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

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 Lüctzow–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.