Charnockite-Gneiss-Complex Relationship in Southern Karnataka
Subscribe/Renew Journal
The major 2900-3000 m.y. thermal event in the gneiss complex, involving the high-grade supracrustal rocks, is correlatable with the progressive metamorphism of amphibolite to granulite facies in the region. This event probably culminated in the production of charnockite around 2600-2700 m.y.
The progressive metamorphism in Karnataka from green schist to granulite facies is shown to be the cumulative effect of polymetamorphism and regional synclinorial structure plunging northward. Post-Dharwar uptilting of the Peninsula has served to accentuate this vertical zonation. As a result deeper crustal levels are exposed southward, involving older supracrustal rocks. The high-grade terrain in Karnataka is, therefore, older than the greenstone terrain. The greenstones and granulites were not juxtaposed against each other because of their differing levels. Parts of the high-grade terrain later evolved into a mobile belt of charnockite-khondalite association. This mobile belt has been interpreted variously as geosynclinal orogenic belt, collision feature similar to the Circum-Pacific belts of the Himalayas, or as a transform zone. The continent-continent collision model is preferred.
Abstract Views: 166
PDF Views: 2