Geophysical Exploration Report of 1 18282EL, Wase LGA, Plateau...

18282EL

Geophysical Exploration Report of

18282EL, Wase LGA, Plateau State.

BRIGO MINING COMPANY LTD.

Electromagnetic and Induced Polarization Exploration Report

By: Dr. Oladele Olaniyan

GISL, Abuja

Geophysical Exploration Report of 18282EL , Safiyo, Wase LGA, Plateau State 2015

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Executive Summary

Geodel integrated Systems Ltd (GISL) was commissioned by BRIGO MINING

COMPANY LTD (“BMCL’’) to undertake preliminary exploration programs and

compile Preliminary feasibility Study (PFS) for the Lead Zinc Project at the

18282EL in Safiyo, Wase LGA, Plateau State, Nigeria.

Between October 15th and 17th, 2014, a preliminary reconnaissance survey

was conducted at the project site, to i) Assess the viability of the exploration

license areas for lead-zinc and other sulfide mineralisations ii) Define the host

rocks, mineralization styles and dominant trend of mineralization iii) Obtain

and analyze some selected samples from the sites iv) Design a systematic

mineral exploration procedure for lead and other associated metallic

mineralization.

In November 2014, GISL planned and conducted an electromagnetic survey

(EM) over a 1 km by 1 km area within the 18282 EL, to delineate conductive

locations and structures, that might be related or controlling the lead zinc

mineralisations within the area. The survey was undertaken with an APEX

Maxmin horizontal loop electromagnetic equipment at a loop separation of

100 m and 50 m respectively. About 2,000 meter cumulative length of

conductors was interpreted from the five frequencies EM survey data.

In January 2015, the Indued polarization survey was conducted across the

interpreted EM anomalies to further define the source and likely geometry of

the conductive structures and bodies. This survey utilizes the Time-domain

GDD 5000 watt transmitter and the 16- channel receiver to map out the

chargeable zone at the subsurface. Though this survey is still ongoing, the

available results show good relationship between the magnetic, conductive

and chargeable zones. Laboratory analysis of some hand samples of sulfide


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mineralisation grades between 60 to 80 percent of lead (Pb) around the

area.

This preliminary feasibility report summarizes the results of the exploration work

done so far, and the projected resource estimate within the 1 km by 1 km

survey area, for the purpose of a small scale mining lease application.


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Table of content Page

1.0 INTRODUCTION 4

1.1 Location, accessibility

1.2 Climate and vegetation

1.3 Topography and Drainage

2.0 RECONNAISSANCE SURVEY 6

3.0 ELECTROMAGNETIC SURVEY 8

4.0 TIME DOMAIN INDUCED POLARIZATION 15

5.0 PROSPECTIVITY MAPPING 29

6.0 CONCLUSION AND RECOMMENDATIONS 32

7.0 STATEMENT OF QUALIFICATION 33


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1.0 Introduction

On the 2nd June, 2014, the Federal Government of Nigeria through the Mining

Cadastre Office granted the exploration license (EL) No 18282EL (Safiyo lead

zinc prospect) to BRIGO MINING COMPANY LTD (“BMCL’’) to explore for lead, zinc

and copper in Plateau State, Nigeria. Plateau state is about 150 km east of

the Federal capital territory (FCT) (Figure 1), and is notably rich in metallic and

industrial minerals such as lead-zinc, copper, manganese, iron ore, niobium,

columbite, tin ore occurring in hosted in intrusive granitoids, pegmatites, as

well as sedimentary sequences.

Figure1: Map of Nigeria showing the location of the Federal capital territory,

Plateau state and the location of the lead-zinc property of Brigo Nigeria Ltd.

The 18282EL area is located on the eastern portion of Plateau state and lies

within Longitudes 10.275E and 10.3E and Latitudes 9.2N and 9.225N (UTM) in

the 1: 50.000 map sheet No 192 of Bashar. The Safiyo Lead zinc property is

defined by 4 vertices as shown in the table below. The area is about 7.2 sq

km on land, 36 cadastral units.

