The emplacement of the granite-migmatite dome of the Montagne Noire Axial Zone (French Massif Central): new insights from AMS and petro-structural studies

Abstract : In the southern French Massif Central, the Montagne Noire Axial Zone is a NE-SW elongated granitic-migmatitic dome surrounded by recumbently folded Palaeozoic sedimentary series with a southern vergence. The Axial Zone is composed of micaschist and augen gneiss, cordierite migmatite, and anatectic Laouzas granite from edge to centre, respectively. Syn- to late kinematic granitoids intrude the dome. Anisotropy Magnetic Susceptibility (AMS) study (135 sites and almost 830 cores) and petro-structural studies have been carried out on anatectic cordierite/garnet granites and migmatites. Thermomagnetic experiments indicate that biotite is the main carrier of the AMS fabric. The attitude of the magnetic foliation complies with the preferred orientation of biotite, schlierens, enclaves and host-rock septa in granite and with migmatitic foliation. The AMS foliation confirms the shape of the Axial Zone inferred from the migmatitic and gneissic envelopes. The southward dipping foliation recognized in both flanks is in agreement with an asymmetric dome, overturned to the North. Conversely, the magnetic linear fabric exhibits a contrasted pattern with a dominant NE-SW trend, and also a N-S one. The different models invoked to account for the tectonic setting of the Montagne Noire Axial Zone will be discussed on the basis of these new AMS results as well as petro-structural observations.
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Submitted on : Thursday, December 24, 2009 - 10:42:12 AM
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Nicolas Charles, Michel Faure, Yan Chen. The emplacement of the granite-migmatite dome of the Montagne Noire Axial Zone (French Massif Central): new insights from AMS and petro-structural studies. Mechanics of Variscan Orogeny: a modern view on orogenic research, Sep 2007, Orléans, France. 1 p. ⟨insu-00442946⟩

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