Contrasting Styles of Lower Crustal Metamorphism from a Granulite Suite of Rocks from Angul, Eastern Ghats Belt, India: Implications for the India–Antarctica Correlation

• Published in: Journal of Petrology
• Main Authors: Banerjee, Aparupa, Ganguly, Proloy, Das, Kaushik, Sorcar, Nilanjana, Bose, Sankar
• Other Authors: University Grants Commission, Department of Science and Technology, JSPS KAKENHI, Ministry of Earth Sciences, P.G. acknowledges Science and Engineering Research Board
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2023
• Subjects: Antarc*; Antarctica
• Online Access: http://dx.doi.org/10.1093/petrology/egad065; https://academic.oup.com/petrology/advance-article-pdf/doi/10.1093/petrology/egad065/51354479/egad065.pdf; https://academic.oup.com/petrology/article-pdf/64/9/egad065/51792137/egad065.pdf

Abstract The present work is focussed on a suite of high-grade rocks including mafic granulite, aluminous granulite, khondalite, charnockite, and augen gneiss along with medium-grade rocks like olivine-bearing metanorite, gabbro, and porphyritic granite of the Angul domain at the northern margin of the Proterozoic Eastern Ghats Province (EGP). Based on the petrological and geothermobarometric data, two distinct metamorphic events have been identified. The imprints of the earlier event (MA1) are preserved in the mafic granulite, aluminous granulite, khondalite, augen gneiss, and fine-grained charnockite, but those are best preserved in mafic granulite and aluminous granulite. In mafic granulite, orthopyroxene + clinopyroxene + plagioclase ± garnet+ ilmenite ± quartz assemblage was stabilised at the peak MA1 conditions, whereas the peak MA1 assemblage is represented by Fe3+-garnet + hematite + magnetite + cordierite + K-feldspar + plagioclase + sillimanite + quartz + melt in aluminous granulite. Phase equilibria modelling and thermobarometric data suggest the P–T conditions of >850°C, 7 to 8 kbar for this event. The retrograde metamorphism (MA1R) involved minor decompression (down to ~5 kbar) and subsequent cooling to form biotite- and hornblende-bearing mineral assemblages in aluminous granulite and mafic granulite, respectively. Texturally constrained monazite (U–Th–total Pb) and zircon (U–Pb) data from the former rock suggest ca. 1200 Ma age of the MA1 metamorphism, which was associated with granitic and charnockitic magmatism as constrained from oscillatory-zoned zircon domains in the augen gneiss and fine-grained charnockite. The rock ensemble was affected by a younger metamorphic event (MA2), which is texturally characterised by partial replacement of hornblende (developed during MA1R) to orthopyroxene ± clinopyroxene + plagioclase ± ilmenite + melt assemblage in mafic granulite. Moreover, biotite of aluminous granulite has undergone dehydration melting to produce garnet + cordierite-bearing ...