18282EL


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Table 1: Exploration License No: 18282EL vertex coordinates in GCS, WGS1984.

FID State Topo Sheet (sq. km) Easting Northing

1

Plateau Bashar (192) 7.2

10.275 9.2

2 10.275 9.225

3 10.3 9.225

4 10.3 9.2

At the request of BRIGO MINING COMPANY LTD (“BMCL’’), Geodel integrated

Systems Ltd (GISL) designed and conducted a preliminary exploration over

the Safiyo lead zinc prospect in Plateau State, Nigeria. GISL exploration

approach is summarised in the chart presented below:

Figure 2: GISL Lead zinc exploration program

Reconnaissance Survey

•Pre-existing data acquisition and processing- Airborne Magnetic data

•Preliminary ground truthing

•Laboratory analysis of random samples from mined pits

•Choice of survey area (1 km by 1 km)

Electromagnetic Survey

•Survey planning

•Profile cutting

•Frequency domain electromagnetic survey

EM Data Processing and Presentation

•Stacking and Plotting of the EM responses at five frequencies

•Conductivity mapping

•Geological interpretation

IP survey

•Acquisition of Time domain polarization data over the interpreted electromagnetic anomalies

•IP data processing , plotting and interpretation

•Suitable Drill target selection


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Figure 3: Survey layout and details of exploration license 18282EL

2.0 Reconnaissance Survey

The exploration program commenced with the acquisition and processing of

the existing airborne magnetic data, in order to understand regional trend of

subsurface magnetic structures and lineament patterns of the area. The

airborne magnetic data was acquired at 500 m line spacing and 200 m flight

height. The total magnetic intensity field was acquired and it is mostly

dominated by long wavelength, which indicates that most magnetic sources

in the area are deep seated. Magnetic data enhancement techniques were

used to amplify the short wavelength, to reflect the near surface lineaments.

Both directional and normalised derivatives were computed- first and second

vertical derivative, tilt angle, horizontal gradient and analytical signal.

In all the computed magnetic derivatives, the dominant trend of magnetic

lineament is north-northeast (NNE), with a northwest (NW) fault pattern. 1 km

by 1 km area (in red box) was selected based on the interpreted subsurface


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magnetic lineament patterns. Thus, subsequent exploration was conducted

investigation was conducted within the selected pilot area.

Figure 3: The computed second vertical derivative of the total magnetic field

over the 18282 EL. The red square box is the 1 km by 1 km area selected for

the pilot study.

In October 15-17, 2014, a preliminary ground truthing was conducted at the

project site, to i) assess the viability of the exploration license areas for lead-

zinc and other sulfide mineralisations ii) define the host rocks, mineralization

styles and dominant trend of mineralization iii) obtain and analyze some

selected samples from the sites, and iv) design a systematic mineral

exploration procedure for lead and other associated metallic mineralization.

During this three day exercise, it was observed that the area is a sedimentary

basin (Benue Trough) and there were no much rock exposures, except along

river channel road cut and mined pits. Visit was paid to a local mining site,


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few kilometers to the east of the project area to study the subsurface

geology and obtain samples for analysis.

Figure 4: The sedimentary sequences at the site are made up of alternating

sandstone, siltstone and mudstone. It was observed at the pit site that the

disseminated and patchy lead-zinc mineralisation is hosted within the

sandstone units of about 1m thickness as shown in the picture.


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Figure 4b: Reconnaissance Magnetic map showing all the BMCL lead

prospects, locations of the mined pits (Figure 4a) and the 1km by 1 km

selected for the pilot exploration.

3.0 Electromagnetic Survey procedure

In November 2014, GISL planned and conducted an electromagnetic survey

(EM) over a 1 km by 1 km area within the 18282 EL, to delineate conductive

locations and structures, that might be related or controlling the lead zinc

mineralisations within the area. The survey was undertaken with APEX MaxMin

horizontal loop electromagnetic equipment at a loop separation of 100 m

and 50 m respectively (Figure 6). Multiple and parallel EM conductors were

interpreted cumulating to about 2,780 meter length of conductors from the

five frequencies EM survey data.


