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http://dx.doi.org/10.9719/EEG.2021.54.2.213

Studies on the Ore Mineralogy and Litho-geochemistry of the Sheba Deposit, Barberton Greenstone Belt, South Africa  

Altigani, Mohammed Alnagashi Hassan (Department of Geology of Minerals Wealth, Faculty of Petroleum and Minerals, Alneelain University)
Publication Information
Economic and Environmental Geology / v.54, no.2, 2021 , pp. 213-232 More about this Journal
Abstract
Ore criteria at the Sheba Deposit indicate orogenic mineralization type. Rocks and mineral assemblages suggest low formation-temperature of green-schist facies. Pyrite found in two generations; Type1 is irregular grains, contains higher arsenic and gold contents, compared to the relatively younger phase Type2 pyrite, which is composed of euhedral grains, found adjacent to late quartz-carbonate veins or at rims of type1 pyrite. Two gold generations were identified; type1 found included in sulphides (mainly pyrite). The second gold type was remobilized (secondary) into free-lodes within silicates (mainly quartz). Gold fineness is high, as gold contains up to 95 wt. % Au, Ag up to 3.5 wt. %, and traces of Cu, Ni, and Fe. Pyrite type2 contains tiny mineral domains (rich in Al, Mn, Hg, Se, Ti, V, and Cr). Zoning, and replacement textures are common, suggesting multiple mineralization stages. The distribution and relationships of trace elements in pyrite type2 indicate three formation patterns: (1) Al, Mn, Hg, Se, Ti, V, Cr, and Sn are homogeneously distributed in pyrite, reflecting a synchronous formation. (2) As, Ni, Co, Zn, and Sb display heterogeneous distribution pattern in pyrite, which may indicate post-formation existence due to other activities. (3) Au and Ag show both distribution patterns within pyrite, suggesting that gold is found both in microscopic phases and as chemically bounded phase.
Keywords
Sheba; pyrite mapping; zoning; LA-ICP-MS; EMP;
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