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Petrology and U–Pb geochronology of zircon in a suite of charnockitic gneisses from parts of the Chotanagpur Granite Gneiss Complex (CGGC): evidence for the reworking of a Mesoproterozoic basement during the formation of the Rodinia supercontinent

By
Subham Mukherjee
Subham Mukherjee
Department of Geological Sciences, Jadavpur University, Kolkata 700032, India
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Anindita Dey
Anindita Dey
Department of Geological Sciences, Jadavpur University, Kolkata 700032, India
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Sanjoy Sanyal
Sanjoy Sanyal
Department of Geological Sciences, Jadavpur University, Kolkata 700032, India
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Mauricio Ibanez-Mejia
Mauricio Ibanez-Mejia
Department of Earth and Environmental Sciences, University of Rochester, Rochester, NY 14627, USA
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Upama Dutta
Upama Dutta
Department of Applied Geology, Indian School of Mines, Dhanbad 826004, India
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Pulak Sengupta
Pulak Sengupta
Department of Geological Sciences, Jadavpur University, Kolkata 700032, India
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Published:
January 01, 2017

Abstract

Understanding the evolution of the Chotanagpur Granite Gneiss Complex (CGGC) of the East Indian Shield is crucial to decipher the role of the Indian Shield in the formation of the Rodinia supercontinent. The area around Deoghar–Dumka exposes a suite of granulite-facies orthogneisses (variably retrogressed to amphibole–biotite gneiss) that enclose remnants of Palaeoproterozoic metasedimentary and meta-igneous rocks. Results from mineral chemistry, laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS) U–Pb dating of zircon and limited bulk-rock compositions of the studied rocks suggest that the magmatic protoliths of the felsic orthogneisses had A-type chemistry, and that these were emplaced at approximately 1450 Ma presumably in a continental rift setting. Intense deformation and metamorphism of the felsic rock culminated at approximately 9 kbar and 850°C along an apparent geothermal gradient of 26°C km−1. These peak metamorphic conditions were successively followed by initially a steeply decompressive and then a weakly decompressive retrograde pressure–temperature path. The shape of the retrograde pressure–temperature path and the estimated geothermal gradient at the metamorphic peak are interpreted to be the products of continent–continent collision; U–Pb dates of metamorphic zircon overgrowths suggest an age of approximately 943 Ma for the collisional event. This study demonstrates that ‘Grenville-age’ orogenesis thoroughly reworked the approximately 1450 myr-old basement of the CGGC during the formation of the Rodinia supercontinent.

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Geological Society, London, Special Publications

Crustal Evolution of India and Antarctica: The Supercontinent Connection

N. C. Pant
N. C. Pant
University of Delhi, India
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S. Dasgupta
S. Dasgupta
Jamia Millia Islamia, India
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Geological Society of London
Volume
457
ISBN electronic:
9781786203380
Publication date:
January 01, 2017

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