The Supergene Mn-minerals in Gangpur Group, Eastern India and their Genesis

Manganese mineralization in the Precambrian Gangpur Group of rocks in Sundargarh district of Odisha occur as pockets or small ore bodies associated with metapelites and metapsamites. Different varieties of hypogene metamorphic manganese minerals belonging to Mn-oxides, Mn-carbonates, Mn-silicates, M...

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Bibliographic Details
Published in:Journal of the Geological Society of India 2020-10, Vol.96 (4), p.337-348
Main Authors: Dash, Nilima, Nayak, Bibhuranjan, Mohapatra, Birendra Kumar
Format: Article
Language:English
Subjects:
Carbonates
Chemical precipitation
Diagenesis
Earth and Environmental Science
Earth Sciences
Evolution & development
Geology
Hydrogeology
Iron
Low temperature
Manganese
Manganese minerals
Manganites
Metamorphism
Mineralization
Minerals
Ores
Oxidation
Oxides
Precambrian
Precipitates
Pyrolusite
Rock
Rocks
Sepiolite
Silicates
Titanates
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Summary:Manganese mineralization in the Precambrian Gangpur Group of rocks in Sundargarh district of Odisha occur as pockets or small ore bodies associated with metapelites and metapsamites. Different varieties of hypogene metamorphic manganese minerals belonging to Mn-oxides, Mn-carbonates, Mn-silicates, Mn-titanates have been reported from this Group. Although the Mn-bearing rocks and the Mn-ores host several supergene Mn-minerals, no detailed and comprehensive study on these minerals has been carried out so far. The present paper describes the microstructural and microchemical characteristics of the supergene Mn-minerals viz., vernadite, manganite, cryptomelane, romanechite, Fe-Mn sepiolite, nsutite, pyrolusite, and lithiophorite with a view to establish their paragenetic sequence and genetic evolution. These minerals have formed due to solution-remobilization-precipitation, oxidation and/or hydration, diagenesis and as a product of direct alteration. It is inferred that only one variety of manganite is formed due to retrograde metamorphism. While vernadite, cryptomelane and romanechite precipitated from Mn-rich solutions at low temperatures, Fe-Mn sepiolite formed as a direct alteration product of tephroite. Manganite and nsutite formed both as solution-precipitates as well as oxidation products of other Mn-minerals. While further oxidation leads to the formation of pyrolusite at a later stage, lithiophorite is the last mineral to form during weathering and lateritization.
ISSN:0016-7622
0974-6889
DOI:10.1007/s12594-020-1562-5