Oxygen Fugacity and Water Activity during Thermal Peak and Retrogression of Granulites around the Sarvapuram Area, Karimnagar Granulite Terrane, Andhra Pradesh, India
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This work has been possible through a Post – Doctoral Fellowship (Indian Institute of Technology, Bombay) and UGC–RFSMS fellowship (Banaras Hindu University) to PCS. We are thankful to the Late Prof. R.K. Lal for his motivational guidance to think this way. We thank two anonymous reviewers for their valuable comments and suggestions, which upgraded significantly a previous draft of the manuscript. Dr. Lian Liu is thanked for his editorial efforts.

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    Abstract:

    The investigated area around Sarvapuram represents a part of the Karimnagar granulite terrane of the Eastern Dharwar Craton, India. Garnet–bearing gneiss is hosted as enclaves, pods within granite gneiss and charnockite. It is largely made up of garnet, orthopyroxene, cordierite, biotite, plagioclase, K–feldspar, sillimanite and quartz. The peak metamorphic stage is represented by the equilibrium mineral assemblage i.e. garnet, orthopyroxene, cordierite, biotite, plagioclase, sillimanite and quartz. Breakdown of the garnet as well as preservation of the orthopyroxene–cordierite symplectite, formation of cordierite with the consumption of the garnet + sillimanite + quartz represents the decompressional event. The thermobarometric calculations suggest a retrograde P–T path with a substantial decompression of c. 3.0 kbar. The water activity (XH2O) conditions obtained with the winTWQ program for core and symplectite compositions from garnet–bearing gneiss are 0.07–0.14 and 0.11–0.16 respectively. The quantitative estimation of oxygen fugacity in garnet–bearing gneiss reveal log fO2 values ranging from ?11.38 to ?14.05. This high oxidation state could be one of the reasons that account for the absence of graphite in these rocks.

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P. Chandra SINGH, D. PRAKASH.2019. Oxygen Fugacity and Water Activity during Thermal Peak and Retrogression of Granulites around the Sarvapuram Area, Karimnagar Granulite Terrane, Andhra Pradesh, India[J]. Acta Geologica Sinica(),93(6):1900-1908

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History
  • Received:August 30,2018
  • Revised:December 05,2018
  • Adopted:
  • Online: December 24,2019
  • Published: