P-T Conditions of Metamorphism of Supracrustal Rocks in the Sandur Schist Belt, Dharwar Craton, Southern India

Compositions of co-existing mineral pairs, viz., (a) cordierite- gedrite- garnet- biotite, (b) staurolite-biotite-garnet-muscovite-chlorite and (c) andalusite-staurolite-biotite-gamet in metapelites, and (d) amphibole-plagioclase pair in metabasalts of the Sandur schist belt in the eastern block of the Dharwar craton, Southern India, yield metamorphic temperatures and pressures in the range of 550°-600° C and 4-5.2 kbar, respectively. Textural relationships of the minerals in the above mineral assemblages suggest the development of cordierite, gedrite, garnet, staurolite and biotite during the main-fabric forming event (regional metamorphism). Increase in the grade of metamorphism from greenschist to amphibolite facies associated with the main deformational event is observed from the central to the peripheral portions of the belt; this can be attributed to the steep thermal gradient produced by the syntectonic granitoids. Andalusite post-dates all the other metamorphic minerals and its development outlasts the main deformational episode in the belt. Andalu∼ite is a product of thermal metamorphism, superimposed on regional metamorphism and its growth coincides with the upliftment of the terrain during the emplacement of Iate- to post-kinematic granitoids, which, under comparatively low pressure regime (∼3.75 kbar), maintained earlier peak metamorphic temperatures.