Early Proterozoic Melt Generation Processes beneath the Intra-cratonic Cuddapah Basin, Southern India |
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Authors: | ANAND, M. GIBSON, S. A. SUBBARAO, K. V. KELLEY, S. P. DICKIN, A. P. |
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Affiliation: | 1 DEPARTMENT OF EARTH SCIENCES, UNIVERSITY OF CAMBRIDGE, CAMBRIDGE CB2 3EQ, UK 2 DEPARTMENT OF EARTH SCIENCES, INDIAN INSTITUTE OF TECHNOLOGY, MUMBAI, POWAI, 400 076, INDIA 3 DEPARTMENT OF EARTH SCIENCES, OPEN UNIVERSITY, MILTON KEYNES MK7 6AA, UK 4 DEPARTMENT OF GEOLOGY, McMASTER UNIVERSITY, HAMILTON, ONT. L8S 4M1, CANADA |
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Abstract: | Early Proterozoic tholeiitic lavas and sills were emplaced duringthe initial phase of extension of the intra-cratonic CuddapahBasin, southern India. 40Ar39Ar laser-fusion determinationson phlogopite mica, from the Tadpatri Fm maficultramaficsill complex, constrain the age of the initial phase of extensionand volcanism in the basin at 1·9 Ga. Despite their EarlyProterozoic age, the igneous rocks are unmetamorphosed, undeformedand remarkably fresh. They exhibit a wide range in MgO contents(428 wt %) and have undergone varying degrees of accumulationor crystal fractionation. Variable La/Nb ratios (1·23·7)and |
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