- 1Department of Geological Sciences, Jadavpur university, Kolkata-700032, West Bengal, India (sirinaroychoudhury@gmail.com)
- 2Department of Geology, Institute of Science, Banaras Hindu University, Varanasi-221005, India (sirinaroychoudhury@gmail.com)
- 3Department of Geology, University of Delhi, North Campus, Chhatra Marg, Delhi-110007,India (deyanindita.ju@gmail.com)
Granulite facies wollastonite-scapolite assemblage is commonly associated with grossular-andradite rich (granditic) garnet. Origin of grandite garnet has been variously attributed to iron metasomatism related to non-pervasive H2O-rich fluid infiltration from adjacent granitic or pelitic sources, or a result of vapour-deficient metamorphic reactions during near isobaric cooling, in addition to the influence of temperature and fO2.
The meta-supracrustal rocks of the Madukkarai Supracrustal Unit (MSU), within the granulite terrane of South India, expose an interlayered platformal sequence of metapelites, marbles, calcsilicates, meta-psammites and quartzites deposited during the Mesoproterozoic and metamorphosed during the. The present study records the occurrence of a wollastonite-free, scapolite-clinopyroxene-calcite- garnet-amphibole-epidote bearing calc-silicate granulite from the MSU near the Palghat Cauvery Shear Zone. The studied calc-silicates preserve grandite garnet, in close association with clinopyroxenes and scapolite.
Using the internally consistent thermodynamic dataset, quantitative topologies in P-T (for fixed XCO2) and isobaric T-XCO2 topologies in the CaO-MgO-Al2O3-SiO2-H2O-CO2 (CMASV) system were constructed, to trace the P-T-X (fluid) evolutionary history of the studied calc-silicate granulites. The effects of Fe2+, Fe3+ and Na+ on the CMASV topologies were analysed. Interpretation of the ‘frozen-in’ reaction textures and the findings from the activity adjusted CMASV topologies, integrated with the P-T evolutionary history of the intercalated pelitic granulites, supports the view that garnet-amphibole followed by epidote, formed as a result of temperature decrease, with the influx of moderately water-rich fluid (XCO2 =0.4-0.6, ~440-640 °C, at ~4.5-6 kbar). Reactions in the logfO2 vs logfCO2 topology in the system SiO2-FeO-CaO-CO2-O2 (SFC-CO2-O2) indicates the ‘essenite’ component in clinopyroxene to be a probable source of Fe+3 for grandite formation.
How to cite: Roy Choudhury, S. and Dey, A.: Metamorphic evolution of calc-silicate granulites from the Granulite Terrane of South India, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-712, https://doi.org/10.5194/egusphere-egu25-712, 2025.
