Metamorphosed fragments of oceanic crust in the upper Paleozoic Chonos accretionary complex, southern Chile

Hervé, F; Greene, F; Pankhurst, R.J. 1994 Metamorphosed fragments of oceanic crust in the upper Paleozoic Chonos accretionary complex, southern Chile. Journal of South American Earth Sciences, 7 (3-4). 263-270. 10.1016/0895-9811(94)90012-4

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Abstract/Summary

A 15 km2 body of metabasite with occasional pillow structures occurs within the Paleozoic accretionary complex in Isla Italia and Isla Dring. Trace elements and REE geochemistry indicate similarities between the metabasites and either plume-related mid-oceannic ridge basalts (P-type MORB) or ocean-island tholeiite basalte. The chemistry of relict clinopyroxenes is also indicative of an ocean-floor basalt protolith. The metabasites exhibit very low-grade metamorphism (pumpellyite-stilpnomelane-actinolite assemblage), comparable to the grade of the sorrounding semi-pelitic mélange as determined by illite crystallinity studies. Isotopic modification of the RbSr system in the metabasites occurred during high fluid-pressure metamorphism, probably by introduction of metamorphic fluids from the sorrounding metapelites. A relatively early tectonic emplacement of the body into the accretionary complex before metamorphism and the generation of the main regional S2 foliation is proposed to explain these characteristics, in contrast to its previous interpretation as a late intrusion into the sorrounding metamorphic rocks.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1016/0895-9811(94)90012-4
Programmes:	BAS Programmes > Pre 2000 programme
ISSN:	08959811
Date made live:	15 Mar 2017 09:55 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/516516

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