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In this study, we present precise pressure-temperature (P-T) and age constraints of ultrahigh-temperature (UHT) metamorphism of the Bhandara-Balaghat granulite (BBG) domain at the southern margin of the Central Indian Tectonic Zone (CITZ). Supracrustal and metaigneous granulites of this domain, which lie as detached pods and lenses of various sizes within felsic gneiss-migmatite association record protracted high-T crustal anatexis events, broadly synchronous with and/or punctuated with felsic and mafic plutonism. Magnesian metagreywacke protolith of the supracrustal suite records extensive biotite melting and subsequent melt extractions at deep crustal, UHT metamorphic conditions (T ! $9008C at P$8 kbar), producing restitic mineral assemblages of garnet þ rutile, garnet þ cordierite and garnet þ aluminous orthopyroxene. The diversity of the mineral assemblages is related to the domainal-scale variation of the bulk rock composition. In situ chemical age dating of five monazite grains, which occur in the different textural settings of the garnet þ cordierite þ orthopyroxene þ rutile-bearing granulite reveals two age domains: (1) Pervasive $1.6 Ga domain, which is recorded in monazites occurring as inclusions in garnet and in the leucosome matrix is correlated with the timing of the UHT metamorphism. (2) $1.47 Ga domain reflects a fluid-mediated recrystallization event leading to dissolution and re-precipitation of older monazite. The $1.6 Ga monazite chemical ages provide robust constraints on the timing of the earliest stage of tectonothermal processes in the CITZ (defined here as the 'Central Indian Orogeny'). The significance of the $1.6 Ga hot orogenesis in interorogen correlation is discussed.

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In this study, we investigate the geological significance and the antiquity of lower crustal granulite facies metamorphism from the Rengali Domain, which lies in between the Singhbhum Craton in the north and the Eastern Ghats Mobile Belt in the south. Petrographic, mineral compositional, metamorphic reaction history and geothermobarometric studies of two representative metapelite granulite samples reveal widespread biotite melting at peak granulite facies metamorphic conditions of 7.8 ± 0.13 kbar, 849 ± 31°C and subsequent melt extraction, producing a mixture of residual granulites and melts in the Rengali Province. Depending on local bulk rock compositional variations, biotite melting produced peak metamorphic assemblages of garnet + cordierite in the more aluminous compositional domain, while garnet + orthopyroxene + cordierite resulted in domains of intermediate alumina. During post-peak cooling, there were localized developments of biotite + sillimanite + quartz symplectites replacing garnet and cordierite and biotite + quartz intergrowths after orthopyroxene. Application of garnet-orthopyroxene and garnet-biotite Fe-Mg exchange thermometers to co-existing garnet rim and symplectitic biotite show the extent of cooling to 610-660°C. Electron microprobe geochronology of texturally well constrained monazites indicates the timing of peak granulite metamorphism at 3057 ± 17 Ma and its metamorphic reheating at 2781 ± 16 Ma. The present findings when collated with available geological and geophysical data appear to indicate that the studied granulites and the associated granite gneisses, charnockite and enderbite suite of rocks of the Rengali Domain are part of the exhumed lower continental crust of the Singhbhum Craton. The significance of this Neoarchaean orogenesis in the 'Ur' supercontinent assembly is discussed.

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