Structure and Geochemistry of Metabasites from Chandrapur- Narengi area of Guwahati city, Kamrup District (Metro), Assam, India

摘要

The amphibolites and hornblende biotite schist of Chandrapur-Narengi area, designated as metabasites, occur in alternations with quartzofeldspathic gneisses, which form an important lithologic unit of the Precambrian Gneissic and Migmatitic Complex (PGMC). Although discontinuous in patches, they are persistent in the direction of tectonic transport. The field relations, structures, petrography and major and trace-element geochemistry are discussed and a probable tectonic setting is suggested. The geochemical signatures indicate a volcano-sedimentary sequence relating island arc tholeiites with a close affinity towards calc alkaline basalt and oceanic island arc basalt and the metabasites are the metamorphosed equivalent of intrusive and extrusive tholeiitic basic rocks as well as sedimentary derivation. A single geochronological data is available from PGMC which is Paleoproterozoic and the overlying cover rocks (Shillong Group) of Shillong basion have been dated as Mesoproterozoic. Therefore the Assam-Meghalaya Plateau (Shillong Plateau) is suggested as a product of Post Archean suite of the Indian Peninsula.