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Petrogenesis of the Puerto Eden igneous and metamorphic complex, Magallanes, Chile : Late Jurassic syn-deformational anatexis of metapelites and granitoid magma genesis

Calderon, M.; Herve, F.; Massonne, H.-J.; Tassinari, C.G.; Pankhurst, Robert; Godoy, E.; Theye, T.. 2007 Petrogenesis of the Puerto Eden igneous and metamorphic complex, Magallanes, Chile : Late Jurassic syn-deformational anatexis of metapelites and granitoid magma genesis. Lithos, 93 (1-2). 17-38. 10.1016/j.lithos.2006.03.044

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Abstract/Summary

A suite of schists, gneisses, migmatites, and biotite granitoids from the Puerto Edén Igneous and Metamorphic Complex (PEIMC) and biotite–hornblende granitoids of the South Patagonian batholith (southern Chile) has been studied. For that purpose, the chemistry of minerals and the bulk rock composition of major and trace elements including Rb–Sr and Sm–Nd isotopes were determined. Mineralogical observations and geothermobarometric calculations indicate high-temperature and low-pressure conditions (ca. 600–700 °C and 3 to 4.5 kbar) for an event of metamorphism and partial melting of metapelites in Late Jurassic times (previously determined by SHRIMP U–Pb zircon ages). Structures in schists, gneisses, migmatites and mylonites indicate non-coaxial deformation flow during and after peak metamorphic and anatectic conditions. Andalusite schists and sillimanite gneisses yield initial 87Sr/86Sr ratios of up to 0.7134 and εNd150 values as low as − 7.6. Contemporaneous biotite granitoids and a coarse-grained orthogneiss have initial 87Sr/86Sr ratios between 0.7073 and 0.7089, and εNd150 values in the range − 7.6 to − 4.4. This indicates that metamorphic rocks do not represent the natural isotopic variation in the migmatite source. Thus, a heterogeneous source with a least radiogenic component was involved in the production of the biotite granitoids. The PEIMC is considered as a segment of an evolving kilometre-sized and deep crustal shear zone in which partial melts were generated and segregated into a large reservoir of magmas forming composite plutons in Late Jurassic times. A biotite–hornblende granodiorite and a muscovite–garnet leucogranite show initial 87Sr/86Sr ratios of 0.7048 and 0.7061, and εNd100 values of − 2.6 and − 1.8, respectively, and are thus probably related to Early Cretaceous magmas not involved in the anatexis of the metasedimentary rocks.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.lithos.2006.03.044
Programmes: BGS Programmes > NERC Isotope Geoscience Laboratory
ISSN: 0024-4937
Additional Information. Not used in RCUK Gateway to Research.: Text not available
Additional Keywords: Upper Jurassic, Petrogenesis, Argillaceous rocks & sediments, Gondwana
NORA Subject Terms: Earth Sciences
Related URLs:
Date made live: 18 Sep 2008 14:17
URI: http://nora.nerc.ac.uk/id/eprint/3465

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