Geophysical imaging of the inner structure of a lava dome and its environment through gravimetry and magnetism

Volcanic lava domes are compound edifices resulting from complex growth processes including intrusion and extrusion phases, explosions and collapses. Here, we present the study of a complex volcanic system, located in the Chaîne des Puys volcanic field (French Massif Central, France) and centred on the Puy de Dôme volcano, an 11,000 years old volcano. Our approach is based on a morpho-structural analysis of a high resolution DTM (0.5 m) and geophysical imaging methods. Both gravity and magnetic high resolution surveys have been carried out on the lava dome and the nearby volcanic structures. We computed 3D inverse and 2D forwards models. Based on our current knowledges about volcanic dome structure, the geophysical models allow us to propose a synthetic geological model of the inner structure of the Puy de Dôme and surrounding areas. This model suggests a scenario for the formation of the lava dome and the inferred intrusions located on both sides. The Puy de Dôme could possibly be the southern tip of the northern intrusion.