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Figure 5: Horizontal loop EM survey design in NW direction across the

dominant magnetic trend.

Figure 6: HLEM data acquisiton along the survey line with MaxMin transmitter and

receiver.


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EM Data presentation and interpretation

The horizontal co-planar loop EM data of each line are presented in stacked

profile plans of the inphase and quadrature components for each frequency and

coil separation.

The quadrature is largely unaffected by the coil separation and orientation errors,

and does respond better to very poor conductors. These two facts have proven

very useful in the evaluating and outlining of the weak to moderately high

conductors at the project site as described below.

Figure 7: EM interpretation along one of the survey profiles.

Plot of successive survey line data in figures below, highlights the continuity of

conductors across profiles at the subsurface.


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Figure 8: the stacked sections of the Northern sections.


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Figure 9: the stacked section of the southern profiles.

Plot of successive survey line data in figures below, highlights the continuity of

conductors across profiles at the subsurface. The total cumulative length of

the interpreted conductors is about 2.6 km as shown in the table below:


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Figure10: Conductivity mapping and estimation of length of the conductors.

The quadrature responses at the 222 Hz and 444 Hz frequencies were gridded

at one meter interval using the kriging method, to help understand the spatial

distribution and continuity of the Interpreted conductive structures at the

subsurface.

The black and yellow lineaments and patterns are the low / negative

quadrature responses, which represent the locations of conductors that will

be further investigated and explained.


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Figure 11: Gridded map of the quadrature response at frequency 222 Hz

The quadrature responses at the 444 Hz frequency were plotted on the

processed magnetic derivative. This was undertaken to highlight the

correlation between the Interpreted conductors and the magnetic

lineaments locations.

In the second derivative of the magnetic field, the inflection point between

the highs (pink) and low (blue) are the locations of the magnetic source,

while low/negative response in the HLEM data represents locations of

conductors. Locations favorable for these two interpretative indexes have

been delineated by red and green broken lines at different level of

confidence. The locations delineated with red lines are linear conductors

coinciding with locations of magnetic lineaments, while the greens are

conductive locations that fall within the corridor of a magnetic lineament.


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Figure12: EM and Magnetic data integration.

4.0 INDUCED POLARIZATION SURVEY

As a follow up to the geophysical electromagnetic survey, Time Domain

Induced Polarization (TDIP) survey was conducted for BRIGO MINING

COMPANY LTD (BMCL), across the interpreted electromagnetic anomalies.

The ground geophysical survey was conducted by GISL crew during the

months of February and March in 2015. The acquired IP data were processed

and plotted to generate 2-D pseudosections showing the variation of the IP

chargeability, resistivity and the metal factor coefficient computed by

dividing the duo.

Time domain, IP data were collected along the EM profiles using GDD 5000

watt transmitter and 16-channel receiver figure 13 and 14. The setup utilized

pole-dipole array, conductor cables, two steel current electrodes and eight


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non-polarizable copper sulphate electrode pots spaced at 20 m apart, while

the first current electrode was always put at infinity (~five times the spacing).

The current was injected with a 2 seconds on and 2 seconds off duty cycle

into the ground via a 5000 watt transmitter (Tx), while the receiver measures

the decay of the primary voltage. 50 readings were stacked to improve the

signal/ noise ratio.

Figure 13: Field set up of the GDD 5000 Transmitter and 16C receiver.

The IP reading for each surveying day were downloaded to a computer and

entered into a database on a daily basis. Quality control of the acquired

data was done using the Geosoft oasis Montaj IP module. Where the decay

curve and the noise level of each channel are reviewed and noisy channels

were eliminated.


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Figure 14: The IP data were acquired over the interpreted EM anomalous

bodies in the NW direction. The red points are the electrode locations along

the survey profile, at a spacing of 20 m. The background map is the EM

quadrature responses at 444 Hz, the black- yellow are the conductive zones

and structures, while the pink area are not conductive.

