Modified Gulf of California model for South Georgia,north Scotia Ridge, and implications for the Rocas Verdes back-arc basin, southern Andes

Alabaster, T.; Storey, B.C.. 1990 Modified Gulf of California model for South Georgia,north Scotia Ridge, and implications for the Rocas Verdes back-arc basin, southern Andes. Geology, 18 (6). 497-500. 10.1130/0091-7613(1990)018<0497:MGOCMF>2.3.CO;2

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Abstract/Summary

New field mapping and an integrated trace element and Nd isotopic study have been undertaken on the Jurassic-Cretaceous Larsen Harbour Complex on the island of South Georgia, recognized as a displaced part of the southern Andes ensialic, autochthonous Rocas Verdes marginal basin. Five basalt groups (Groups I-V) are identified from trace element data; initial Nd isotopic compositions suggest that they are derived from only two sources. Magmas produced during early stages of continental lithospheric attenuation (Groups I-III) were derived by varying degrees of partial melting and fractional crystallization from a large ion lithophile element (LILE)-enriched, low-ϵNd mantle source relative to normal (N)-type mid-ocean ridge basalt (MORB). Magmas produced during later stages of rifting (Groups IV and V) were, however, derived from a high-ϵNd asthenospheric mantle source similar to N-type MORB, unaffected by earlier LILE enrichment. Our data do not concur with previous suggestions that the Larsen Harbour Complex and, by implication, the Rocas Verdes formed in a supra-subduction-zone setting. On the basis of geologic and geochemical evidence, we favor basin formation along an oblique-slip margin akin to that of the Gulf of California.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1130/0091-7613(1990)018<0497:MGOCMF>2.3.CO;2
ISSN:	0091-7613
Date made live:	14 Jun 2018 13:23 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/520274

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