COMMON OCCURRENCE OF THE MIOCENE CALC-ALKALINE VOLCANISM ALONG THE WESTERN CORSICAN MARGIN (MARCO CRUISE)

During the MARCO cruise, systematic exploration along the western and northern Corsican margins was carried out by dredging. The composition s of the dredged rocks range from basalt to amphibole-biotite bearing andesite with a broad calc-alkaline character. A Miocene age has been obtained for the amphibole-biotite andesite sample DR02 both by Ar-40- Ar-39 dating on hornblende (16.0 +/- 0.4 My) and using fission-track m ethod on apatite (17.2 +/- 0.8 My). The southwestern Corsican volcanic zone represents the direct extension of the Miocene Sardinian graben volcanism north of 42 degrees 00 N. It could either be synchronous wit h or post-date the oceanic opening event. Such an are volcanism probab ly results from the subduction to the north of the Liguro-Piemont ocea n beneath Europe, the Provencal-Ligurian basin being in back-are posit ion with respect to the studied volcanic centres. ((C) Academie des sc iences / Elsevier, Paris.).