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.

Discovery of Early Tonian Calc‐alkaline and Shoshonitic Metamafic Rocks from the North Purulia Shear Zone, Chhotanagpur Gneissic Complex, Eastern India: Implications of Proterozoic Sub‐continental Lithospheric Mantle

“…Shoshonitic garnetiferous amphibolites were emplaced during the exhumation of the crust along a shear zone in a post-collisional tectonic set-up. Previous studies indicate that extension-related calc-alkaline granites were emplaced at about 998 ± 10 Ma (Chakraborty et al, 2019a;Das et al, 2020). Upwelling of the asthenospheric mantle beneath the thinned orogenic lithosphere caused the high heat flow.…”

Petrogenesis of a nepheline syenite from parts of the Chotanagpur Granite Gneissic Complex: implications for Neoproterozoic crustal extension in the East Indian Shield

“…The present study does not provide any direct constraints on the timing of intrusion of the magmatic protolith and the superimposed deformation and metamorphism. Nevertheless, a large geochronological dataset suggests that the rocks of the CGGC underwent high-temperature granulite-grade metamorphism and developed a strong metamorphic fabric (S 2 ) during the Grenvillian orogeny (~1000-950 Ma; Chatterjee et al 2008Chatterjee et al , 2010Maji et al 2008;Karmakar et al 2011;Rekha et al 2011;Sanyal & Sengupta, 2012;Mukherjee et al 2017Mukherjee et al , 2019bChakraborty et al 2019;Dey et al 2019a,c). Field studies suggest that the magmatic protolith of the studied nepheline syenite cuts across this S 2 fabric of the Grenvillian metamorphites and hence is coeval with the mafic dykes that occurred in different parts of the NPSZ and SPSZ (Reddy et al 2009;Mukherjee et al 2018b;Das et al 2019).…”

Current and emerging analytical techniques for geochemical and geochronological studies

“…SHRIMP was the first ion microprobe dedicated to geological isotopic studies and opened up zircon geochronology by in-situ isotopic analysis, as these minerals are some of the toughest minerals on the planet, can survive extreme temperature-pressure conditions and carry the genetic information (Anani et al, 2020). These crystals also sometimes contain microscopic inclusions, such as gas bubbles, that provide a unique window of critical information on aspects such as conditions on Earth as life arose and the first continents formed (Chakraborty, Ray, Chatterjee, Deb, & Das, 2019). SHRIMP technique was developed by Prof. William Compston (Photo 2) at the Research School of Earth Sciences, Australian National University, Canberra in the early 1980s.…”