Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4697844 | Ore Geology Reviews | 2010 | 20 Pages |
Abstract
The field setting, mineralogical, geochemical, genetic and depositional features of Late Archean metasedimentary manganese, as well as Cenozoic supergene manganese and ferromanganese ores, along the ~Â 75Â km long linear tract of the Anmod-Bisgod region in the Western Dharwar Craton, southern India, are described. The 2700Â Ma metasedimentary manganiferous formation is underlain by stromatolitic limestone/dolomite and quartzite/arenite and also occurs within the former. The older quartzite/arenite, which contains redox-sensitive detrital pyrite and uraninite as well as thucolite, indicates sedimentation under anoxic to oxic transitional palaeoenvironmental condition, whereas the younger stromatolitic limestone/dolomite indicates development of oxygen in the depositional environment. The manganese ore types have been classified into three categories, one of which is a Mn-rich duricrust once capping the Late Archean manganiferous formation. It formed during a Cenozoic lateritic weathering event and was eroded in response to crustal uplift. Perhaps uniquely, clastic deposits of the eroded Mn-duricrust occur in mineable quantities in the form of fluvial palaeochannel fills. These cryptomelane-rich supergene ores are also suitable for radiometric dating. Knowing their age would help to constrain the timing of Mn-duricrust formation and, indirectly, the regional weathering event responsible for the extensive laterite occurrences of southern India.
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Authors
M.S. Sethumadhav, Yanni Gunnell, Mohamed Muzamil Ahmed, Chinnaiah Chinnaiah,