Abstract The Eastern Ghats Belt (India) bears testimony to the assembly and dispersal of both the Columbia and Rodinia supercontinents, and possibly the formation of East Gondwana. The belt itself is a collage of different lithotectonic and isotopic domains, and therefore the petrological evolution of each domain is to be considered separately prior to the formation of the belt. In this paper, we present an updated review on the petrological and tectonic evolution of the different domains along with geochronological constraints. We develop tectonic models to show how different lithotectonic domains fit into supercontinent cycles in the Proterozoic period.

Abstract A suite of Mg–Al granulites from two new localities in the Eastern Ghats Province are investigated to put constraints on: (a) the thermal and baric evolution of these rocks; (b) the timing of high-grade metamorphisms (chemical dating of monazite); (c) the tectonic setting where the high-grade metamorphisms occurred; and (d) a possible link between India and East Antarctica during the formation of the Rodinia supercontinent. Supporting the proposition of polymetamorphism over single metamorphism, our study documents at least two distinct phases of high-grade metamorphism that occurred in two contrasting tectonic settings. Reconstructed pristine spinel composition from oxide aggregates, the Al content of coronitic orthopyroxene over sapphirine and spinel, and the constraints of the FeO–MgO–Al 2 O 3 –SiO 2 (FMAS) topology in the FMAS system document temperatures in excess of 1070°C at 8–9 kbar pressure (>1100°C GPa −1 ). This study shows that such an extreme metamorphic condition was reached along a counter-clockwise P – T trajectory presumably in an extensional setting at approximately 1.2 Ga. The eventual collision of India and East Antarctica reworked the near-isobarically cooled assemblages of the first event, and triggered exhumation of the former lower crust to the upper-crustal depth along a steeply decompressive trajectory during the formation of the Rodinia supercontinent ( c . 0.95–0.90 Ga). Supplementary material: Representative electron microprobe analyses of monazite in wt%, calculated apparent ages and ± 2σ error are available at https://doi.org/10.6084/m9.figshare.c.3771044

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.

Abstract The Southern Granulite Terrane of India exposes remnants of an interbanded sequence of orthoquartzite–metapelite–calcareous rocks across the enigmatic Palghat–Cauvery Shear Zone (PCSZ), which has been interpreted as a Pan-African terrane boundary representing the eastward extension of the Betsimisaraka Suture Zone of Madagascar. Zircon U–Pb geochronology of metasedimentary rocks from both sides of the PCSZ shows that the precursor sediments of these rocks were sourced from the Dharwar Craton and the adjoining parts of the Indian shield. The similarity of the provenance and the vestiges of Grenvillian-age orogenesis in some metasedimentary rocks contradict an interpretation that the PCSZ is a Pan-African terrane boundary. The lithological association and the likely basin formation age of the metasedimentary rocks of the Southern Granulite Terrane show remarkable similarity to the rock assemblage and timing of sedimentation of the Palaeoproterozoic to Neoproterozoic shallow-marine deposits of the Purana basins lying several hundred kilometres north of this terrane. Integrating the existing geological information, it is postulated that the shallow-marine sediments were deposited on a unified land-mass consisting of a large part of Madagascar and the Indian shield that existed before Neoproterozoic time, part of which was later involved in the Pan-African orogeny. Supplementary material: Details of the zircon U–Pb LA-MC-ICP-MS analyses of samples are available at http://www.geolsoc.org.uk/SUP18793 .

Abstract Available lithological, petrological and geochronological data on the rocks of the Eastern Ghats Belt (EGB), which has a key role to play in any model of Indo-Antarctic correlation in Precambrian and Cambrian times, have been synthesized and interpreted. Longitudinal lithological subdivisions of the belt are mostly not supported by recent geochronological data, which rather suggest a fourfold division based on protolith ages of the ortho- and paragneisses. Mineral ages show prominent tectonothermal events at Mesoproterozoic, Grenvillian and Pan-African times. However, not all of the imprints of all the events are preserved in all the geochronological domains. In the most well-studied Domain II, three phases of metamorphism are recorded — an early ultra high-temperature metamorphism with an anticlockwise P – T path, a second granulite facies event at c. 1000 Ma, with a retrograde trajectory of near-isothermal decompression, and a third of amphibolite facies. The available information, however, is not conclusive as to whether or not the entire EGB experienced polyphase UHT metamorphism. The propagation of the Grenvillian orogenic front in the EGB is identified.