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Locating hidden terrane boundaries in East Antarctica with detrital feldspar Pb isotopes


Mulder, J and Halpin, J and Daczko, N and Meffre, S and Orth, K and Thompson, J and Morrissey, L, Locating hidden terrane boundaries in East Antarctica with detrital feldspar Pb isotopes, Australian Geoscience Council Convention Abstracts, 14-18 October 2018, Adelaide, South Australia, pp. 362. (2018) [Conference Extract]

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The assembly of eastern Gondwana involved the amalgamation of Indo-Antarctica and Australo-Antarctica along the Kuunga orogen. The location of the suture or sutures between Indo-Antarctica and Australo-Antarctica within the Kuunga orogen remains debated as key geological relationships are concealed beneath ice. The most recent interpretation identifies the ‘Mirny Fault’ as a key suture between crust of Indo-Antarctic and Australo-Antarctic affinity. However, sparse exposure of bedrock in this region precludes traditional geological characterisation of the crust on both sides this structure.

Here, we test the Mirny Fault as a key suture between Indo-Antarctica and Australo-Antarctica using Pb isotopes of detrital feldspars from offshore sediments referenced to new and compiled feldspar Pb isotopic data from onshore exposures of Indo-Antarctica and Australo-Antarctica. The feldspar Pb-isotope signature of Indo-Antarctica forms a broad population with ˛⁰⁷Pb/˛⁰⁴Pb ratios of 15.5—16.1 and ˛⁰⁶Pb/˛⁰⁴Pb of 17—19. In contrast, Australo-Antarctica has a feldspar Pb-isotope signature characterised by a tight cluster of ˛⁰⁷Pb/˛⁰⁴Pb (15.5—15.8) and ˛⁰⁶Pb/˛⁰⁴Pb (16.5—17) ratios, which is distinct from Indo-Antarctica. Locally-derived Holocene sediments offshore of the Mirny region contain detrital feldspars with Pb-isotope compositions recording a contribution from both Indo-Antarctica and Australo-Antarctica.

The presence of Australo-Antarctic and Indo-Antarctic crust near the Mirny Fault supports the interpretation of this structure as a fundamental terrane boundary. We interpret the Mirny Fault as the key suture between Indo-Antarctica and Australo-Antarctica and trace this boundary into the interior of East Antarctica to connect with an inferred Gondwanan-aged suture within the Gamburtsev Subglacial Mountains.

Item Details

Item Type:Conference Extract
Keywords:Antarctica, Gondwana, Kuunga Orogen, feldspar
Research Division:Earth Sciences
Research Group:Geology
Research Field:Geochronology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Halpin, J (Dr Jacqueline Halpin)
UTAS Author:Meffre, S (Dr Sebastien Meffre)
UTAS Author:Orth, K (Dr Karin Orth)
UTAS Author:Thompson, J (Mrs Jennifer Thompson)
ID Code:131213
Year Published:2018
Deposited By:Oceans and Cryosphere
Deposited On:2019-03-06
Last Modified:2019-03-07

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