IP Data Presentation

1. Pseudosection

The IP chargeability and resistivity data pseudosections were plotted using

the IP module of Oasis Montaj software. The software contours the IP

chargeability values acquired at different depths and locations, and also

assign a color scale as defined by the user. The uppermost image is the IP

chargeability plot, middle is the resistivity, while the lower section is the metal

factor coefficient. This plot presents a vertical section showing the variation of

IP chargeability and conductivity of materials at the subsurface along the

survey profile.


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On the pseudosection, the high IP chargeability portions are in color pink,

while the low IP areas are in green-blue color. In the resistivity section, the low

areas are in blues, while the pink areas are the high resistive area. The metal

content coefficient enhances structures that have high IP values and low

resistivity by normalizing the IP values by the resistivity values.

Pseudosection of some of the IP profiles are presented and briefly described

below in figures 15 – 19.

Figure 15: Pseudosection Plot of Line 0. The uppermost image is the IP chargeability plot, middle is the resistivity, while the

lower section is the metal factor coefficient. The section from west to east has a dipping near-surface high IP

chargeability and resistive body from at 640400 - 640480 E along the line. Another high IP zone with relatively low

resistivity occurs from 640567E to 640632E, at about 40 m depth; three parallel west dipping high IP and high resistivity

zones occur at locations 640863E, 640959E and 641049E about 20m depth.


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Figure 16: Pseudosection plot of Line 50S. The uppermost image is the IP chargeability plot, middle is the resistivity, while

the lower section is the metal factor co-efficient. A near surface high IP and resistivity body occurs at the start of the

section; two extensive IP anomalies occur at the depth of close to 30 – 40 m, locations 640500E and 640800E along the

profile.


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Figure 17: Pseudosection plot of Line 150S. The uppermost image is the IP chargeability plot, middle is the resistivity, while

the lower section is the metal factor coefficient. Moving from west to east, the section begins with a very low v-shaped

resistive zone extending from the near surface to depth, next to it is a very high chargeability and resistive west-dipping

zone at location 640583E and 25m depth.


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Figure 18: Pseudosection plot of Line 150N. The uppermost image is the IP chargeability plot, middle is the resistivity, while

the lower section is the metal factor coefficient. Moving from east to west, a relatively high resistive and west dipping

high chargeability structures occur between 641248E and 641320 E. Other deeper high chargeability bodies occur at

locations 641055E, and 641944E at depths 60 m and 40 m respectively.


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Figure 19: Pseudosection plot of Line 250N. The uppermost image is the IP chargeability plot, middle is the resistivity, while

the lower section is the metal factor coefficient. Moving from west to east, the section begins with a high chargeability

zone at about 40 – 50 m, this has a corresponding low resistive zone.


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2. Plan maps

False color contour maps of the inverted resistivity and chargeability results are

displayed at selected depths. Line data are positioned using UTM coordinates

gathered at the survey stations during the field work. This display illustrates the

regional distribution of the geophysical trends, outlining strike orientations and

possible fault offsets. The plan maps are plotted for both resistivity and

chargeability at depth 20 m, 40 m and 60 m.

The IP chargeability at about 20 t0 30 m is very broad and irregular in shape. This

chargeability at this depth seems to be more related to the clayey – silty clay

overburden that occurs in most part of the area. They appear as conductive

and widely spread with no definite pattern (figures 20 and 21).

At a further depth of 50 to 80 m the chargeability and resistivity occur in a

definite pattern, mostly trending in the N-S and NNE directions. This is interpreted

to be due to high chargeable metals, occurring in disseminated form within a

very resistive medium in the project area. The sulfide mineralisations in this

region are mostly hosted within the sandstone formation.


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Figure 20: Plan map of the IP Chargeability at 20 m depth

Figure 21: Plan map of the Resistivity at 20 m depth.


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Figure 22: Plan map of the IP Chargeability at 50 m depth

Figure 23: Plan map of the Resistivity at 50 m depth


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Figure 24: Plan map of the IP Chargeability trend at 80 m depth

Figure 25: Plan map of the Resistivity trend at 80 m


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3. 3-D chargeability model

The series of parallel 2-D IP pseudosections were further developed into a 3-D

voxel model to show the relative continuity of the conductive and chargeable

zones across the survey area.

