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Subgreenschist facies metamorphism of metabasites from the Precordillera terrane of western Argentina; constraints on the later stages of accretion onto Gondwana

Doug Robinson, Richard E. Bevins and Nora Rubinstein
Subgreenschist facies metamorphism of metabasites from the Precordillera terrane of western Argentina; constraints on the later stages of accretion onto Gondwana
European Journal of Mineralogy (June 2005) 17 (3): 441-452

Abstract

The metamorphic character of metabasites of the Precordillera terrain of western Argentina provides constraints that help to distinguish between contrasting models for the tectonic settings during the late stages of the accretion of this terrain onto the margin of Gondwana in late Palaeozoic times. EPMA results are given for chlorite, pumpellyite and amphibole. Metamorphic conditions are constrained to a low-temperature/low-pressure setting at approximately 250-350 degrees C and 2-3 kbar, with geothermal gradients of between 30 and 35 degrees C/km. The metamorphic character of the rocks and the derived P-T conditilons demonstrate that the metamorphism did not develop in an ocean-floor setting as previously proposed. Neither is the metamorphic character compatible with being derived from enhanced heat flow in an extensional setting at the western edge of the Precordillera in the mid-Ordovician, following docking against Gondwana. The most compatible model is one in which the metamorphism developed as a result of collision between the Chilenia and Precordillera terrains in early Devonian times. The metamorphism also constrains the subduction depth to < approximately 15 km if the leading edge of the Precordillera was subducted westwards beneath Chilenia. However, the metamorphic character is better linked to subduction of the leading edge of Chilenia eastwards against the Precordillera.


ISSN: 0935-1221
EISSN: 1617-4011
Serial Title: European Journal of Mineralogy
Serial Volume: 17
Serial Issue: 3
Title: Subgreenschist facies metamorphism of metabasites from the Precordillera terrane of western Argentina; constraints on the later stages of accretion onto Gondwana
Affiliation: University of Bristol, Department of Earth Sciences, Bristol, United Kingdom
Pages: 441-452
Published: 200506
Text Language: English
Publisher: Schweizerbart'sche Verlagsbuchhandlung (Naegele u. Obermiller), Stuttgart, Federal Republic of Germany
References: 39
Accession Number: 2005-044758
Categories: Igneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch maps
S34°00'00" - S30°00'00", W70°00'00" - W68°00'00"
Secondary Affiliation: National Museums and Galleries of Wales, GBR, United KingdomUniversidad de Buenos Aires, ARG, Argentina
Country of Publication: Germany
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United KingdomTwickenhamUKUnited Kingdom
Update Code: 200526
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