Combined Sr-O isotope relationships and petrogenesis of Andean volcanics of South America

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Authors:Déruelle, Bernard; Harmon, Russell S.; Moorbath, Stephen
Author Affiliations:Primary:
Univ. Yaoundé, Fac. Sci., Dep. Earth Sci., Yaounde, Cameroon
Volume Title:Nature (London)
Source:Nature (London), 302(5911), p.814-816. Publisher: Macmillan Journals, London, United Kingdom. ISSN: 0028-0836
Publication Date:1983
Note:In English. 22 refs.
Summary:Active andesitic-type volcanism in the southern Andes (lat. 42-36°S) is characterized by low Sr- and O-isotopic compositions (87Sr/86Sr 0.7036- 0.7043, delta 18O 5.2-6.8per mille). In contrast, volcanic centres in the Central Andes (lat. 24-21°S) are significantly enriched in both 87Sr and 18O. The first combined Sr- and O-isotope study is presented of the southern volcanic zone (SVZ) in Chile (crustal thickness <40 km) and of the southern part of the central volcanic zone (CVZ) in the borderlands of Bolivia, Chile and Argentina (crustal thickness approx 60-70 km). Only one of 13 volcanic centres studied (Lascar) exhibits a correlated increase in both 87Sr and 18O parallel with the basalt-andesite-rhyolite compositional change, indicative of contamination by upper crust through a fractional crystallization-assimilation mechanism. The other centres of the CVZ, for which there is an overall Sr-O correlation, document the variable contamination of mantle-derived magmas at depth in the lower crust which had been thickened by Mesozoic and earlier plutonism. [T.R.]
Subjects:Alkaline earth metals; Assimilation; Crust; Differentiation; Fractional crystallization; Geochemistry; Igneous rocks; Isotopes; Magmas; Metals; O-18/O-16; Oxygen; Petrology; Pollution; Sr-87/Sr-86; Stable isotopes; Strontium; Upper crust; Volcanic rocks; Andes; Argentina; Bolivia; Chile; South America
Abstract Numbers:84M/2956
Record ID:1986061313
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from PASCAL, Institute de l'Information Scientifique et Technique
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