| Summary: | © 2013 Dr. Ling Chung The crustal architecture of previously adjacent basement terranes in SE Australia, Tasmania and northern Victoria Land, Antarctica is a legacy of late Neoproterozoic-Paleozoic subduction along the east Gondwana margin, highlighting the Cambro-Ordovician Delamerian-Ross orogeny. Structures in this ancient crust were reactivated during late Mesozoic-Cenozoic Gondwana breakup. Tasmania and the offshore South Tasman Rise (STR) lay in a crucial location at the centre of these continental fragments and potentially contain clues regarding the nature of Gondwana dispersal. This study reports results of a systematic thermochronological study that has been carried out on STR dredge samples and Tasmanian dolerites to uncover the history of the ancient subduction system and the post-break up thermal history recorded in their crust. Oceanic investigations (ODP, IODP, magnetic and seismic surveys and swath mapping, etc) have been conducted across the STR and the western transform boundary over the past few decades. Important results have been previously reported and form the foundation towards understanding the tectonic significance of this region. In particular, the interpreted seismic profiles along with basement dredge materials provide essential structural, stratigraphic and petrological controls as in situ investigations are not possible. Nevertheless, only limited geochronological data are available and the regional thermal history is still sparse. In this study a systematic low-temperature thermochronological study has been carried out, applying 40Ar/39Ar, AFT, ZHe and AHe dating techniques to the STR dredge samples to disclose the tectonic evolution of study area. Results suggest that the western and eastern terranes of the STR (W-STR and E-STR, respectively) evolved differently prior to east-Gondwana breakup. While the 40Ar/39Ar data from the W-STR suggest late Cambrian-early Ordovician ages (~495-460 Ma), results from the E-STR suggests a much younger early Carboniferous (Mississippian) age ...
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