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Preservation of a fragmented late Neoproterozoic-earliest Cambrian hyper-extended continental-margin sequence in the Australian Delamerian Orogen

G. M. Gibson, D. C. Champion and T. R. Ireland
Preservation of a fragmented late Neoproterozoic-earliest Cambrian hyper-extended continental-margin sequence in the Australian Delamerian Orogen (in Sedimentary basins and crustal processes at continental margins; from modern hyper-extended margins to deformed ancient analogues, G. M. Gibson (editor), F. Roure (editor) and G. Manatschal (editor))
Special Publication - Geological Society of London (March 2015) 413 (1): 269-299

Abstract

Mafic and ultramafic rocks intercalated with metamorphosed deep-marine sediments in the Glenelg River Complex of SE Australia comprise variably tectonized fragments of an interpreted late Neoproterozoic-earliest Cambrian hyper-extended continental margin that was dismembered and thrust westwards over the adjacent continental margin during the Cambro-Ordovician Delamerian Orogeny. Ultramafic rocks include serpentinized harzburgite of inferred subcontinental lithospheric origin that had already been exhumed at the seafloor before sedimentation commenced, whereas mafic rocks exhibit mainly enriched- and normal-type mid-ocean ridge basalt (E- and N-MORB) compositions consistent with emplacement in an oceanic setting. These lithologies and their metasedimentary host rocks predate deposition of the Cambrian Kanmantoo Group and are more likely to represent temporal equivalents of the older Normanville Group or underlying Neoproterozoic Adelaide Supergroup. The Kanmantoo Group is host to basaltic rocks with higher degrees of crustal contamination and yields detrital zircon populations dominated by 600-500 Ma ages. Except for quartz greywacke confined to the uppermost part of the sequence, metasedimentary rocks in the Glenelg River Complex are devoid of detrital zircon, and are interstratified with subordinate amounts of metachert and carbonaceous dolomitic slate suggestive of deposition in a deep-marine environment far removed from any continental margin. Seismic reflection data support the idea that the Glenelg River Complex is underlain by mafic and ultramafic rocks, and preclude earlier interpretations based on aeromagnetic data that the continental margin incorporates a thick pile of seawards-dipping basaltic flows analogous to those of volcanic margins in the North Atlantic. Correlative hyper-extended continental rift margins to the Glenelg River Complex occur along strike in formerly contiguous parts of Antarctica.


ISSN: 0305-8719
EISSN: 2041-4927
Coden: GSLSBW
Serial Title: Special Publication - Geological Society of London
Serial Volume: 413
Serial Issue: 1
Title: Preservation of a fragmented late Neoproterozoic-earliest Cambrian hyper-extended continental-margin sequence in the Australian Delamerian Orogen
Title: Sedimentary basins and crustal processes at continental margins; from modern hyper-extended margins to deformed ancient analogues
Author(s): Gibson, G. M.Champion, D. C.Ireland, T. R.
Author(s): Gibson, G. M.editor
Author(s): Roure, F.editor
Author(s): Manatschal, G.editor
Affiliation: Geoscience Australia, Canberra, A.C.T., Australia
Pages: 269-299
Published: 20150331
Text Language: English
Publisher: Geological Society of London, London, United Kingdom
Number of pages: 31
References: 99
Accession Number: 2015-101491
Categories: Solid-earth geophysicsIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Includes appendices
Illustration Description: illus. incl. block diags., sects., strat. cols., 2 tables, geol. sketch maps
S37°30'00" - S37°30'00", E141°24'00" - E141°24'00"
Secondary Affiliation: Australian National University, AUS, Australia
Source Note: Online First
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 201544
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