The South Tasman Rise (STR) consists of the west- and east-South Tasman Rise, which are submerged continental fragments that were part of the East Gondwana Continent. The STR formed following the extension between Antarctica and Australia that generated the Tasmanian Gateway. It is located between Tasmania and Antarctica and represents a vital, but often overlooked, link to understand the geological evolution of both North Victoria Land and Tasmania. Reconstruction of Gondwana shows that STR was contiguous to several continental fragments that are now thousands of km apart. Because of its central location in the plate boundary framework that developed within East Gondwana, the STR underwent all the major tectonic events that led to the dispersal of Gondwana. The STR is therefore a centrepiece in understanding the complex tectonic history of this region. Extensive sampling of STR rocks took place during AGSO cruise 147. Investigation on the metamorphic rocks of the STR pointed out interesting correlations with rocks from the Wilson Terrane and the Lanterman Metamorphics (Antarctica) and from Tasmania (Berry et al., 1977). Based on this evidence, and aiming at clarifying the correlation between mainland Australia, Tasmania and Antarctica, we undertook a detailed petrologic and geochronologic study on magmatic rocks dredged at 10 different sites from South Tasman Rise. Seven of these rocks yield Cambrian ages in the range 487-507 Ma, consistent with the Ross-Delamerian orogen; one sample is a granite gneiss of late Proterozoic crystallization age (ca. 740 Ma), which corresponds to the Wickham event (Tasmania) or Beardmore orogen (Antarctica); one sample has Grenville age (Fioretti et al., 2005); and one sample is Late Devonian (ca. 363 Ma), an age that is well represented in Australia, Tasmania and Antarctica. Petrographic observation, geochemical investigation and zircon typologic study are presented here to characterize these rocks, and to test their possible correlation with coeval rocks in Antarctica and Australia.
Fioretti, A., Bergomi, M., Caironi, V., Korsch, R., Tunesi, A., Visonà, D. (2014). U-Pb SHRIMP zircon dating of magmatic rocks dredged from the South Tasman Rise (Australia). In RENDICONTI Online della Società Geologica Italiana (pp.68-68).
U-Pb SHRIMP zircon dating of magmatic rocks dredged from the South Tasman Rise (Australia)
BERGOMI, MARIA ALDINA;TUNESI, ANNALISA MARIA;
2014
Abstract
The South Tasman Rise (STR) consists of the west- and east-South Tasman Rise, which are submerged continental fragments that were part of the East Gondwana Continent. The STR formed following the extension between Antarctica and Australia that generated the Tasmanian Gateway. It is located between Tasmania and Antarctica and represents a vital, but often overlooked, link to understand the geological evolution of both North Victoria Land and Tasmania. Reconstruction of Gondwana shows that STR was contiguous to several continental fragments that are now thousands of km apart. Because of its central location in the plate boundary framework that developed within East Gondwana, the STR underwent all the major tectonic events that led to the dispersal of Gondwana. The STR is therefore a centrepiece in understanding the complex tectonic history of this region. Extensive sampling of STR rocks took place during AGSO cruise 147. Investigation on the metamorphic rocks of the STR pointed out interesting correlations with rocks from the Wilson Terrane and the Lanterman Metamorphics (Antarctica) and from Tasmania (Berry et al., 1977). Based on this evidence, and aiming at clarifying the correlation between mainland Australia, Tasmania and Antarctica, we undertook a detailed petrologic and geochronologic study on magmatic rocks dredged at 10 different sites from South Tasman Rise. Seven of these rocks yield Cambrian ages in the range 487-507 Ma, consistent with the Ross-Delamerian orogen; one sample is a granite gneiss of late Proterozoic crystallization age (ca. 740 Ma), which corresponds to the Wickham event (Tasmania) or Beardmore orogen (Antarctica); one sample has Grenville age (Fioretti et al., 2005); and one sample is Late Devonian (ca. 363 Ma), an age that is well represented in Australia, Tasmania and Antarctica. Petrographic observation, geochemical investigation and zircon typologic study are presented here to characterize these rocks, and to test their possible correlation with coeval rocks in Antarctica and Australia.
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