral included on the surface of the quartz. Grain shape may be equant, subequant to irregular, stretched or elongated depending on the prevalent factor during crystallization. The composition of monocrystalline quartz in sand grain is often associated with igneous origin while polycrystalline quartz may have either igneous or metamorphic origin.

Heavy minerals are minerals that have specific gravity greater than 2.8. Heavy minerals in any sediment are in a sense the survivors of selective weathering, and they tend to be mostly concentrated within finer grained portions of sediments. Both effects of settling velocity and abrasion tend to concentrate the minerals in the fine-grained portion. The separating fluid used for this analysis was bromoform with specific gravity of 2.85. The selected 25 samples were screened through a 75µm sieve size to obtain uniform grain size. 10g of each of the screened samples was subjected to heavy mineral separation using bromoform. The separated minerals of each sample were later dried and mounted on a glass slide with the aid of Canada balsam (Sato, 1966). Each slide was subsequently viewed under the petrographic microscope and relative abundance of each mineral grain was calculated to give its number

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008 percentage. Generally, each heavy mineral is identified by its colour. The three toughest ultra-stable minerals (i.e. zircon, rutile and tourmaline) were used to calculate the ZTR index of the sediments (i.e. their mineralogical maturity). The ZTR for each of the selected samples was calculated using the formula-

Z+T+R X 100

Total no of NO

Where NO = Non-opaque, Z=Zircon, T=Tourmaline and R=Rutile.

Plate 5: Photomicrographs of heavy minerals (Mag. x100) (where Z- Zircon, K- kyanite, R- Rutile Si- Sillimanite, S- Staurolite, T- Tourmaline, O- Opaque mineral) This formula is referred to as Hubert’s (1962) scheme. From the calculated percentage, ZTR<75% implies immature to sub-mature sediments; ZTR>75% indicates mineralogically matured sediments Provenance study should reveal transportation history of any sedimentary particle. Hence, sediments with well rounded heavy mineral grains indicate a long transportation history. Sediments having rounded tourmaline or zircon for instance, indicate a long transport history and those with angular to sub-angular indicate that such sediments have not traveled too far. Angular and rounded tourmalines seen in the same specimen indicate multiple source areas. Other sedimentological studies carried out are: Lithofacies Identification and x-ray diffraction analysis. The lihofacies identification was achieved by carrying out whole rock description in the field coupled with visual and binocular microscopic description of collected samples on the basis of the following: i. Rock type, ii. Textural characteristics and iii. Mineralogical composition. Three samples were analyzed for phase identification. The samples were ground in a ceramic mortar prior to when X-ray diffraction was performed on a pressed portion of each sample using Phillips PW 1050 diffractometer equipped with Cu X-ray source and operated at 40kV and 30Ma (Philips and Philips, 1980). RESULTS AND DISCUSSION From the analyses, sediments of the study area can be seen to be predominantly bimodal, with the major class in the 1.25-2.50 Q. Average modal class corresponds to the medium grained sands. An average graphic mean of

φ98.0

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008 was derived for the sands. This indicates that majority of the sands are medium grained. Standard deviation values range between )92.0(83.154.0 φφφ averageof− , meaning that majority of the sands are well sorted.

The sediments are largely mesokurtic while others are leptokurtic to platykurtic. Skewness varies over a wide range (positively skewed to strongly coarse skewed). Histogram plots on some of the results obtained from granulometric analysis are shown in Figure 3a, while summary of the granulometric analysis result is shown in Table 1.

Plate 6: Photomicrograph of a fine-grained sandstone..

Plate 7: Photomicrograph of a medium-grained sandstone.

.

Grain roundness varies between 0.15 and 0.85 and ranged in shape from sub-angular to sub-rounded, Plates 1and 2. Compaction is moderate with little or no cementing material. Cementation and authigenic mineral growth are lacking probably due to early bitumen impregnation. The grain morphology viewed under petrological microscope shows low- high sphericity Plates 1 and 2. Quartz is present on average of 95%. They have low relief and show wavy and undulose extinction. They appeared colourless. Brown coloured biotite was observed under cross-polarized light. It is pleochroic and occurs as thin flakes. It constitutes about 2% of the sand content. Muscovite was equally identified constituting about 3%. The result of mineralogical analysis is shown in Table 2. Provenance Almost all samples examined under the petrographic microscope for their quartz varieties indicate the type referred to by Krynine (1940) as common quartz. They exhibited xenomorphic or allotriomorphic irregular (anhedral) to subequant shape. They are sometimes with re-entrance angles. Generally, quartz types sometimes

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008 contain no inclusions other than a small amount of randomly scattered vacuoles, which were probably created during crystallization (Plate 3). These quartz types were genetically classified by Krynine (1940) as being plutonic igneous quartz derivable from granite gneiss or a granite batholith. The quartz types show a very significant similarity with the metamorphic quartz type in that their composite grain boundries are often straight and in addition grains have wide different optic orientation. Euhedral water clear quartz crystals, which are indicative of volcanic source rock, are generally absent.

The percentage of opaque minerals in all the samples constitutes about 50%. Non-opaque minerals identified include: staurolite, tourmaline, rutile, sillimanite, zircon, kyanite, zoisite, epidote, garnet and hornblende. The amount of shape and colour of zircon (being the most ubiquitous and abundant non-opaque heavy mineral in the sediments) show that it predominates and its shapes are only fairly mechanically altered (commonly euhedral to subhedral) due to their high stability and lack of good cleavage. They appear commonly colourless. The proportion of tourmaline is next to that of zircon in nearly all the samples. It is usually brown in colour (sometimes greenish) or brownish yellow. Its shape is commonly euhedral. Rutile is relatively abundant in most samples; only the red coloured variety was recognized. Staurolite, sillimanite and kyanite are equally in small proportion. Photomicrographs of the heavy minerals are shown in Plates 4 and 5. From the ZTR computation indices, average ZTR index calculated is greater than 75%, consequently the sands are said to be mineralogically mature. Lithofacies and Textural Characteristics From physical examination and binocular microscopy, two main facies and two sub-facies were established from outcrop sections within the study area. These include: a.Sandstone facies with two sub-facies- i. Fine-grained sandstone ii. Medium-grained sandstone. b. Shale facies. A (i).Fine Grained Sandstone Sub-facies This facies (Plate 6) occurs mostly at the lower sections below shale sequence in outcrops where identified. This facies contains millimetre scale shale laminae and displays a dark-grey to black colouration in all the outcrops where it was observed. The grain sizes range from very fine to coarse, sub angular to sub rounded grains, they appeared moderately sorted, with mica and carbonaceous materials as accessories. A (ii). Medium-Grained Sandstone Sub-facies This sub-facies (Plate 7) was well represented almost in the outcrops. It is black in colour with grain sizes ranging from very fine to very coarse, sub-angular to sub rounded, moderately sorted and consolidated. B. Shale Lithofacies This lithofacies occurs in most cases at the lower section of the outcrop where observed. It is basically dark grey and fissile. It is characterized by millimetre scale of very fine to fine grain, and well sorted sand laminae. Mica, pyrite and carbonaceous materials occur as accessories. X-ray diffraction (XRD) result The compounds identified in the samples are presented in Table 3. The identified compounds confirm the result of the mineralogical study where quartz has a proportion of over 90% of the total mineralogical composition of the bitumen impregnated sediments. Bitumen Saturation Bitumen saturation refers to the wt. % or vol. % bitumen present per unit mass or volume of oil sands. The following categories of oil sands have been identified, Coker, (1988): i. Rich sands – Sb > 10wt. % (>19.2 vol. %) ii. Intermediate sands – Sb > 5 to < 10wt. % (9.9 to < 19.2 vol.)

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008 iii. Lean sands – Sb > 2 TO < 5 wt % (>4 to <9.9 vol. %) Result of the bitumen analysis showed that the tar sand deposits belong to category one (i.e. rich sands) with an average bitumen saturation of 22.1%, Table 4. The degree of saturation was found to be lowest in sediments with poorest sorting, having appreciable quantities of fine. It is therefore expected that those factors will in no doubt influence the bitumen withdrawal efficiency. SUMMARY AND CONCLUSION From physical and binocular microscopic examinations, two main and two sub-facies were established from outcrop sections within the study area. These include:Sandstone facies with two sub-facies ( fine-grained sandstone and medium-grained sandstone), and shale facies. The particle size distribution of the deposits as seen in this study varies without a definite pattern. Mostly, the sands are medium grained and moderately sorted with no significant fines. Except for few locations with poor sorting, the bulk of the sediments are moderately sorted. This quality, coupled with insignificant fines content will in no doubt enhance both bitumen saturation and withdrawal efficiency positively. The sands as observed from the analyses can be characterized as being chemically and mechanically stable with ZTR > 75%. The quartz content on the average is greater than 90% with little or no feldspar. Minor components are mica (biotite and muscovite) and heavy minerals (mostly zircon and tourmaline). These facts were equally confirmed the X-RD analyses. The sub-angular/sub-rounded shapes of the grains coupled with little of fines may be indication of fairly long period of sediments transportation.

REFERENCES Adegoke, O.S. 1969. Eocene Stratigraphy of Southern Nigeria, Bulletin Bureau de Resaerch Geologic ET Miners Memoirs. 69. 22-243. Adegoke, O.S. 1977. Stratigraphy and paleontology of the Ewekoro Formation (Paleocene) of SW Nigeria, Bulletin American Paleontologist; 71, No 295, 375 pp. Adegoke, O.S.,Ako, B.D., Enu, E.I., 1980. Geotechnical Investigations of the Ondo State bituminous sands Vol. 1. Geology and Reserves Estmate. Unpub. Rept., Geological Consultancy Unit, Department of Geology, University of Ile-Ife, 257pp. Agagu, O.K., 1985. A geological guide to bituminous sediments in Southwestern Nigeria. Unpubd. Rept., Department of Geology University of Ibadan, 34pp. Akinmosin, A., Olabode, O.T., and Bassey, C.E., 2005. Provennance study of bituminous sands in eastern Dahomey basin, southwestern Nigeria based on heavy minerials and quartz varieties. Ife Journal Science 7, (1) Ako, B.D., Alabi, A.O., Adegoke, O.S., and Enu, E.I., 1983. Application of Resistivity sounding in exploration for Nigerian Tar Sand, Energy Exploration and Exploitation 2, (2) 155-164. Coker, S.L.J., 1990. Heavy mineral potential with the mineable areas of the Okitipupa oil sand deposits; Nigeria. Abstracts. N.M.G.S. Conf. Kaduna. Elueze, A.A., and Nton, M.E., 2004. Organic geochemical appraisal of limestones and shales in part of eastern Dahomey Nigeria. Jour. Of Mining and Ekweozor, C.M. 1986. Characteristics of the non-asphaltene products of mild chemical degradation of asphatenes. Org. Geochem. 10, 1053-1058.

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008 Ekweozor, C.M. 1990. Geochemistry of oil sands of Southwestern Nigeria ln: B.D. Ako, E.I. Enu(editors, Occurrence, utilization and economics of Nigerian tar sands: A workshop held in Ogun State University Ago-Iwoye, Nigeria on 29-31 May, 1990. Published by the Nigerian Mining and Geosciences Society, Ibadan Chapter, 50-62. Ekweozor, C.M., and Nwachukwu, J.L., 1989. The origin of tar sands of SouthWestern Nigeria. N.A.P.E. Bull. 4 (2) 82-84. Enu, E.I. 1987. The paleonenvironment of deposition of Late Maatritchtian to Paleocene black shales in the eastern Dahomey basin, Nigeria. Geologie en Mijinbouww. 66p, 15-20. Enu, E.I. 1990. Textural and occurrence of tar sands in Nigeria ln: B.D. Ako, E.I. Enu(editors, Occurrence, utilization and economics of Nigerian tar sands: A workshop held in Ogun State University Ago-Iwoye, Nigeria on 29-31 May, 1990. Published by the Nigerian Mining and Geoscience Society, Ibadan Chapter, 11-26. Enu, E.I. and Adegoke, O.S., 1984. Potential Industrial mineral resources associated with the Nigerian tar sands 27th International Geological Congress. Book of abstracts VII. 345, Moscow. GreenSmith J.T. 1978. Petrology of sedimentary rocks. George Allen and Unwin Ltd 214pp. Hubert J.T. 1962. Zircon-Tourmaline-Rutile maturity lndex and interdependence of the composition of heavy minerals assemblages with the gross composition and texture of sandstones. Journ. Sed Pet. 32 440-450. Jones, H.A. and Hockey, R.D., 1964. The geology of southwestern Nigeria Bulletin Geological Survey, Nigeria. No 31 100PP. Klemme, H.D., 1975. Geothermal Gradients, Heatflow and Hydrocarbon Recovery. In : A.G. Fischer and S. Judson (eds), Petroleum and Global Tectonics. Princeton, New Jersey, Princeton Univ. Press, pp. 251-304. Kingston, D.R., Dishroon, C.P. and Williams, P.A., 1983. Global Basin Classification System. AAPG. Bull., 67, 2175-2193. Kogbe, C.A., 1976. Geology of Nigeria. Second revised edition. Published by Rock view (Nig.) 455pp. C.A., Kogbe (Editor). Krynine, P.D., 1940. Petrology and Genesis of the Third Bradford Sand. Pennsylvania State Coll. Bull. 29, 134p. Ogbe, F.G.A., 1972. Stratigraphy of Strata Exposed in Ewekoro Quarry, Southwestern Nigeria. In African Geology pp 305-322. Oluwole, A.F., Adegoke, O.S., Kehinde, L.O., Nwachukwu, J.I., Coker, S.J.L., Wallace, D., Asubiojo, O.I. and Ogunsola, O., 1985. Nigerian Tar Sands. In: Proceedings of 3rd Intern. California, Chap. 33, 373-379. Omatsola, M.A and Adegoke, O.S., 1981. Tectonic evolution and Cretaceous stratigraphy of the Dahomey Basin J. Min. Geol. 18 (1) 130-137. Oronsaye, W.I., 1980. The accuracy of grain size analysis by sieving method. Jour. Tain. Geol. 15 (2), 153-157. Osinowo, T., Ademodi, B. and Adeniran, S.A., 1983. Bituminuos Tar Sands 0f Nigeria: Analysis of Oils- Parts l, Journal of The Nigerian Soc. Of Chemical Engineers, No 1, pp. 44-46. Philips, W.J. and Philips, N., 1980. Introduction to Mineralogy for Geologists. Wiley, London

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Akinmosin, A and Osinowo, O.O: Continental J. Earth Sciences 3:8 - 21, 2008 Sato, T., 1966. Heavy Minerals in Sandstone. Geology Monthly, Japan, No. 141, 34-38. Received for Publication: 24/06/2008 Accepted for Publication: 03/07/2008 Corresponding Author Akinmosin, A Department of Earth Sciences, Olabisi Onabanjo University, Ago-Iwoye.

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Continental J. Earth Sciences 3:22 - 27, 2008 ©Wilolud Online Journals, 2008.

TRACE ELEMENTS DISTRIBUTION AND ENRICHMENT IN SOILS OVERLYING BARITES VEIN DEPOSITS IN THE PAYA DISTRICT, MIDDLE BENUE TROUGH, NIGERIA

Adubok, A .S1 and Imoekparia, E.G2 1Geology Department, Gombe State University, Gombe, 2Geology Department., University of Benin, Benin

City

Abstract The Paya Barites deposit typifies the numerous small (hidden) and uninvestigated barites mineralization that abound within the Benue Trough, Nigeria. Geological field studies and geochemical analysis of soils around the mineralized ridge was carried in order understand the general structural trend as well as assessing the trace elements distribution. Results of field geological investigations indicate Barites mineralization in vein systems, occurring as infillings in joints and fractures within an East – West trending ridge. Trace element geochemistry of soils overlying these veins revealed relative high values of Pb, Mn, Cu and Sr around the zone of mineralization. However, average Ba content of soils overlying the barites veins is similar in content to the regional background values indicating that the soils overlying the mineralized veins are not enriched in barium (Ba). Results obtained from this study have implications for pedogeochemical studies of blind barites deposits. KEYWORDS: Soils, Barites, Veins, Geochemical Analysis, Trace Elements, Pedogeochemical

INTRODUCTION The occurrence of barites (BaSO4) in Nigeria was first reported by Tate (1959) revealing barites mineralization around Keana - Aloshi, Akiri-Wuse, Shata/ Chiata / Ibi and Gbende-Gboko areas within the Middle Benue Trough with tentative reserves of about 40,000 tonnes. This report generated a lot of research interest over the years, all with the view of determining the structural orientation, geologic affinity and the ore content of such mineralizatiion and their possible industrial application. Reserves of some of these deposits have been established and in some cases found to be economical, with the Azara deposits developed by the Nigerian Barite Mining and Processing Company, a subsidiary of the Nigerian Mining Corporation. The national gross production of this very essential raw materials is however, quite inadequate as compared to its high demand both locally and internationally. This therefore, necessitated a vigorous and detailed study of known barites deposits and the search for new ones in potential geologic environments of which the Benue Trough is known to be prolific (Turaki 1976; Ford 1981; Ogbeide 1981 and Chukwu 1994). These investigations and the mining of barites the world over have however, been restricted to exposed (known) and relatively large ore bodies with little attention paid to remote, concealed or hidden smaller occurrences which will be the saving grace for the future (Brobst 1979). It is in line with this, that a geochemical survey of soils overlying one of such smaller barites deposits is undertaken in order to understand the distribution of elements in the primary environment and the primary dispersion trend of such elements. This research is undertaken with the hope of collaborating, the findings of other researchers, most especially, the findings of Ogbeide, 1981, who undertook a reconnaissance survey around Azara area of the Middle Benue Trough aimed at detecting more barite veins and geochemical anomalies likely to be associated with barites mineralization. It is believed that trace element geochemistry remains the best approach in detecting and identifying such hidden small ore bodies or to a greater extend, delineating areas of possible alluvial barite occurrences. Location and Physiography of the study area The study area is located within sheet 212, south east of Shendam town, Plateau State. It lies between longitude 9o 54’ 48’’ E to 9 59’ 55’’ E and latitude 8o 34’ 18’’ N to 8o 42’ 43’’ N. (fig.1). It is located about 45km south east of Mabudi in Langtang South Local Government Area. It can be assessed eastwards from the Langtang- Ibi highway at Yelwan - Shendam through Mabudi.

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Adubok, A .S and Imoekparia, E.G: Continental J. Earth Sciences 3:22 - 27, 2008 The Paya area is generally a low lying plain with the only upland being the mineralized barite ridge trending in an east-west direction. The ridge, which extends for about 1km, is approximately 2130feet (649.22m) high and less than 50m wide. Most part of the study area is covered by lateritic cap and overlain by thick layers of dark humus topsoil due to insitu weathering as a result of the flattish topography. The area gently slopes from Naki-Wase towards Gbaldum to Paya, but rises gently from Paya towards Yamini and south -east wards. The laterites at the mineralized zone (ridge) have been ferrugenized but boulders of decomposed sandstones are however exposed through farming activities. It is intensely fractured, brecciated and eroded, exposing the sandstone beds and associated barite veins in the direction of the major W – E trend similar to the trend of other deposits within the Benue Trough (Offodile and Olayemi 1975; Turaki 1976 and Akponor 1993).

Geology The Paya barites mineralization is found within the keana Sandstone, which is Cenomanian in age and overlying the Albian Arufu-Uomba- Gboko Formation, generally refered to as the Asu River Group within the middle Benue Trough (Obaje et al 1999), Keana Formation is a feldspathic sandstone that is believed to have originated from tectonically active province of granitic composition (Hoque et al 1984). However, the felspathic composition decreases with increasing maturity of the depositional environment. The formation is a medium to coarse-grained sandstone, milky to gray in colour, poorly to well sorted and shows an increase in grain size and little intercalations of siltstones with depth. The zone enclosing the mineralized ridge is baked to (dark) gray colour. The presence of large phenocrysts within the barite crystals is indication that they are part of a later intrussion. Non barite-bearing sandstones are however, medium grained and light in colour. The Paya barite veins occur at the crest of the ridge. Well-developed barite crystrals are observed within the mineralized ridge, indicative of the presence of already existing fractures and bracciated zones to accommodate the intruded fluid of secondary geologic episode and allowed for the growth of such crystals. Mineralization at the surface, are in small veinlet systems (about 5cm) but tend to merge with depth thereby forming larger veins, they are exposed where eroded but generally covered by laterites which, in some locations have been ferrugenized. The barite occurs as pure white crystal without any form of impurity, however, some samples were

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Adubok, A .S and Imoekparia, E.G: Continental J. Earth Sciences 3:22 - 27, 2008 observed to have phenocryst of sorrounding country rocks. Unlike most other barite veins within the Benue Trough that occur in association with quartz (Ogbeide 1981), the Paya barite neither showed any appreciable quartz presence nor sulphide minerals which are commonly associated with barite mineralization (Chukwu 1994). Geochemical results however, indicate enrichment in elements associated with sulphide mineralization Table 1. Trace Elements Distribution in Soils overlying Paya barite

Elements Content (ppm)

Sample No.

