Prograde polyphase regional metamorphism of pelitic rocks, NW of Jamshedpur, eastern India: Constraints from textural relationship, pseudosection modelling and geothermobarometry

Prakash, D and Patel, DK and Yadav, MK and Vishal, B and Tewari, S and Yadav, R and Rai, SK and Singh, CK (2020) Prograde polyphase regional metamorphism of pelitic rocks, NW of Jamshedpur, eastern India: Constraints from textural relationship, pseudosection modelling and geothermobarometry. In: Geological Magazine, 157 (7). pp. 1045-1067. (In Press)

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Abstract

The study area belongs to the Singhbhum metamorphic belt of Jharkhand, situated in the eastern part of India. The spatial distribution of the index minerals in the pelitic schists of the area shows Barrovian type of metamorphism. Three isograds, viz. garnet, staurolite and sillimanite, have been delineated and the textural study of the schists has revealed a time relation between crystallization and deformation. Series of folds with shifting values of plunges in the supracrustal rocks having axial-planar schistosity to the folds have been widely cited. Development of these folds could be attributed to the second phase of deformation. In total, two phases of deformation, D1 and D2, in association with two phases of metamorphism, M1 and M2, have been lined up in the study area. Chemographic plots of reactant and product assemblages corresponding to various metamorphic reactions suggest that the pattern of metamorphic zones mapped in space is in coherence with the temporal-sequential change during prograde metamorphism. The prograde P-T evolution of the study area has been obtained using conventional geothermobarometry, internally consistent winTWQ program and PerpleX software in the MnNCKFMASHTO model system. Our observations suggest that the progressive metamorphism in the area is not related to granitic intrusion or migmatization but that it was possibly the ascending plume that resulted in the M1 phase of metamorphism followed by D1 deformation. The second and prime metamorphic phase, M2, with its possible heat source generated by crustal overloading, was preceded by D1 and it lasted until late-to post-D2 deformation.

Item Type:	Journal Article
Publication:	Geological Magazine
Publisher:	Cambridge University Press
Additional Information:	Copyright of this article belongs to Cambridge University Press
Keywords:	prograde Barrovian metamorphism; textural relationship; pseudosection modelling; geothermobarometry; eastern India
Department/Centre:	Division of Mechanical Sciences > Centre for Earth Sciences
Date Deposited:	11 Nov 2020 10:10
Last Modified:	11 Nov 2020 10:10
URI:	http://eprints.iisc.ac.in/id/eprint/66863

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