Gold
The great majority of gold deposits in Zambia are mesothermal
lode deposits (veins and more dispersed occurrences in brittle
and brittle-ductile shear zones). Most are localized within structures
related to the Mwembeshi Shear Zone in central Zambia. This major
inter-cratonic shear zone was undoubtedly trans-crustal in vertical
extent and clearly acted as an important conduit for fluid flow
and magma emplacement.
It also exhibits a history of multiple reactivation throughout
the Lomamian and Lufilian (Pan-African) Orogenies (c. 950-450
Ma) and was even reactivated during Karoo rifting. Consequently
there was considerable potential for the genesis of substantial
lode deposits, particularly where dilational zones (releasing
bends, dilatational jogs, etc.) facilitated maximum fluid flow,
and where the shear zone traversed the carbonate rocks, carbonaceous
siltstones, and ironstones of the lower Katanga sequence which
would have proved highly efficient chemical traps for hydrothermal
gold. Significant skarn and breccia deposits were probably developed
adjacent to syntectonic granitoidal and even syenitic intrusions
associated with the shear zone although to date only relatively
small occurrences have been identified in the Mumbwa area around
the Hook Granite Complex and satellitic intrusions.
A similar prospectivity can be assigned to the poorly-known Kapiri
Mposhi - Kipushi Shear Zone and adjacent NNE-trending zones of
deformation.
In eastern Zambia, key targets related to the Mwembeshi Shear Zone include areas where it traverses the restricted occurrences of volcanosedimentary rocks (eg. Sasare area) and also the offset zones related to the West Mvuye and Chindeni Dislocations, the former appearing to have been a focus for fluid flow (and wallrock alteration) and the latter as it also traverses mafic volcanic rocks.
Within the Zambezi Belt south of the Mwembeshi Shear Zone, thrusting and faulting of the complex Basement-Muva-Katanga terrain was accompanied by widespread de-watering, resulting in the genesis of a considerable number of gold prospects, screening of which could pinpoint optimum potential in terms of host structure and country rocks. Similar and probably more substantial fluid flow occurred within the early Lufilian thrust zones of the Domes Region of north-western Zambia to generate complex copper ± gold ± uranium lodes within the lower Katanga sequences and these represent important exploration targets.
In north-eastern Zambia a similar lode-gold potential, not yet investigated, exists within the Luongo Fold and Thrust Zone, the Chambeshi Fold and Thrust Zone, and the Shiva Ngandu Fold Zone, where leaching of Basement rocks and de-watering, quite possibly on a massive scale during the Irumide-age crustal shortening, could have created conditions favourable for gold metallogenesis. The minor occurrences of palaeoplacer gold within the lower Mporokoso Group littoral sediments of the Bangweulu Block have some similarities to Witwatersrand-type mineralization and merit a basin-wide evaluation.
Vein and disseminated chalcopyrite in quartzite
Copper
Combined reserves and resources of copper-cobalt ore in operating
mines of the Copperbelt exceed two billion tonnes and these have
mostly been delineated for exploitation after privatization of
the industry has been completed. Somewhat similar styles of copper
mineralization, variously containing gold, uranium, and cobalt,
are evident in the Domes Region to the west of the Copperbelt
and are attractive exploration targets. Recognition that a number
of these deposits are hosted by thrust zones, however, offers
greater opportunities for locating deposits at higher elevations
within the Katanga sequence than normally anticipated. Precious-metal
enrichment is also more probable in such zones, and manto-type
copper-gold deposits may be developed in adjacent carbonate and
shale units. Recognition of thrust-hosted copper mineralization
also encourages critical evaluation of the established synsedimentary
or syndiagenetic model for the Copperbelt mineralization in the
search for new deposits. Widespread scapolitization of the Katanga
sequence in the Domes Region attests to another phase of hydrothermal
activity, involving NaCl-brines probably derived by dissolution
of evaporites, and the occurrence of copper enrichment (0.8%)
in scapolite-schists in the Mujimbeji prospects of the Kabompo
Dome indicates yet another potential type of exploration target.
Vein, breccia, and skarn deposits of copper are likely to be developed in any area where the copper-rich lower Katanga succession has been overprinted by faulting or intruded by felsic to mafic bodies, features particularly evident in central and western Zambia. The regional coincidence of evaporites (n the Lower Roan), granitic intrusions, widespread scapolitic alteration, and Cu (Fe)-Co-Au-U mineralization also offer the intriguing possibility for the occurrence of deposits belonging to the enigmatic Fe-oxide (REE-Cu-Au-U) spectrum of deposit-types which includes, amongst many other, Olympic Dam. The granitic association of copper in the Irumide Belt near Mkushi also merits a careful re-evaluation of the genesis and potential of this style of mineralization. Copper-bearing massive sulphide deposits of possible exhalative origin discovered in the Lusaka area and south-eastern Zambia point to additional targets for copper exploration.