Zn Pb Mn Co Ba Sr Cu

SS1 13 87 570 30 40 28 14 SS2 72 525 870 20 550 320 40 SS3 41 228 1740 32 140 80 32 SS3B 32 224 370 13 108 60 17 SS3C 26 180 1160 28 94 51 22 SS4 38 98 420 12 206 106 48 SS5 10 70 100 22 45 28 24 SS6 42 38 1776 n.d 1230 140 20 SS7 24 80 900 n.d 40 12 38 SS7B 88 1460 2400 50 286 180 120 SS7C 84 3280 4880 12 156 53 138 SS8 4 27 180 5 14 9 6 SS9 26 54 480 n.d 16 6 4 SS10 4 n.d 48 n.d 25 15 3 SS11 32 53 878 n.d 50 31 24 SS12 6 38 45 n.d 25 12 3 SS12B 5 30 30 8 22 16 16 n.d = not detected Geochemical Investigations Early barite mineralizations were usually, mostly identified through surface geologic mapping due to the fact that they stand as distinct resistant ridges above the surrounding environment. They are known to be resistant to chemical weathering processes. Deposits cutting stream channels or rivers are also exposed but few deposits are however, flat, residual or even buried. Such veins are very difficult to identify and therefore requires some special techniques. Geochemical exploration technique has been described as the best and the most successful for the identification of these blind deposits against the geophysical methods. In Nigeria, the only geophysical method used for the search of barite is the magnetic survey, using a portable Proton Magnetometer (Offodile 1977). The geochemical technique is achieved through sampling of stream sediments, soils, bedrocks or even vegetation. For good results and cost effectiveness soils and stream sampling are more applicable for reconnaissance survey. But due to the chemical inertness of barite to chemical weathering, its boulders are not likely to be transported very far from source and boulder tracing could prove to be a good method. Sampling Soil and rock samples were randomly collected to determine their petrography and trace element composition and distribution. Seventeen (17) soil samples were collected from pits of about 35cm deep and results obtained from analyses of these samples were used to assess the geochemical paragenesis, mineral assemblages, geochemical halos and the probable application of pedogeochemistry in the future search for barite through pathfinder elements that will be established

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Adubok, A .S and Imoekparia, E.G: Continental J. Earth Sciences 3:22 - 27, 2008 Analyses Trace element analyses of the soil samples were carried out by instrumental method. 0.5g of the soil samples were weighed into 150ml glass beaker and 10ml of distilled water, concentrated hydrochloric, nitric acid and perchloric acid were added and boiled until white fumes were formed. 10ml of concentrated nitric acid and 50ml of distilled water were again added and heated for about 10 minutes before filtering into a volume and made up to 100ml after cooling. Each element was determined using the VGP Systems Atomic Absorption Spectrophotometer (AAS), Model No.210 after setting the wavelength and Lamb Current of elements of interest along with their standards. Results obtained are given in table 1. These are compared with the result of reconnaissance survey of the Benue Trough (Ogbeide 1981) Table 2. Table 2: Comparative Chemical content of soils around barite in Paya and other areas of the Benue Trough

Conc. Range (ppm) Mean (ppm)

Element 1 2 1 2 Ba 25 – 1179 14 - 1230 177 180 Pb 10 – 44 27 – 3280 12 384.24 Zn 4 – 43 4 – 88 32.18 Cu 4 – 66 3 – 120 11 27.29 Mn 5 – 2400 30 – 4880 439 994.47 Sr 4 – 34 6 – 320 8 67.47 Co n.d 5 – 50 14.29 DISCUSSION OF RESULTS Included in Table 2 for comparison, is result the of` a reconnaissance survey on sediments and soils around barite bearing zones within the Benue Trough (Ogbeide 1981). This gives an idea of the regional trace elements distribution in soils of the barite bearing zones of the Benue Trough (1) as compared with results obtained from the study area (2). Looking at the respective elements and relative abundance, it is seen that a strong relationship is established between the barite mineralization and some elements due to their relative abundance as compared with the regional values. Elements such as manganese (Mn), lead, copper, strontium and Zinc show relative abundance. This could be explained by the fact that the ionic radii of divalent barium (A1.43), allows it to be captured by the divalent ions of strontium; manganese oxides are also known to be very important carriers of Ba; copper – lead – zinc – iron oxides are ganques associated with barite mineralization and this association lay credence to barite being a low temperature hydrothermal ore (Ogezi and Akponor 1994) Results show that Ba content ranges from 16ppm to 1230ppm. Ranges for other elements include Zn (4-88ppm), Pb (30-3280ppm), Mn (30-4880ppm), Co (5-50ppm), Sr (6-320ppm) and Cu (3-120ppm). Evaluation of the data revealed that soil samples no. 2, 3, 3B, 3C, 4, 7B and 7C are enriched in all the elements. Amongst these samples, nos. 3, 3B, 3C and 4 were collected directly at the top the ore- bearing vein, while samples 2 and 7B were collected near the mineralized ridge, except sample 7C collected within the alluvial sands north-east wards of the ridge. Contrarily, all other samples show low content of the assessed trace elements most especially, samples 8, 9, 10, 11, 12 and 12B collected at various distances away from the ore-bearing ridge. Of note are the discriminatory values of these elements in samples collected on the mineralized ridge and those in samples from adjoining sections. However, few samples from the mineralized ridge, such as sample 3B has relatively low Mn (370ppm), Cu (17ppm) and Co (13ppm) and sample 4 has low Co (12ppm). As seen from tables 1 and 2, Zn concentration ranges from 4-88ppm with an average of 33.18ppm.The highest values of 72ppm, 84ppm, 88ppm were obtained from samples SS2, SS7B and SS7C. These and samples SS3, SS3B, SS3C and SS4 with relatively high values are from locations around the ore–bearing ridge (except 7C in the alluvial soils of River Wase). High concentrations of zinc around the mineralized ridge could be due to chemical leaching from the ore body. Lead and Manganese values ranged between 27-3280ppm and 30-4880ppm, averaging 384.24ppm and 994.47ppm respectively. These elements show the same trend of distribution but with average content far surpassing that of zinc. Their paragenesis and high level of susceptibility to weathering could be responsible for these concentrations because their sulphides are known to

26

Adubok, A .S and Imoekparia, E.G: Continental J. Earth Sciences 3:22 - 27, 2008 have very close affinity for barium bearing minerals. Though, minerals such as ankerites and siderites were not identified on the field, they are known to always occur within barite veins; introducing oxidation effect on the mineralized veins and normally generating abundant oxides of iron and manganese. In the same manner, galena, though not identified, are known to be very common gangues of barite from where lead can be leached and enriched. Cobolt (Co) content is generally low ranging from 5-50ppm (average of 14.29ppm), 50ppm was obtained from sample 7B, East of the ridge towards the alluvial soils, between Paya and Yamini, while sample 1 with 30ppm is north of the ore –bearing ridge, west ward of Gbaldum. Sample 3 (32ppm) and 3c (28ppm) is just within the ridge, while Strontium also showed affinity to the ore – bearing ridge as indicative of the high concentrations in samples ss2, ss7b, ss6, ss4 and ss3 with values of 320ppm, 180ppm, 140ppm, 106ppm and 80ppm respectively. With the exception of ss6 that is further down slope, all the other samples with high strontium values are located around the ore – bearing ridge, ss3B with 60ppm is on the ridge. Generally, the value ranges from 6-320ppm (67.47ppm). Likewise, Copper (Cu), ranged from 3-120ppm (average 27.29) and not showing any distinctive anomaly. Its average content around the mineralized ridge is however, generally higher. This is Similar to strontium, where ss7B, ss2, ss4 and ss3 are also enriched. There is a general enrichment of strontium in the local environment as compared to the regional values. Barium (Ba) has values of 14-1230ppm, averaging 180ppm. Ss3, ss3b, ss3c and ss4 sampled at the crest of the ridge gave Ba contents of 140ppm, 108.94ppm and 206ppm respectively. Again the sloppy area round the ridge, south to southeast wards as indicative of samples ss2, ss6 and ss7b are highly enriched, having values of 550ppm, 1230ppm, and 286ppm respectively. Generally, Ba has close values for both local and regional enrichment. The average Ba content in soils overlying the barite veins is about 180ppm. This compares favourably with the average regional background value of 177ppm (Ogbeide 1981). The chemical inertness of barite may be responsible for this lack of anomalous enrichment, even around the ore veins. This is however, in contrast with the findings of Ogezi and Aponor (1994) who opined that the low temperature hydrothermal fluids (source of barite mineralization) were more concentrated in trace elements and light earth elements, especially the incompatible elements-Ba, Sr and K. Assessment of the relative abundance of the elements reveal a strong relationship between the barite mineralization in Paya area and the concentration of Sr, Pb, Zn, Cu and Mn. Table 3 illustrates the trace element enrichment by samples and this can be correlated with the enclose geological map of the study area. Table 3. Subdivision of the samples according to their level of enrichment

Concentration values (ppm)

Element Low Average High Samples with low concentr. Samples with high concentration

Zn 4,5,6,10,13 24,26 32-88 1,3c,5,7,8,9, 10,12, 12b 2,3,3b,4,6,7b,7c,11 Pb 27, 30, 38 53, 54, 70 87-3280 5,6,7,9,10,11,12,12b 1,2,3,3b,3c,4,7b,7c Mn 30, 45, 48 100-570 870-4880 1,3b,4,5,8,9,10,12,12b 2,3,3c,6,7,7b,7c,11 Co 5, 8 12, 13 20-50 1,3b,4,5,8,9,10,12,12b 2,3,3c,6,7,7b,7c,11 Sr 6-16 28-31 51-320 1,5,7,8,9,10,11,12,12b 2,3,3b,3c,4,6,7b,7c Cu 3-17 20-24 32-120 1,3b,3c,5,6,8,9,10,11,12,12b 2,3,4,7,7b,7c Ba 14-25 40-94 108-1230 1,3c,5,7,8,9,10,11,12,12b 2,3,3b,4,6,7b,7c CONCLUSION From the field and geochemical investigations, it can convincingly be concluded that the barite mineralization has a very high affinity for elements such as Mn, Pb, Zn, Sr and Cu. This is demonstrated by their relative high concentration at the local environment than the regional values. It is believed that these anomalies are related to the mineral paragenesis and topography of the area – being flat lying, the leached elements are not widely dispersed. This may also account for the restriction of the anomalous values around the mineralized ridge as indicated by the enrichments in samples ss2, ss6, ss7b and ss3. High trace elements concentrations are restricted to the mineralized ridge and areas eastwards, towards Yamini and surrounded by the alluvial soils of the two

27

Adubok, A .S and Imoekparia, E.G: Continental J. Earth Sciences 3:22 - 27, 2008 major rivers, River Kwazu, River Pai and River Wase. Locations of ss8, across River kwazu, on the southern portion, ss5, 11, 12 and 12b at the far northern and northeastern parts did not show any appreciable enrichment. Ba showed no significant re-concentration in soils overlying the barite veins in the study area. Its value was similar to background values indicating that it was not enriched in soils overlying the mineralized veins. This may imply that Ba may not be too significant an element in pedogeochemical studies for blind (buried) and or alluvial barite deposits. This finding also, does not support the submissions of (Chukwu 1994) who recorded high Ba - Pb anomaly dispersion through geochemical stream sediments and residual soil profile studies in the Arufu – Akwana areas. Manganese (Mn), lead (Pb), copper (Cu), strontium (Sr) and zinc (Zn) could however, serve as good pathfinder elements for this purpose. REFERENCES Akponor, J.A.I, (1993): Aspects of some Exploration and Exploitation of Barite in the Azara - Akiri –Wuse areas in the Middle Benue Trough, University of Jos M.Sc Project, Unpublished Brobst , D.A. (1979): United State Bureau of Mines Year Book,1981, pp141-149 Chukwu, D.U. (1994): Factors Controlling Prospecting in the Benue Trough: A case Study of Barite in the middle part of the Trough, 30th N.M.G.S Annual Conference, Abst. Vol., pp4 Ford, S.O (1981): The Economic Mineral Resources of the Benue Trough, Journal of the Earth Evolution Sciences, 2: 154 - 163 Hoque, M and Nwajide, C.S (1984): The Tectono-Sedimentological Evolution of an Elongated Intracratonic Basin (Aulogen), The case of the Benue Trough of Nigeria. Journ. of Mining and Geology, 21(1&2): 19-26 Obaje, N.G., Olu O.K and Peters W (1999): Biostratigrphic and Geochemical Control of Hydrocarbon Prospects in the Benue Ttrough and Anambra Basin, Nigeria, NAPE Bulletin, Vol.14 (01): 18-54 Offodile, M.E (1977): The Economic Significance of some of the Cretaceous Events in the Benue Valley. Journal of Mining and Geology, Abstr.Vol.14:67 Offodile, M.E. and Olayemi, G.M. (1975): Reconnaissance Survey of Areas around Barite Occurences in Benue Plateau State. Report of the Nigerian Mining Corporation, unpublished. Ogbeide, D.A. (1981): Nature of Geochemical Dispersion in Sediments and Soils around Barite, Plateau state. Uunpublished M.Phil. Thesis, University of Ibadan, pp1-136 Ogezi, A.E. and Akponor, J.A. (1994): Aspects of the exploration and exploitation of Barite Deposits in Azara – Wuse – Akiri areas, Plateau State in the Middle Benue Trough. 30th NMGS Conference, Jos, abstr. Vol. p3 Tate, R.B. (1959): Memorandum of the Geological Survey of Nigeria on the Barite Deposits of the Benue Province, Unpublished Report No. 1266 Turaki, U.M. (1976): The Barite Deposits of Azara, Proceedings of the 17th Annual Conference of N.M.G.S, Jos. Received for Publication: 16/06/2008 Accepted for Publication: 12/07/2008 Corresponding Author Adubok, A .S

Geology Department., Gombe State University, Gombe Email: www.sanizandi@yahoo.com

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Continental J. Earth Sciences 3:28 - 32, 2008 ©Wilolud Online Journals, 2008. SPECTRAL ANALYSIS OF AEROMAGNETIC DATA OVER LONGUDA PLATEAU AND ENVIRONS,

NORTH-EASTERN NIGERIA

Kasidi S. and Ndatuwong L.G. Department of Physics, Adamawa State University, Mubi, Adamawa state

ABSTRACT The investigation involve the analysis of lineraments and spectral analysis of total -intensity magnetic field data over the Longuda Plateau and environs, Guyuk area. The total magnetic field map exhibit direction of NE-SW and E-W lineraments. The NE-SW lineraments coincide with Longuda basalts while the E-W coincide with the Yola arm of Benue Trough. Result from spectral analysis of the aeromagnetic data indicate two depth source model. The depth to deeper magnetic sources ranges from 1900m to 2620m and could be identified with the basement. The shallow magnetic source ranges from 512m to 670m this could be attributed to near surface intrusive. And laying river valleys in the study area. The results obtained from the study compared favorably with that from Gravity studies. KEYWORDS: Basement, Benue Trough, Magnetic field, Basalts, lineaments and intrusive.

INTRODUCTION The study area is located between longitude 11 °30’ and 12o 00’lE and latitude 9°30’ and 10o00’ N in North-Eastern Nigeria (Fig.1). It lies in the Guyuk sheet within the cretaceous Benue trough. The area is predominately hilly as the name implies and is drained mainly by the Benue and Gongola rivers. Airborne magnetic surveys provide a quick means of geological mapping. The magnetic data give information about geological patterns at depth about the metamorphic basement on which younger sedimentary rock lie, and trough light on the presence of major structures which may have influenced its development. The present work is an attempt to analyze aeromagnetic data over Longuda Plateau, Guyuk area which believes will contribute a better understanding of the geology of the area. GEOLOGICAL SETTINGS Geological studies in the Benue trough have been widely reported in literature by Gtatchley and Jones, 1965, Burke et al 1970; Carter et al, 1963; Offodile, 1976; Osazuwa et al 1981 and Offegbu 1985. The earliest documented sediment deposition in the area was in aptain-ALbian period when fluvioclastic sediments of Bima formation were laid unconformably on the basement in the fitted wrench fault basin. The structural deformation which later caused the basin to sag, led to the development of a trough which allowed the upper cretaceous Marine deposition. This transgressive episode led to the deposition of Yolde, Dukul, Jessu, Sekule and Numanha sedimentary formation, all these formation flanks the younger basalts of Longuda plateau. These sediments outcrops as inliers to Bima formation in Dadiya syncline (Fig. 1 ) The lithofacies consist of the continental arenaceous Bima formation believed to be braided stream sediments (Braide, 1982). This formation is the single largest occuimg lithofacies in the area, found NW, SW and NE ward. The Yolde formation outcrops in places such as Bamban, Yolde, North West of Galengu. The Dukul, Jessu, Sekule and Numanha formation are shallow marine depositions of limestone, shale and mudstone and they are found mainly as narrow strips of rocks in the study area, such as at Banju Guyuk etc. continental conditions followed the marine and resulted in the deposition of Lamja formation which consist of sand stone, coal, shale and limestone. The Longuda Basalt of tertiary age terminates the lithological succession in the area. The basalts covers approximately 160km2 and is located centrally in the area, these Longuda basalt is flanked by the cretaceous sediments of the Benue trough in the study area. The basalts extends in the NW -SE direction with a minor arm extending SW towards Bambam town. It is an olivine rich basalt of fine grained texture. River Valley alluvium is confined to the

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Kasidi S. and Ndatuwong L.G: Continental J. Earth Sciences 3:28 - 32, 2008 banks of the Benue and Gongola rivers. Sediments in the area were subjected to tectonism before the tertiary resulting in the existence of folds and faults, prominent among the folds are the Lamurde anticline and the Dadiya syncline south western part of the study area. The faults are found in the NW and NE part of the study area.

MATERIALS AND METHODS Contoured aeromagnetic data over the Longuda Plateau, Guyuk area have been compiled by the geological survey of Nigeria (GSN) (Fig.2) as part of the Nigeria wide geological survey data. The data were acquired along a series of NE-SW with a flight line spacing of 2km, average flight elevation of 150m above terrain and a nominal tie line spacing of 20km. The geomagnetic gradient was removed using the international geomagnetic reference field formula (IGRF). The map is published on the scale of 1:1000

Fig 1: Geological Map of study area (Adapted From Carter et al , 1963

The magnetic data were also subjected to 2-D spectral analysis for depth estimates to their sources. 2-D technique for spectral analysis of magnetic anomalies has been described by several authors (Bhattacharyya, 1966, Spector and Grant 1970, Cornard et al 1983, Nur et al, 1994). For the analysis of this data, the mathematical formulation of Nur et al 1994 were used. Given a residual magnetic anomaly map of dimension L x L, digitized at equal intervals, the residual total intensity anomaly values can be expressed in terms of a double Fourier series expansion; N,M

30

Kasidi S. and Ndatuwong L.G: Continental J. Earth Sciences 3:28 - 32, 2008 The Fourier transformation of a section of magnetic survey digitized in a square grid therefore forms a rectangular matrix of coefficient which can be reduced to a set of average amplitudes dependent only on the frequency (Hann et ai, 1976). These average amplitude fully represent a spectrum form which the depth to magnetic sources can be estimated. To carry out spectral analysis, the area under study was divided into blocks of 16 x 16 data points making sure that as much as possible, the essential part of an anomaly contains more than one maximum or minimum. The data for each block was subjected to 2-D Fourier transformation.

Fig.2: Total intensity aeromagnetic map of Guyuk area (for absolute values add

32,000 gammas) The average amplitude Spectrum all waves falling within a given frequency range is then computed by summing the Fourier amplitudes and dividing by the sum of the number of frequencies. These average amplitudes are then plotted against the frequency on a semi-log scale. Straight lines of best fits are drawn through the different segments of the spectrum. The depths to the magnetic source are related to the slopes of the lines segment by the relation.

