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Two morphologies of pyrophanite in Mn-rich assemblages, Gangpur Group, India

Published online by Cambridge University Press:  05 July 2018

B. R. Nayak  and
B. K. Mohapatra
B. R. Nayak
Affiliation:
Regional Research Laboratory, Bhubaneswar - 751 013, Orissa, India
B. K. Mohapatra
Affiliation:
Regional Research Laboratory, Bhubaneswar - 751 013, Orissa, India
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Abstract

Pyrophanite is widely distributed in metamorphic Mn-rich rock assemblages of the Gangpur Group, India. It occurs in two distinct habits: as an independent phase, and as an exsolved phase within hematite. The well developed large sized crystals coexist with spessartine in Mn-silicate facies rocks. In contrast, the exsolved crystals occur as fine needle/bleb-like crystallites intergrown with hematite in Mn-silicate-oxide facies rocks. Compositionally the exsolved crystals are enriched in iron, present in both the ferric and ferrous states. The two morphologies of pyrophanite attest to their formation under different environmental conditions. The independent pyrophanite is formed from a Mn-Ti rich precursor under low oxygen fugacity conditions while the hematite-pyrophanite intergrowth evolved from an Fe-Mn-Ti rich precursor under higher fO2 conditions.

Keywords

pyrophanitemanganese depositshematiteGangpur GroupIndia
Type
Research Article
Information
Mineralogical Magazine , Volume 62 , Issue 6 , December 1998 , pp. 847 - 856
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1998

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