Structure and U-Pb dating of the Saint-Arnac pluton and the Ansignan charnockite Agly Massif: a cross-section from the upper to the middle crust of the Variscan Eastern PyreneesReport as inadecuate




Structure and U-Pb dating of the Saint-Arnac pluton and the Ansignan charnockite Agly Massif: a cross-section from the upper to the middle crust of the Variscan Eastern Pyrenees - Download this document for free, or read online. Document in PDF available to download.

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In the Agly Massif Pyrenees, two Variscan plutons, the Saint-Arnac pluton and the Ansignancharnockite, intrude different levels of a c. 10 km thick crustal section. The Saint-Arnac pluton intrudesthrough upper crustal rocks and the Ansignan charnockite cuts mid-crustal country-rocks. A structural studyof these plutons based on the anisotropy of magnetic susceptibility technique, combined with a kinematicstudy of the country-rocks, shows that the structures and emplacement modes of the plutons are compatiblewith those of the other plutons of the Pyrenees emplaced during the D2 transpressive phase. U–Pb dating onzircons from the Saint-Arnac pluton yields a 308.3 1.2 Ma age for a diorite and a 303.6 4.7 Ma age for agranodiorite. The charnockite was previously dated at 315 Ma. The emplacement ages of these two intrusionsare thus separated by at least 5 Ma. First, numerous sills and laccoliths, such as the Ansignan laccolith, wereinjected in the middle crust, and this induced heating and thickening. Subsequently, the large Saint-Arnacpluton was injected in the upper crust at the beginning of formation of a gneissic dome.



Author: Olivier, Philippe; - Gleizes, Gérard; - Paquette, Jean-Louis; - Muñóz Sáez, Carolina; -

Source: http://repositorio.uchile.cl/



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