Z = SL

2π Where S=slope, L=length of square side (Negi et al 1983). The depth estimate for four blocks that covers the study are presented in Table 1. Table 1: Depth of magnetic sources obtained for Longuda plateau and environs

Block 1 D1=1900m D2=546m

Block 3 D1=2620m D2=552m

Block 2 D1=1972m D2=512m

Block 4 D1=670m D2=647m

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Kasidi S. and Ndatuwong L.G: Continental J. Earth Sciences 3:28 - 32, 2008

RESULTS AND DISCUSSION Generally, there would always be a magnetic susceptibility contrast across a fracture zone due to oxidation of magnetic to hematite, and / or infilling of fracture planes by dyke like bodies, whose magnetic susceptibilities are different from those of their host rocks. Such geological features may appears as thin elliptical closures or nosing on anaeromagnetic map. Bearing this in mind, prominent elliptical closures and nosing of contours were identified on the magnetic map. These features represent geological lineaments. Their positions are indicated by lines drawn parallel to the elongation and through the center of the anomalies and they are presented in Fig.3. The main trend of the lineamerments is NE-SW with a subordinate E-W trend. Aeromagnetic anomalies over the study are consist of slow to fast varying types. The NE-SW lineament is a concentrated sequence restricted to the plateau central zone of the area and coincident with the Longuda Basalt flow (Fig.3), while the E-W occupies the broader part of the area and coincident with the sedimentary cover. Few other rapid varying anomalies exist particularly in the SW of the area and they area probably caused by basic intrusive within the sedimentary rocks. The magnetic lineamennents of Fig.3 are mainly attributed to Precambrian basement fractures which were initiated prior to the formation of the Benue right (Osazuwa et al, 1981). Their relative concentration between Guyuk and Cham, and between Bangu and Giwano could signify a more intense fracturing of the basement in this zone.

Fig.3 Magnetic linearment map derived from anomaly ‘closure’ and ‘nosing’ of fig.2

Depth estimates from spectral analysis of magnetic data indicate a two depth source model. The depth of the deeper source range from 1900m to 2620m, this could be identified with basement. The shallow source range from 512m to 670m, this could be attnbuted to near surface intrusive and low-laying river valleys. The deeper depth Estimate are in agreement with those from gravity data over the upper Benue trough by (Osazuwa et al 1981). Recently, exploration works for hydrocarbon began in the upper Benue trough. In the present study area, hydrocarbon prospects are largely doubtful because of the presence of basalt in the area whose emplacement may have destroyed geological traps. Secondly, the high temperature that accompanied their emplacement may have converted any existing liquid hydrocarbon to gas. This could be lost by escape through fractures in the area.

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Kasidi S. and Ndatuwong L.G: Continental J. Earth Sciences 3:28 - 32, 2008 Thirdly, depth estimates in the area generally low to favour hydrocarbon formation except in the NE section (Table 1 block 3) where the estimated depth is up to 2620m. This area is probably part of Shani sub-basin which adjoins the study area.

ACKNOWLEDGMENTS The authors wish to thank Adamawa State University through the Physics Department for providing research grant for this work. The anonymous reviewers are also appreciated.

REFERENCES Bhattacharya, B.K (1966). Continuous spectrum of the total magnetic field anomaly due to a rectangular prismatic body. Geophysics.31 (1): 97-121 Braide, S.P. (1982). Studies on the sedimentation and tectonics of the Yola Arm of the Benue trough. Facies Architecture and their tectonic significance. Jourm. Min. Geol. :280 (1): 23-26 Burke, K Dessauvagie, T.F .J and Whiteman, Al (l 970). Geological history of the Benue Valley and Adjacent areas: In T.F. J. Dessauvagie and AJ. Whiteman (eds)., African Geology. University of Ibadan Press, Nigeria, 187-205. Carter, J.D. Barber, W. and Talt,E.A.(1963). The geology of parts of Adamawa, Bauchi and Borno provinces in N.E. Nigeria Geol. Surv. Nigeria Bull. .30: 40-46. Connard, G Couch, R. and Gemperle, M.(l 983). Analysis of.aeromagnetic measurements from the cascade Range in central Oregon, Geophysics 48:376-390. Cratchley, C.R and Jones, GP. (1965). An interpretation of geology and gravity anomalies of the Benue valley Nigeria Overseas Geol. Surv. London, Geophysics paper (1). Hann, A, Kind, and Mishra, D.C.(l976). Depth estimation of magnetic source by means of Fourier amplitude spectra. Geophysics. Prosp. 24: 287-305 Negi, J.G. Aurawal, P.K and Rao, KN.N (1983). Three dimensional model of the Konya Area of Maharashtra State (India) based on spectral analysis of aeromagnetic data,Geophysics, 48: 964-974. Nur, M.A. Onuha, K. M. and Ofoegbu C.O.(1994). Spectral Analysis of aeromagnetic data over the middle Benue trough, Nigeria. Joum. Min. Geol. 30, (2):-211-217 Offodile, M.E.(l976). The Geology of the middle Benue Nigeria Pulb. Paleontol Inst.University of Uppsala Sp. 30 (4) 166p. Ofoegbu, C.O. (1985). A review of the geology of the Benue trough of Nigeria. Afr. Earth, Sci. 3 (2): 283-291. Osazuwa, lB. Ajakaye, D.E. and Verheijen, P.J.(l 981). Analysis of the structure of part of the upper Benue right valley on the bases of new geophysical data. Earth Evol. Sc. 2:126-135 Spector, A and Grant, F.S(1970). Statistical Model for interpreting aeromagnetic data. Geophysics 2 (25): 293-303 Received for Publication: 06/06/2008 Accepted for Publication: 12/07/2008 Corresponding Author Kasidi S. Department of Physics, Adamawa State University, Mubi Email: Kasidisimon2002@yahoo.co.uk

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Continental J. Earth Sciences 3: 33 - 39, 2008 ©Wilolud Online Journals, 2008.

GEOCHEMICAL AND MINERALOGICAL COMPOSITION OF ISHARA SANDSTONE DEPOSIT, SOUTH WESTERN NIGERIA.

Akinmosin, A1, Osinowo, O.O2. 1Earth Sciences Dept., Olabisi Onabanjo University, Ago-Iwoye, Ogun State, 2Department of

Geology, University of Ibadan, Ibadan. Oyo State, Nigeria.

ABSTRACT A total number of eleven [11] sandstone samples were collected at Ishara Remo in Ogun state in order to classify the deposit of the Ise Formation asexposed in this area on the bases of its chemical and mineralogical make-up. Out of these, nine [9] samples were selected for both geochemical andpetrographic studies. Relative concentration of the major oxide groups – silica and alumina alkali oxides, iron oxide and magnesia has been used to classify the deposit. The result of the geochemical analysis on the selected samples shows that the classification agrees with parameters of log SiO2 / Al2O3 < 1.5and either of log K2O / Na2O or log FeTO3+ MgO /Na2O = 0. On the basis of these, the sandstone could be classified as sub-greywacke or rather low rank greywacke. The ratio of the alkali [Na2O / K2O] > 0 also shows that the sandstone deposit is immature. Moreover, quartz, feldspar and rock fragments were microscopically identified with quartz constituting less than 90% of the total mineral constituent, while feldspar constitutes less than 25% and rock fragments make up more than 15%. On the basis of this also, the deposit can equally be classified as greywacke. KEYWORDS: Sandstone, Greywacke, Lithostratigraphic, Geochemical, Mineralogical and Petrological.

INTRODUCTION Sedimentary rocks are classified generally based on texture, cement, and groups. These groups can be subdivided into three: detrital / clastic, biogenic and chemical sediments. Sediments belong to the clastic group, which could be clean having silica cement, matrix rich-greywacke and the arkosic type. The Dahomeyan is an extensive sedimentary basin extending almost from south-Ghana to Benin (precisely the Benin hinge-line). The Dahomey basin (Fig.1) is a marginal pull-apart basin (Klemme, 1975) or Margin sag basin (Kingston et al., 1983), which was initiated during the early Cretaceous separation of African and South American lithospheric plates. Geology and stratigraphy of the basin has been described by various workers: Jones and Hockey, 1964; Omatsola and Adegoke, 1980; Omatsola and Adegoke, 1981; Agagu, 1985; Elueze and Nton, 2004; Akinmosin, 2005. In most parts of the basin, the stratigraphy is dominated by sand and shale alternations with minor proportion of limestone, [Agagu, 1985]. In all, eight lithostratigraphic units have been identified and described by these workers. The present work was carried out in Ishara, Ogun state, southwestern Nigeria. It is a transition zone between sedimentary and basement complex lying between latitudes 6

057

1 and 6

059

1N; and longitudes 3

039

1 and 3

041

1E

(Fig. 2). This study intends to classify the sandstone deposit of Ise Formation (oldest lithostratigraghic unit of the Dahomey basin) as exposed in this area on the bases of its chemical and mineralogical make-up.

STRATIGRAPHY. The reviewed work of Omatsola and Adegoke (1981) on the Cretaceous stratigraphy of the Dahomey basin has recognized three formations belonging to the Abeokuta group. These are: the Ise Formation, consisting essentially of continental sands, grits and siltstones, overlying the basement complex. Neocomian to Albian age has been assigned to this Formation. Overlying the Ise Formation is the Afowo Formation, which consists of

34

Akinmosin, A, Osinowo, O.O: Continental J. Earth Sciences 3: 33 - 39, 2008

FIG.1: East-West geological section showing the Dahomey Basin and upper part of the Niger Delta (After Whiteman, 1982).

course to medium-grained sandstones with variable interbeds of shales, siltstones and clay. The sediments of this formation were deposited in a transitional to marginal marine environment turonian to Maastritchtian age has been assigned to this formation. The araromi formation consists essentially of sand, overlain by dark-grey shales and interbedded limestone and marls occasional lignite bands. The formation conformably overlies the Afowo Formation and Maastrichtian to Paleocene age has been assigned (Omatsola and Adegoke, 1981). Overlying the Abeokuta group conformably is the imo group, which comprises of shale limestone and marls. The two-lithosratigraphic units under this group are: Ewekoro formation consists of thick fossiliferous limestone. Adegoke (1977) described the formation as consisting of shaly limestone 12.5m thick which tends to be sandy and divided it into three microfacies. Ogbe (1972) further modified this and proposed a fourth unit. It is Paleocene in age and associated with shallow marine environment due to abundance of coralline algae, gastropods, pelecypods, echinoid fragments and other skeletal debris. Akinbo Formation lies on the Ewekoro Formation and it comprises of shale, glauconitic rock bank, and gritty sand to pure grey and with little clay. Lenses of limestone from Ewekoro formation grades literally into the Akinbo shale very close to the base. The base is characterized by the presence of a glauconitic rock. The age of the formation is Paleocene to Eocene. Overlying the Imo group is the Oshoshun formation. It is a sequence of mostly pale greenish-grey laminated phosphatic marls, light grey white-purple clay with interbeds of sandstones. It also consists of claystone underlain by argillaceous limestone of phosphatic and glauconitic materials in the lower part of the formation are Eocene in age (Agagu, 1985). The sedimentation of the Oshoshun Formation was followed by a regression, which deposited the sandstone unit of Ilaro Formation (Kogbe, 1976). The sequence represents mainly coarse sandy estuarine deltaic and continental beds, which show rapid lateral facies change. The coastal plain sands are the youngest sedimentary unit in the eastern Dahomey basin. It probably overlay the Ilaro Formation unconformably, but convincing evidence as to this is lacking (Jones and Hockey, 1964). It consists of soft, poorly sorted clayey sand and pebbly sands. The age is from Oligocene to Recent.

MATERIALS AND METHODS A total number of eleven sandstone samples were collected at different locations from exposed Ishara sandstone deposits. Out of these samples, nine were systematically selected for laboratory analyses. They were first disaggregated cautiously to preserve the grain shapes and later subjected to mineralogical and chemical analyses. The mineralogical analysis was carried out petrographically with the prepared thin sections viewed under both

35

Akinmosin, A, Osinowo, O.O: Continental J. Earth Sciences 3: 33 - 39, 2008 polarized and crossed nicols. The proportion of the mineral composition of each sample was estimated in percentage. X-ray fluorescence [XRF] analysis was later carried out on the nine [9] selected samples for their major oxides composition (Fairchild et al, 1999). RESULTS AND DISCUSSION Geochemical Analysis Result of the geochemical analysis carried out the analysed samples is presented in Table 1. The concentration of three major oxide groups has been used to classify sandstones: silica and alumna, alkali oxides, and iron oxide plus magnesia. The enrichment of SiO2over Al2O3by mechanical and chemical process produces quartz arenites [orthoquartzites]. Silica [quartz] enrichment is a measure of sandstone maturity, and is a reflection of the duration and intensity of weathering and destruction of other minerals during transportation. Abundant alkalis [Na2O and K2O] characterize immature sandstones such as arkoses and greywacke. The ratio of Na2O is determined by the sum of provenance and diagenesis. The following are the parameters for the classification of sandstone based on chemical approach. They are used according to Blatt and others, 1972; Herron, 1988; Pettijohn and others, 1972; and Potter, 1978:

i.

When log SiO2/ Al2O3

>1.5, such sandstone is termed arenites.

ii

iii

iv.

When log SiO2 / Al2O3 < 1 and log( K2O/ Na2O) < 0, it is termed greywacke

When log (SiO2/ Al2O3) < 1.5, log( K2O / Na2O) >0 and log (FeTO3 + MgO) /

( Na2O + K2O), it is termed an Arkose.

When log (SiO2 / Al2O3) < 1.5 and either log ([K2O / Na2O) < 0 or log (FeTO3

+ MgO / K2O / Na2O) > 0, it is termed to be lithic arenite (including sub-

greywacke and protoquartzites).

Based on the above parameters, the ratio of the oxides of each analyzed

sample has the following results:

For example:

i. In sample A-

Log SiO2/Al 2O3 = 0.4992.

Log K2O/Na2O = 0.22.

Log FeTO3 + MgO/K2O + Na2O = 0.075

ii . In sample C –

Log SiO2/Al 2O3 = 0.89.

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Akinmosin, A, Osinowo, O.O: Continental J. Earth Sciences 3: 33 - 39, 2008

Log K2O/Na2O = 0.20.

Log FeTO3 + MgO/K2O + Na2O = 0.20.

iii . In sample E -

Log SiO2/Al 2O3 = 1.25.

Log K2O/Na2O = 0.20.

Log FeTO3 + MgO/K20 + Na2O = 0.13.

iv. In sample G -

Log SiO2/Al 2O3 = 1.27.

Log Na2O/K2O = 0.20.

Log FeTO3 + MgO/Na2 + K2O = 0.21.

TABLE 1: GEOCHEMICAL RESULT OF THE ANALYZED SAMPLES.

SAMPLE SAMPLE SAMPLE SAMPLE SAMPLE SAMPLE SAMPLE SAMPLE SAMPLE A B C D E F G H I

SiO2 72.89 82.65 81.72 81.75 81.72 83.09 85.52 83.25 73.19

Al 2O3 23.09 9.90 10.62 10.40 4.54 7.80 4.50 7.85 22.30

K2O 0.10 0.08 0.08 0.08 0.08 0.07 0.08 0.06 0.10

Na2O 0.06 0.05 0.05 0.05 0.05 0.06 0.05 0.05 0.06

Fe2O3 0.19 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.02

MgO 0.00 0.19 0.14 0.15 0.21 0.20 0.21 0.18 0.00

FeO 0.07 0.00 0.01 0.01 0.00 0.02 0.02 0.01 0.08

CaO 3.54 2.75 2.90 2.85 2.90 2.79 2.74 2.76 3.61

TiO2 0.04 0.04 0.03 0.04 0.05 0.03 0.05 0.05 0.06

SO3 0.00 0.03 0.01 0.01 0.00 0.02 0.04 0.03 0.00

MINERALOGICAL ANALYSIS The following range of classification was used according to Klein, 1963; McBride, 1963; Okada, 1971; Pettijohn, Potter and Siever, 1972. This classification takes three major components into consideration, which are quartz, feldspar, and rock fragments. The following are the parameters for mineralogical classification:

i When quartz is greater than 90%, it is termed Quartz arenites. ii When feldspar constituent is greater than 25%, it is termed Arkose. iii When the fine-grained matrix is greater than 15%, it is termed Greywacke.

The prepared sections were viewed under the petrological microscope, it was observed that the sandstones are poorly sorted with very fine grained matrix (almost opaque under polarized light), see Plates 1and 2 Based on this study, it was found out that the quartz percentage is less than 90%, and also the proportion of feldspar is less than 25%. Consequent upon this, the sandstone can be said to belong to the class of greywacke having matrix proportion greater than 15% [Folk, 1974] and [Pettijohn, 1975].

37

Akinmosin, A, Osinowo, O.O: Continental J. Earth Sciences 3: 33 - 39, 2008 CONCLUSIONS Result of the above studies indicate that the sandstone has matrix proportion of greater than 15%, hence minerallogically, it can be classified as greywacke. Moreover, values of less than 1 and greater than 1 were obtained for the ratios of log SiO2 / Al2O3 and log FeTO3 + MgO / K2O + K2O respectively. The sandstone deposit can equally be classified as sub-greywacke or low rank greywacke from geochemical point of view. REFERENCES Adegoke, O.S.,1977. Stratigraphy and Paleontology of the Ewekoro Formation (Paleocene) of Southwestern Nig. Bull. Am. Paleontol, 71(293): 375. Agagu 0.A., 1985. A geological guide to Bituminous sediments in Southwestern Nigeria. Unpublished Report, Department of Geology University of Ibadan. Akinmosin, A., Odewande, A.A., and Akintola, A.I. 2005. Geochemical Composition and Textural Features of Some Carbonate Rocks in Parts of Southwestern Nigeria. Ife Journal of Science 7, (1): 101-111. Akinmosin, A., Olabode, O.T., and Bassey, C.E., 2005. Provenance Study of Bituminous Sands in Eastern Dahomey Basin SW Nigeria Based on Heavy Mineral and Quartz Varieties. Ife Journal of Science 7(1): 123-129. Akinmosin, A., Oredein, O.S., and Odewande, A.A., 2005. Sedimentological and Reservoir Description of Afowo Oil Sand Deposits, Southwestern Nigeria. Ife Journal of Science 7(1): 35-45. Blatt H, Middleton G., and Murray R., 1972. Origin of sedimentary rocks; Eaglewood cliffs New Jersey Prentice-Hall. Pp 634. Folk R.L.,1974. Petrology of sedimentary rocks. Hemphills Austin Texas. Pp. 159. Herron M.M., 1988. Geochemical classification of terrigenous sands and shales from core or log data. Journal of Sedimentary petrology. 58(5): 820-829. Jones H.A. and Hockey R.D., 1964. The Geology of part of Southwestern Nigeria. Bull. Geol. Surv. Nig. 31: 101. Kingston, D.R., Dishroon, C.P., and Williams, P.A., 1983. Global basin classification system. American Association of Petroleum Geologists Bulletin, 67: 2175-2193. Klemme, H.D, 1975. Geothermal gradient, heat flow and hydrocarbon recovery. In: A.G. Fisher and S. Judson (eds). Petroleum and global tectonics. Princeton University Press. Pp. 251-304. Klein, G.deV.,1963. Analysis and review of sandstone classification in the North America Geological literature; Bull Geol. Soc. America 74: 555-556. Kogbe C.A., 1976. Geology of Nigeria second revised edition Publ by Rockview [Nig] Ltd. Pp 4455. C.A Kogbe [Editor]. McBride E.F., 1963. Classification of common sandstones. Jour. Sed. Petrology 33: 664-669. Fairchild, I., Graham, H., Martin, Q.,and Maurice, T., 1999. Chemical Analysis of Sedimentary Rocks in: Techniques in Sedimentology (ed. T. Maurice), 274-354. Ogbe, F.G.A., 1972. Stratigraphy of Strata Exposed in Ewekoro Quarry, Southwestern Nigeria. In: African Geology pp 305-322. Okada H., 1971. Classification of sandstone: analysis and proposal: Jour. Geol. 79: 509-525. Omatsola, M.E and Adegoke, O.S., 1980. Tectonic Evolution of the Dahomey basin [West Africa] and its

38

Akinmosin, A, Osinowo, O.O: Continental J. Earth Sciences 3: 33 - 39, 2008 implication in the opening of the North and South Atlantic. Broc. 26

th Int. Geol. Paris pp 268.

