Identification et caractérisation du volcanisme du bassin de Lodève par l'étude des inclusion vitreuses des cristaux de quartz

The dicovery of melt inclusions perfectly well preserved in quartz automorphic phenocrysts of the greso-conglomeratic levels of Rebejac formation (Red Permian), allowed us to confirm how important is the volcanic component contribution and to define its main characteristic properties. It concerns rhyolitic volcanism, with potassic tendency, characterized by high volatiles content. Two magmas with different geochemical properties could be defined. Dynamisms are principally explosive ones, of pumicefall type, seldom effusive ones, with lava flows, domes or ignimbrites. Quartz from pumice falls were explained as a former contribution connected to a synsedimentary volcanic activity; quartz from pumice flows are coming from the destruction of indurated layers. These data lead us to consider the Lodeve basin as a real volcano-sedimentary one