Emplacement of ellipsoid-shaped (diapiric?) granite: Structural and gravimetric analysis of the Oulmès granite (Variscan Meseta, Morocco)

Granite emplacement gave way to a 2 km-thick strain aureole, which includes both the uppermost part of the stock and the surrounding host rocks. The strain aureole is characterized by a gently-dipping planar-linear fabric with a generally weak N-S oriented stretching lineation. In the granite, the fabric of the strain aureole consists of a solid-state, locally mylonitic, foliation. In the host rocks, a secondary foliation develops which crenulates the older regional foliation. Magmatic structures, mainly consisting of steeply dipping N-S oriented magmatic foliation, are preserved in the central part of the pluton. The 3D shape of the granite has been modelled from gravity data and, together with the observed magmatic flow along subvertical planes and the strain recorded in the aureole, leads us to envisage a diapiric-dominated mechanism for the emplacement of the Oulmès granite. Drawing on the petrogenesis of peraluminous granites, the diapiric ascent of the granite probably has not exceeded 10 km.