Omatsola, M.E and Adegoke O.S.,1981. Tectonic and cretaceous stratigraphy of the Dahomey basin. Jour. of mining Geol. 154 (1): 65-68. Pettijohn, F.J., Potter P.E and Siever R., 1972. Sand and Sandstone. New York, Springer. Pp 618. Pettijohn, F.J., 1975. Sedimentary rocks. Harper and Row, New York, 3

rd Edition.

Potter P.E., 1978. Petrology and Chemistry of modern big river sands. Journal of Geology, 86 (4): 423- 449. Whiteman, A.J., 1982. Nigeria: Its Petroleum Geology, Resources and Potential, Vol2, Graham and Trotman, London. Received for Publication: 06/06/2008 Accepted for Publication: 12/07/2008 Corresponding Author Akinmosin, Adewale, c/o Earth Sciences Department, Olabisi Onabanjo University, Ago-Iwoye. waleakinmosin2001@yahoo.com

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Akinmosin, A, Osinowo, O.O: Continental J. Earth Sciences 3: 33 - 39, 2008

PLATE 1: A PHOTOMICROGRAPH OF ISHARA SANDSTONE SHOWING THE SAND-SIZE FRAMEWORK AND THE FINE-GRAINED MATRIX.

PLATE 2: A PHOTOMICROGRAPH OF ISHARA SANDSTONE UNDER POLARIZED LIGHT.

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Continental J. Earth Sciences 3: 40 - 46, 2008 ©Wilolud Online Journals, 2008.

THE GEOLOGY AND GEOPHYSICAL STUDIES OF A GRAVEL DEPOSIT IN UNIVERSITY OF ILORIN, SOUTHWESTERN NIGERIA

Raji, W. O. and Bale, R. B. Department of Geology and Mineral Sciences, University Of Ilorin, Kwara State, Nigeria. ABSTRACT Vertical electrical drilling and horizontal profiling methods of electrical resistivity have been employed to study the occurrence of gravel deposit in an area of 3.36sqkm within the University of Ilorin permanent site, Southwestern Nigeria. The petrological characteristics of the deposit were also investigated for assessing it suitability as construction aggregate materials. The gravel deposit varies from conglomeratic sandstone to sand- supported conglomerates. They are unsorted to poorly sorted and dominated by angular to sub-angular pebble clast. Results from the analysis of the geophysical data showed that the study area is underlined by three to four geoelectric layers. These layers are the top soil, the gravel layer, the weathered rock and the fresh basement rock. The top soil is 0.3m-0.9m thick but absent in elevated places due to erosion. The gravel layer is 1.8 – 7.2m with 110-490 Ωm resistivity values. The weathered basement is often undifferentiated from the gravel layer, but where established, it has a thickness of 2.3-8.3m and characterized by 530-5099Ωm resistivity values. The gravel layer has an average thickness of 3.1m and amounts to an estimated reserve of 20.13x102 tonnes. Depth to the fresh basement rocks is generally shallow, often less than 15m. High proportion of rough edges (angular/subangular) particles in the gravel aggregates and the abundance of quartz, feldspar and mica minerals which are not chemically reactive with Portland cement recommend the gravel as suitable for construction purposes. Also, the 1:8 ratio of the thickness of the overburden to that of the gravel qualifies the deposit to be an economically exploitable deposit. KEYWORDS: vertical Electrical Drilling; Horizontal Profiling; Electrical Resistivity; Geoelectric Layer; Overburden, Gravel deposit

INTRO DUCTION Gravel is one of the industrial and building raw materials available to mankind. It is useful in the construction of roads, bridges, houses, dams, just a few to mention. Gravel comprises of different particle sizes which include pebbles, cobbles and boulders. It is a part of clastic sediments resulting from the physical disintegration and chemical decomposition of weathered rocks. Gravel deposit may be residual, elluvial or alluvial. They are often locally derived and accumulate close to or far from source having been transported by running water, ice, wind or shear gravity.

Sedimentologists including Rust (1979), Marek (1991), and Smith and Collins (1993) have defined gravel as an aggregate that contain 50 percent or more of particle greater than 2mm in diameter. In sedimentary formation of Nigeria and particularly in area of thick vegetation cover, rock outcrop are rare and the local geology is not often well elucidated ( Ananaba, et al, 1993). Exploitable sand and gravel in these areas occur mostly along the river banks and channels. In the basement complex areas of Nigeria, gravel deposits may be found close to or far from river channels/banks.They are mostly pavement gravel and derived from the physical breakdown and/or chemical decomposition of fractured rocks overlying the fresh basement rocks (Raji, 2004; Olasehinde and Raji, 2007).

41

Raji, W. O. and Bale, R. B: Continental J. Earth Sciences 3: 40 - 46, 2008 Drainage in the area is dominated by the northward flowing Oyun River and its trellis to subdendritic tributaries.These drainages have a NW-SE, NE-SW and in places E-W trends that suggest deep basement fracture-control. Rocks exposures are most prominent along the Oyun River channel and the rocks are highly fractured both at the surface and the depth. The objective of the VES was to obtain information on the resistivity versus depth assuming horizontal layering, with the aim of determining the thickness and other geo-electric parameters of layer(s) which may be interpreted as gravel deposit. GEOLOGY OF THE AREA The area under study is part of the Basement Complex of Nigeria considered by various workers to be Precambrian to lower Paleozoic in age (Oyawoye, 1970 and Rahman, 1976). The basement rocks consist of a variety of both migmatized to unmigmatised gneisses, schists, amphibolite and quartzites intruded by 600±150Ma granitic to dioritic rocks (Oyawoye, 1970; Rahman, 1976).

The area has been mapped on a topographic base map on scale 1:50,000. The geological map produced is shown in Fig.1.

42

Raji, W. O. and Bale, R. B: Continental J. Earth Sciences 3: 40 - 46, 2008 Rocks Identified in the area are mainly metamorphic and igneous rocks; they consist; (a) The Gneiss Complex: Augen Gneiss; Banded Gneiss; and Granite Gneiss; (b) Granite Suite: Foliated Granodiorite; and Foliated Microgranite; and, (c) Minor intrusions comprising Pegmatites ; and quartzite veins, (d) Quartzites Banded gneiss, granite gneiss and quartzite generated material for the gravel but are not discussed in detail in this report. MATERIALS AND METHOD The field work was carried out between February and June, 2007.The gravel deposit is located at the eastern part of University of Ilorin Permanent campus. The campus is bounded by longitude 4039´E - 4041´E and latitude 8027´N - 8029´N (fig.1). The main campus of the University is situated at about 15 kilometers east of Ilorin Township and occupies about 15,000 hectres of land.

Plate 1: the Gravel deposit exposed along erosional channel

Plate 2: Sieves and clast sizes SAS 4000 ABEM Terrameter and its gadgets was used to carry out both Vertical electrical drilling and resistivity profiling. The coordinates and elevations of stations/location were obtained using GPS. Ten (10) Vertical Electrical Soundings were carried out at predetermined locations (Fig 2) with the spacing of locations being 200m to 300m.The resistivity values from each VES position were plotted against half electrode spacing

43

Raji, W. O. and Bale, R. B: Continental J. Earth Sciences 3: 40 - 46, 2008 on a double logarithms paper while the geoelectric parameters( resistivity, conductivity, thickness and depth) of the gravel deposit were optimally estimated using computer software. Resistivity Profiling was carried out to estimate the lateral extent of the deposit. The values of ‘a’ for the Wenner array was chosen based on the results from the sounding experiments. Geological mapping was carried out to identify the underlying rock types and their distribution. Also, the petrology of the gravels, in particular their sizes, shapes and roundedness were also studied in order to determine the suitability of the gravel aggregate for construction purposes. Shape analysis was carried out by visual inspection and physical measurement of the particles axes while the particle size distribution was obtained by dry sieving using 1/4- 325 mesh sieve (Plate 2). This allowed assessment of the pebble (4mm-64mm) sized materials which are commonly used for construction. RESULTS Qualitative and quantitative interpretations were carried out on each of the VES and Horizontal Profiling Curves using both partial curve matching technique and IP12WIN computer interactive program. Sample of the computer generated curve is presented in Fig. 3 and the summary of the results is presented in Table 1. The results showed a minimum of three and maximum of four geo-electric layers.

Fig. 3: Vertical Elecrtical Sounding Curve for location 10 The first layer corresponds to the top soil. This layer consists of brownish loose sandy-clay with dispersed sand to pebble sizes litho- and lateritic clasts. The thickness and resistivity of the top soil layer vary from 0.3m to 0.9m and 67.2Ωm to 8214Ωm respectively. The mean thickness is 0.4m, this layer is absent in places (i.e. locations/VES 2 and 5) having being eroded. The second geo-electric layer is the gravel deposit. It has varied 1.8m to 7.2m thickness and resistivity of 110Ωm to 490Ωm. The third layer corresponds to the fractured and partly weathered basement rock. It is characterized by resistivity values of 53Ωm to 5099Ωm and thickness of 2.3m to 8.3m. The fourth geo-electric layer corresponds to the fresh basement rock and it has resistivity values of 2675Ωm to 5196Ωm. The gravel deposit is very poorly sorted to unsorted with particles ranging from clay to boulder sizes. The very coarse particles are variable mixtures of pebbles, cobbles and boulders and they are dominantly comprised by rock clasts derived

44

Raji, W. O. and Bale, R. B: Continental J. Earth Sciences 3: 40 - 46, 2008 Table 1: Summary of results from interpretation of ten VES data

VES No No. of layers

Thickness of overburden

Thickness of gravel layer

Depth to the fresh basement rock

1. 2. 3. 4. 5. 6. 7. 8. 9. 10

4 3 4 4 3 4 4 4 4 4

0.34 0 1.00 0.50 0 0.60 0.30 0.30 0.30 0.90

1.90 3.25 2.12 1.90 2.50 6.10 1.80 1.90 2.30 7.20

6.70 9.10 6.00 6.00 10.30 15.00 6.61 6.11 7.90 10.42

from the various underlying lithologies in the immediate vicinity. These lithologies include banded gneiss, granites gneiss, and quartzite. The mineral content is dominated by quartz, feldspar and muscovite with minor tourmaline and garnet. The particles size histograms (Fig. 4.1) show the gravel is dominated by pebble sized clasts while the shape distribution plot (Fig. 4.2) shows the clasts to be more angular to subrounded. The clasts large sizes and their angular shapes underline their textural and mineralogical immaturity. They are essentially first generation deposition very close to the source (Pettijohn, 1987). Table 2: Particle size distribution of the gravel aggregates. Unit of measurements

Silt and Clay Sand Granule Gravel Pebble Gravel Oversize

Size in mm <0.0625 0.0625-2 2-4 4-64 >64 Weight (kg) 0.30 5.59 2.71 14.3 2.10 Weight % 1.20 22.36 10.84 57.20 8.40

0

10

20

30

40

50

60

70

<0.0

625m

m

0.062

5-2m

m

2mm

-4m

m

4-64

mm

>64m

mParticle size

Wei

gh

t per

cen

tag

e

<0.0625mm

0.0625-2mm

2mm-4mm

4-64mm

>64mm

Fig. 4.1: Barchart showing particle size

0

5

10

15

20

25

30

35

40

45

Angular Sub-Angular sub-Rounded Rounded

Wei

ght p

erce

ntag

e

Angular

Sub-Angular

sub-Rounded

Rounded

Angularity Roundedness

Fig. 4.2: Shape distribution of pebble gravel (4-64mm)

RESERVE ESTIMATION Comprehensive ore reserve estimation is best done through drilling at various points once the deposit has been confirmed by both geological and geophysical studies. Knowing the average thickness and the surface area covered by the deposit, the volume can be calculated as follows;

45

Raji, W. O. and Bale, R. B: Continental J. Earth Sciences 3: 40 - 46, 2008 Surface area of the deposit, S = 3.36km2

Average thickness of the gravel layer, T= 3.1m Volume of the reserve, V= 3.36 x 106m x 3.10m. The mean density of gravel is 1.95kg/m3 (Telford et al, 1976) The estimated mass of the gravel in the study area= 3.36x106m2x3.1mx 1.95kg/m = 20.31x 106kg = 20,310 tons DISCUSSION In practice, one of the effective applications of electrical and seismic methods of geophysics is in the investigation of shallow and subsurface deposits, as in the exploration for sand and gravel deposits (Legget and Karrow, 1983; Okwueze et al, 1989). Electrical Resisitivity method of geophysics had been employed in the present study to investigate the occurrence of elluvial and residual gravel deposit in part of University of Ilorin main campus. Vertical electrical soundings (VES) carried out showed the gravel deposit as constituting the second geoelctric layer, below the top soil and above the fractured/weathered layer. The thickness of the gravel layer varies from 1.8m to 7.2m, statistically averaging 3.1m. Horizontal Resistivity Profiling showed that the gravel layer is laterally continuous throughout the mapped area. The thickness of the gravel deposits was also found to increase northwardly towards River Oyun. In addition, there a general decrease in resistivity (increase in conductivity) values of the gravel layer toward the river. Depth to the basement is generally shallow in the area, the highest depth measures 15.00m and the lowest is about 6.00m. Top soil is absent in locations 2 and 5 due to high topographic slope which aided erosion of the topsoil. The gravel is generally coarse. As an aggregate material, the gravel deposit is comprised dominantly by pebble (4mm-64m) sized angular rocks and minerals particles. Rounded particles occur in minor abundance, less than 10%.The petrological properties ( particles sizes and shapes) of the gravel deposit is very comparable and conform with those proved suitable for building and construction purposes. (Smith and Collins,1993) have advanced that suitable aggregate are dominantly comprised by rough edged particles and minerals like mica, feldspar and quartz. CONCLUSION The occurrence and abundance of a gravel deposit in University of Ilorin has been investigated using Electrical Resistivity method of geophysics. Aspects of the size and shape petrological characteristics of the deposit were also considered to determine the suitability or otherwise of the gravel for construction purposes. The gravel deposit occurs as a laterally continuous geoelectric layer with average thickness of 3.1m. It occurs as a very shallow depth, less than 1m. The thickness of the deposit however varies widely up to 7.2m and is dominantly comprised by angular pebble and cobble sized (2mm-64mm) rock particles. The rock particles are formed by weathering and decomposition of lithologies ( banded gneiss, granite gneiss and quartzite) in the immediate vicinity of the deposit. Quartz, feldspar and mica are the abundant minerals in the rock clasts. The study has shown that the deposit is large with a reserve of 20,310 tons. It is a near surface deposit that can be quarried easily by open cast method. The deposit by its very coarse texture, dominantly angular particles recommend the gravel deposit as a suitable aggregate material for building and construction purposes. Geologically the gravel deposit is a residual to elluvial texturally immature sediment. REFERENCE Ananaba, S. E., Owu, N. N., and Iwuagwu, C. J., (1993): Geophysical study of the gravel Deposit in Ihiagwa, Owerri, Nigeria. Journal of Mining and Geology. 29(2): 95-100. Legget, R.F. and Karrow, P.F.,1983: Handbook of Geology in Civil Engineering. McGraw-Hill Book Company,New York p.12.1-12.22. Marek. C. R., (1991): Basic properties of aggregate, in Barksdale, R. D., ed., 1991, The aggregate handbook for

46

Raji, W. O. and Bale, R. B: Continental J. Earth Sciences 3: 40 - 46, 2008 construction, Ch.3, Washington, D.C., National Stone Association, p5-16. Okwueze,E.E,: Mbonu,E.W,: Ezeanyim, V. I. and Okon-Umorem, O. E., 1989. Geophysical Investigation for gravel deposits in Ikono Local Government Area of Akwa Ibom State. Olasehinde, P. I. and Raji, W. O., (2007): geophysical studies of fractures of Basement Rocks at University of Ilorin, Southwestern Nigeria: Application to groundwater exploration. Water Resources.12: 3-10. Oyawoye, M. O., (1970): The basement complex of Nigeria in Dessaurajie, T. F. J. and Whiteman, A. J. (Ed). African Geology, University Press, Ibadan, Nigeria. Pettijohn, F.J., Potter, P.E. and Siever, R., (1975): Sands and sandstones. 2nd Ed. Springer Verlag, New York p.27. Rahman, M. A., (1976): Review of the basement Geology of South-western Nigeria in Kogbe, C. A. (Ed). Geology of Nigeria p. 441-468, Elizabethan Pub. Lagos. Raji, W. O., (2004): Geophysical studies of the basement fractures at University of Ilorin Permanent Site, Southwestern Nigeria: Application to ground water exploration. Unpublished MS.C. Thesis, University of Ilorin. Rust, B.R., (1979): Facies model 2. Coarse Alluvial Deposits In- Facies model (edit. By Walker, R. G.) Geosciences Canada Series 1. p.9-21 Smith, M.R., and Collins, L., eds., (1993): Aggregates: Sand, gravel and crushed rock aggregate for construction purposes (2nd edition): Geological Society of London, Geological Society Engineering Geology, Special Publication, No.9, p.339. Telford,W.M., Geldart, L.P., Sheriff, R. E. and Keys, D. A., (1976). Applied Geophysics Cambridge University Press, Cambridge; p. 25 Received for Publication: 10/07/2008 Accepted for Publication: 02/09/2008 Corresponding Author Raji, W. O. Department of Geology and Mineral Sciences, University Of Ilorin, Kwara State, Nigeria. lanreraji24@yahoo.com

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Continental J. Earth Sciences 3: 47 - 52, 2008 ©Wilolud Online Journals, 2008.

PRELIMINARY EVALUATION OF THE BIF AND MARBLE DEPOSITS OF THE AREA SOUTH OF MURO KASA, NORTHCENTRAL NIGERIA

Aga Tersoo

Geology Department, Gombe State University, Gombe. Email : tergaus@yahoo.com

ABSTRACT Geological mapping of the western part of Katakwa sheet 228NE in Toto Local Government of Nassarawa State has been done. Major rock units in the area are quartzites , marble, phyllite, mica, schist and banded iron formation(BIF). Structures identified include; foliations, joints, faults, folds and microfolds. The tonnage of the BIF and marble deposits in the study area is estimated to be 111,352,210 tons and 337,529,422 tons respectively. The BIF which occur as elongate bodies on the Muro hills is suitable for steel making while the marble which is calcitic can be used as chief components in the lime and calcium industries. The need to have a detailed geological study of the area is therefore suggested. KEYWORDS: BIF, Marble, tonnage, deposit, Muro Kasa

INTRODUCTION Muro Kasa lies approximately 11 km south of Gadabuke in Toto Local Government of Nassarawa between longitudes 7o15`00``E and 7o16`55``E and latitudes 8o18`51``N and 8o20`36``N. The study area covers about 12.25 square kilometer of the western part of Katakwa sheet 228NE. Gadabuke is accessible from the Nassarawa-Toto road through the Muro Kasa and Muro village(Fig.1). An ENE flowi ng Suwosadu stream in the north and a SSE flowing Tarka stream in the south and their tributaries drain the area. The geology of the area is defined by the Proterozoic metasediments(Fig.2). McCurry (1979) posits that the Toto area sediments were deposited between 1000 and 800 million years ago. In the field, the lithologic units are closely associated, but particular attention was paid to the marble and banded iron formation because of their economic importance. Marble This rock type occupies a large portion of the study area stretching from Muro Kasa and occurs as an elongate body jotting out at the foot of the eastern slopes of the Muro hills. In the eastern section, the marble body is associated with the schist and some quartzites while the one in the south has sharp contact with the BIF. The bodies trend southwards beyond the study area. Two types of marble are recognized in the study area. The first type has alternating bands of grey and white while the second is grey and sometimes greenish in colour. The two varieties are found occurring together especially along the stream channels. The general strike of the marble is N-S and the dip is approximately 70oW.Although boundaries were obscured by soil cover, the Suwosadu and Tarka stream channels were useful in tracing outcrop trends.

