Andean cenozoic volcanism: magma genesis in the light of strontium isotopic composition and trace-element geochemistry

Journal Article · Thu Apr 01 04:00:00 EST 1976 · Geol. Soc. Am., Bull.; (United States)

DOI:https://doi.org/10.1130/0016-7606(1976)87<592:ACVMGI>2.0.CO;2· OSTI ID:7248376

James, D E ^[1]; Brooks, C; Cuyubama, A

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1. Carnegie Institution of Washington, DC

Subduction of the oceanic Nazca plate beneath the western edge of the South American plate is thought by most proponents of plate theory to have generated the tectonic forces and magmatic activity that have structured the Andean orogen. By this view, the Cenozoic andesitic magmas of the Andean stratovolcanoes originated within the oceanic crust of the descending plate or within the mantle adjacent to that plate. Accordingly, these Andean volcanic rocks should exhibit chemical and isotopic compositions similar to those of island-arc andesite of like origin. However, while major- and minor-element analyses reveal that the late Cenozoic volcanic rocks are chemically akin to those of the calc-alkalic suite of circum-Pacific island arcs, they exhibit significantly higher Sr/sup 87//Sr/sup 86/ ratios. The purpose of this paper is to examine these anomalously high isotopic ratios in the light of trace-element geochemistry and to develop from this a model for the genesis of the Cenozoic magma.

• OSTI ID: 7248376
• Journal Information: Geol. Soc. Am., Bull.; (United States), Journal Name: Geol. Soc. Am., Bull.; (United States) Vol. 87:4; ISSN BUGMA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580202* -- Geophysics-- Volcanology-- (1980-1989)
ALKALINE EARTH ISOTOPES
ANDES
CHEMICAL COMPOSITION
CHEMISTRY
GEOCHEMISTRY
IGNEOUS ROCKS
ISOTOPE RATIO
ISOTOPES
MAGMA
MOUNTAINS
ORIGIN
ROCKS
STRONTIUM ISOTOPES
VOLCANIC REGIONS
VOLCANIC ROCKS
VOLCANISM