Fig 26: 3-D voxel model of the IP chargeability effect at about (a) 10 m (b) 50 m.

Black arrows show the trend of high IP chargeability at depth of about 50 m.


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5.0 Prospectivity Mapping

Figure 29: Prospectivity mapping of EM conductors. Three major conductors

were interpreted and labelled 1, 2 and 3. Conductor 3 appears to be multiple

linear conductors.

Figure 30: IP-RES pseudosection plot of Line 0. The interpreted EM conductive

structures correspond with high IP chargeability and resistivity bodies along the

section 1, 2 and 3. The bodies are dipping north-west at an angle of about 75 –

80 degrees. The high resistivity exhibited by this zone could be due to the

silicification of the sandstone or high silica content. These bodies could be

massive at depth at picked up by the EM data. Conductor 1 appear to occur

1 2 3


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near the surface, conductor 2 seems to be faulted, while the broad EM

response at conductor 3 is due to multiple dipping conductors as shown on the

section.

Figure 31: 3-D voxelised northeast trend exhibited by high chargeabilty structure

at the peudodepth of about 30 m.


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The IP survey further provided more information about the geometry of the EM

conductors, as well as the pseudo depth of occurrence.

Conductor ID Length (m) Description

1 830 High and narrow EM response;

coincides with magnetic lineament –

interpreted to be a shallow and NW

dipping conductor. High IP

chargeability

2 950 High and narrow EM response;

coincides with magnetic lineament –

interpreted to be shallow and NW

dipping conductor. High IP

chargeability

3 1000 Broad and low EM response; appears

to be three dipping conductive bodies

merged; partly within a magnetic

lineament corridor; interpreted to be

either a deep conductor

Total 2780 m


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6.0 Conclusion and Recommendation

We consider this survey undertaken so far, as very consistent. Interpreted EM

conductive bodies occur within the magnetic lineament corridors and have

high IP chargeability values. Therefore, we propose target testing via drilling to

be carried out on some of the interpreted conductors. Based on the false

depth, most of the prospective bodies occur further beyond 30 m depth;

therefore, target drilling should be down to 100 m depth.

Diamond core drilling method is proposed at five locations along the survey

lines as a safety net to increase the confidence level and decrease risks prior to

for resource estimation drilling. The core drills aims to basically drill prospecting

holes to test the high signature areas from the geophysical investigations to

confirm the presence or absence of mineralization and the signature responses

associated with the mineralization. It also provides crucial information about the

sub-surface to be able to take informed decisions about exploration drilling

planning.

Criteria considered for the initial target selections include i) occurrence with 500

m of the magnetic lineament corridor, ii) EM anomaly zone based on the FDEM

survey, iii) High IP chargeability zone based on the TDIP survey and

corresponding high resistivity expected from silicified sandstone or high quartz

content rocks.

Detailed geochemical sampling of the cores should be undertaken during the

test drilling to further characterize the lead-zinc and other mineralisations that

occur at the subsurface.


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7.0 STATEMENT OF QUALIFICATION

Olaniyan Oladele F.

- BSc Geology (2002), University of Ado-Ekiti, Nigeria

- MSc Geoinformatics (2007), ITC, Netherlands

- Ph.D. Exploration Geophysics, Laurentian University, Sudbury, Ontario,

Canada.

For the past 10 years, I have been actively involved in mineral exploration

projects in most part of Nigeria and other parts of the world including Canada,

and Ghana.

A member of Canadian Exploration Geophysicists Society (KEGS)

A member of Council of Nigerian Mining Engineers and Geoscientist (COMEG)

A member of Nigerian Mining and Geosciences Society (NMGS)

An associate member of the Society of Exploration Geophysicist (SEG)

Dated and signed at Sudbury, Ontario, Canada this 10th day of June, 2015.

_____ ____________

Olaniyan Oladele (Ph.D.)

Geophysical Exploration Report of 1 18282EL, Wase LGA, Plateau...

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