The late Archean high-grade terrain of south India and the deep structure of the Dharwar Craton

Abstract

The Dharwar Craton of southern India is an Archean continental fragment showing a continuous exposed crustal section from low-grade genisses and greenstone basins in the north to granulites in the south with more than eight kilobars paleopressure, corresponding to nearly thirty kilometers depth. Low-potassium acid to intermediate "gray gneiss' was massively accreted 3.4 to 3.0 Ga ago and was capped by tholeiitic to komatiitic flows and their sedimentary detritus 3.0 to 2.6 Ga ago. Juvenile crust formation recommenced 2.6 Ga ago. Termination of this quasi-modern magmatism by suturing of the island arc(s) coincided with large-scale wrenching of the South India continent, which created channelways for the rise of metasomatizing solutions from the mantle. The Craton as a whole has been nearly inert since latest Archean, though the tectonized southern region was affected by Proterozoic remobilization. -from Author