Gold, base metals, and diamonds in Botswana

Abstract

The geological framework of Botswana includes cratonic regions comprising parts of ancient stable blocks of Archean metamorphosed rocks, mobile regions which have suffered tectonism at various periods during the Proterozoic, and platform regions on which unmetamorphosed Proterozoic and Phanerozoic sedimentary and volcanic rocks have been preserved. Superficial deposits mantle much of the country, rendering mineral exploration unusually difficult.Gold is confined mainly to the Archean greenstone belts of the Rhodesian Craton. Many abandoned mines in the Tati have recently been reassessed; a few occurrences may have some potential but most are subeconomic.Base metal mineralization is becoming increasingly significant in the economic outlook of the country. Major nickel-copper sulfide orebodies, with reserves of over 30 X 10 6 metric tons, have been proved at Pikwe and Selebi within the Limpopo mobile belt. Two medium-sized nickel-copper deposits are known in the Tati belt. Important copper occurrences in calcareous metasediments within the Matsitama schist belt on the margin of the Rhodesian Craton are being reinvestigated, and extensive stratiform copper mineralization has been delineated in the Damaran mobile of northwestern Botswana. The geological environment of the latter is similar to that of the Zambian Copperbelt, but exploration is not yet sufficiently advanced to have proved a viable orebody.Banded iron-formations occur principally in the belts and as part of the sedimentary succession in the platform regions, but none is currently of economic interest. Minor manganese deposits are also associated with the platform sequence overlying the Kaapvaal Craton and Limpopo belt.Kimberlites appear to be restricted to two distinct regions. The Orapa kimberlite district in central Botswana contains 30 known pipes, including the Orapa diamond mine, and at least two other economic occurrences. A group of four concealed kimberlites and other isolated pipes have been detected in southern Botswana.The metallogenic evolution of the various mineral districts is discussed and it is concluded that the potential for further discoveries in Botswana is good.