Abstract
Lesser Antilles arc presents three main periods of volcanic activity. The oldest period is occurring during the Eocene-Oligocene, then there has Miocene period, and the last period is occurring from the Plio-Pleistocene to recent. At the southern part of the arc, the magmatic products overlapped the three periods. Whereas at the northern part of the arc, the magmatic products evolve into two distinct branches suggesting a migration of the volcanism. Saint Barthelemy is an island belong to the northern part of the Lesser Antilles arc, illustrating the oldest period activity of the arc. Geochemical study of this key island will permit us to characterize the sources and the potential contamination of the magmas generated in the Lesser Antilles arc from Eocene to Early Miocene. We present new major and trace element and Sr, Nd, Pb and Hf isotope data from lava samples from the Saint Barthelemy island. The samples range from basalt to rhyolites, with mainly andesite and they belong globally calc-alkaline series. The trace element patterns of Saint Barthelemy lavas present enrichment of the large ion lithophile element (LILE) relative to the high field strength elements (HFSE) and anomalies which are typical of subduction zone and of fluid participation. Rare earth element patterns of magmatic rocks from Saint Barthelemy show an increase of LREE/MREE ratios through time. Sr-Nd-Pb isotope variations show all the samples from Saint Barthelemy are located in the Arc worldwide domain in agreement with their origin from a subduction environment. Furthermore, Saint Barthelemy samples show isotopic ratios more similar with the Saint Martin island than Martinique for the same period comforting the distinct evolution of the northern part relative to the southern part of Lesser Antilles arc.