Other Base Metals and Rare Metals
Zinc and lead deposits discovered to date are hosted entirely
by carbonate rocks occurring stratigraphically at the Lower Roan
- Upper Roan transition. Considerable potential remains in the
Kabwe area, and the Katanga-age carbonate sequences northwest
of Mumbwa offer a similar potential. The migration of NaCl-rich
brines, indicated by the distribution of scapolite in north-western
Zambia, could have led to extensive mobilization of Pb and Zn
and the subsequent genesis of vein and replacement deposits in
lower-Katanga carbonate rocks and even in overlying Kundelungu
carbonate units. The common occurrence of vein and replacement
deposits of barite within the early Proterozoic sequences of
the Bangweulu Block, where caught up in the Luongo Fold and Thrust
Zone, also suggest the activity of NaCl-enriched brines and thus
imply that conditions heretoo may have been favourable for the
transport and precipitation of Pb and Zn.
Substantial resources of iron have been identified, mostly in lower Katanga successions, and the requirement here is for thorough evaluation of known deposits within the context of potential demand from a burgeoning Zambian industrial and manufacturing sector and a wider demand throughout central Africa. Manganese occurrences also are known but there is potential for the discovery of further supergene-enriched deposits throughout the Muva terrains of northern Zambia.
No major layered intrusions have been identified in Zambia but the mostly likely hosts for orthomagmatic nickel deposits are gabbroic intrusions south and east of Lusaka and the possible faulted extensions of the Great Dyke near Mpala Gorge in the southern part of the country. Some of the sediment-hosted occurrences of metal associated with gabbroic bodies in north-western Zambia also have modest potential.
The tin (-tantalum) potential lies in a thorough re-evaluation of the Choma Tin Belt in southern Zambia and in detailed prospecting of the pegmatitic areas of eastern Zambia. The Hook Granite Complex and granitic bodies intruding the Irumide Belt merit some attention for tin and/or tungsten mineralization and the unusual scheelite-bismuth mineralization of the Unda Unda area, 80 km east of Lusaka, would be a priority for tungsten exploration. Syntectonic and post-tectonic granitic magmatism associated with the Irumide Orogeny in north-eastern Zambia may have led to tin and tungsten enrichment in the Chambeshi Fold and Thrust Zone and Shiwa Ngandu Fold Zone.
Diamonds
The abundance of diamonds and indicator minerals in Zambia highlight
the considerable exploration potential. The most favourable terrains
are the stable cratonic Bangweulu Block and possibly the Kabompo
area of western Zambia where alluvial diamonds are particularly
abundant. The rift-related kimberlites and associated rocks of
eastern Zambia have limited potential as they were probably derived
from younger, locally diamond-depleted, mantle.
Emeralds
Systematic exploration of the Ndola Rural area utilizing a combination
of radiometric surveys and soil geochemistry, supported by detailed
mapping, offers considerable potential for the discovery of additional
deposits of the high-quality gemstones.
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Other Gemstones
Amethyst crystals |
Industrial Minerals
Zambia is favoured with considerable resources of feldspar (Pan-African
pegmatite bodies), silica sand (Muva-age quartzites), limestone
(mostly lower Katanga), and a variety of rock types potential
suitable for dimension stone. Numerous occurrences of ball clay
and brick clay are evident throughout the country but the quality
of the clays has rarely been thoroughly investigated. Good quality
talc has yet to be discovered but the focus of interest would
be on hydrothermally altered ultramafic rocks and on metamorphosed
dolomites in the Lusaka and Copperbelt areas. Major targets for
barite exploration would be vein and replacement deposits in
the Luongo Fold and Thrust Belt of the Bangweulu Block. Any search
for phosphate (apatite) would necessitate re-evaluation of the
carbonatite-hosted deposits associated with the Karoo-age rifts
of southern, central, and eastern Zambia. Medium- to high-grade
graphite deposits are confined to the high-grade metamorphic
terrains of eastern Zambia.
Uranium
The greatest potential for uranium appears to be vein and disseminated
mineralization hosted by Lower Roan and Upper Roan sequences
and most commonly occurring within the footwall rocks immediately
underlying some of the copper orebodies of the Copperbelt and
Domes Region. It also shows significant enrichment in the thrust-hosted
copper (± gold) mineralization of the Domes Region. Calcrete
deposits within the basal sandstones of the Kalahari sequence
in western Zambia may be analogous to the calcrete deposits of
Namibia and thus merit investigation.
Coal
Additional coal resources are most likely to be found in the
fault-bounded Karoo basins of the Mid-Zambezi Rift, particularly
in the Mulungwa Coalfield, the area between the Mulungwa and
Siankondobo Coalfields, and in the Siambabala area. Some limited
potential also exists in the Luangwa and Luano Valleys.
Hydrocarbon
The petroleum potential of Zambia can be considered unexplored.
The Luangwa and Mid-Zambezi graben have a favourable history
of lower-Karoo hydrocarbon generation and upper-Karoo development
of structural traps during rifting. Potential reservoir units
occur in the lower-Karoo Luwumbu Formation and upper-Karoo Escarpment
Grit in the luangwa graben and in the Siankondobo and Gwembe
Formations of the lower Karoo in the Mid-Zambezi graben.