Sinking of the Dharwar Basin (South India): implications for Archaean tectonics

摘要: Abstract Archaean tectonic regimes can be constrained by structural analysis of greenstone belts and adjacent granite-gneiss masses. The late Bababudan belt (Dharwar craton, South India) contains a low-grade volcanosedimentary basin sequence (the Dharwar Supergroup) which unconformably overlies previously eroded basement made up mainly granite gneiss. Fabric trajectories, kinematic indicators superimposed deformation patterns show that greenstones have undergone radial converging downward flow with respect to underlying rocks, as well strike-slip shearing. This is attributed the progressive sagduction (gravity-sinking) into its along decollement horizon transcurrent We propose model for may explain common features many (such decollements upright fold patterns) are sinking supracrustals their basement. results our study other field investigations in crust evidence from cratons (Zimbabwe Pilbara), raise possibility unique continental regime existed during Archaean, controlled emplacement dense volcanic traps, mantle underplating thermal blanketing crust. differs observed within modern lithosphere it characterized pervasive development gravity (i.e. Rayleigh-Taylor) instabilities between traps rest It allowed heat material transfer through has seen an efficient recycling mechanism young periods underplating. diapiric phenomenon independent boundary forces acting at limits protocontinents associated time space large-scale accretion events crust, perhaps hot-spot environments.