Mineralogy, chemistry and genesis of Nishikhal manganese ores of South Orissa, India |
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Authors: | B C Acharya D S Rao R K Sahoo |
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Institution: | (1) Regional Research Laboratory (CSIR) Bhubaneswar-751 013, India, IN |
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Abstract: | Manganese ores of Nishikhal occur as distinctly conformable bands in the khondalite suite of rocks belonging to the Precambrian
Eastern Ghats complex of south Orissa, India. Manganese minerals recorded are cryptomelane, romanechite, pyrolusite, with
minor amounts of jacobsite, hausmannite, braunite, lithiophorite, birnessite and pyrophanite. Goethite, graphite, hematite
and magnetite are the other opaque minerals and quartz, orthoclase, garnet, kaolinite, apatite, collophane, fibrolite, zircon,
biotite and muscovite are the gangue minerals associated with these ores. The mineral chemistry of some of the phases, as
well as the modes of association of phosphorous in these ores have been established. The occurrence of well-defined bands
of manganese ore; co-folding of manganese ore bands and associated metasedimentary country rocks; the min-eral assemblage
of spessartite-sillimanite-braunite-jacobsite-hausmannite; the geochemical association of Mn-Ba-Co-Ni-Zn together with the
Si versus Al and Na versus Mg plots of the manganese ores suggest that the Nishikhal deposit is a metamorphosed Precambrian
lacustrine deposit. Continental weathering appears to be the source for manganese and iron. After deposition and probable
diagenesis, the manganese-rich sediments were metamorphosed along with conformable psammitic and pelitic sediments under granulite
facies conditions, and subsequently underwent supergene enrichment to produce the present deposit.
Received: 14 March 1995 / Accepted: 11 April 1996 |
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