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Please use this identifier to cite or link to this item: http://repository.iitr.ac.in/handle/123456789/6294
Title: Crustal accretion and metamorphism of Mesoarchean granulites in Palghat-Cauvery Shear Zone, Southern India
Authors: Choudhary A.K.
Jain A.K.
Singh, Sandeep
Manickavasagam R.
Chandra K.
Published in: Journal of the Geological Society of India
Abstract: This work provides unequivocal evidence of the existence of Mesoarchean granulite facies metamorphic event in the Palghat-Cauvery Shear Zone (PCSZ) of South India. Charnockite samples from two prominent hills at Kollaimalai (KM) and Pachchaimalai (PM) as well as from two quarries within the Bhavani Shear Zone (BSZ) have been analyzed for their Sm-Nd and Rb-Sr ages to investigate the existence or otherwise of the Archean granulite facies events within the PCSZ. The Rb-Sr whole-rock isochron ages for massive charnockites from both the hills appear to be contemporaneous at 2.9 Ga with the initial Sr isotopic ratios of 0.7012 and 0.7014, respectively. However, the Rb-Sr data for whole-rock samples of basic granulites from one of the quarries within the BSZ indicate open system behavior, while the charnockites from the other quarry have insufficient spread in 87Rb/86Sr ratios and do not yield any isochron. The Sm-Nd data, on the other hand, do not distinguish between the massive charnockite and the lowland charnockite and yield Depleted Mantle model ages in the range 2.98±0.3 Ga for all of them. The T CHUR for all of these rocks are highly positive. Both the Sr isotopic ratios and positive T CHUR values for these rocks strongly suggest a mantle source for all of them. An upper age limit of 3.28 Ga may be assigned to the crustal accretion of the protolith of all these rocks on the basis of their Nd model ages. The Rb-Sr isochron ages of 2.9 Ga for the two massifs could be the age of granulite facies metamorphism. Thus, the metamorphism in the KM and PM Hills took place within 100 Ma of crustal accretion of these rocks and probably was part of the same geological event of crust formation and metamorphism. The open system behavior with respect to Rb-Sr isotopes in the basic granulite from Bhavani is possibly due to the migration of Sr isotopes, triggered during the later shearing of these rocks. © 2011 Geological Society of India.
Citation: Journal of the Geological Society of India (2011), 77(3): 227-238
URI: https://doi.org/10.1007/s12594-011-0029-0
http://repository.iitr.ac.in/handle/123456789/6294
Issue Date: 2011
Keywords: Granulite facies metamorphism
Rb-Sr and Sm-Nd geochronology
Southern Granulite Terrain
ISSN: 167622
Author Scopus IDs: 7102838901
57211729470
7406400956
6602462208
57198245254
Author Affiliations: Choudhary, A.K., Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee 247 667, India
Jain, A.K., Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee 247 667, India
Singh, S., Department of Earth Sciences, Indian Institute of Technology Roorkee, Roorkee 247 667, India
Manickavasagam, R., Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee 247 667, India
Chandra, K., Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee 247 667, India
Funding Details: Acknowledgements: The authors are grateful to the Department of Science and Technology, New Delhi for sanctioning the National Facility on Geochronology/Isotope Geology to the IIT Roorkee and deeply appreciate the support extended by Drs. K.R. Gupta, M. Prithviraj and Ch. Sivaji. Research in South India has been made possible through funds made available to AKJ and AKC by the DST. The authors are also thankful to the Director IIT Roorkee for his support and encouragement. Elaborate comments by Dr. Y.J. Bhaskar Rao (NGRI, Hyderabad) on this work are gratefully acknowledged.
Corresponding Author: Choudhary, A. K.; Institute Instrumentation Centre, Indian Institute of Technology Roorkee, Roorkee 247 667, India; email: akc.iitr@gmail.com
Appears in Collections:Journal Publications [ES]

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