Thermal structure and history of granitic rocks in the Dharwar craton, South India

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The Dharwar craton in South India is one of the typical Archaean continental crust in the world, and comprises the hart of Gondwana super continents. The craton is composed mainly of Peninsular gneisses originated from the early to middle Archaean TTG and late Archaean Closepet granites.1.This research Program provided systematic data on the petrographical properties of granitic rocks in the whole area of the craton, such as modal compositions and mineralogical properties of major rock forming minerals. We found that most granitic rocks contained considerable amounts of K-feldspar, and the Archaean TTG was not always poor in K-feldspar.2.K-feldspar was mostly low microcline with maximum ordering in the central to northern part of the Dharwar craton, while in the southern part of the amphibolite-granulite transition zone, orthoclase became dominant and high temperature-form K-feldspar (low sanidine) occurred in the Kerala Khondalite belt of the southern most part of India. K-feldspar in Archaean granitoids was not always low microciline, as formerly believed to be strictly low microcline.3.Geochemical studies including major and trace elements analyses suggested that, the genesis of Peninsular gneisses in the Dharwar craton was not simple ; they derived partly from early to middle Archaean TTG, and contained late Archaean granites synchronous with the Closepet granites, and then, totally metamorphosed (or poly-metamorphosed) at the time of atest Archaean.