Please use this identifier to cite or link to this item: http://hdl.handle.net/2440/124651
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Type: Journal article
Title: Cambro-Ordovician magmatism in the Delamerian orogeny: implications for tectonic development of the southern Gondwanan margin
Author: Foden, J.
Elburg, M.
Turner, S.
Clark, C.
Blades, M.
Cox, G.
Collins, A.
Wolff, K.
George, C.
Citation: Gondwana Research, 2020; 81:490-521
Publisher: Elsevier
Issue Date: 2020
ISSN: 1342-937X
1878-0571
Statement of
Responsibility: 
John Foden ... Morgan L.Blades, Grant Cox, Alan S.Collins, Keryn Wolff, Christian George ... et al.
Abstract: The Delamerian Orogen formed at the final stages of assembly of the Gondwana supercontinent. This system marks the initiation of subduction of the Pacific oceanic lithosphere along a prior rifted and extended passive margin. This paper explores the magmatic consequences following the early Cambrian initiation at the palaeo-Pacific margin in South Australia (SA) and western Victoria. Our data reveal a 50 Ma syn- to post-Delamerian tectono-magmatic history. Sampled from drill core from beneath the eastern Murray Basin cover in eastern SA, boninitic high Mg andesite from drill hole KTH12 and 516.1 ± 2 Ma quartz diorite suggest that first subduction established a volcanic arc within easternmost SA. Pacific-ward trench retreat then resulted in arc migration to reach the Mt Stavely Belt and Stawell Zones in western Victoria by ~510 Ma where boninitic arc magmatism continued until ~490 Ma. In the SA foreland of the Delamerian Orogen, early (522 ± 4 Ma) alkali basalt gave way to intrusion and extrusion of MORB-like tholeiites of back-arc basalt character. Through much of the middle and late Cambrian the SA Delamerian was in the back-arc and under extension but with periodic compression resulting from periodic Pacific-Australian plate coupling beneath the forearc in western Victoria. In SA syn-tectonic I- and S-type granites reflect interaction of MORB-like back-arc magmas and their transported heat with continental-derived sediment of the Kanmantoo Group. The termination of the Delamerian orogeny at ~490 Ma was accompanied by buoyancy-controlled, exhumation and erosion. This was driven by delamination of a mafic, crustal underplate, whose re-melting at 1.5 to 2 GPa and 1050 °C generated the unique 495 ± 1 Ma Kinchina/Monarto adakite. Delamination resulted in lithospheric mantle thinning and local convective overturn allowing upwelling of the asthenosphere to drive the post-kinematic magmatic phase of the Delamerian, yielding voluminous 490 Ma–470 Ma A-type granites.
Rights: © 2020 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
RMID: 1000014182
DOI: 10.1016/j.gr.2019.12.006
Grant ID: http://purl.org/au-research/grants/arc/DP0773913
Appears in Collections:Geology & Geophysics publications

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