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Aga Tersoo: Continental J. Earth Sciences 3: 47 - 52, 2008

Fig. 1: Location Map of Study Area in Muro Kasa

Fig.2.Simplified Geological Map of Nigeria; 10 = Toto Schist Belt ( After Ajibade, et al 1986 )

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Aga Tersoo: Continental J. Earth Sciences 3: 47 - 52, 2008 T1 T4 Fig.3. Surface Sketch of the two BIF Bodies West of Muro

(A) (B) Fig .4. Surface Sketch of (A) Marble in contact with BIF and (B)Large Marble Body South of Muro

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Aga Tersoo: Continental J. Earth Sciences 3: 47 - 52, 2008 Banded Iron Formation Banded Iron Formation outcrop in two bands in the northern section of the study area striking approximately in the N-S direction (Fig. 3). The western arm is approximately 120m wide and occupies about 3.5% of the study area while the eastern arm, which occupies about 5% of the study area varies in the width at different points along its length between 170 and 230m.The eastern body is somewhat displaced to about 100m by a fault line. The bodies are characterized by regular alternating thin layers of iron and quartzites. Their contact with schist and marble is sharp. Generally, the iron ore layer varies in thickness from 5 to 10 mm while the quartz rich layers are less than 10mm thick. The bands are regular and parallel but occasionally, the quartz bands are white, brown to pale-grey coloured and alternate with dark iron ore rich bands consisting of iron-oxides, usually some silica. Gangue minerals associated with the iron ores include quartz, zircon and apatite ( Aga, 2000 ). Evaluation of both the BIF and marble bodies were carried out to access the potentials of the huge deposits. METHODOLOGY Estimation of BIF and Marble Reserves The vertical thickness of the BIF estimated from contours is averagely 30m. Measurements on sections within boreholes on the marble around Muro Kasa indicate that the thickness varies from 29.70 to 33.05m.The specific gravity of the BIF is 3.60g/cm3 and the densities of the marble range between 2.49 and 3.17g/cm3. Estimation of the Muro Kasa BIF reserves was done using the block method. The planar surface on the map of the two BIF bodies were subdivided into blocks of regular geometric form T1, T2, …T11 ( Fig.3 ) and the volume of each block calculated. Blocks T1, T5, T7, T8, T10 and T11 are trapeziums and have surface areas 59, 150m2, 44,500m2 , 39,600m2, 104,250m2, 105,600m2 and 201,250m2 respectively. Blocks T2, T3, T4 and T8 are rectangular and have surface areas 81,400m2, 114,000m2, 71,000m2 and 209,000m2 respectively. Block T6 is a semi-circle and has an area of 1,289m2. Total volume of the BIF bodies = Total surface area x average depth = 1, 031, 039m2 x 30m = 30, 931, 170m3 Total mass of BIF bodies = Total volume x mean density = 30, 931, 170 x 3.6 x 103 = 1. 1135221 x 1011 kg. = 111, 352, 210 tons of BIF The same block method was employed to estimate the reserve of the marble bodies. The planar surface of the marble bodies was divided into blocks of regular geometric forms A1, A2,…A6 (Fig. 4). Area of blocks A2, A4 and A5 which are trapeziums are 171,000m2, 1,210,000m2, and 1,018,500m2 respectively. Block A1 is a semi-circle while A3 is a rectangle with areas of 45,402m2 and 253,000m2 respectively. A6 is a trapezium less blocks S1 and S2, with an area of 1,101,453m2. Total volume of the marble bodies = Total surface area x average depth = 3,798,355m2 x 31.4m = 119, 268, 347 m3. Total mass of marble body = Total volume of marble x mean density of the marble = 199,268,347 x 2.83 x 103 = 3.3753 x 1011 kg

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Aga Tersoo: Continental J. Earth Sciences 3: 47 - 52, 2008 = 337,529,422 tons. From the calculation, the total tonnage of the BIF and marble deposits in the study area sums up to 11,352,210 tons and 337,529,422 tons respectively. This overall tonnage calculation was however restricted to 30.0m and 31.4m depth range for BIF and marble deposit respectively. This estimate could however be surpassed as considerable quantities occur beyond this depth range. Larger scale mapping such as on 1:4,000 or 1:1000 would increase the accuracy of the tonnage value obtained. RESULTS AND DISCUSSION Chemical Composition Evaluation of mineral deposits such as BIF and marble in terms of its usage is largely dependent upon chemical analyses which were carried out by Anike, et al (1990) and Tegure (1989) respectively. These data are given in Tables 1 and 2. The result for BIF in Table 1 indicates that the Fe (29.59-36.72%), FeO (33.57-42.72%) and Fe2O3 (3.77-5.85%). This portrays a high magnetite content of the ores.SiO2 content is between 43.12 and 43.12%, CaO accounts for 2.42 to 5.56% and MgO ranges from traces to 3.62%.Each of the other oxides: Al2O3, TiO2, MnO and P2O5 have values less than 0.5%,sulphur content is 0.11-0.21% and the LOI averages 0.5%. Table 1: Chemical Analysis of Banded Iron Formation ( BIF ) from Muro Hill ( After Anike, et al 1990 ) Oxides Samples

TM-1A TM-2A TM-3A TM-4A TM-6A TM-7A SiO2 55.78 54.73 51.31 43.12 53.12 49.46 TiO2 0.10 0.08 0.11 0.22 0.22 0.24 Al 2O3 0.11 0.26 0.53 1.41 0.11 0.48 Fe2O3 5.28 5.76 4.72 4.99 3.77 5.85 FeO 34.16 33.57 35.52 42.75 34.67 34.08 MnO 0.06 0.05 0.03 0.49 0.06 0.04 MgO Tr 1.42 2.02 2.02 1.41 3.62 CaO 2.42 3.22 3.85 3.10 5.56 3.64 P2O5 0.27 0.22 0.37 0.24 0.17 0.23 S 0.16 0.19 0.20 0.15 0.21 0.11 LOI 0.40 Nd 0.81 0.11 0.76 Nd Total 98.74 99.49 99.47 98.60 100.06 97.75 Fe 30.23 30.12 30.91 36.72 29.59 30.58 Fe2+/Fe3+ 0.14 0.15 0.12 0.11 0.10 0.15 Table2: Chemical Analysis of Muro Kasa Marble ( After Tegure, 1989 ) Oxides Samples

1 5A 12 5B 13 SiO2 1.20 1.03 1.05 0.48 0.14 CaO 39.66 44.27 46.64 47.39 42.95 MgO 3.92 4.07 3.53 4.32 1.96 Fe2O3 0.80 2.13 0.80 1.60 1.92 FeO 0.56 1.92 0.56 1.12 1.34 MnO 0.04 0.04 0.02 0.02 0.02 TiO2 0.03 0.02 Nd Nd Nd P2O5 Tr Tr Tr Tr Tr Al 2O3 8.51 1.64 3.28 1.50 6.54 Na2O 0.67 0.36 1.48 0.31 0.83 K2O 0.29 0.19 0.79 0.19 0.19 LOI 43.71 43.39 43.27 43.03 43.46

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Aga Tersoo: Continental J. Earth Sciences 3: 47 - 52, 2008 From table 2, the marble contains 39.66% CaO, 1.5 to 8.51% Al2O3, SiO2(0.48-1.3%), an average of 3.56% MgO and high LOI value of 43.71%. The high LOI value is probably due to the CO2 content. The Fe2+/Fe3+ratio ranges from 0.10 to 0.15 and the Mn2+/Fe total ratio varies from 0.00 to 0.01.The phosphorus content(0.17-0.37%) compares favourably with other known iron ores. For example, phosphorus content of the Itakpe hill iron deposit is 0.87-0.92% and Agbaja ironstone ores has 1.3-1.8 % P205. On the basis of this data, the iron ores in Toto area can also be used for steel making. The investigated marble marble is calcitic ( Aga, 2000 ) and about 94% pure, hence would be very useful in lime production. Lime is essential material in construction, manufacturing and chemical industries, especially in the production of plaster and alkali chemical ( Tegure, 1989 ).The calcitic nature of the marble makes it suitable for the production of ferrous metallurgical flux. Other possible uses of the marble include terrazzo flooring, toothpaste and animal feed production; glass making, road aggregates and decorative materials manufacture. CONCLUSION Banded Iron Formation(BIF) and marble deposits occur associated with the Proterozoic low grade schist belts of the basement complex of Northwestern Nigeria. The presence of 111,352,210 tons and 337,529,422 tons of the BIF and marble were estimated. They both have a wide potential of utilization. Inspite of the wide spread occurrence of these deposits, they have not received the attention they deserve as potential national reserves. ACKNOWLEDGEMENT The author wish to thank Dr. E. E. Ntekim of Federal University of Technology, Yola and Dr. E. C. Ashano of the University of Jos for their constructive criticism. REFERENCES Aga, T (2000): The Geology and the Evaluation of the BIF and Marble Deposits of the Area South of Muro Kasa (Katakwa Sheet 228NE).Unpublished BSc Project. University of Jos. 73p. Ajibade, A. C (1976): Provisional Classification and Correlation of the Schist Belts of Northwestern Nigeria. In Geology of Nigeria (ed) C .A. Kogbe. Elizabethan Publishing Co. Lagos. Pp 85-90. Anike, L. O; Umeji, A. G; Onyeagocha,A. C (1990): Geology and Geochemistry of the Muro Banded Iron Formations, S.W. Plateau State. Jour.Min. and Geol.26(2),21-26. McCurry, P (1976): A Review of the Geology of the Precambrian to Lower Palaeozoic Rocks of Nigeria. In: Geology of Nigeria. C. A. Kogbe (ed). Elizabethan Publishing Co. Lagos. Pp 13-37. Tegure, A. E (1989): The Geology and Petrogenesis of Part of Muro Hills Marble Deposit Sheet 228 (Katakwa) Nigeria. Unpublished MSc.Thesis. University of Jos.117p. Received for Publication: 10/07/2008 Accepted for Publication: 02/09/2008

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Continental J. Earth Sciences 3: 53 - 58, 2008 ©Wilolud Online Journals, 2008. APPLICATION OF ELECTRICAL RESISTIVITY METHOD FOR GROUNDWATER EXPLORATION IN

A SEDIMENTARY TERRAIN. A CASE STUDY OF ILARA-REMO, SOUTHWESTERN NIGERIA.

Ariyo, S.O and Banjo, A.A. Department of Earth Sciences, Olabisi Onabanjo University. Ago-Iwoye.

ABSTRACT. A geophysical evaluation using Electrical Resistivity method for groundwater exploration at Ilara-Remo, southwestern Nigeria was carried out. The investigation involved the utilization of Vertical Electrical Sounding (VES) technique with schlumberger electrode array system. The studied area is located within the sedimentary basin (Dahomey basin) of southwestern Nigeria, ferrigenous sandstone was found to be the major rock type in the study area. The data acquired from the ten (10) VES stations were interpreted using the partial curve matching method and computer assisted iteration technique. The VES results of the data revealed three to five layers which include the topsoil, clayey/sandy clay, clayey sand, conglomeratic sandstones and sandstones/wet sands with resistivity values ranging from 133.3-1305.6Ωm, 41.6-1924.5 Ωm, 488.4-9658.3 Ωm, and 164.1-8095.6 Ωm. The sanstones/ wet sands constitute the main aquifer units. From the overall results the studied area can be classified as prolific zones for groundwater development. KEY WORDS: Electrical, Groundwater, Exploration, Sedimentary terrain, Southwestern Nigeria.

INTRODUCTION The availability of quality water resources has always been the primary concern of societies in (Semi Arid and Arid region, even in areas of more abundant rainfall, the problem of obtaining an adequate supply of quality water is generally becoming more acute due to ever increasing population and industrialization. As a result of this, surface water cannot be dependable throughout the year, hence, the need to look for other alternatives to supplement surface water. This makes the world to depend on the largest available source of quality fresh water which lies underground and this is referred to as Groundwater. It is the water held in the subsurface within the zone of saturation under hydrostatic pressure below water table. The groundwater can be in sedimentary terrain where it is less difficult to exploit except for its chemical composition. It can also be in the basement complex terrain where it can be a bit difficult to locate especially in area underlain by crystalline unfractured or unweathered rock. The research for groundwater today has become essential, due to its cheapness and its chance of obtaining quality water from the bedrock. Therefore, the application of geophysics to the successful exploration of groundwater in sedimentary terrain requires a proper understanding of its hydrogeological characteristic. Evidence has shown that geophysical methods are the most reliable and the most accurate means of all surveying method of subsurface structural investigations and rock variation (Carruthers, 1985 and Emenike, 2001). Several methods employed in groundwater exploration include electrical resistivity, gravity, seismic, magnetic, remote sensing, electromagnetic e.t.c out of which the resistivity method is the most effective for locating productive well since the Vertical Electrical Sounding (VES) method can provide information on the vertical variation in the resistivity of the ground with depth and the Constant Separation Traversing (CST) provides a means of determining interval variation in the resistivity of the ground (Olayinka and Mbachi, 1992 , Olorunniwo and Olorunfemi 1987, Ariyo,2003).

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Ariyo, S.O and Banjo, A.A: Continental J. Earth Sciences 3: 53 - 58, 2008 AIM OF THE STUDY The research work was carried out in order to have an insight into the subsurface geology of Ilara, Ogun State Southwestern Nigeria with the following objectives:- (1).To detects subsurface layering and thickness and their resistivities. (2). To investigate the hydrological conditions of the area with the view of delineating the potential area for

groundwater development. (3). To locate possible and suitable site for productive boreholes in the study area. (4). To calculate the geo-electric parameters such as resistivity, anisotropic coefficient, longitudinal

conductance etc. in order to delineate good aquifer zone, (5). To detect depth of bedrock and soil profile. LOCATION AND ACCESSIBILITY OF THE AREA The study area is one of the major towns in Remo-North Local Government area of Ogun State Nigeria. It lies within the sedimentary terrain of southwestern Nigeria between longitude 3o 42.5'E and 3o 44.5' E and latitude 6o55.5' N and 6o57.5' N and cover an area extent of approximately 9.18 km2. The study area is accessible; it is linked with some town like Ode Remo, Akaka, Ilisan and Irolu via motorable roads and some villages by footpath. (Fig. 1).

FIG.1 LOCATION MAP OF THE STUDY AREA SHOWING THE VES POINTS

2.5 GEOLOGY OF THE STUDY AREA Ilara lies in the sedimentary basin. It covers part of the Abeokuta group of the Dahomey basin. The Abeokuta group consists of coarse grained poorly sorted micaceous and ferruginous sandstone. The sandstone is arkosic and has fair to good bedding. Minor intercalation of marine shale and mudstone to exist (Adegoke et al, 1976).The age of the basal members of the formation is not known. It is certainly diachronous and is probably not older than Maastrichtian. (Fig 2)

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Ariyo, S.O and Banjo, A.A: Continental J. Earth Sciences 3: 53 - 58, 2008 FIG. 2: GEOLOGICAL MAP OF THE STUDY AREA METHODS OF DATA AQUISTION AND INTERPRETATION The type of geophysical surveying method used during the course of this project, is the Electrical Resistivity method, which investigates the subsurface conditions by passing electric current into the ground through a pair of current electrodes and measuring the resulting voltage difference between a pair of potential electrodes. The Electrical Resistivity method is based on the principle of measurement of physical parameters of the formation namely the electrical resistivity and the factors, which control the electrical resistivity of rocks, include the amount and arrangement of the rock grains, porosity of the rock, and the salinity of saturating subsurface water. Interpretation of electrical resistivity is usually very difficult in the absence of other geophysical data, not withstanding, the apparent resistivity curves obtained during the field procedure can be interpreted both qualitatively and quantitatively, but the quantitative method seems to be the simpler of the two, due to its simple theoretical basis, and best used for the logarithm curves of VES. The data of the vertical Electrical sounding (VES) are usually presented as a series of apparent resistivity with increasing electrodes separation. These curves give a qualitative representation of the variation of the resistivity with the depth. Several authors have introduced many methods of interpreting resistivity data obtained in the field, such method includes numerical method of interpretation, interpretation by curve matching technique and interpretation by auxiliary point, method (Zohdy, 1965) or with the computer assisted program. But in the course of this work only two methods of interpretation were adopted and these are partial curve matching and computer iteration programme called RESIST. This consists of comparing successive portions of the field curve with schlumberger theoretical master curves of similar shapes.

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Ariyo, S.O and Banjo, A.A: Continental J. Earth Sciences 3: 53 - 58, 2008 The apparent resistivity is plotted against electrode spacing on a transparent bi-logarithm paper of the same modules as the theoretical curves. The field curves on the transparent sheet are super imposed over the master set. Matching starts from the left hand side of the profile towards the right hand side, then the profile is adjusted towards the left, right, up and down but always ensuring parallelism of co-ordinate axes until best fit of the field curve against one of the theoretical curves is obtained. The computer iteration method involves two main stages, which are a follows:

1. Determination of an initials model from the field data, which is achieved by curve matching 2. From the results of the curve matching, models for computer modeling are obtained which give

the final accepted geoelectric structure. A fast observation is allowed based on this alteration nature of the program. The layered parameters are altered until a good fit is achieved between the observed and calculated values. The iteration process of curve can go as far as 30 times in achieving a perfect match, after which the computer displays the final result of the iteration in form of curve and the layer parameters. This method is the most efficient method of all the interpretation methods in terms of speed and accuracy. RESULTS AND DISCUSSION RESULTS The interpretation of the sounding curves was done both qualitatively and quantitatively. The qualitative interpretation entails the observation of the sounding curves as plotted on the bi-logarithm graph paper. Ten VES stations were conducted in the study Area using the Schlumberger array. The result revealed the presence of three to five (3-5) layers. LAYERS VES CURVES. Two VES stations (VES 1 and 3) in the study area have 3 geoelectric layers. The topsoil has resistivity values of 1305.6 and 207.8 ohm-m and thickness values of 1.2 and 2.0m respectively. The second layer which was classified as sandy has resistivity values of 730.3 and 1924.5 ohm-m respectively. The last layer is sandstone with resistivity values of 5823.8 and 1355.4 ohm-m. The depth to basal rock is 6.5 and 20,2 m respectively. The shallow depth to basal rocks in these VES stations may not be able to sustain accumulation of quantity groundwater. LAYERS VES CURVES. These VES curves comprises of VES 4.6.7, and 8 VES stations. They revealed the presence of 4 geoelectric layers which has been classified as topsoil, sandy/ clayey sand, conglomeritic sandstone and sandstones. The topsoil has resistivity values ranges between 191.0 and 660.0 ohm-m with an average thickness of 1.8m. The second layer has resistivity values vary between 276.9 and 995.5 ohm-m with an average thickness of 4.98m. The resistivity value for layer 3 varies between 5589.6 and 8646.7 ohm-m while that of layer 4 was 379.2 and 8095.6 ohm-m. There is decrease in resistivity values between layer 3 and 4 in VES 4, 7, and 8 stations which is an indication of water saturated zone. LAYERS VES CURVES. These set of VES curves were found in VES stations 2, 5, 9, and 10. They displayed 5 geoelectric layers which are classified as topsoil, sandy clay, conglomeratic sandstones, sandstones and wet sand. The resistivity of these geoelectric layers ranges between 133.3 and 516.9 ohm-m, 41.6 and 287.9 ohm-m, 4200.0 and 8383.7 ohm-m, 2822.3 and 9658.3, and 164.1 and 1077.0 ohm-m respectively. The depth to basal rocks ranges between 35.1 and 111.8 m. These VES stations can be classified as prolific zones for groundwater development in the study area. GEO-ELECTRIC LAYER Geo-electric section of the study area was produced, revealing three to four geo-electrical layers; the top soil, clay/sandy clay/clayey sand/ sandy, the conglomeritic sandstone and sandstone/wet sand as illustrated in Figs 3 and 4.

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Ariyo, S.O and Banjo, A.A: Continental J. Earth Sciences 3: 53 - 58, 2008 The top soil which is the first layer has resistivity values ranging from 133.3Ωm to 1305.62Ωm and depth ranging from 0.6m to 2.4m. The second layer which can either be clay/sandy clay/clayey sand/sandy has resistivity values ranging from 41.6Ωm to 1924.5Ωm and depth ranging from 2.4m to 20.2m. The third layer which contains conglomeritic sandstone has relatively high resistivity values ranging from 488.4Ωm to 9658.3Ωm and depth ranging from 20.8m to 111.8m.

Fig. 4 : Geoelectric section through VES 6-10

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Ariyo, S.O and Banjo, A.A: Continental J. Earth Sciences 3: 53 - 58, 2008 The last layer is made up of sandstone/ wet sand has resistivity values ranging from 164.1Ωm to 8095.6Ωm. This layer has the potential for groundwater. The sandstone/ wet sand are the main aquifers in the study area; they are usually associated with high porosities and permeabilities. (Ariyo, 2005). They should also constitute the object of further exploration for groundwater in the area. It should be noted that sandstone/ wet sand are found at different depth in the study area.

