Journal
JOURNAL OF STRUCTURAL GEOLOGY
Volume 82, Issue -, Pages 80-92Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jsg.2015.10.006
Keywords
Saint-Laurent - La Jonquera pluton; Granitoid; AMS; Magnetic fabric; Magmatic fabric; Axial zone; Syntectonic emplacement; Transpression; Variscan; Alpine; Pyrenees
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Funding
- Spanish Ministry of Education and Science programa de Acciones Integradas Hispano-Francesas [HF2005-0002]
- French Foreign Office Programme Egide Picasso [10817TE]
- Geosciences Environnement Toulouse Laboratory
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The structural study of the Saint-Laurent - La Jonquera pluton (Eastern Pyrenees), a Variscan composite laccolithic intrusion emplaced in metasedimentary and gneissic rocks of the Roc de Frausa dome, by means of the anisotropy of magnetic susceptibility (AMS) technique has allowed the determination of the nature and orientation of its magmatic fabrics. The magmatic foliation has a predominant NE SW strike and the mean lineation is also NE SW trending with a shallow plunge. A strain gradient is measured so that the tonalites to granodiorites that form the basal parts of the pluton, and are intruded into amphibolite-facies metamorphic rocks, recorded the highest anisotropies, whereas the monzogranites and leucogranites, emplaced into upper crustal, low-grade metamorphic rocks, are weakly deformed. These results point to the synkinematic sequential emplacement of multiple granitoid sheets, from less to more differentiated magmatic stages, during the Late Carboniferous D-2 event characterized by an E -W-trending dextral transpression. The magmatic foliation appears locally disturbed by the effects of two tectonic events. The first of them (D-3) produced mylonitization of granitoids along NW-SE retrograding shear zones and open folds in the host Ediacaran metasediments of the Roc de Frausa massif, likely during late Variscan times. Interference between D-2 and D-3 structures was responsible for the dome geometry of the whole Roc de Frausa massif. The second and last perturbation consisted of local southward tilting of the granitoids coupled to the Mesozoic-Cenozoic cover during the Alpine. (C) 2015 Elsevier Ltd. All rights reserved.
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