Geologic and Geophysical Studies in the Mont Dore Geothermal Area, France

Abstract

Mont Dore Volcano in central France grew during two period since about 4 m.y. B.P. The older period lasted from about 4 m.y. to 1.8 m.y. B.P. and was highlighted by the formation of a caldera, apparently in response to the eruption of a pumiceous, rhyolite ash flow. The younger period lasted from 0.8 to 0.25 m.y. B.P. and was characterized by the emplacement of domes, flows, and associated pyroclastic debris of intermediate compositions, principally along the east and south margins of the caldera. A Bouguer gravity low of about 20 milligals suggests that the caldera is filled with 1 km of low density rocks, and a similar depth of caldera fill is suggested by electric soundings. Several thermal springs within the caldera are surface evidence of convecting geothermal fluids that may be driving by residual thermal energy associated with magmatism of Mont Dore.