Petrochronology of the Terre Adelie Craton (East Antarctica) evidences a long-lasting Proterozoic (1.7-1.5 Ga) tectono-metamorphic evolution - Insights for the connections with the Gawler Craton and Laurentia

摘要

The Terre Adelie Craton displays superimposed strain fields related to the Neoarchean (2.6-2.4 Ga, M1) and Paleo-Mesoproterozoic (1.7-1.5 Ga, M2) metamorphic events. M1 is a regional granulite fades event, constrained by P-T modelling at -0.8-1.0 GPa - 800-850 et, followed by a decompressional retrogression in the upper amphibolite fades at -0.6 GPa - 750 degrees C. M2 Stage 1 P-T peak is constrained at 0.6-0.7 GPa - 670-700 degrees C, followed by a steep P-T path down to 0.3 GPa - 550 degrees C. Retrogression after M2 PT peak occurred in a context of dextral shearing along the Mertz Shear Zone along with thrust motions within the eastern Terre Adelie Craton. In this paper, we present a series of 63 new Ar-40/Ar-39 ages of biotite and amphibole pairs in mafic rocks from a complete traverse of the Terre Adelie Craton. Ar-40/Ar-39 Ar dating constrains M2 amphibolite facies metamorphism at a regional scale between 1700 and 1650 Ma, during stage 1 peak metamorphism. During retrogression, lower amphibolite fades recrystallization mainly occurred along vertical shear zones and mafic dykes between 1650 and 1600 Ma (Stage 2), followed by amphibolite to greenschist facies metamorphism until after 1500 Ma (Stage 3). At the scale of the Mawson continent, this event is related to the growth of an active margin above an oblique subduction zone. The supra-subduction model best explains opening of Dumont D'Urville and Hunter basins at 1.71 Ga followed by their rapid closure and metamorphism at 1.70 Ga. In this context, episodic shear zone reactivation and magmatic dyke emplacement led to a partial reequilibration of the Ar-40/Ar-39 system until <1500 Ma. This latter phase of mafic magmatism largely coincides with a hot spot event at the scale of the Gawler Craton and western Laurentia paleocontinent. (C) 2019 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.