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Revisiting the Australian-Antarctic ocean-continent transition zone using petrological and geophysical characterization of exhumed subcontinental mantle


McCarthy, A and Falloon, TJ and Sauermilch, I and Whittaker, JM and Niida, K and Green, DH, Revisiting the Australian-Antarctic ocean-continent transition zone using petrological and geophysical characterization of exhumed subcontinental mantle, Geochemistry Geophysics Geosystems, 21, (7) Article e2020GC009040. ISSN 1525-2027 (2020) [Refereed Article]


Copyright Statement

Copyright 2020 the authors. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0)

DOI: doi:10.1029/2020GC009040


The final lithospheric breakup of the Australian‐Antarctic rift system remains controversial due to sparse geological constraints on the nature of the basement along the ocean‐continent transition (OCT) zones. We present new interpretations of multichannel seismic reflection transects and new petrological data of dredged mantle rocks along the East Antarctic margin (Seamount B, offshore Terre Adélie). By combining both data sets, we show that a 50–100 km wide domain of cold and fertile subcontinental mantle was exhumed along the magma‐poor Antarctic margin. This study represents only the second locality, along with the Iberia‐Newfoundland margins, where the importance of exhumed mantle domains along OCTs can be clearly identified. The dredged peridotites preserve characteristics similar to mantle xenoliths found in syn‐ to post‐rift volcanism at the eastern end of the Australian margin (Victoria and Tasmania), indicating the exhumation of fertile subcontinental mantle during rifting between Australia and Antarctica. Seamount B represents the initial stages of exhumation of cold subcontinental lithosphere along an OCT during rifting. This thick mantle domain was likely affected by melt impregnation at high pressure (8 kbar), leading to the formation of plagioclase‐pyroxenites. The combination of continental rifted blocks, a wide domain of volcanic‐poor subcontinental mantle and (ultra‐) slow spreading is analogous to OCTs from the Jurassic Western Tethys and Iberia‐Newfoundland rifted margins. Additionally, evidence of melt stagnation at high pressure suggests that magmatism along the Australian‐Antarctic rifted margins was sufficient to form magnetic anomalies that can be used as isochrons despite their formation in lithosphere other than mature, steady‐state ocean crust.

Item Details

Item Type:Refereed Article
Keywords:East Antarctica, seamount B, exhumed mantle, subcontinental mantle, pyroxenite, lherzolite, melt impregnation, olivine, clinopyroxene, orthopyroxene, spinel, pargasite, plagioclase, laser ablation ICP-Ms trace element geochemistry
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and metamorphic petrology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:McCarthy, A (Mr Anders McCarthy)
UTAS Author:Falloon, TJ (Dr Trevor Falloon)
UTAS Author:Sauermilch, I (Miss Isabel Sauermilch)
UTAS Author:Whittaker, JM (Associate Professor Jo Whittaker)
UTAS Author:Green, DH (Professor David Green)
ID Code:139766
Year Published:2020
Deposited By:Earth Sciences
Deposited On:2020-07-02
Last Modified:2020-08-17
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