Petrochemical studies of amphibolits from the Western part of Dudatoli Syncline, lesser Garhwal Himalaya

Abstract

Lenticular sills of amphibolites are frequently observed in the low to medium grade metamorphic rocks of the Dudatoli group (Kumaun Supergroup) of Precambrian age. These amphibolits are the result of metamorphism of pre-existing mafic igneous rocks under low to medium grade PT conditions and consist essentially of hornblende + plagioclase + pyroxene + epidote +chlorite + iron oxide and clays. Geochemically these ortho-amphibolites are tholeiitic, show associaton with non-orogenic environment and a shift to calc-alkaline derivatives with progressive differentiation. A comparison with other well known Igneous complexes indicates them to be derivatives of alkaline basaltic magma. This paper records the petrography, chemical characters and a probable origin of these amphibolites.