REFERENCE Adegoke , O.S., Agumanu, R.E., Benkheil J, and Ajayi , P.O. (1976):New stratigraphic sedimentologic and structural data on the Kerri-Kerri Formation, Bauchi and Bornu States, Nigeria. Journal of African Earth Sciences 5: 249-277. Ariyo, S.O. Oduwole, M.O and Mosuro, G.O. (2003): Hydro-geopghysical,evaluation of groundwater potentials of Awa-Ijebu, Southwestern Nigeria. Journal of the Nigerian Association of Hydrogeologist (NAH) 14 : 31-36. Ariyo, S.O. (2005). Geoelectrical characterisation of aquifers and Geochemical study of groundwaters in the basement complex/sedimentary transition zone around Ishara, Southwestern, Nigeria. Unpublished M.Sc Thesis. University of Ibadan, Ibadan, Nigeria. 139pp.

Carruthers, R.M. (1985): Review of geophysical techniques for groundwater exploration in crystalline basement terrain. British Geological Survey Report. NORGRG 85/3. Emenike,E.A.(2001):Geophysical exploration for groundwater in a Sedimentary Environment. A case study from Nanka over Nanka Formation in Anambra Basin, Southeastern Nigeria. Global Journal of Pure and Applied Sciences 7 (1):1-11. Olayinka, A.I and Mbachi, C.N.C (1992). A technique for the interpretation of electrical sounding from crystalline basement Areas of Nigeria. Journal of Mining and Geology 27: 63-69. Olorunniwo,M.A and Olorunfemi, M.O (1987). Geophysical investigation for groundwater in Precambrian terrain, a case history from Ikare, Southwestern Nigeria. Journal of African Earth Sciences 6: 787-796. Zohdy, A.A (1965): An Auxillary point method of electrical sounding Interpretation and its relations to the Dar Zarrock parameters. Geophysical 30: 644-660. Received for Publication: 24/09/2008 Accepted for Publication: 02/11/2008 Corresponding Author Ariyo, S.O Department of Earth Sciences, Olabisi Onabanjo University. Ago-Iwoye. Ogun State. E-mail address: ariyof@yahoo.com.

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Continental J. Earth Sciences 3: 59 - 70, 2008 ©Wilolud Online Journals, 2008.

GROUND WATER POTENTIALS OF NUMAN AND ENVIRONS, ADAMAWA STATE, NORTH-EASTERN, NIGERIA.

E.Y. Mbiimbe1, H.I. Ezeigbo2 and E.F.C. Dike1

1Department of Geology, Gombe State University, P.M.B 127 Gombe State Nigeria, 2Department of Geology, University of Nigeria, Nsukka.

ABSTRACT Numan town is situated along the confluence of rivers Benue and Gongola and is a road junction town about some 60 km west of Yola. Lithologic logs of 7 boreholes, field measurement data, stream flow and meteorological data and hydrochemical data generated from sampling and analysis of groundwater from 17 points (7boreholes and 10 handdug wells) were evaluated to establish the potentials of groundwater in Numan area. The area receives about 800mm of rainfall annually out of which 80% is lost through surface runoff and evapotranspiration while about 20% goes to recharge the groundwater system. Groundwater in the area is hosted in three aquifer systems all tapping from three geologic formations- the Bima Formation, the Yolde Formation and the Quaternary river course alluvium. Handdug wells tap their water from mainly the upper unconfined aquifer whose depth ranges from 0- 40m and the boreholes are completed in either the middle semi confined aquifer 40 -75m or the lower confined aquifer 75-240m (depth range of 0-240m). The computed aquifer parameters gave a mean hydraulic conductivity of 5.6 x10 -1m/day, a Transmissivity of 65.67m2/day groundwater velocity of 2.43m/yr, groundwater discharge of 612.69m3/yr, a groundwater reserve of 1.01x1010m3 which is capable of supporting a population of 1.4m for one year on an average of 220/l/day/head and a mean borehole yield of 20 m3/hr. Results of the hydrochemical analysis indicate that most of the water samples agreed with both the WHO 2006 and the NIS 2007 drinking water quality standards. However isolated samples especially from the upper unconfined aquifer tested moderately hard to very hard (106-421mg/L). Few cases of high NO3

- (88-132mg/L) in

HW6 HW10 HW11, high Fe2+ (1-2mg/L) in HW1 and HW2, were recorded. Two dominant water types were recorded; Ca2+-HCO3

- (from four boreholes and seven handdug wells) and Na++K+-HCO3

- (from three boreholes and three handdug wells). This

study suggests that Numan and environs could be considered as a potential source of sustainable groundwater supply as a good alternative to the existing sources of supply. It would however require an improved waste management system and proper well completion methods to check the encroachment of surface generated pollution. KEY WORDS: Groundwater, potential, Numan and environs, aquifer parameters and hydrochemistry

INTRODUCTION Groundwater potential of an area is determined by the ability of the area to supply adequate quantity of groundwater of potable quality to satisfy the demands of that area (Callist, 2006) it is now recognized that groundwater development via shallow hand dug wells and deep boreholes is common source of water supply to most rural-semi urban communities in the developing countries. The understanding of the geometry and configuration of this subsurface resource is still a major challenge to most groundwater resources development and management agencies. A vital and most crucial aspect to be addressed prior to embarking on any groundwater development project is to ascertain the potential of the available resource within the area. It is in line with this objective that this investigation was carried out to establish the groundwater potential of Numan and environs with the view of providing a data base on the available resources and the possibilities of sustainable development to meet the demands of the people in the area. Using available borehole data complemented with field sampling and analysis, this research aims at: determining the occurrence and distribution of groundwater in the study area, providing information on the

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E.Y. Mbiimbe et al: Continental J. Earth Sciences 3: 59 - 70, 2008 quantity and quality of groundwater in the area and suggesting options for a more sustainable development and management of groundwater in the area. Study area Numan is situated along the banks of rivers Benue and Gongola. The area of this investigation lies between latitudes 9o 25I N and 9o 35I N and longitudes 12 o 00I E and 120 100 E covering a land area of 3422.5km2 fig 1. The area receives an annual rainfall of 800mm which falls between the months of March to October with August as the peak. The rainfall data used for this study was obtained from UBRBDA Yola for the period of ten hydrological years (1986-1996). The temperature ranges from 13oC during the Harmattan (December to January) to a maximum of 44oC during the months of March to May. The mean monthly temperature is 37.2 o C. The measured relative humidity for the area is within the range of 25.6% in February and 78.9% in August with a mean monthly value of 64.6 %.( UBRBDA Yola 1996). The total runoff of river Benue for a period from 1988/89 -1992/93 is about 15435.74x106 m3/year out of which only 6.8% goes to recharge the adjacent aquifers as baseflow while the remaining 93.2% is considered as direct runoff as obtained from hydrograph separation.

Fig. 1 Location map of Numan and Environs in Nigeria (inset), showing access

roads.

Geology The study area forms part of the Yola arm of the upper Benue Trough. The geology of the area is defined by the Precambrian Basement Complex rocks, the Cretaceous Bima Sandstone and the Yolde Formation while river course alluvium constitutes the Quaternary deposits. The Bima Sandstone consists of a thick sequence of feldspathic sandstones, grits, pebble beds and shale-clay intercalations (Offodile, 1992). It is a highly cemented and indurated sequence that varies from laminated sandstone to coarse grained cross bedded sandstone (Carter et al 1963, Allix 1983) The Yolde Formation forms a series of transition from continental to marine sedimentation. It is diachronous, made up of calcareous sandstones and shales and shows lateral variation in thickness (Barber et al, 1954, Reyment, 1955). It represents sedimentation in a high to moderate near shore littoral environment (Mode 1993). Its estimated thickness at the type locality (Yolde) is about 150m and consists of fine grained sandstone and thin bedded siltstone at the base with layers of shaly limestone (Carter et al, 1963). The Quaternary river course alluvium occurs along the flood plains of rivers Benue and Gongola and consists of loose sands, moderately sorted and highly permeable (Obiefuna et al, 1999). The geology of the area is summerised in Fig. 2 Hydrogeology Groundwater plays an important rule in domestic and public water supply as an alternative to the supply from the surface water treatment plant. Development of groundwater in Numan area is commonly through shallow dug wells and deep boreholes. (Fig. 3) Groundwater in the area is under water table conditions and confined

61

E.Y. Mbiimbe et al: Continental J. Earth Sciences 3: 59 - 70, 2008 conditions. Groundwater under water table conditions occurs within weathered overburden and Quaternary river course alluvium whose thickness varies from place to place (2-10m). It is phreatic in nature and consists of gravely sands of the river course alluvium. Recharge into this aquifer is from direct rainfall and the depth of occurrence ranges from 0 -40m and is subject to seasonal fluctuations. Groundwater from this source is

Fig.2 Geologic map of the study area.

harnessed through handdug wells and surface impoundments like ponds and is used for domestic and agricultural needs. Correlation of existing borehole logs from SW-NE reveals that groundwater under confined conditions is hosted in two aquifer systems thus the middle semi confined aquifer system and the lower confined aquifer system. (Fig.4) The middle semi confined aquifer system forms part of the underlying material beneath the upper water table aquifer system and is separated from it by a semi confined layer of shale /clay material of varied thickness. It is composed of sandstone, medium to coarse grained whitish, grey and poorly cemented sands. It occurs at depth below 40m and is exploited by most boreholes (BH1, BH2, BH3, BH4, BH5, and BH6). The measured maximum thickness is about 77m. An artesian condition with a positive hydraulic head was reported in a borehole in Numan town believed to be tapping from this aquifer system (GSN, 1965). The pressure built up in this system depends on the thickness of the overlying shale/clay units which varies laterally across the area with the highest thickness of 30m in BH6 and the least 10m in BH5. The lower confined aquifer system occurs at depth below 75m and has an average thickness of 50.6m. Two out of the seven boreholes used for this study have their base in this aquifer (BH8 & BH9). This aquifer consists of coarse grained, whitish grey and poorly cemented sandstones with dark shale intercalations. It is confined in nature with the shale intercalation acting as the confining layer. The average measured saturated thickness within the depth of investigation is 99.4m. A summary of the characteristics of the groundwater systems is presented in Table 1 MATERIALS AND METHODS Lithologic logs used for this study were obtained from Adamawa State Water Board Yola, Rural Water Supply and Sanitation Agency (RUWASSA) Yola, stream flow and meteorological data were provided by the Upper Benue River Basin Development Authority (UBRBDA) Yola, while the hydrochemical data used was generated from field sampling and laboratory analysis of water samples from 7 boreholes and 10 handdug wells. In this study, six (6) major parameters were considered; hydraulic conductivity (K), Transmissivity (T), groundwater velocity (V), groundwater discharge (Q), groundwater reserve (Qa) and aquifer thickness (b). Groundwater velocity was calculated using Todd (1980) equation while the groundwater discharge was

62

E.Y. Mbiimbe et al: Continental J. Earth Sciences 3: 59 - 70, 2008 obtained using Guisti 1978 relation (Q =10kit where k is hydraulic conductivity, I the hydraulic gradient and t the aquifer thickness). An estimate of the groundwater reserve was determined from Brassington 1990 formula (Qa= b x sy x area; where b=average saturated thickness of the aquifer, sy =the specific yield). The available driller’s record is incomplete so Storativity and specific yield could not be evaluated. Available pumping test

Fig. 3 location map of sample points.

Fig. 4 correlation of some borehole logs along SW-NE line showing the three

aquifer systems in the study area. data for six boreholes was used in computing aquifer parameters. A summary of the computed results are presented in Table 2. Hydrochemistry and groundwater quality Water samples were collected from all the available groundwater sources in the area for analysis. Using field measuring kits pH reading, hydraulic head for hand dug wells, temperature and TDS were measured right in the field. A total of seven deep boreholes and ten hand dug wells were sampled for analysis. The ten (10) handdug wells include HW1, 3, 4, 6, 8, 9, 10, 11, 13, and HW 14The collected samples were analysed in the soil science and chemistry laboratories of the Federal University of Technology Yola, Adamawa state northeastern Nigeria. The cations were analysed using adsorption flame photometer and atomic absorption spectrophotometer (AAS) Spectronic 20D while the anions were analysed using general volumetric titrimetric methods with EDTA and Phenolphthalein as the indicators. Results of the chemical analysis were interpreted using the hydrochem computer software and are presented in the piper 1944 trilinear diagram( fig 5) Water quality is commonly defined by a multitude of chemical, physical and biological properties which determine the suitability of the water for domestic, industrial or agricultural use (Bachmat et al, 1980.) Groundwater quality generally depends on the quality of water recharging the source, the length of the flow path, mineralogy of the soils and aquifer materials, the residence time in the groundwater flow system and human activities (Thomas et al, 1993). In order to establish the quality of groundwater in the study area four parameters were considered and the results were compared with WHO (2006) standards and Nigerian industrial standard for drinking water, (NIS, 2007), (Table 3). The parameters chosen are Cl-, NO3- , HCO3

-and hardness. These parameters in addition to being used as pollution indicators can also be used as indices to check on- site sanitation (Mike et al, 1999). The results of the hydrochemical analysis are presented in Table 4

63

E.Y. Mbiimbe et al: Continental J. Earth Sciences 3: 59 - 70, 2008

RESULTS Groundwater Systems A correlation of borehole log s across the area in a SW-NE direction shows that there are three groundwater systems-the upper unconfined, the middle semi confined and the lower confined groundwater systems. (Table 1) The analysis of the stream flow data and other meteorological data for the river Benue shows that there is effluent hydraulic connectivity between the river and the adjoining groundwater system. The mean annual discharge of river Benue is about 1.67x 1010m3/year the mean runoff in the river is about 1.54 x1010 m3 per annum. The baseflow from the adjoining aquifers into the river is 1.12x1010 m3and this represents about 6.8% of the total flow. Numan receives about 800mm (5.12 x10 8m3/yr) of rainfall per year about 65% (3.3 x10 8 m ) of this is lost through evapotranspiration while 15% (7.7x107m3) constitutes runoff and the remaining 20% is considered to be the main recharge into the groundwater systems. Aquifer Parameters Granulometric analysis of available lithologic logs from six boreholes (BH2, BH4, BH6, BH7, and BH8) and driller’s data from pumping test were used in computing aquifer thickness and hydraulic conductivity while Cooper-Jacobs (1946) method was used to determine the transmissivity for the 6 boreholes in the study area. The method relates (T,Kand b): T=Kb where T= transmissivity , K = hydraulic conductivity and b= aquifer thickness or the screen length. Table 1: Summary of groundwater systems in the study area from borehole logs Groundwater system Depth range (m) Thickness (m) Source of recharge Lithology Water table or phreatic system Unconfined

0-40 2-10 Direct precipitation Gravely sands/weathered overburden

Semi confined system

40-75 77 Percolation from the overlying semi permeable shale/clay units and baseflow from the river bed

Whitish, grey sandstone medium –coarse grained, poorly cemented

Confined system 75-241 50.6 Baseflow /regional flow from adjoining basins

Whitish –grey Coarse grained sandstone

64

E.Y. Mbiimbe et al: Continental J. Earth Sciences 3: 59 - 70, 2008 Table2: Summary of aquifer parameters from the study area using pumping test data from single wells

Borehole number

Saturated aquifer thickness (m)

Drawdown (m)

Transmissivity (m 2/day)(T)

Hydraulic conductivity (k)(m/day)

BH2 63.5 21.5 26.09 4.11x10-1 BH 4 75.0 16.5 17.25 2.3x10-1 BH 5 57.0 7.0 37.05 6.5x10-1 BH 6 150.0 26.0 4.95 3.3x10-2 BH 7 173.0 21.0 276.8 1.60 BH 8 78.0 10.15 32.76 4.2 x10-1 Mean 99.4 17.0 65.8 5.6 x10-1

DISCUSSION The area receives a moderate amount of rainfall (800mm) annually 65% 0f this is lost through evapotranspiration , 15% constitute direct surface runoff while 20% goes to recharge the groundwater system. The high percent evapotranspiration is probably due to high maximum daily temperature experienced in the area for most part of the year as well as poor vegetation cover. While the surface runoff is favoured by urban development through pavement of roads and other drainage systems, the recharge into the groundwater system is supported by highly permeable loose sand of the Quaternary river course alluvium (Obiefuna et al 1999). Correlation of bore logs in a SW-NE directions reveal that there are three aquifer systems- the upper unconfined (0-40m) mostly tapped by handdug wells, the middle semi confined aquifer (40-75m) that serves some boreholes (BH3, 4, 5, 6&7) and the lower confined aquifer (75-241m) The borehole yields range from 9.0 m3/hr to 31.7 m3 /hr with an average of 20 m3 /hr. The mean hydraulic conductivity (K) determined from the available pumping test data is 5.6 x10 -1m/day and a Transmissivity of 67.8m2/day, these results agree with Brassington 1990 moderate yielding aquifers. The calculated groundwater velocity of 2.42m/yr is moderate to allow sustainable infiltration /percolation into the groundwater regime. The groundwater reserve of 1.01x1010m3

is capable of supporting a population of 1.4m for one year on an average of 220/l/day/head and a mean borehole yield of 20 m3/hr is sufficient for sustainable development of groundwater. The hydrochemical results show that most samples are within maximum permissible limits for drinking water quality of WHO (2006) and the NIS (2007). Hardness of 150 mg/L and above was recorded in Hw 3, 6, 8, 10 & 11. NO3

- concentration of 50mg/L and above was recorded in 3 samples (Hw6, 10, 11), these same samples also recorded high concentrations of TDS, electrical conductivity (EC) and are among those samples with Fe2+ concentration of 0.6 and above. For hardness, NO3

-,TDS and EC in high concentration it is most likely to be due to input from domestic effluents into wells closer to waste disposal sites. A plot of the major cations and anions in the piper 1944 trilinear diagram (fig. 5) reveals that there are two dominant water types in the study area; Ca2+- HCO3

- type and Na+ +K+ – HCO3- type, (table 6 ). The Ca2+- HCO3

- type according to Arthur (1995) is associated with areas with temporary hardness which agrees with results in table 5 (hardness of 106-136 mg/L). This was recorded in four out of the seven boreholes sampled. The second water type recorded in seven out of the ten handdug wells is mostly associated with influx of domestic effluents rich in sodium and bicarbonate which gives the water similar characteristics as those originating from alkali carbonate rocks (Arthur, 1995). Additional bicarbonate could also be released from the break down of weak carbonic acid formed by rainwater and carbon dioxide recharging these aquifers.

