Refined geological history of the polyphase plutonometamorphic complex in the Thala Hills area (Enderby Land, East Antarctica) from zircon SHRIMP dating and implications for Neoproterozoic amalgamation of Gondwanaland
Evgeniy Mikhalsky, Dmitry Krylov, Nickolay Rodionov, Sergey Presnyakov, Sergey Skublov, Oleg Myasnikov, 2017. "Refined geological history of the polyphase plutonometamorphic complex in the Thala Hills area (Enderby Land, East Antarctica) from zircon SHRIMP dating and implications for Neoproterozoic amalgamation of Gondwanaland", Crustal Evolution of India and Antarctica: The Supercontinent Connection, N. C. Pant, S. Dasgupta
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The Thala Hills area occupies a key position in Gondwanaland reconstructions near the India–Sri Lanka–Antarctica junction. We present U–Pb zircon isotopic age determinations from SHRIMP II obtained on four granite gneiss samples. Three high-temperature tectonomagmatic episodes may be distinguished in the study area at c. 980–970, c. 780–720 and c. 545–530 Ma. The c. 980–970 Ma event corresponds to the Rayner Structural Episode that affected East Antarctica, including the Sør Rondane Mountains to the west and Kemp Land to the east. The c. 780–720 Ma episode included two events at approximately 780 Ma (high-grade anatexis) and 720 Ma (syntectonic granitoid emplacement), and was roughly coeval with tectonomagmatic events in Dronning Maud Land of East Antarctica, as well as in other Gondwanaland regions, such as Madagascar, Sri Lanka and eastern Africa. The c. 780–720 Ma episode may be correlated with the East African Orogeny. These correlations argue for a similar geological evolution and conjugate position for Dronning Maud Land and Enderby Land despite a postulated Cambrian Lützow–Holm Bay suture separating them. The Cambrian (c. 545–530 Ma) episode was manifested by high-grade anatexis that confirms previously identified late Neoproterozoic–Cambrian tectonothermal activities in the study area.
Supplementary material: Trace element compositions of zircons and whole-rock chemical compositions obtained by previous studies are available at https://doi.org/10.6084/m9.figshare.c.3738332
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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.