Metamorphic History of the Sandur Schist Belt, Karnataka

The Sandur schist belt is predominantly characterised by greenschist facies of regional metamorphism, which increases to amphibolite facies near the periphery of the schist belt. The higher facies rocks are marked by the appearance of metamorphic index minerals like garnet, andalusite, staurolite and cordierite. Study of the 'Si - Se' tectonites suggests that metamorphism is progressive, where chlorite and micas grow 'synkinematically' and garnet, andalusite, staurolite and cordierite grow post-kinematically with reference to first phase of folding (F₁). Static growth of garnet, andalusite, staurolite etc., following the first phase of folding (F₁), and their subsequent rotation with reference to second phase of folding (F₂) clearly indicates a time gap between F₁ and F₂. Formation of assemblages of higher grade metamorphic minerals along the border region of the schist belt, is possibly due to influx of additional heat from some source (? intrusi ve granite) at a late tectonic stage.