DSpace
 

DSpace at IIT Bombay >
IITB Publications >
Article >

Please use this identifier to cite or link to this item: http://dspace.library.iitb.ac.in/jspui/handle/10054/10344

Title: Early Proterozoic melt generation processes beneath the intra-cratonic Cuddapah Basin, southern India
Authors: ANAND, M
GIBSON, SA
SUBBARAO, KV
KELLEY, SP
DICKIN, AP
Keywords: eastern dharwar craton
element concentrations
geochemical evidence
isotope systematics
continental-crust
mantle sources
baltic shield
onega plateau
magmas
plume
Issue Date: 2003
Publisher: OXFORD UNIV PRESS
Citation: JOURNAL OF PETROLOGY, 44(12), 2139-2171
Abstract: Early Proterozoic tholeiitic lavas and sills were emplaced during the initial phase of extension of the intra-cratonic Cuddapah Basin, southern India. Ar-40-Ar-39 laser-fusion determinations on phlogopite mica,from the Tadpatri Fm mafic-ultramafic sill complex, constrain the age of the initial phase of extension and volcanism in the basin at 1.9 Ga. Despite their Early Proterozoic age, the igneous rocks are unmetamorphosed, undeformed and remarkably fresh. They exhibit a wide range in MgO contents (4-28 wt %) and have undergone varying degrees of accumulation or crystal fractionation. Variable La/Nb ratios (1.2-3.7) and epsilon(Nd) values (1 to -10) suggest that some, but not all, of the mafic rocks have been affected by crustal contamination. This appears to have taken place in magma chambers at similar to9 kbar, i.e. the base of the continental crust. Forward modelling of major and trace elements (Fe and Nd) and inverse modelling of rare earth elements suggest that the primary Cuddapah melts were generated by similar to10-15% partial melting of a lherzolite mantle source. This corresponds to a mantle Potential temperature of similar to1500degreesC. The thickness of the mechanical boundary layer predicted by the geochemical modelling is 70 km with a minimum initial lithospheric thickness of 120 kin. This corresponds to a stretching factor of 1.6-1.8. Richter's (1988) secular cooling model for the Earth predicts that, at 1.9 Ga, the ambient mantle had a potential temperature of similar to1500degreesC (i.e. similar to200degreesC hotter than Phanerozoic mantle). If the cooling model is correct then Proterozoic lithospheric stretching and mantle melting beneath the intra-cratonic Cuddapah Basin could have been caused by passive rather than active rifting.
URI: http://dx.doi.org/10.1093/petrology/egg073
http://dspace.library.iitb.ac.in/xmlui/handle/10054/10344
http://hdl.handle.net/10054/10344
ISSN: 0022-3530
Appears in Collections:Article

Files in This Item:

There are no files associated with this item.

View Statistics

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

 

Valid XHTML 1.0! DSpace Software Copyright © 2002-2010  Duraspace - Feedback