First stage of the Cantal stratovolcano (Massif Central, France) construction between 9.5 and 8.0 Ma: geology and geochemistry of the Elanceze area.

Recent cartography of the Elanceze area resulted in the identification of a residual ancient topographic relief comprised of basaltic and intermediate silica-saturated lavas partly covered by brecciated formations, emplaced d uring the first stage of edification of the Cantal stratovolcano (9.5-8.0 M a). The ancient relief has been the subject of a specified petrological stu dy. Although the corresponding mineralogical and geochemical data are rathe r consistent with the assumption of a differentiation mainly governed by fr actional crystallization. the study of some incompatible trace element diag rams suggests that this process cannot have occurred in closed-system. A mo del of crustal assimilation coupled with fractional crystallization involvi ng an amphibole-bearing cumulate is proposed. (C) 2001 Academie des science s / Editions scientifiques et medicales Elsevier SAS