Subduction-related fluids influence on the Oligo-Miocene transitional magmatism of the Sulcis area (SW Sardinia, Italy)

Abstract

The Sardinia-Corsica microplate was involved in OligoMiocene times in a SE-ward drift and counterclockwise rotation from the European margin in western Mediterranean to its current position. This movement was caused by the roll-back play of a NWward subducting oceanic plate under this margin and produced the detachment of this microplate from the continental margin and the openning of the Liguro-Provençal basin. As a result of the subduction abundant calc-alkaline magmatism of orogenic affinity occurred, mostly in the western sectors of Sardinia. In the final stages of the Miocene subduction and magmatism, coinciding with an increase in extensional tectonics, in the Sulcis area magmatism shifted from typical orogenic andesites to more evolved products of transitional character, ranging from trachydacites to rhyolites, with the relevant presence of peralkaline magmas (comendites), which were emplaced mostly as widespread ignimbrites reaching up to 20 km3 in volume and forming a pile over 200 m thick.