65

E.Y. Mbiimbe et al: Continental J. Earth Sciences 3: 59 - 70, 2008 Table3. WHO and NIS standards for drinking water quality

Parameter

Units

WHO (2006) drinking water quality standards maximum permissible limits

Nigerian industrial standards for drinking water quality(NIS 2007) maximum permissible limits

Aluminum(Al3+)

mg/L 0.2 0.2

Chloride (Cl-)

mg/L 250 250

Color

TCU 15 15

Odor Threshold numbers

3 NA

Copper (Cu2+)

mg/L 1.0 1.0

Corrosivity

Non corrosive NA

Fluoride(F-)

mg/L 2.0 1.5

Iron (Fe2+)

mg/L 0.3 0.3

Magnesium(Mg2+) mg/L 0.05 0.2 Mercury(Hg+) mg/L 0.002 0.001 pH

6.5-8.5 6.5-8.5

Arsenic(As2+) mg/L NA 0.01 Barium(Ba2+) mg/L NA 0.7 Chromium(Cr6+) mg/L NA 0.05 Cyanide(CN-) mg/L 0.2 0.01 Conductivity µS/Cm NA 1000 Hardness(as CaCO3) mg/L NA 150 Lead(Pb+2) mg/L 0.015 0.01 Nickel(Ni2+) mg/L NA 0.02 Nitrate(NO3

-) mg/L 10 50 Sodium(Na+)taste threshold mg/L 30-60 200

Silver

mg/L 0.1 NA

Sulphate (SO42-)

mg/L 250 100

Total dissolved solids (TDS)

mg/L 500 500

Zinc (Zn2+)

mg/L 5.0 3.0

66

Table 4: Results of chemical analysis of groundwater samples from the study area.

s/no Water source

Location Temp 0C

Conductivity µs/cm

TDS mg/L

pH Ca2+ mg/L

Mg2+ mg/L

Na+ mg/L

K+ mg/L

SO42+

mg/L Cl-

mg/L HCO3

- mg/L

NO3-

mg/L Fe2+ mg/L

Hardness mg/L

1.0 BH1 Nu 1 33.0 350 224 6.5 36 11.2 13 6.0 10 16 133 13.7 0.6 136 2.0 BH2 Nu 4 33.0 340 218 6.5 32 11.4 15 6.0 0 40 112 0 0.6 127 3.0 BH4 Nu 6 35.0 210 135 6.0 28 13.4 18 6.0 0 16 212 0 0.5 125 4.0 BH5 Nu7 31.9 370 237 6.5 16 6.0 17 6.0 10 8.0 100 8.8 1.6 67 5.0 BH8 Dem 1 30.0 70 45 6.5 6 2.7 9 5.0 12 16 180 17.6 0 26 6.0 BH9 Dem 2 33.8 300 192 6.5 27.2 9.2 12 6.0 5 12 106 4.4 0.6 106 7.0 BH 10 DEM 35.0 260 167 6.5 32.8 7.8 17 6.0 0 2.0 80 4.4 0.65 144 8.0 HW1 ITALIYA 32.2 60 38 6.3 4 2.2 13 5.0 20 20 84 13.2 2.0 19 9.0 HW3 FARAI 1 33.0 220 141 6.7 12 9.3 29 6.0 5 48 60 8.8 1.0 68 10 HW 3 FARAI 2 32.4 1320 846 6.9 120 30 29 6.0 80 28 168 17.6 0 421 11 HW6 DAKANTA 32.9 880 564 7.1 54 17 15 3.4 70 52 100 88 0.06 199 12 HW 8 SABON

PEGI 34.4 1070 686 6.9 60 20 15 4.0 45 16 204 44 0.1 231

13 HW 9 KUKUMTO 33.8 110 71 6.8 8.0 2.0 16 4.0 7.0 36 200 35.2 0.7 28 14 HW 10 GADINA 1 32.4 334 214 6.3 72 17 22 6.0 26 8.0 53 88.0 0.1 250 15 HW11 GADINA 2 - 1400 897 6.0 140 16 18 6.0 40 28 22 132 0 415 16 HW 13 SABOGARI

MISSIONARY 31.8 300 192 6.3 26 10 18 6.0 12 32 120 22.0 0.1 105

17 HW 14 SABONGARI PALMAS

30.3 220 141 6.0 28 10 20 6.0 10 8 260 22.0 0.1 109

67

E.Y. Mbiimbe et al: Continental J. Earth Sciences 3: 59 - 70, 2008 Table 5: Hardness of individual groundwater sources from the study area Location Well no Hardness mg/L Water type Gindin kuka BH1

136 Slightly hard

Gwaidamala BH2

127 Slightly hard

Opp. Sakato BH4

125 Slightly hard

Unguwan Maizakara BH5

67 Slightly soft

Demsa L.G. Secretariat BH8

26 Soft

GSS Numan BH9

106 Slightly hard

Bakatsalle BH 10

144 Slightly hard

Italiya Hw 1 19 Soft Farai 1 Hw 3 68 Moderately soft Farai 2 Hw 4 421 Hard Dakata Hw 6 199 Moderately hard Sabon pegi Hw 8 231 Moderately hard Kukomto Hw 9 28 Soft Gadina 1 Hw 10 250 Moderately hard Gadina 2 Hw 11 421 Hard Sabon gari missionary Hw 13 105 Slightly hard Sabon gari palmas Hw 14 109 Slightly hard CONCLUSION The study has identified three aquifer systems in the area within the depth bracket of 0-240m. The upper unconfined aquifer receives recharge from direct rainfall and is tapped mainly by the handdug wells (0-40m total depth). This aquifer is presently under the treat of surface generated pollution mostly associated with domestic/household waste. The middle semi confined aquifer occurs at depth below 40m and is a source of supply to boreholes completed within 40-75m. The quality of water from this aquifer is still within the limits for drinking water quality of WHO (2006) And NIS (2007). The lower confined aquifer is tapped by very few boreholes 75-241m. Groundwater chemistry suggests that the upper aquifer has isolated cases of high concentrations of NO3

-, (88-132mg/L), high TDS (546-897 mg/L) Fe2+ (.5-2 mg/L), moderately hard to very hard (144 -421 mg/L). The quality of the water from the middle and the lower aquifers is generally acceptable as it falls within the maximum permissible limits of WHO (2006) and NIS (2007). Two dominant water types are identified from the piper diagram – Na+ +K+ -HCO3

-and the Ca2+ - HCO3- water types. The study area

therefore has high potentials for sustainable groundwater development to meet the needs of the populace. It is however suggested that development of groundwater through handdug wells should ensure high protective aprons and well points should be sited at good safety distances from waste disposal sites.

68

E.Y. Mbiimbe et al: Continental J. Earth Sciences 3: 59 - 70, 2008 TABLE 6: Summary of water chemistry data

ACKNOWLEDGEMENTS The authors acknowledge the contributions of the staff and management of Adamawa state water board, RUWATSAN, Soil Science Department of FUT Yola and UBRBDA Yola.

Sample

Na+ mg/L, meq/L

K+ mg/L meq/L

Ca2+ mg/L meq/L

Mg2+ mg/L meq/L

Cl- mg/L meq/L

HCO3-

mg/L meq/L

SO42-:

mg/L meq/L

TDS (mg/L)

(Cations/Anions

Comments

BH1 13.0 0.57

6.0 0.15 36.0 1.80

11.20.92 16.0 0.45 133.0 2.18 10.0 0.21 225.2 1.2 Ca2+-HCO3-

BH 2 15.0 0.65

6.0 0.15

32.0 1.60

11.40.94 40.0 1.13 112.0 1.84

0.0 0.00 216.4 1.1 Ca2+-Cl-

BH 4 18.00.78

6.0 0.15 28.0 1.40

13.4 1.10 16.00.45 212.0 3.47 0.0 0.00 293.4 0.9 Ca2+-HC03-

BH 5 17.00.74

6.0 0.15 16.0 0.80

6.0 0.49 8.0 0.23 100.0 1.64 10.0 0.21 163 1.1 Ca2+-HC03-

BH 8 9.0 0.39 5.0 0.13 6.0 0.30 2.7 0.22 16.0 0.45 180.0 2.95 12.0 0.25 230.7 0.3 Na+ +K +-HC03-

BH 9 12.00.52

6.0 0.15

27.2 1.36

9.2 0.76 12.0 0.34 106.0 1.74 5.0 0.10 177.4 1.3 Na ++K+ -HC03-

BH 10 17.0 0.74

6.0 0.15

32.8 1.64

7.8 0.64 2.0 0.06 80.0 1.31 0.0 0.00 145.6 2.3 Ca2+-HC03-

HW 1 13.0 0.57

5.0 0.13 4.0 0.20

2.2 0.18 20.0 0.56 84.0 1.38 20.0 0.42 148.2 0.5 Na ++K+ -HC03-

HW 3 29.0 1.26

6.0 0.15 12.0 0.60

9.3 0.77 48.0 1.35 60.0 0.98 5.0 0.10

169.3 1.1 Na ++K+ -HC03-

HW 4 29.0 1.26

6.0 0.15 120.0 5.99

30.0 2.47 28.0 0.79 168.0 2.75

80.0 1.67 461 1.9 Ca2+-HC03-

HW 6 15.0 0.65

3.4 0.09

54.0 2.69

17.0 1.40 52.0 1.47 100.0 1.64

70.0 1.46 311.4 1.1 Ca2+-HC03-

HW 8 15.0 0.65

4.0 0.10 60.0 2.99

20.0 1.65 16.0 0.45 204.0 3.34

45.0 0.94 364 1.1 Ca-2+HC03-

HW 9 16.0 0.70

4.0 0.10 8.0 0.40 2.0 0.16 36.0 1.02 200.0 3.28

7.0 0.15 273 0.3 Na+ +K+ -HC03-

HW 10 22.0 0.96

6.0 0.15 72.0 3.59

17.0 1.40 8.0 0.23 53.0 0.87 26.0 0.54 204 3.7 Ca2+-HC03-

HW 11 18.0 0.78

6.0 0.15

140.0 6.99

16.0 1.32 28.0 0.79 22.0 0.36 40.0 0.83

270 4.7 Ca2+-HC03-

HW 13 18.0 0.78

6.0 0.15

26.0 1.30

10.0 0.82 32.0 0.90 120.0 1.97

12.0 0.25

224 1 Ca-2+HC03-

HW 14 20.0 0.87

6.0 0.15

28.0 1.40

10.0 0.82

8.0 0.23

260.0 4.26

10.0 0.21

342 0.7 Ca2+-HC03-

69

E.Y. Mbiimbe et al: Continental J. Earth Sciences 3: 59 - 70, 2008 REFERENCES Allix, P. (1983): Environment Mesozoiques de la Partie Nord Oriental du Fosse de

laBenoue(Nigeria),Stratigraphique Sedimentologic Evolution Geodynamique Thesies 2eme cycle trav. Lab. Sc. de Terre Marseille St Jerome (B) 21 200p

Arthur W.H., (1995): Water quality data: analysis and interpretation CRS press, Boca Raton/New

York/London/Tokyo pp 88-93 Bachmat Y, Gredehhoeft J, Barbara H, Hohz D, and Scoh S, (1980): Groundwater Management: The Use of

Numerical Models in Water Resources Monograph 5 Amer.Geoph. Union Washington D C P 12 Barber W.M., Tait E.A., and Thompson J.H, (1954): Ann Rep. Geol. Surv. of Nigeria: 18-20 Brassington R,(1990): Field Hydrogeology Geol. Soc. of Prof. Handbook, Open University Press Million

Keynes/Halted Press. New York/Toronto Pp48-62. Callist T. (2006) Groundwater mapping and its implications for rural water supply in Uganda in forum for

groundwater issue three December 2006 p1-2 Carter J.D., Barbar W., Tait E A. and Jones J.P. (1963): The Geology of Parts of Adamawa, Bauchi Bornu

Provinces in North Eastern Nigeria. Bull Geol. Surv. of Nigeria 30 1-109. Cooper H.H. Jr and Jacob C.E. (1946): A Generalized Graphical Method for Evaluating Formation of

Constants and Summerising Well Field History, Trans.Amer. Geophysical Union,V 27 Pp 526-534. Dike E.F.C (1994): Geology And Hydrogeology of Misau and environs in Water Resources Jour of the

Nigerian Association of Hydrogeologists Vol 4 Nos 1&2 P57-63 Guisti E.V.(1978): Hydrogeology of the Kerst of Pnerto Rico. US Geol.Surv.Prof.Paper 1012 Pp 68. Mike B., Mai N. and Pedley S. (1999): On-Site Sanitation and Urban Aquifer Systems in Uganda,Water Lines

International Jour. of Appropriate Technologies for Water Supply and Sanitation vol 17 No 4 P10. Mode W.A. (1993): Ethology and paleo-environment significance of trace fossils from Cenomanian-Turonian

sediments in the Upper Benue Trough Jour. of Min and Geol. Vol 29 Pp 111-117. NIS (2007): Nigerian Industrial Standard for Drinking Water Quality, NIS 554 Obiefuna G.I., Nur A. Baba A U and Bassey N.E. (1999): Geological and geotechnical assessment of selected

gully sites in Yola area, North East Nigeria, Jour of Environmental Hydrology No, 6 Vol 7. 13 Offodile M.E. (1992): An approach to groundwater study and development in Nigeria Mecon Services Ltd ,Jos Piper A. M., (1944) A graphical procedure in the geochemical interpretation of water analysis, Amer. Geophys.

Union trans vol. 25 pp 914-923 Reyment R.A.(1955): The Cretaceous Ammonoidea of southern Nigeria and southern Cameroon, Bull. Geol.

Surv. Nigeria, 25 1-112. Thomas E. Reilly and David W.P.(1993): Factors affecting areas contributing recharge to wells in shallow

aquifers,U.S Geol.Surv. Water Supply Paper 2412

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E.Y. Mbiimbe et al: Continental J. Earth Sciences 3: 59 - 70, 2008 Todd D.K. (1980): Groundwater Hydrology 2nd ed. John Wiley&Sons, New York/London/Sydney p 535. UBRBDA (1986-1996): Upper Benue River Basin Development Authority Year Book. WHO (2006): 2006 edition of the Drinking Water Standards and Health Advisories EPA 822-R-06-013 Received for Publication: 24/10/2008 Accepted for Publication: 27/12/2008 Corresponding Author E.Y. Mbiimbe Department of Geology, Gombe State University, P.M.B 127 Gombe State Nigeria.

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Continental J. Earth Sciences 3: 71 - 76, 2008 ©Wilolud Online Journals, 2008.

ENHANCING VALUE OF NIGERIAN GEMS THROUGH LAPIDARIES

Aga, T1 and Ashano, E. C2 1Geology Department, Gombe State University, Gombe, 2Geology and Mining Department, University of Jos,

Nigeria. ABSTRACT Various geological reports on Nigerian Geology reviewed indicate that gemstones occur in all the geologic units of Nigeria. They are however concentrated within the 400km long and 150km wide NE-SW trending pegmatite belt of Central Nigeria. At present only one Lapidary situated in Jos exist in the country where gems are faceted and polished into different shapes. Surprisingly, demand for cut and polished Nigerian gems which have several uses is on the increase internationally. This paper will attempt to look at the various gems in Nigeria in the light of the mineral supply process. However, more emphasis will be laid on the techniques of processing the gems. KEYWORDS: Gems, Lapidary, pegmatite, faceting, polishing

INTRODUCTION A gem sometimes called precious stone or stone is a naturally occurring material desirable for its beauty, valuable in its rarity, and sufficiently durable to give lasting pleasure (Ron, 2003). Statistics of gem production in Nigeria are meager. Stones found in Nigeria include; emerald, sapphire, amethyst, garnet, tourmaline, topaz and zircon. Available geological reports and visits to some mine sites tend to suggest that Nigeria host the largest quantity of colourless topaz in the world (Aga, 2004).The processing of gems and rocks is refered to as lapidary studies and the factory where stones are cut and polished is called a Lapidary. Nigeria at present has only one Lapidary situated in Jos. Nigeria`s art of gem cutting is at its infantile stage. There are less than 1000 persons in the country who have acquired such a skill (Aga, 2004). In order to achieve maximum results, a cutter must be familiar with factors that may affect the overall value of his/her finished stone. These include; refractive index, position of inclusion(s) if present, optical phenomena, cleavage planes, colour and so on. Geological Occurrence Generally, gems can form in different geologic environments in the earth thus giving rise to various types including hydrothermal, pegmatite, magmatic and metamorphic and alluvial gems. In Nigeria, these various geologic environments exist within the four distinct units viz Basement, Younger Granite Complexes, Sedimentary Basins and Recent lavas and volcanic pipes (Ajibade, 1976). Fig. 1 shows these units and a pegmatite belt of Central Nigeria. The pegmatite occurs as a NE-SW trending belt about 400 km long and 150km wide beginning from Abeokuta area in the Southwest to Bauchi in the North Central parts. Occurrences of gemstones in Nigeria are reported within the Pan African Granites, Mesozoic Younger Granites and Proterozoic Pegmatite. Mainly, emeralds and sapphires are hosted in quartzofeldspatic and aplitic veins within the Pan African Granites and at contacts between Sedimentary belt and the Pan African Granites in western Nigeria. In the Mesozoic Granites, the gems (emerald and sapphire) occur in roof zones and greisens within the rock, while the Paleozoic Pegmatite host mainly semi precious aquamarine, topaz, gem quality tourmaline and sapphire (Aga, 2004).

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Aga, T and Ashano, E. C: Continental J. Earth Sciences 3: 71 - 76, 2008 Fig. 1: Simplified Geological Map of Nigeria Showing Pegmatite Belt of Central Nigeria ( Ajibade et al, 1989)

Fig 2: Preliminary Location Map of Nigerian Gemstones (Modified After NIMAMOP Report,1999) Fig. 2 shows a preliminary mineral location map of Nigerian gemstones. Classification of Nigerian gems is mostly based on size and recognized value (Tables 1). Companies adopt any of the three classifications based on Management preferences. Two out of the four precious stones known worldwide occur in Nigeria. These are emerald and sapphire which appear as green and blue respectively. The rest are semi precious stones (Table 2). Two varieties of garnet namely almandine and spessartite are common in Nigeria. Nigerian Tourmaline occur black/brown as schorl, pink as rubellite, blue as indicolite and green as verdelite. In Nigeria, most original discoveries of gemstones have been as a result of observation accidents due to searches or operations for other substances. Most of the prospecting is done by amateur collectors and used to be concentrated on dipping up unconsolidated stream gravels, placer accumulations and certain bedrock masses.

Key ∆ - Mines ₀ - Prospect GM - Gemstone

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Aga, T and Ashano, E. C: Continental J. Earth Sciences 3: 71 - 76, 2008 Table 1: Classification of Nigerian Gems Based on Size

S/N Company 1 Company 2 Company 3 Size(mm) Size(mm) Size(mm) 1 1 1 1 2 1-2 1-2 1-2 3 2-4 3-9 3-9 4 4-5 10-14 10-20 5 10-14 14-20 Above 20 15 and above - -

Source: Aga (2004) Table2: Classification of Nigerian Gems Based on Composition, Colour, Hardness and Specific Gravity

Gemstone

Precious Stones Hardness Specific Gravity Composition Common Colour

Emerald Be3Al2Si6O18 Green 7.50 - 8.50 2.71 Sapphire Al2O3 Blue 9.00 3.99 Semi Precious Stones Amethyst SiO2 Purple 7.00 2.60 Aquamarine Be3Al2Si6O18 Blue 7.50 2.68 Garnet Ca3Al3(SiO4)3 Red 6.50 - 7.50 3.50 Topaz Al2(F,OH)2SiO4 Colourless 8.00 3.56 Tourmaline Na(Mg,Fe)3Al6(BO3)3(SiO15)(OH,F)4 Black, Pink,

Green 7.00 - 7.50 3.05

Quartz SiO2 Colourless 7.00 2.66 Zircon ZrSiO4 Red, Orange 7.50 4.00 –

4.70 Source: Bateman (1950) MATERIALS With minimal effort and a nominal investment, it is possible to establish a successful gemological detective centre and accurately identify most gems. On a small scale, one can begin with just three basic instruments including the loupe, Chelsea filter and dichroscope. Used together, these three simple, portable instruments can enable one to properly identify almost eighty percent of the coloured gemstones encountered in Nigeria. A hand magnifier sometimes called the Jeweler`s loupe is used essentially to detect chips, cracks, symmetry in cutting, sharpness of facet edges and the presence of flaws. The Chelsea filter otherwise known as emerald filter is a pocket sized colour filter and is quite simple instrument. It is designed to allow only two wavelengths of light (red and green) to be transmitted. Nigerian sapphires could be separated from sapphire look alike with this instrument. The calcite-type dichroscope is a small pocket sized tabular instrument used for transparent coloured gemstones. It differentiates stones based on differences in colour shades. The refractometer is used to measure the refractive index (R.I) of stones. Generally, the higher the R.I., the more brilliant the stone. Gems exhibiting phosphorescence like Nigerian emeralds can be studied using (UV) lamps. A good microscope is necessary to magnify the materials under study and with a slight modification, the microscope can also be adopted for use as dichroscope, polariscope, refractometer and spectroscope (Matlins and Bonanno, 1986). The spectroscope is a relatively small instrument that analyses light passing through a stone. The polariscope is used primarily to differentiate genuine from synthetic amethyst. Estimated cost of establishing a moderately good gemological factory with these simple equipments is conservatively put at N250,000.

