Petrology and U–Pb geochronology of zircon in a suite of charnockitic gneisses from parts of the Chotanagpur Granite Gneiss Complex (CGGC): evidence for the reworking of a Mesoproterozoic basement during the formation of the Rodinia supercontinent

Abstract

Understanding the evolution of the Chotanagpur Granite Gneiss Complex (CGGC) of the East Indian Shield is crucial to decipher the role of the Indian Shield in the formation of the Rodinia supercontinent. The area around Deoghar–Dumka exposes a suite of granulite-facies orthogneisses (variably retrogressed to amphibole–biotite gneiss) that enclose remnants of Palaeoproterozoic metasedimentary and meta-igneous rocks. Results from mineral chemistry, laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS) U–Pb dating of zircon and limited bulk-rock compositions of the studied rocks suggest that the magmatic protoliths of the felsic orthogneisses had A-type chemistry, and that these were emplaced at approximately 1450 Ma presumably in a continental rift setting. Intense deformation and metamorphism of the felsic rock culminated at approximately 9 kbar and 850°C along an apparent geothermal gradient of 26°C km−1. These peak metamorphic conditions were successively followed by initially a steeply decompressive and then a weakly decompressive retrograde pressure–temperature path. The shape of the retrograde pressure–temperature path and the estimated geothermal gradient at the metamorphic peak are interpreted to be the products of continent–continent collision; U–Pb dates of metamorphic zircon overgrowths suggest an age of approximately 943 Ma for the collisional event. This study demonstrates that ‘Grenville-age’ orogenesis thoroughly reworked the approximately 1450 myr-old basement of the CGGC during the formation of the Rodinia supercontinent.

The geological evolution of the Gangpur Schist Belt, eastern India: Constraints on the formation of the Greater Indian Landmass in the Proterozoic

“…The Mesoproterozoic overprint is synchronous with the emplacement of A‐type felsic orthogneisses ( c . 1.45 Ga) in the Deoghar–Dumka area in the eastern part of the gneiss complex (Mukherjee et al., ). The early Neoproterozoic 1.03–0.96 Ga ages can be correlated with the Grenville‐age high‐grade metamorphism accompanied by regional deformation and granite magmatism that pervasively affected a large part of the CGC (Acharyya, ; Chatterjee et al., ; Maji et al., ; Rekha et al., ; Sanyal & Sengupta, ; Sanyal et al., ).…”

“…922 Ma. The closure of the rift basin due to compressional tectonics during continent–continent collision between 900 and 780 Ma formed the regional S 3 fabric at amphibolite facies condition (Chatterjee et al., ; Karmakar et al., ; Maji et al., ; Mukherjee et al., ; Sanyal & Sengupta, ; Sanyal et al., ).…”

“…The terrane has a polychronous evolutionary history involving granitic and charno‐enderbitic magmatism at 1.70–1.64 Ga and c . 45 Ga respectively (Mukherjee et al., ; Saikia et al., ), granulite facies metamorphism and partial melting at c . 1.65 and c .…”

“…1.65 and c . 1.0 Ga (Chatterjee, Crowley, & Ghose, ; Chatterjee & Ghose, ; Dey et al., ; Karmakar et al., ; Maji et al., ; Mukherjee et al., ; Rekha et al., ; Sanyal & Sengupta, ; Sanyal et al., ), anorthosite emplacement at c . 1.55 Ga (Chatterjee et al., ), nepheline syenite intrusion at c .…”

“…1.55 Ga (Chatterjee et al., ), nepheline syenite intrusion at c . 0.92 Ga, and amphibolite facies metamorphism/deformation between 900 and 780 Ma (Chatterjee, Banerjee, Bhattacharya, & Maji, ; Karmakar et al., ; Maji et al., ; Mukherjee et al., ; Sanyal & Sengupta, ; Sanyal et al., ). The North Singhbhum Mobile Belt is dominated by a volcanosedimentary succession of interlayered quartzite, schist, and phyllite intercalated with ultramafic, mafic, and felsic volcanic and plutonic rocks.…”