ACCRETIONARY EVOLUTION OF THE RAMAGIRI SCHIST BELT, EASTERN DHARWAR-CRATON

The gold mineralized Ramagiri Schist Belt is a volcanic dominated, lat e Archaean belt in the eastern Dharwar Craton. Based on the lithologic al association, mode of occurrence of rocks, geochemical characteristi cs of mantle derived rocks and the metamorphic grade of rocks, the bel t is divided into three blocks that are tectonically interleaved with and surrounded by granitic rocks of distinct histories. The eastern bl ock has amphibolite facies rocks, dominantly basic metavolcanics havin g light rare earth element (LREE) depleted patterns with minor banded ferruginous quartzite (BFQ). The central block includes mafic and fels ic volcanics, pyroclastics, gabbroic and felsic dykes, argillites and BFQ. The volcanic rocks as well as the intrusives have LREE enriched p atterns. The central block has dominantly greenschist facies rocks. Th e western block is made up of fine grained metabasalts with well prese rved pillow structures at places, and retrogressed chlorite-actinolite and chlorite-carbonate schists in shear zones, serpentinite and BFQ. These rocks have net to moderately LREE depleted patterns. The associa ted serpentinite is of residual origin, probably representing obducted pieces of Archaean oceanic lithosphere. Available age information and required tectonic settings of the volcanics necessitate subduction re lated magmatism and corroborate the idea of crustal genesis by accreti onary processes in the eastern Dharwar Craton during late Archaean.