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Aga, T and Ashano, E. C: Continental J. Earth Sciences 3: 71 - 76, 2008 DISCUSSION Prefaceting and Faceting Prefaceting and Faceting are techniques involved in the art of taking a rock or crystal and turning it into a more refined and polished product in a lapidary. The former include ; sorting, sawing and preforming while the later involves cutting and polishing. Dopping and calibrating are intermediary stages between prefacting and faceting. Nigerian gemstones extracted from vein, pocket vein and pocket occurrences are broken or crushed where necessary and concentrated by various combinations of hand picking, washing and screening. Most times, picking is repeated as many times as possible. This process is refered to as sorting and is dependent upon the percentage of flaws such as inclusions in a gemstone. Based on this, Nigerian gems are grouped into grades A, B, C and D in a decreasing order of purity. The term `shango` is used to describe grade D. Certain techniques are used to remove identified stains or flaws to enhance the aesthetic values of the gemstone. For instance, sawing is carried out on gems to remove flaws identified during sorting. Such flaws may be noticed in the middle of the crystal, as observed in most Nigerian aquamarines. In such a case, the crystal is cut into two pieces along the crack line. A liquid such as oil or water is used to wash away debris and keep the stone and the saw blade from overheating, which could cause damage to both. Preforming, otherwise known as grinding, usually done with silicon carbide wheels or diamond-impregnated wheels, is used to shape gemstones to a desired rough form, called perform. Sawing is similar to grinding but uses finer abrasives. Its purpose is to remove deep scratches left by coarser abrasives during grinding. Dopping is the process where a preformed stone is attached to the flat end of a dop stick with wax as a cement over source of heat. Dop wax consists basically of a mixture of shellac and sealing wax, although quite often other ingredients such as beeswax and clay are added. Certain stones are susceptible to damage by heating and for these a lower temperature dop wax should be used. A calibrate stone is a gemstone that has been cut to predetermined size, prior to faceting and polishing. Care must be taken at this stage and it requires serious concentration. Allowance of +0.2mm should be left in the sizes of the various shapes calibrated. This is achieved through the use of Vernier calipers, etc. The girdle is around three percent for all the stones. The performing machine can be used for calibrating. Faceting is the art of taking a transparent rock or crystal and making flat faces (facets) on it to make the light refract and reflect from the stone better. The most commonly used facetron in Nigeria is the NRS faceting machine (Fig.3).This machine is used in faceting gems into eight common shapes in the country viz pear, round, octagon, square, oval, marquise, triangle and heart. The cutting and polishing of the table( Fig 4) which must be fifty percent is achieved with the use of a table polisher. Polishing is meant to remove all small quantities of stone and can be used, especially when faceting small stones, to do ultrafine shaping of the stone. Sometimes this is not achieved due to some errors like: less-meet, over-meet, unbalanced girdle, small table, large table, double facet, lapmark, quilet and girdle chips. These errors are corrected by refaceting, careful sanding, relapping and/or repolishing. Fig 4 shows parts of a faceted stone. Uses and Markets Nigerian gems are primarily used for decoration purposes, in jewelry products and fashioning of materials. The typical products include : brooches, chips, bracelets, earrings, hair ornaments, crystal watches, flower vases, etc. For example, Nigerian tourmaline has been used as a calibration standard for nanometer (because of its piezoelectricity). It is also used as a standard to check possible effects of water soluble boron in mixed fertilizers .Also, both natural and synthetic corundum are ground and graded as abrasive; it is the major compound used in the polishing of eye glasses.

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Fig.3 : Faceting Machine

Fig. 4: Parts of a Faceted Stone

Gemstones of Nigerian origin are sold in their raw, sawn, preformed, calibrated or cut and polished forms. Over ninety percent of the gemstones are sold in their crude form and exported out of the country. Emerald and sapphire are relatively more expensive than the semi-precious types. Prices of preformed stones are approximately seventy five percent higher than rough ones. The cut and polished stones are almost three times more expensive than the rough ones. A visit to most online shops reveal that sawn and preformed stone from Nigeria are in high demand most especially rubellite and topaz. CONCLUSION Geological evidences indicate that different gemstones occur in the country, especially within the pegmatite belt. Most of the gems are exported in rough forms and therefore sold at a value one third of the ones polished. Techniques required to enhance these gems are simple and the basic equipments required are not quite expensive. The need to have more lapidaries in the country is therefore suggested. ACKNOWLEDGEMENT The authors wish to thank the Management of Geotess Nigeria Limited, Jos for engaging Aga, T in a three month training in the art of cutting and polishing of gemstones at their Lapidary.

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Aga, T and Ashano, E. C: Continental J. Earth Sciences 3: 71 - 76, 2008 REFERENCES Aga, T (2004): The Viability of Establishing a Lapidary in Nigeria. Unpublished MSc Seminar. University of Jos. 75pp. Ajibade, A. C (1989): Provisional Classification of the Schist Belts of Northwestern Nigeria. In Kogbe, C. A (ed). Geology of Nigeria. 2nd Edition. Rockview International, Jos. Pp 85-90. Bateman, A. M (1950): Economic Mineral Deposits. 2nd Edition. John Wiley and Sons Inc. New York. Pp 834-854. Matlins, A. L and Bonano, A. C (1986) : Gem Identification Made Easy. Gemstone Publication. London. 270pp. NIMAMOP Report (1999): Ministry of Solid Minerals Publication. P 20 Ron, S (2003): How to Tumble and Polish your Stone. Ron.shannon@simpatico Received for Publication: 07/09/2008 Accepted for Publication: 27/12/2008 Corresponding Author Aga, T Geology Department, Gombe State University, Gombe, Nigeria.

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Continental J. Earth Sciences 3: 77 - 82, 2008 ©Wilolud Online Journals, 2008. DENTAL FLUOROSIS FROM DRINKING WATER CONSUMPTION IN LANGTANG TOWN, PLATEAU

STATE, NIGERIA.

Dibal, H.U., Lekmang, I.C. and Lar, U.A. Geology and Mining Department, University of Jos, Jos, Plateau State, Nigeria

ABSTRACT The study area is defined by latitudes 9o.00’ and 9o.15’ N and longitudes 9o.45’ and 9o.50’ E; with approximately an average population of 300,000 inhabitants. The area is faced with problem of water supply especially during the dry season, when they resort to scanty supplies from hand – dug wells and streams. The aim of the study was to determine how drinking water has contributed towards dental fluorosis in Langtang town and environs. Fifteen (15) water samples were picked from various water sources and determined for their fluoride contents. The ion chromatographic analyzer ICA model was used. Fluoride concentration ranges from 0.11 to 6.62 mg/l, with the wells having the highest and the stream having the lowest of 0.11mg/l. Over 74% of the water in the study area has fluoride concentration above the World Health Organisation (WHO) standard limits of 1.5mg/l and 26% below the limits. Fluoride is probably being leached from fluoride bearing minerals (biotite, fluorite, hornblende, topaz, etc) from the host rock (migmatite gneiss,rhyolite) since they constitutes over 90% of the geology of the study area Questionnaire results revealed that 23.75% of the respondent do not show evidence of mottled teeth because they were not born in the area. Some 76.25% of those born in the study area show evidence of mottled teeth. The greater numbers of respondents with mottled teeth however, fall within the age 1 to 20 years of age. About 76% of the interviewed respondents, who showed evidence of dental fluorosis, could not ascertain the cause (s) nor proffer solution to the problem. Those with mottled teeth find it difficult to chew with them as they are susceptible to breakage. Most teenagers, especially girls are often shy of the coloured teeth

KEY WORDS: Dental fluorosis, Mottledteeth, Skeletal fluorosis, Susceptible, Aquifer, Osteopathic outgrowth.

INTRODUCTION Fluoride is found in rocks, plants, animals, air, and water in varying concentrations.The element fluorine is highly reactive and because of its reactivity, it exists in the ionic form as fluoride. It enters the human body by ingestion, inhalation and in extreme cases through the skin. Fluoride absorbed into the body, if not excreted can cause teeth mottling (dental fluorosis) or on prolonged exposure to high levels of fluoride, skeletal fluorosis may result (Hui, 1985). Mild mottled teeth may have little public health significance, apart from causing embarrassment to the affected. It may however, bring about excessive wearing of the teeth and difficulty in mastication (Hui, 1985). Severe fluorosis makes teeth more susceptible to dental caries. In skeletal fluorosis, the skeleton increases in density and osteophytic outgrowth appears on the long bones, vertebrae, and ribs Langtang town is situated at the southern part of the Jos Plateau, situated between the Pre- Cambrian Basement Complex rocks and the Cretaceous sedimentary rocks of the middle Benue Trough. It is defined by latitudes 9o 00 ′ and 9o 15′ N and longitudes 9o.45′ and 9o.50′ E Langtang has approximately an average population of 300,000 inhabitants. The town and its environs are faced with great challenges of water supply especially during the dry season. Women and children travel long distances to obtain water for household uses. To alleviate this problem the Federal Government in collaboration with the Plateau State Government constructed two large dams with one serving as a feeder to the other. The construction of these dams did not solve the problem of water supply in the area as it is not fully in operation and appears to be inadequate. The inhabitants still rely on groundwater from hand dug wells and streams as a major source of water supply for drinking and other

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Dibal, H.U et al: Continental J. Earth Sciences 3: 77 - 82, 2008 household uses. Cases of teeth mottling has been reported in the area and other related areas in the northeastern parts of Nigeria with severe fluorosis index among all categories of age groups (Wongdem et al, 2001; Dibal and Lar, 2005; Lar, et al, 2007). The aim of this work is to; 1. determine the concentration of fluoride in the natural water system of the area

2 determine how drinking water has contributed towards the development of dental flourosis in Lantang town and its environs

3 the perception of the inhabitants towards teeth mottling GEOLOGY AND HYDROGEOLOY Langtang town in Langtang North Local Government area where the study was undertaken is situated on the Precambrian basement rocks. The area is comprised of migmatites, granite gneiss (basement rocks), biotite granite (Younger Granites), rhyolite and plugs of mafic rocks and pegmatites all intruding into the basement unit, which constitutes over 60% of the area. The migmatite gneiss forms the lower plains, underlying the entire area while, the granite gneisss rhyolite and the biotite granite forms the higher grounds reaching heights of about 600 to 800 meters above sea level. There is no particular trend to show that they were (biotite granite) formed in the same way as that of the Jos Plateau (ring dykes) but occur as stocks. Situated between the granite gneiss and the migmatite gneiss are massive bodies of rhyolite rocks trending in the NE – SW direction .They are fine grained rocks with quartz and feldspars as the major minerals. They melted the granite gneiss as portion of it were found in their matrix as xenoliths. HYDROGEOLOGY The Bapkwai stream is the the major stream that drains the entire Langtang area. It is flooded in the rainy season and dries up during the dry season. During the dry season the sands are scooped before water could be obtained. Two aquifer systems occur in this area; the weathered overburden aquifer and the fractured aquifer. The weathered overburden aquifer is variable in thickness mostly in the range of 10 to 15 meters thick and the fractured aquifer is between 25 - 30 meters thick. Water levels almost come to the surface during the rainy season but begin to go down as soon as the rain is over. As at the time of the study, there was no available record about the yield of the two aquifers, but yield may probably be in the range of 1 – 2 l/s METHODOLOGY Water samples were collected from wells, streams and dams in two plastic containers of 2 liters capacity each in December 2006 and January 2007. Waters from stream were sampled upstream, middle and downstream. The conductivity, pH, temperature of each water sample were measured on the spot, using temperature/conductivity meter (Oakton pH 5/6) under hygienic condition. Depths to water in wells were determined using a steel tape. Questionnaires were also administered to respondent at the Junior Secondary School Langtang and the Local Government Secretariat. Random observations of teeth mottling were also carried out on children ages between 1 to 11 in Langtang Town and its environs. SAMPLE PREPARATION AND ANALYSIS The cations magnesium, calcium, potassium and sodium were analysed using Atomic Absorption Spectrophotometer (A.A.S) with the lowest detection limit of 0.01 ppm and titration method for the anions (chloride, sulphate bicarbonate and carbonate).The anion (F-) was determined using an ion chromatographic analyzer (ICA) a product of Yokogawa - Japan equipped with conductivity and UV detectors. The method of the ion chromatographic analyzer is described by (Ubom and Tsuchiya, 1988). RESULTS Table 1 shows the levels of dissolved constituents in the study area. Table 2 is the results of observation made on respondent and Table 3 shows the methods of water storage practiced by the inhabitants. Fig 1 shows the geology of the area and sampling points. Fluoride concentration ranges from 0.11 to 6.62 mg/l, with the wells having the highest and the stream having the lowest of 0.11mg/l (Table 1). On the average over 74% of the water in the study area has fluoride concentration above the World Health Organisation (WHO 2004) standard limits of 1.5mg/l and 26% below the limits. From questionnaire results and observation carried out randomly on children between age 1 to 11 years, teenagers between the ages of 11 and 20 years at the Government Day

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Dibal, H.U et al: Continental J. Earth Sciences 3: 77 - 82, 2008 Secondary School Langtang and workers at the Local Government Secretariat totaling 181 persons, results revealed that 23.75% of the respondents do not show evidence of mottled teeth because they were not born in the study area. Whereas the remaining 76.25% who were all born in the study area all show evidence of mottled teeth. The greater number of respondents with mottled teeth however, falls within the age 1 to 20 with each having 96.6% and 87.7 % of dental fluorosis respectively. 61.5% of the respondents store their water in clay pot, 34.3% in plastic containers and 4.1% in steel containers. Table 2: Observation of teeth mottling among respondents.

Age Limit 1-10 11-20 21 above Number observed

24 71 86

Number given birth to in the study area

23 56 46

Number with no dental fluorosis

2 9 32

Number with dental fluorosis

22 62 54

% of people with dental fluorosis

91.6% 87.3% 62.7%

Table3: Water storage method in the study area

Storage material Frequency Percentage Clay pot 104 61.5% Plastic containers 58 34.3% Steel containers 7 4.1%

DISCUSSION Fluoride concentration, Water Consumption and Geology Results of the study indicates that groundwater is used for cooking and drinking especially during the raining season since it is perceived to be purer (due to low turbidity) than surface water (stream or dam water, which tend to be highly turbid), which is used for cleaning and washing. Some households use alum to remove turbidity in their drinking water without knowing that alum treatment has been found to decrease fluoride concentration in water (Njenga, 1982). Boiling of drinking water is practiced by some inhabitants of the area to disinfect the water of microbial contamination. However, boiling has no effect on the levels of fluoride in the water. It has earlier been reported that fluoride levels in the streams are higher than any other source of water supply in the area ((Wongdem et al, 2002). However, the present study is at variance with these findings as the groundwater is found to contain more fluoride than the surface water. This is possible because interaction between groundwater and fluoride bearing minerals is enhanced as the water moves within the host rock. The surface water will obviously contain lower fluoride because of dilution from rainfall during the rainy season. Fluoride is probably being leached from fluoride bearing minerals (biotite, fluorite, hornblende, topaz etc) from the host rock (migmatite gneiss and rhyolite) since they constitutes over 90% of the geology of the study area Although, the wells dry up in the dry season, interactions with the inhabitants revealed that dependence on the groundwater sources (wells) is more than the surface water which incidentally has more fluoride. Fluoride consumption and dental fluorosis Results from the administered questionnaires and random examination of teeth of children in the study area revealed that 76% of the inhabitants suffer from dental fluorosis (91% of the children are within the age 1-10, 87.3% within age 11-20 and 62.7% of people within the age of 21 and above). This has correlated positively to

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Dibal, H.U et al: Continental J. Earth Sciences 3: 77 - 82, 2008 the facts that, all the individual that have dental flourosis were all born in the area and were exposed to high levels of fluoride from childhood. It was also observed during the study that there are children and adults who, though they were born and raised in the area do not show any evidence of dental fluorosis. Such individuals may be protected by genetic predisposition, or by other environmental factors. (Ekstrand and Ehrenebo, 1979). Methods of water storage Investigation showed that clay pots were the best containers for reducing fluoride in drinking water, with the greatest reduction occurring after 5 days of storage (Wilkister et al, 2001). It is presumed that fluoride gets absorbed on to the sites of the clay minerals contained in the pottery material. This study did not determine whether there is need for regeneration of the absorption capacities of the pots after repeated usage. In spite of the high usage of these pots for water storage, evidences of dental fluorosis in quite a good number of the inhabitants were observed, other water storage containers used in the region (plastic and steel containers) are not known to reduce the fluoride content of the drinking water and only few respondents use it Perception of respondents to dental fluorosis About 76% of the interviewed respondents, who show evidence of dental fluorosis, could not ascertain the cause (s) nor proffer solution to the problem. The study also revealed that those with mottled teeth find it difficult to chew with them as they are susceptible to breakage. Most teenagers especially girls are often shy of the coloured teeth CONCLUSION From the foregoing it can be concluded that drinking water has contributed greatly towards the development of dental fluorosis in Langtang town and evirons.With 74% of the water having fluoride concentration above the World Health Organization limits, which incidentally is the water the inhabitants directly depends on, it has correlated well with the number of people with dental fluorosis.

REFEENCES Dibal, H. U and Lar, U.A. (2005): A preliminary survey of fluoride concentration in the groundwaters of Kaltungo area, water quality and health implications. Journal of Environmental Sciences. Vol. 9 (2): 41 - 52

Ekstrand, L and Ehrenebo, M. (1979): Influence of milk products on fluoride bioavailability in man. Env. Journal Clin. Pharmacology 16: 211 – 205.

Hui, Y. (1985): Principles and Issues in Nutrition, Wadsworth Belmont CA, 769pp.

Njenga, L.W. (1982): Determination of fluoride in water using selective electrode and calorimetric methods. Unpublished M.Sc thesis. University of Nairobi, pp 113.

Lar,U.A., Dibal, H.U., Daspan, R.I and Jaryum, S.W.(2007): Fluoride in waters (surface and groundwater) in Fobur area and environs. Journal of Environmental Sciences. 10 (1): 35- 40.

Ubom, A. U and Tsuchiya, Y. (1988): Determination of anions I natural watersby ion chromatography. Journal of Water Research. 22 (11):1458 – 1465

W.H.O. (2004): Guidelines for drinking water quality. 2nd edition. Geneva

Wilkister, K., Ngoara, M., Mwakio, P. T and Davies, T. C. (2001): The contribution of drinking water towards dental fluorosis: A case study of Njoro Division, Nakuru District, Kenya. Environmental Geochemistry and Health 24:123 - 130

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Wongdem, J.G., Aderinokun, G.A., Sridhar, M. K and Selkur, S. (2002): Prevalence and distribution pattern of enamel fluorosis in Langtang town. African Journal of Medical Sci. Fluoride 35

Received for Publication: 07/06/2008 Accepted for Publication: 27/12/2008 Corresponding Author Lekmang, I.C. Geology and Mining Department, University of Jos, Jos, Plateau State, Nigeria

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Table 1: Dissolved constituents in the study area

Location Bapkwai 1 Katang Bangon Makong Pajat 1 Pajat 2 Shishiri Pajat 3 Pajat 4 Bapkwai 2 Bakin Kogi Pajat 5 Konkong Gunung 1

Source Stream Well Dam Dam Well Well Well Well Well Stream Well Well Well Stream Date of sampling 7/12/2006 7/12/2006 8/12/2006 8/12/2006 8/12/2006 9/12/2006 9/12/2006 9/12/2006 9/12/2006 13/12/2006 13/12/2006 13/12/2006 13/12/2006 16/01/2007Parameters Conductivity(MV) 21 17 60 23 18 23 17 16 14 24 21 18 24 22 Temperature (o C) 26.5 31.1 27.2 26.1 33 31.2 32.7 33.8 33.7 31 28.5 33 32.4 31 pH 7.46 7.38 8.31 8.01 7.69 7.77 7.06 7.78 7.41 7.68 7.56 7.59 7.34 7.5 Calcium (Mg/l) 17.7 18.34 6.31 6.01 18.04 15.72 7.98 20.68 31.35 14.42 17.18 18.04 17.47 _ Magnesium 6.04 10.48 2.6 2.27 8.21 11.54 1.27 13.91 14.1 4.92 6.04 8.2 4.91 _ Sodium 42.5 94.99 20.74 20.5 83.23 101.7 28.53 99.26 117.5 29.23 42.49 83.23 48.88 _ Potassium 1.16 1.77 0.6 0.2 0.47 0.04 ND 0.64 48.2 0.89 1.15 0.46 ND _ Bicarbonate 280 427 122 110.8 293 403 85.4 433.1 329.4 207.4 280 292.8 195.2 _ Sulfate ND 16.5 ND ND 4.12 ND ND ND ND ND ND 4.12 ND _ Chloride 7.1 7.1 7.1 7.1 28.4 24.82 18 28.4 7.1 7.09 7.09 28.36 35.46 _ Fluoride 1.23 1.25 1.45 1.24 2.21 6.62 1.76 6.18 4.41 0.11 1.23 2.21 2.94 2.22 Carbonate 6.5 6 6 6 6 6 6 9 12 12 6.5 6 6 _ ** ND Not detected

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