Trace Element Geochemistry of Parts of the Closepet Granite, Mysore State, India1

V. Divakara Rao2, U. Aswathanarayana and M. N. Qureshy
National Geophysical Research Institute, Hyderabad-7, A.P., India
Centre of Advanced Study in Geology, University of Saugar, Sagar, M.P., India
National Geophysical Research Institute, Hyderabad-7, A.P., India
1Contribution to the Indian National Programme of the International Upper Mantle Project.
2Work reported in this communication forms part of the Ph.D. thesis of the author.

Summary: Trace elements in twenty samples of the Closepet granite (grey and pink varieties) and the related rocks have been determined by neutron activation analysis (Th, Rb, and Cs), fluorometry (U), flame-photometry (K), and emission spectroscopy (Pb, Sr). The trace element contents of the grey and pink varieties are generally similar. An analysis of the magnitudes of the trace element and other ratios (K/Rb, 235; Th/U, 6·4; U/K (× 104), 0·7; K/Cs (× 10−4), 3·6; Th/K (× 104), 5·3; Fe2O3/(FeO+Fe2O3), 0·27) as well as 87Sr/86Sr initial ratio (0·705; Crawford, 1969) of the Closepet granite indicate two possible modes of genesis: Either the granite magma was not highly differentiated and the vapour phase was relatively insignificant; the crystallization of the magma took place under essentially non-oxidizing conditions; the pink variety, which followed the grey variety, crystallized under essentially the same conditions as the grey variety. Or the Closepet granite had a two-stage history—palingenesis (starting from the Peninsular gneiss) and metasomatism involving the enrichment in K, Rb, Pb, and Th and depletion of Sr and Cs, among others.

Mineralogical Magazine; June 1972 v. 38; no. 298; p. 678-686; DOI: 10.1180/minmag.1972.038.298.04
© 1972, The Mineralogical Society
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