Neoarchaean Felsic Volcanic Rocks in Tracing Evolution of Arcs: An Insight from Geochemical Data of the Gadag Schist Belt, Western Dharwar Craton

Quartz porphyry of rhyolitic composition though a volumetrically minor is an important component metavolcanic successions in the Gadag schist belt western Dharwar craton. The quartz porphyries are calc-alkaline, enriched light rare earth elements (Lan/Ybn ~ 10–20) and with strong negative Eu anomaly (Eu/Eu*N=0.45–0.58). These features, coupled high K2O/Na2O (0.8 to 1.46), low Nb/Th (<1), Lan/Smn ratios 4.2 6.0, suggest that magma formed from melt generated by partial melting basaltic crust, subsequently modified crustal assimilation crystal fractionation. geological setting geochemical relationships magmatism at convergent plate tectonic setting. zircon U-Pb age 2588.0 ± 2.4 Ma for porphyry, together 2732 similar volcanic rocks Chitradurga further south, 2614 felsic volcanics Shimoga belt, point extended period episodic arc craton least ~144myr.