Erosion of the mantle lithosphere at the edge of the Massif Central plume, as recorded by protogranular xenoliths from Forez

The protogranular peridotite xenoliths sampled by Miocene basanites from Forez (NE French Massif Central) were initially equilibrated in the garnet stability field, at a depth of 50-60 km. Then, they were re-equilibrated in the spinel field owing to isobaric heating up to 1 100-1 200 degrees C. This event was associated with LILE enrichment, recording pervasive infiltration of volatile- or carbonate-rich small melt fractions. These two processes are ascribed to the thermal and chemical effects of lithospheric erosion, at the edge of the Massif Central mantle plume.