The Hospitalet gneiss dome (Pyrenees) revisited: lateral flow during Variscan transpression in the middle crust

International audienceA new structural and kinematic study of the Hospitalet dome (Pyrenees) is presented. This dome corresponds to the eastern half of an EW-trending antiformal structure made of an orthogneissic core intruded by granitoids, partly covered by Upper Proterozoic to Lower Ordovician metapelites. Its Variscan evolution can be split into four stages: (i) development of a strong high temperature pervasive deformation associated with subhorizontal foliations and lineations, and with non-coaxial top-to-the-east kinematics; (ii) formation of a south-verging overturned megafold; (iii) emplacement of calc-alkaline granitoids; and (iv) formation of mylonitic bands on the southern border of the dome, with reverse dextral kinematics. The flat lying pervasive high-T deformation is interpreted as a large lateral flow developed in a dextral transpressive regime inducing an important uncoupling between the middle and upper crusts. The next stages happened in a progressive deformation in the same transpressive regime