Locating hidden terrane boundaries in East Antarctica with detrital feldspar Pb isotopes
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...
Main Authors: | , , , , , , |
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Format: | Conference Object |
Language: | English |
Published: |
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2018
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Subjects: | |
Online Access: | http://agcc.org.au/ http://ecite.utas.edu.au/131213 |
Summary: | 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 15.516.1 and ⁰⁶Pb/⁰⁴Pb of 1719. In contrast, Australo-Antarctica has a feldspar Pb-isotope signature characterised by a tight cluster of ⁰⁷Pb/⁰⁴Pb (15.515.8) and ⁰⁶Pb/⁰⁴Pb (16.517) 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. |
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