Neoproterozoic granitic activity in syn‐collisional setting: Insight from petrology, geochemistry, and zircon–monazite geochronology of S‐type granites of the Chotanagpur Granite Gneissic Complex, eastern India

Abstract

The evidence of a long‐lived Grenvillian orogeny around 1.0 Ga is preserved in the eastern part of India in the form of large‐scale syn‐collisional granitic activity and high‐grade metamorphism in the Chotanagpur Granite Gneissic Complex (CGGC). Geochemically, granitoid rocks of CGGC were classified as ferroan, per‐aluminous, and calc‐alkalic to alkali‐calcic S‐type granites which were generated from the anatexis of meta‐sedimentary protolith (khondalite) in a volcanic‐arc to syn‐collisional setting. Relatively high crystallization temperatures (800–850°C for garnetiferous granite gneiss, 770–830°C for megacrystic granite gneiss, and 639–725°C for pink granite) of these rocks were calculated by geothermometric calculations. The REE modelling testified that 40–45% partial melting of the khondalite in H2O undersaturated condition at around 5‐kbar pressure might have given rise to the parent magma of the garnetiferous granite gneiss (GGG). LA‐ICPMS zircon (U–Pb) dating yielded the crystallization ages of the megacrystic granite gneiss (MGG) and pink granite (PG) as ~1.0 Ga, and EPMA monazite (U–Th–total Pb) dating suggested that the GGG was metamorphosed during 1.0 Ga. The 1.0–0.90 Ga age of high‐grade metamorphism and anatexis in the CGGC may be correlated with that in the Rayner Complex–Eastern Ghats Belt in the Indo‐Antarctic sector, which is considered as the result of Indo‐Antarctic collision during the assembly of Rodinia.