The Rauer–Rengali connection in the Indo-Antarctica amalgam: evidence from structure, metamorphism and geochronology

Abstract

India and East Antarctica collided during assembly of the Rodinia supercontinent at around 1 Ga. Granulites related to this orogeny are exposed in the Eastern Ghats Province (EGP) in India, and these are believed to have been contiguous with granulites of the Rayner Province in East Antarctica at that time. In the Indian segment, we describe a shear zone between the EGP and the Rengali Province to its north along which strongly foliated bands of garnetiferous quartzofeldspathic gneisses, khondalites and charnockites are intercalated. The foliation is consistently east–west trending and subvertical, with downdip intersection lineations. Maximum asymmetry in horizontal sections and textural analysis using electron backscattered diffraction (EBSD) analysis confirm that the transport vector during shearing was horizontal. The shear zone is interpreted as a dextral strike-slip fault that operated under greenschist-facies conditions, juxtaposing 1 Ga EGP granulites with 2.8 Ga cratonic granulites to the north. The corresponding region in East Antarctica is represented by the Rauer Group, where intercalations between 2.8 and 1.0 Ga, vertically orientated lithologies, are observed alongside 0.5 Ga shear zones. These features in the Rauer Group can be correlated with those in the Rengali Province, further supporting existing palaeogeographical reconstructions of Gondwana.

Origin of orthopyroxene-bearing felsic gneiss from the perspective of ultrahigh-temperature metamorphism: an example from the Chilka Lake migmatite complex, Eastern Ghats Belt, India

“…In the proposed Indo-Antarctic fit, the position of the Eastern Ghats Province was adjacent to the Rayner Province of East Antarctica (Harley, 2003;Dasgupta and Sengupta, 2003;Bose et al, 2011a) and the Chilka Lake area was positioned close to the Prydz Bay area of the Rayner Province. This geographical fit was later geologically vindicated in recent studies (Bose et al, 2016a, Sawant et al, 2017. On the basis of metamorphic characters, geochronological constraints and published Pb-isotopic signatures (Flowerdew et al, 2013), Bose et al (2016a) argued that the Chilka Lake area was a part of the Prydz Bay before it joined to the rest of the Eastern Ghats Province during c. 550−500 Ma.…”

Origin of magmatic and tectonic fabrics in the Remal granite-gneiss, Singhbhum Craton, India

“…The contact between the Singhbhum Craton and the Rengali Province, the Barakot-Akul Shear Zone, operated in the greenschist facies and is associated with dextral strike-slip movement (Misra & Gupta, 2014). This shear zone is interpreted as part of a dextral strike-slip step-over zone, the southern boundary of which is the Kerajang-Brahmani Shear Zone (Crowe et al 2003;Misra & Gupta, 2014;Sawant et al 2017), which is also associated with similar kinematics and deformation conditions. This latter shear zone represents the terrane boundary between the Rengali Province and the Eastern Ghats Mobile Belt (Dobmeier & Raith, 2003).…”

“…However, the manner of juxtaposition of the Rengali Province and the Singhbhum Craton is still a matter of debate. While some workers postulate the Rengali Province to be a rotated slice of the Bastar Craton, which was juxtaposed against the Singhbhum Craton by movement along a system of dextral strike-slip shear zones (Misra & Gupta, 2014;Sawant et al 2017;Gupta et al 2020), other workers believe that the Rengali Province represents the exhumed root of the Singhbhum Craton that was thrust back onto the craton along the Sukinda Thrust (Mahapatro et al 2012;Bose et al 2021). If the Rengali Province was indeed thrust onto the Singhbhum Craton along the Sukinda Thrust then the footwall across the thrust, i.e.…”

Petrological evolution of the Eastern Ghats Belt- Current status and future directions

“…An alternative idea is that the northern boundary of the EGP with the Rengali Province is a strike-slip shear zone that possibly operated around 0.5 Ga (Misra and Gupta, 2014); the affinity of the Rengali Province could also be with the Bastar Craton. Sawant et al (2017) pointed out structural, metamorphic and geochronologic similarities between the EGPRengali contact zone and the Rauer Group of East Antarctica, that also evolved as a c. 0.5 Ga strike-slip shear zone. It appears, therefore, that the ancestry of the Rengali Province as well as the nature and timing of tectonothermal events are poorly understood.…”