- GeoRef, Copyright 2004, American Geological Institute.
The origin of the giant manganese deposits of the Kalahari manganese field has been highly contentious for many years. Proposed models cover a diverse spectrum of genetic processes, from large-scale epigenetic replacement mechanisms, to submarine volcanogenic-exhalative activity, to purely chemical sedimentation whereby the influence of volcanism is of reduced significance. In this paper, attention is drawn to the potential metallogenic importance of glacial processes occurring prior to the development of the Kalahari deposits, as manifested by the occurrence of an older diamictite unit (Makganyene Formation). Hence, the "snow-ball earth" scenario as proposed for Neoproterozoic Fe-Mn formations may provide an attractive explanation for the required levels of dissolved Mn in the anoxic parts of the Kalahari palaeodepository. However, the primary source of Mn, the processes leading to the characteristic cyclic development of iron formation and Mn sediment, and the likely influence of a postulated sudden oxygenation during, or prior to, the deposition of the Kalahari ores, are aspects of a long-standing enigma that still await resolution.