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Please use this identifier to cite or link to this item: http://repository.iitr.ac.in/handle/123456789/4621
Title: Isotopic evidence of Middle Proterozoic magmatism from Bombay High Field: Implications to crustal evolution of western offshore of India
Authors: Rathore S.S.
Vijan A.R.
Singh M.P.
Prabhu B.N.
Sahu A.
Published in: Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences
Abstract: Precambrian granitic basement rocks obtained from well BH-36 of Bombay High Field, western offshore of India has been studied both by Rb-Sr and K-Ar dating methods. Seven basement samples chosen from two cores have yielded whole rock Rb-Sr isochron age of 1446 ± 67 Ma with an initial 87Sr/86Sr ratio of 0.7062 ± 0.0012. This age has been interpreted as the formation/emplacement time of the granite. Two biotite fractions of different grain size separated from a sample CC6B2T have yielded Rb-Sr mineral isochron age of 1385 ± 21 Ma. However, these fractions when studied by K-Ar dating method have yielded slightly higher but mutually consistent ages of 1458 ± 43 Ma and 1465 ± 43 Ma, respectively. Further, two biotites separated from additional samples CC5B9T and CC6B3B have yielded K-Ar ages of 1452 ± 42 Ma and 1425 ± 40 Ma with an overall mean age of 1438 ± 19 Ma. This mean K-Ar age is indistinguishable from whole rock Rb-Sr isochron as well as mineral isochron age within experimental error. The similarity in the whole rock and biotite ages obtained by different isotopic methods suggests that no thermal disturbance has occurred in these rocks after their emplacement/formation around 1450 Ma ago. The present study provides the evidence for the existence of an important Middle Proterozoic magmatic event around 1400-1450 Ma on the western offshore of India which, hitherto, was thought to be mainly confined to the eastern Ghats, Satpura and Delhi fold belt of India. This finding may have an important bearing on the reconstruction of Proterozoic crustal evolution of western Indian shield. © Printed in India.
Citation: Proceedings of the Indian Academy of Sciences, Earth and Planetary Sciences(2004), 113(1): 27-36
URI: https://doi.org/10.1007/BF02701996
http://repository.iitr.ac.in/handle/123456789/4621
Issue Date: 2004
Publisher: Indian Academy of Sciences
Keywords: Basement rocks
Bombay High Field
Granite
Mumbai offshore basin
Rb-Sr/K-Ar dating
ISSN: 2534126
Author Scopus IDs: 7006353080
6506631668
55469492400
7004454063
7103304797
Author Affiliations: Rathore, S.S., Forward Base Office, Assam and Assam Arakan Basin-Tripura, ONGC, Agartala 799 014, India
Vijan, A.R., KDM Inst. of Petroleum Exploration, ONGC, Dehradun 248 195, India
Singh, M.P., KDM Inst. of Petroleum Exploration, ONGC, Dehradun 248 195, India
Prabhu, B.N., Regional Chemical Laboratory, ONGC, Sibsagar, Asam 785 640, India
Sahu, A., Forward Base Office, Assam and Assam Arakan Basin-Tripura, ONGC, Agartala 799 014, India
Corresponding Author: Rathore, S.S.; Geochronology Laboratory, KDM, Institute of Petroleum Exploration, Dehradun 248 195, India; email: ssrathore62@hotmail.com
Appears in Collections:Journal Publications [CE]

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