Archaean granulite facies metamorphism at the Singhbhum Craton–Eastern Ghats Mobile Belt interface: implication for the Ur supercontinent assembly

Abstract

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.

Tectonic juxtaposition of crust and continental growth during orogenesis: Example from the Rengali Province, eastern India

“…Timing of this thrusting event is yet to be known, but recent geochronological data show that the syn-kinematic granite emplacement within this Rengali granulite occurred at ca. 2.80 Ga which closely matches with the dominant monazite Th-U-Pb age from the pelitic granulite (Mahapatro et al, 2012;Bose et al, 2013). The timing of the M 1 event is still uncertain, but it must be older than 2.80 Ga based on available textural and field relation criteria and limited geochronological data .…”

“…However, the implication of such high-P metamorphic event was not explored further in their study. A recent study by Mahapatro et al (2012) on pelitic granulite enclaves from the same area did not report any high-pressure metamorphism. These workers identified biotite dehydration melting to produce metapelitic granulite.…”

Petrological and geochemical evolution of the Central Gneissic Belt, Rengali Province, eastern India: Implications for the Neoarchean growth and orogenesis

“…1a) where the lithology is dominated by a vast body of ca. 2800 Ma granitoid gneiss (Misra et al, 2000;Crowe et al, 2001;Mahapatro et al, 2012;Bose et al, 2016), referred to as the Pal Lahara gneiss (Saha, 1994). This vast body also contains dismembered bodies of amphibolites and granulites and is interpreted to have formed along the Singhbhum Craton margin during the Neoarchean time (Misra et al, 2000;Crowe et al, 2001).…”

“…Mafic granulites from the eastern part of the Central Gneissic Belt indicate a high-pressure (11-12 kbar) metamorphism followed by cooling and decompression to mid-crustal level (Bose et al, 2015). Pelitic granulite, on the other hand, records much lower pressure (6-8 kbar) granulite metamorphism (Mahapatro et al, 2012;Bose et al, 2015).…”

“…Petrological, structural and geochronological data from this province suggest its evolution through episodic orogenic pulses since the Neoarchean time (Crowe et al, 2001(Crowe et al, , 2003Mahapatro et al, 2012;Bose et al, 2016;Bhattacharya et al, 2016). This study is primarily focused on the central part of the Rengali Province (Fig.…”