The Areachap Group represents a mid-Proterozoic fossil island arc environment consisting of amphibolite, hornblende gneiss, quartz-feldspathic gneiss, calcsilicates and pelitic schists. Chemical compositions of these highly deformed upper amphibolite/granulite grade metamorphosed rocks indicate protoliths ranging from rhyolite/rhyodacite, calc-alkaline basalt, tholeiite to ultramafic igneous rocks and sediments. The above-mentioned assemblage is typical of an island arc environment. Island arc environments are ideal hosts for volcanic hosted massive sulphide (VHMS) type deposits and may successfully be explored by using the VHMS lithogeochemical alteration model. VHMS deposits not only yield strategic base metals such as zinc (Zn), copper (Cu) and lead (Pb), but significant grades of gold (Au) and silver (Ag) are associated with these deposits. The Areachap Group presents a metallogenic province containing one economic deposit, the Prieska Zn-Cu mine, as well as several sub-economic deposits, including the Areachap mine and other lesser prospects at Boksputs, Kantienpan, Jacomynspan and Rokoptel. The Prieska Zn-Cu mine is the most significant VHMS deposit of the Areachap Group and occurs within the Copperton volcanic centre. This abandoned mine delivered 47 Mt sulphide ore at 1,7 % Cu and 3,8 % Zn with traces of Ag and Au. Four volcanic centres were previously identified in the Areachap Group, namely Upington, Klein Begin, Boksputs and Copperton. Exploration activities were loosely subdivided into the same regions. Regional lithogeochemical sampling campaigns were conducted for the four subproject areas and approximately 5 000 rock samples were analysed for the twelve major oxides and ten trace elements. The region of interest, the Boksputs Subvolcanic area, with a well-established infrastructure, is situated near Groblershoop (50 km east) and Marydale (30 km southeast) in the Northern Cape province and is part of the geological Areachap Group. Several high copper anomalies and the tholeiitic lithological composition of the Boksputs Subproject resulted in this area being selected as the main target region. It was attempted to discriminate between different trace element populations using probability plots, but this was not successful. The complexity of the probability plots was attributed to the large variation in different rock types included in the data set. Corrections were made by determining threshold values for each rock type, but this refinement proved unsuccessful, indicating that the rock classification used was incorrect. Option areas were finally selected, based primarily on absolute Cu values. These areas were mapped in . more detail prior to ground electromagnetic (EM) surveys and drilling. To test the target selection, a proto-lithological map of the area, based on cluster analyses of the lithogeochemical dataset, was drawn. The proto-lithological maps formed the basis of the follow-up work and the application of the VHMS conceptual model. A conductor in the Kantienpan target area was located with a time domain electromagnetic (TDEM) survey and this was drilled. The drilling intersected a massive sulphide body with a tonnage of approximately 5 Mt and an average grade of 4.09 % Zn, 0.49 % Cu and traces of Au and Ag. The orebody was evaluated financially and it was found to be uneconomic as a stand-alone operation. However, if the Kantienpan deposit is considered as an alternative to imported concentrate for the Zincor smelter, this study suggests that the project may be economically feasible. Furthermore, it must be stated that the Areachap Group remains only partly explored and that a world class VHMS deposit may be discovered within the next few years. / Dissertation (MSc)--University of Pretoria, 2008. / Geology / unrestricted

Unconformity-type uranium deposits from the Athabasca Basin are considered to be the result of mixing between oxidized basinal brines and basement-derived reduced fluids/gases, and/or reduced basement rocks. Graphite and/or its breakdown products are suggested to be responsible for uranium mineralization by acting as a reductant that could trigger deposition of uranium. Also, graphite is considered to be indicative of basement structures; being often concentrated along structures which can be identified as electromagnetic (EM) conductors. Thus, exploration for uranium deposits is often focused on the search for EM conductors. Underlying the sedimentary rocks of the basin in the Dufferin Lake zone are variably graphitic pelitic schists (VGPS); altered to chlorite and hematite (Red/Green Zone: RGZ), and locally bleached equivalents near the unconformity during paleoweathering or later fluid interactions. These altered zones are texturally similar rocks within “graphite-depleted zones” as the unconformity is approached. Both zones are characterized by a lower concentration of carbon and sulfur, with the bleached zone showing higher concentrations of uranium and boron, the latter corresponding to high dravite content. The major element composition of the graphite-bearing pelitic schists and altered equivalents (RGZ) are similar. Raman analyses indicate that well-ordered carbon species (graphite to semi-graphite) are present in the pelitic schists, with both types more common within shear zones. In contrast, only rare low-ordered carbon species (carbonaceous matter) were detected in the graphite-depleted samples within the RGZ. This variation is interpreted to be the result of graphite consumption by oxidizing fluids migrating downward from the Athabasca Group. This graphite consumption may have resulted in the production of a mobile reductant (gas or fluid), which may have played a subsequent role in the deposition of uranium mineralization. Secondary fluid inclusions (FI) examined in different quartz vein generations using microthermometry and Raman analysis, provide an indication of the fluids that have interacted with these rocks. Monophase vapor are the dominant type of fluid inclusions in the VGPS, whereas aqueous two-phase (L+V) and three-phase (L+V+Halite) FI occur in the RGZ. CH4-dominant and N2-dominant FI identified using Raman could be the result of fluid(s) interaction with the graphitic lithologies. This would have generated the breakdown of graphite to CH4 and associated feldspars/micas to NH4/N2. CH4, N2 and H2 (resulting from the decomposition of NH4+) represent possible reductants of uranium-bearing brines. Two brines in the RGZ: a regional basinal fluid and an evolved fluid possibly related to U mineralization; similar to other nearby deposits, are observed. These suggest that the basinal brines have circulated in the basement rocks and have been able to evolve by interaction with the basement rocks to possibly be related to uranium mineralization.

