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Mesozoic-Cenozoic evolution of the North Patagonian Batholith in Aysen, southern Chile

Pankhurst, R. J.; Weaver, S. D.; Herve, F.; Larrondo, P.. 1999 Mesozoic-Cenozoic evolution of the North Patagonian Batholith in Aysen, southern Chile. Journal of the Geological Society, 156 (4). 673-694. 10.1144/gsjgs.156.4.0673

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Abstract/Summary

A detailed Rb-Sr geochronological and geochemical study has been carried out on granitoids of the North Patagonian batholith in Aysén. The results for 25 plutonic bodies reveal a complex age pattern. The principal zones defined are, from west to east: Late Cretaceous (a single 76 Ma pluton), Early Cretaceous (c. 135 Ma), Eocene (c. 45 Ma), and Early Miocene (25-15 Ma), reverting to mid-Cretaceous (120-90 Ma) in the Main Cordillera. The igneous suite is typically metaluminous and calc-alkaline, with hornblende-biotite granodiorite and tonalite dominant, although small bodies of Late Miocene/Pliocene (c. 10-5 Ma) peraluminous leucogranite occur sporadically. Tertiary plutonism extends to gabbroic compositions and is concentrated in the vicinity of the dextral strike-slip Liquine-Ofqui fault zone. The highest initial 87Sr/86Sr ratios (c. 0.7050) occur in the Early Cretaceous group, with a sharp decrease to 0.7034–0.7045 that persists until a Late Miocene reversal to higher values (0.7040–0.7048). These variations are reflected by Nd isotopes, but trends in the ɛSr, v. ɛNd, diagram show that this is not due to contamination from the accretionary complex into which the batholith was emplaced. An origin by melting of mafic crustal underplate and lower crust is suggested for the main magma suite. The discrete episodes of magmatism correlate with significant changes in subduction kinematics.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1144/gsjgs.156.4.0673
Programmes: BAS Programmes > Pre 2000 programme
ISSN: 0016-7649
Additional Keywords: granites, absolute age, isotopes, petrogenesis, tectonics
Date made live: 22 Oct 2013 10:58 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/503606

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