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CCOOPPPPEERR MMIINNEERRAALLIISSAATTIIOONN IINN NNOORRTTHH WWEESSTTEERRNN ZZAAMMBBIIAA

The copper mineralisation of North Western Zambia, where the Kasempa property is

located was formed 600 million years ago, when that part of the world was a sea.

The copper, cobalt and nickel which was present in the sea water, was precipitated

as a mud by bacteria. The bacteria common at the time was desulfovibrio vulgaris

and desulfovibrio nigrificans, Figure 1.

Figure 1: Desulfovibrio bacteria, responsible for precipitating copper from sea

water 600 million year ago in North Western Zambia

That metal rich mud was later metamorphosed to rock over eons, Figure 2.

Figure 2: Sediments metamorphosed into rocks, with time

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Figure 3: Copper sulphide mineral formed following metamorphosis of the

copper rich mud

The sulphide minerals formed, suffered intense weathering in the subsequent

millions of years, turning them into oxides, Figure 4. Very often, the copper went into

solution and was precipitated later, often when the copper rich solution contacted the

water table, this precipitation led to an enriched zone, called the supergene enriched

zone.

It is customary, in 8 out of 10 cases, that sulphides are usually found below theoxidised, or supergene enriched zone. Only deep drilling can confirm this.

Figure 4: Copper rich mud, metamorphosed into copper minerals, then

oxidised into malachite

This part of Zambia never suffered mountain building as the Zambian Copperbelt; as

a result, the ore deposits are flat, uniform and widespread. The repercussions of thisphenomenon are that mining will be relatively easy, and the deposits will be large.

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To mine a deposit of this nature, it is recommended that the overburden (waste)

stripped to expose the ore, be taken as far as possible. This is to be done so as not

to sterilise good ground which will contain copper below and will need to be mined. If

a valley can be located, such terrain is ideal for storage of overburden, as the

ensuing footprint will usually be small. The spinoff of this method of storingoverburden is that permitting from the environmental council will be easier.

A bankable feasibility study will be needed if the venture will expand beyond the

realms of small scale mining. To prepare such a document, the extent of the

orebody will need to be delineated. Delineation will entail drilling to establish the

thickness and grade of the ore. Drilling, Figure 5, can be accomplished by

recirculation drilling (RC), or diamond drilling. Both have the ability to provide ore

samples for chemical analysis, Figures 6 and 7.

Often, intricate geostatistical calculations are carried out to improve the confidence

level of the calculations. These days, spreadsheets are available to carry out such

calculations. Normally a confidence level of 95% is the accepted norm by banking

institutions.

Figure 5: Drilling machine at the Trident deposit in that part of Zambia

Figure 6: Drill chips from recirculation drilling at the Sentinel ore deposit in

Kabompo in North West Zambia

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Figure 7: Drill cores from diamond drilling, note bands indicating that the

sediments were deposited in layers, before being metamorphosed into rock

Drilling is an expensive exercise. In that part of Zambia, recirculation drilling costs

$85 per metre while diamond drilling costs $150 per metre. Diamond drilling is more

definitive, as shown in Figure 7, as the cores can show the actual extent of the

orebody. This is more convincing from an investors point of view. In addition, cores

can also be an essential part of the mine planning process as they can indicate the

geotechnical conditions to be expected. They can also be used in designing themilling circuit in the processing plant.

Ramoutar Seecharran MSc(Eng), CEng, REng

Mining Consultant