The study area comprises the Archaean Manica Greenstone Belt and the Vumba Granite Gneiss, the Proterozoic Messica Granite Gneiss of the Zimbabwe Craton, the possibly allochthonous metasedimentary sequence of the Frontier Formation, the granitoids of the Mozambique Metamorphic Province, which are subdivided into Vanduzi Migmatite Gneiss, the Chimoio Granodiorite Gneiss, the Nhansipfe Granitic Orthogneiss and the Pan-African Tchinhadzandze Granodiorite Gneiss. The rock sequences in the two provinces are cut by mafic intrusions. The greenstone belt comprises mafic to ultramafic and pelitic schists and serpentinites of the Macequece Formation and metasediments ofthe M'BezaNengo Formation. The mafic to ultramafic schists and the serpentinites have chemical signatures of komatiites. The Vumba Granite Gneiss comprises the northern and southern Vumba granitoids dated at 3885±255 Ma, and 2527±632 Ma respectively. They vary from metaluminous to peraluminous, have normative QAP compositions of granodiorites and monzogranites and chemical signatures of mantle fractionates and volcanic-arc granitoids. The Early Proterozoic Messica Granite Gneiss is 2348±267 Ma old, is metaluminous and has QAP compositions of monzogranites and chemical signatures suggesting a crustal source and a volcanic-arc environment. The Frontier Formation comprises quartzite and pelitic schists. The Vanduzi Migmatite Gneiss comprises stromatic and stictolithic types. Two mineral assemblages are distinguished as they contain either garnet or hornblende. The Mid-Proterozoic Chimoio Granodioritic Gneiss is 1236±201 Ma old. It is granodioritic and metaluminous with a chemical signature of volcanic-arc granitoids. The Late Proterozoic Nhansipfe Granitic Orthogneiss is dated at 981 ±83 Ma and varies from metaluminous to peraluminous. The Rb, Nb and Y contents are typical of within-plate granitoids, whereas Ga, Zr, AI, Ce andY are typical of A-type granitoids. The age of the mafic intrusions falls between ~500 and ~11 00 Ma. The rocks typically contain plagioclase, hornblende and clinopyroxene with or without garnet and orthopyroxene. The chemistry of the rocks is typical of sub-alkaline tholeiites. The Tchinhadzandze Granodiorite Gneiss may be part of a Pan African event which lasted till ~450-~500 Ma. The normative feldspar compositions and Rb, Ba and Sr contents are typical of granodiorites. It is metaluminous and has Rb, Y and Nb contents typical of volcanic arc granitoids. The planar fabrics in the Archaean granite-greenstone belt are characterized by E-W to SW-NE strikes and steep dips to N and S and to NW and SE. The mineral lineations and fold axes plunge 60° and 30° respectively towards the E. Within the Mozambique belt, around the central part and in the extreme east of the study area, the planar fabrics have essentially N-S strikes and steep dips to E and Win contrast with complex deformation observed in the migmatites and megacrystic granitoids. The study area can be subdivided into three metamorphic blocks, namely, one of low-grade greenschist facies, one of medium-grade amphibolite facies and a third block of high-grade metamorphism. / Dissertation (MSc)--University of Pretoria, 2012. / Geology / unrestricted