Emplacement of the Aya Variscan granitic pluton (Basque Pyrenees) in a dextral transcurrent regime inferred from a combined magneto-structural and gravimetric study

Magmatic structure, three-dimensional shape and emplacement mode of the Aya pluton, Variscan Pyrenees, have been studied by combining magneto-structural and gravimetric studies. The Aya pluton displays a fabric, acquired using the anisotropy of magnetic susceptibility technique, comparable to that of several other plutons in the Pyrenees, with shallow-plunging lineations and steep foliations trending E-W and NE-SW, forming an S pattern in map view. Gravity modelling was used to determine the probable root of the pluton, directly below the most basic (gabbro-dioritic) facies, This has a funnel shape, with an EW-trending elliptical horizontal section and a maximum depth of 3.5 km. These different data demonstrate that this pluton was synorogenically emplaced during the main D2 Variscan tectonic phase, in a dextral transcurrent regime.