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A common parentage for Deccan Continental Flood Basalt and Central Indian Ocean Ridge Basalt? A Geochemical and isotopic approach

Ray, D.; Misra, S.; Widdowson, M. and Langmuir, C. H. (2014). A common parentage for Deccan Continental Flood Basalt and Central Indian Ocean Ridge Basalt? A Geochemical and isotopic approach. Journal of Asian Earth Sciences (In Press).

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A comparison of geochemical and Sr-Nd-Pb isotopic compositions for Deccan Continental Flood Basalts (CFBs) and Central Indian Ridge (CIR) basalts is presented: these data permit assessment of possible parental linkages between the two regions, and comparison of their respective magmatic evolutionary trends in relation to rift-related tectonic events during Gondwana break-up. The present study reveals that Mid-Ocean Ridge Basalt (MORB) from the northern CIR and basalts of Deccan CFB are geochemically dissimilar because of: (1) the Deccan CFB basalts typically show a greater iron-enrichment as compared to the northern CIR MORB, (2) a multi-element spiderdiagram reveals that the Deccan CFBs reveal a more fractionated slope (Ba/YbN>1), as compared to relatively flat northern CIR MORB (Ba/YbN<1), (3) there is greater REE fractionation for Deccan CFB than for the northern CIR MORB (i.e., La/YbN~ 2.3 and 1 respectively) and (4) substantial variation of compatible-incompatible trace elements and their ratios among the two basalt groups suggests that partial melting is a dominant process for northern CIR MORB, while fractional crystallization was a more important control to the geochemical variation for Deccan CFB. Further, incompatible trace element ratios (Nb/U and Nb/Pb) and radiogenic isotopic data (Sr-Pb-Nd) indicate that the northern CIR MORBs are similar to depleted mantle [and/or normal (N)-MORB], and often lie on a mixing line between depleted mantle and upper continental crust. By contrast, Deccan CFB compositions lie between the lower continental crust and Ocean island basalt. Accordingly, we conclude that the basaltic suites of the northern CIR MORB and Deccan CFB do not share common parentage, and are therefore genetically unrelated to each other. Instead, we infer that the northern CIR MORB were derived from a depleted mantle source contaminated by upper continental crust, probably during the break up of Gondwanaland; the Deccan CFB are more similar to Ocean island basalt (Reunion-like) composition, and perhaps contaminated by lower continental crust during their evolution.

Item Type: Journal Item
Copyright Holders: 2013 Elsevier Ltd.
ISSN: 1367-9120
Keywords: Deccan CFB; CIR MORB; Central Indian Ocean Ridge; CIOR; isotopic; petrogenesis; upper continental crust; lower continental crust
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 39467
Depositing User: Mike Widdowson
Date Deposited: 20 Feb 2014 16:02
Last Modified: 12 May 2019 19:11
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