CYCLIC VOLCANISM AND SEDIMENTATION IN THE MAHAKOSHAL GREENSTONE-BELT,DISTRICT SIDHI, MADHYA-PRADESH

Several ordered cycles of volcanism and sedimentation have been record ed from the Mahakoshal greenstone belt in the eastern part of the Sidh i district, Madhya Pradesh. Each cycle is characterised by pillow lava -pahoehoe toes, bomb agglomerate-volcanic breccia and tuff, culminatin g with the deposition of massive chert under quiescent conditions. The volcanics and the sediments exhibit linear distribution and were depo sited as a result of eruptions along ENE-WSW trending fissures, parall el to the margins of the belt. The deposition of volcanics and sedimen ts took place over thin Archaean sialic crust where tholeiitic magma d ifferentiated at a depth of less than 15 km.