The Rauer–Rengali connection in the Indo-Antarctica amalgam: evidence from structure, metamorphism and geochronology
Amol Dayanand Sawant, Saibal Gupta, Chris Clark, Surajit Misra, 2017. "The Rauer–Rengali connection in the Indo-Antarctica amalgam: evidence from structure, metamorphism and geochronology", Crustal Evolution of India and Antarctica: The Supercontinent Connection, N. C. Pant, S. Dasgupta
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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.
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The Proterozoic aeon involved at least three major continental readjustments. India and Antarctica appear in most models of supercontinent reconstructions, but their relative position has been the subject of debate. High-resolution petrological and geochronological data, especially from the Proterozoic mobile belts, provide the principal means of resolving this issue. The ice-covered nature of Antarctica allows only limited access to the rocks, and then only in coastal tracts, so detailed studies in more accessible Proterozoic terrains in India assume added significance.
This volume, a follow-up to the XII International Symposium on Antarctic Earth Science, Goa (a SCAR symposium), provides new data from selected locations in east Antarctica (Enderby Land and Dronning Maud Land) and from India, including the Eastern Ghats Mobile Belt (EGMB), Chota Nagpur Gneissic Complex, the Khasi Hills and the Aravalli–Delhi Mobile Belt. The presented geochronological data, constrained by petrological studies, are expected to provide new insights, especially into the EGMB–east Antarctica connection and the rate of continental readjustments in the post-Rodinia break-up.