The backarc mantle lithosphere in Patagonia, South America
The backarc Patagonia mantle underwent pervasive regional re-crystallisation that left only remnants of the pre-existing mantle. Anhydrous xenoliths (dominantly lherzolites and harzburgites, few dunites) are predominant. Xenoliths containing hydrous phases (lherzolites and harzburgites, rare wehrlit...
| Autores: | , , , , , , |
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| Tipo de recurso: | artículo |
| Estado: | Versión publicada |
| Fecha de publicación: | 2004 |
| País: | Argentina |
| Institución: | Consejo Nacional de Investigaciones Científicas y Técnicas |
| Repositorio: | CONICET Digital (CONICET) |
| Idioma: | inglés |
| OAI Identifier: | oai:ri.conicet.gov.ar:11336/75899 |
| Acceso en línea: | http://hdl.handle.net/11336/75899 |
| Access Level: | acceso abierto |
| Palabra clave: | Lithosphere Melting Percolation Reaction Slab https://purl.org/becyt/ford/1.5 https://purl.org/becyt/ford/1 |
| Sumario: | The backarc Patagonia mantle underwent pervasive regional re-crystallisation that left only remnants of the pre-existing mantle. Anhydrous xenoliths (dominantly lherzolites and harzburgites, few dunites) are predominant. Xenoliths containing hydrous phases (lherzolites and harzburgites, rare wehrlites) abundantly occur only at G. Gregores. Bulk-rock and clinopyroxene trace element patterns range from predominant LREE-depleted, LILE-enriched and variably Nb-depleted, to LREE-enriched patterns, with negative Zr, Hf and Ti spikes when amphibole is present. V-shaped trace element patterns are found only in rare non-recrystallised xenoliths. Trace element abundances in potential melts calculated from clinopyroxene are similar to arc magmas, but in southern Patagonia fade eastwards to E-MORB-like compositions. Trace element characteristics of bulk-rock and pyroxenes are interpreted as the consequence of two processes: (1) melting in the region of thermal inversion of the wedge, triggered by infiltration of hydrous components; (2) reactive porous flow of the melts into the overlaying mantle. The component triggering melting is inferred to be slab-derived in the western occurrences and a garnet-facies, asthenosphere-derived melt in the eastern occurrences as a consequence of wedge thickening. Differences between northern and southern Patagonia are interpreted to be due to variable contribution of slab components to the wedge. Compared to the southern region, slab-derived melts are tentatively attributed to the subduction of older and colder segments of the Nazca plate in the North. © 2004 Elsevier Ltd. All rights reserved. |
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