Geology and geochemistry of Pachmarhi dykes and sills,Satpura Gondwana Basin,central India: problems of dyke-sill-flow correlations in the Deccan Traps |
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| Authors: | Hetu C Sheth Jyotiranjan S Ray Ranjini Ray Loÿc Vanderkluysen John J Mahoney Alok Kumar Anil D Shukla Partha Das Subhrashis Adhikari Bikashkali Jana |
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| Institution: | (1) Department of Earth Sciences, Indian Institute of Technology Bombay (IITB), Powai, Mumbai, 400076, India;(2) Planetary and Geosciences Division, Physical Research Laboratory (PRL), Navrangpura, Ahmedabad, 380009, India;(3) Department of Geology and Geophysics, School of Ocean and Earth Science and Technology (SOEST), University of Hawaii, Honolulu, HI 96822, USA |
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| Abstract: | Many tholeiitic dyke-sill intrusions of the Late Cretaceous Deccan Traps continental flood basalt province are exposed in
the Satpura Gondwana Basin around Pachmarhi, central India. We present field, petrographic, major and trace element, and Sr–Nd–Pb
isotope data on these intrusions and identify individual dykes and sills that chemically closely match several stratigraphically
defined formations in the southwestern Deccan (Western Ghats). Some of these formations have also been identified more recently
in the northern and northeastern Deccan. However, the Pachmarhi intrusions are significantly more evolved (lower Mg numbers
and higher TiO2 contents) than many Deccan basalts, with isotopic signatures generally different from those of the chemically similar lava
formations, indicating that most are not feeders to previously characterized flows. They appear to be products of mixing between
Deccan basalt magmas and partial melts of Precambrian Indian amphibolites, as proposed previously for several Deccan basalt
lavas of the lower Western Ghats stratigraphy. Broad chemical and isotopic similarities of several Pachmarhi intrusions to
the northern and northeastern Deccan lavas indicate petrogenetic relationships. Distances these lava flows would have had
to cover, if they originated in the Pachmarhi area, range from 150 to 350 km. The Pachmarhi data enlarge the hitherto known
chemical and isotopic range of the Deccan flood basalt magmas. This study highlights the problems and ambiguities in dyke-sill-flow
correlations even with extensive geochemical fingerprinting. |
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| Keywords: | Volcanism Continental flood basalt Dyke swarm Deccan Traps Gondwana |
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