Damodar Graben: A Centre of Contrasting Magmatism in the Eastern Indian Shield Margin

摘要: Fragmentation of the Protocontinental masses along orthogonal type mega-fractures during cratonisation processes is responsible in breaking-up Indian shield into major crustal blocks. Narmada-Son-Tapti (SONATA) geofracture one such prominent megafracture dissecting across Central India that has given rise to a number grabens, viz., Mahanadi, Godavari and Damodar. The E-W trending Damodar graben at eastern margin, developed central axis Chhotanagpur Gneiss Granulitic Complex (CGGC, >2.0 Ga), which served as basement for Gondwana sedimentation since Upper Carboniferous Mesozoic period. This zone marked by prolonged magmatic activity Paleo-Proterozoic time, culminating eruption Rajmahal basalt Early Cretaceous (116 Ma). development contrasting igneous rock association on either side rift setting, suggest generation magma from diverse source composition depth. emplacement syenite, nepheline alkali granite, basic, ultrabasic rocks massif anorthosite southern part rift, mafic (gabbro-anorthositetroctolite) ultramafic magmatism together with rapakivi granite northern part, are manifestations mid-Proterozoic events. basic was followed pervasive K-rich peraluminous granites. However, dyke swarms dolerite, lamprophyre lamproite age sediments Valley Coal Field adjoining Bengal Basin give testimony reactivation deep seated dislocations. Such kindreds mantle origin known generated period continental margins Western Australia East Antarctica were once joined Eastern India, prior fragmentation Gondwanaland. phases tholeiitic, anorthositic, granitic, alkaline ultrapotassic space time through Tertiary comparable Oslo Norway Rhine Germany. geological history CGGC is, therefore, controlled an intra-continental setting shows over about 2 billion years.