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Geochemistry of flood basalts of the Toranmal section, northern Deccan Traps, India: Implications for regional Deccan stratigraphy

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Title Geochemistry of flood basalts of the Toranmal section, northern Deccan Traps, India: Implications for regional Deccan stratigraphy
 
Creator MAHONEY, JJ
SHETH, HC
CHANDRASEKHARAM, D
PENG, ZX
 
Subject rare-earth element
western-ghats
continental-crust
mantle sources
constraints
volcanism
province
lavas
boundary
mahabaleshwar
deccan traps
geochemical stratigraphy
flood basalts
large igneous provinces
 
Description Tholeiitic lavas forming a flood basalt sequence of 870 m thickness at Toranmal in the northern Deccan Traps have a large range in isotopic ratios [epsilon(Nd)(t) = +2.1 to -15.7, (Sr-87/Sr-86), = 0.70467-0.71416, Pb-206/Pb-204 = 16.699-20.246], similar to that of lavas in the well-studied southwestern part of the province. The basalts with the lowest epsilon(Nd)(t) values display distinctive lows at Nb, Ta, P and Ti, and large positive Pb spikes in their primitive-mantle-normalized element patterns, indicative of significant continental lithospheric influence in their petrogenesis. As in much of the southwestern Deccan, epsilon(Nd)(t) exhibits a rough negative correlation with Mg/Fe and SiO2 and a positive correlation with Fe, consistent with temperature-controlled assimilation. Overall, the Toranmal section appears distinct fron section in the northwestern sector of the province; however, some Toranmal basalts are isotopically and chemically similar to flows in the northeastern Deccan, and a thick pile of lavas resembling the Poladpur Fm of the southwestern Deccan, the closest type-sections of which lie similar to 380 km to the south, is present. If it indeed represents a northern remnant of this formation, the Poladpur Fm, which also extends far into the central and southeastern parts of the province, is one of the most widespread of Decann formations, with a possible original extent greater than or equal to 3 x 10(5) km(2). The Ambenali Fm , which forms a thick sequence lying above the Poladpur in the southwestern Deccan, is not present at Toranmal. Several flows have broad geochemical affinities with the southwestern Bushe and Mahabaleshwar formations, which respectively lie below the Poladlur and above the Ambenali; however, these flows are not in the southwestern stratigraphic order and are probably of relatively local origin as dikes compositionally very similar to these flows are present at Toranmal and a elsewhere in the vicinity.
 
Publisher OXFORD UNIV PRESS
 
Date 2011-08-22T06:29:13Z
2011-12-26T12:56:14Z
2011-12-27T05:44:37Z
2011-08-22T06:29:13Z
2011-12-26T12:56:14Z
2011-12-27T05:44:37Z
2000
 
Type Article
 
Identifier JOURNAL OF PETROLOGY, 41(7), 1099-1120
0022-3530
http://dx.doi.org/10.1093/petrology/41.7.1099
http://dspace.library.iitb.ac.in/xmlui/handle/10054/10345
http://hdl.handle.net/10054/10345
 
Language en