3D gravity modelling of the Aguablanca Stock, tectonic control and emplacement of a Variscan gabbronorite bearing a Ni–Cu–PGE ore, SW Iberia

Abstract

The Aguablanca stock is a Variscan mafic pluton located in the Ossa-Morena zone, southern Iberian Massif, hosting an unusual Ni–Cu–PGE mineralization associated with magmatic breccia pipes which intruded its northern part. The emplacement of the Aguablanca stock and the mineralized breccia pipes are related to the activity of the Cherneca ductile shear zone, a Variscan sinistral shear zone that favoured magma ascent through the upper crust. A detailed gravity study has been carried out in order to investigate the 3D geometry of the Aguablanca intrusion and to get insights about the emplacement mechanism and tectonic controls of the mineralization. The three-dimensional gravity modelling shows that the stock has an inverted drop geometry with a feeder zone in contact with the Cherneca ductile shear zone. The inferred orientation of the feeder zone suggests that the emplacement probably took place along an open tensional crack formed within the strain field of the adjacent Cherneca ductile shear zone. The modelling of the breccia pipes hosting the Ni–Cu–PGE ore shows that they are included inside the feeder zone, thus their emplacement is probably controlled by successive opening events of this tensional crack.