Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

U. K. Pandey ¹, Tikam Chabria ¹, P. Krishnamurthy ¹, R. Viswanathan ¹, B. Kumar ²

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Begumpet, Hyderabad - 500 016, IN
2 National Geophysical Research Institute, Hyderabad - 500 007, IN

Abstract

Carbon isotope studies on calcite - graphite system yield narrow Δ Cat - Gr values, varying from 3.9 to 4.3, indicating equilibrium between coexisting calcite and graphite. Calcite - graphite geothermometry has assigned temperatures ranging from 630° to 700°C for the calc - granulites found to the NE of Usilampatti area. The inferred temperatures correspond to the retrograde temperatures obtained by cation exchange thermometry on the granulites from other areas in the Madurai Block. These temperatures may correspond to the late isobaric cooling event. X-ray diffraction studies indicate well ordered nature of these graphites and corroborate the findings of isotope geothermometric inferences.

Keywords

Geothermometry, Calc-Granulite, Calcite-Graphite, Carbon-Oxygen Isotopes, X-Ray Diffraction, Usilampatti, Tamil Nadu.

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