HR: 1340h
AN: V53A-0601    [Abstracts]
TI: Time Evolution of the Basse Terre Island (Guadeloupe, French West Indies) Effusive Volcanism from New K-Ar Cassignol-Gillot Ages.
AU: * SAMPER, A
EM: samper@geol.u-psud.fr
AF: Geochronologie UPS-IPGP, Sciences de la Terre, Universite Paris-Sud, batiment 504, Orsay, 91405 France, Metropolitan
AU: QUIDELLEUR, X
AF: Geochronologie UPS-IPGP, Sciences de la Terre, Universite Paris-Sud, batiment 504, Orsay, 91405 France, Metropolitan
AU: QUIDELLEUR, X
AF: Paleomagnetisme, IPGP, Tour 14, 4 place Jussieu, Paris, 75252 France, Metropolitan
AU: MOLLEX, D
AF: Geochronologie UPS-IPGP, Sciences de la Terre, Universite Paris-Sud, batiment 504, Orsay, 91405 France, Metropolitan
AU: KOMOROWSKI, J C
AF: Geochimie et Volcanologie et Observatoires volcanologiques, IPGP, Tour 46, 4 place Jussieu, Paris, 75252 France, Metropolitan
AU: BOUDON, G
AF: Geochimie et Volcanologie et Observatoires volcanologiques, IPGP, Tour 46, 4 place Jussieu, Paris, 75252 France, Metropolitan
AB: Radiometric dating and geochemistry of effusive volcanics have been combined with geomorphological observations in order to provide a general evolution model of the volcanic island of Basse Terre, Guadeloupe (French West Indies). More than forty new Cassignol-Gillot K-Ar ages distributed within the entire island, together with the twenty ages (Blanc, 1983; Carlut et al., 2000) previously obtained with the same technique, makes the Guadeloupe Island the best place to study the evolution of volcanic processes within the Lesser Antilles Arc. Dating was performed on the carefully separated groundmass in order to avoid K loss due to weathering and excess argon carried by mafic minerals. Ages obtained are relatively younger than previously thought on Basse Terre and range from a few ka to 2.79+-0.04 Ma. When available, the paleomagnetic polarity of the dated flows agree with the GPTS and a very good coherence of ages is observed for each massif. Our results demonstrate the general north to south migration of volcanism through time. It correlates with the main volcanic stages previously identified. The 2.75 Ma Basal Complex, the 1.81+-0.03 \_ 1.15+-0.02 Ma Septentrional Chain, the 1.02+-0.02 Ma \_ 0.606+-0.02 Ma Axial Chain, the 442+-6 \_ 207+-28 ka Mateliane \_ Sans Toucher Complex and the $<$ 200 ka Complex of La Grande Decouverte, which outlines a relative continuity in the Basse Terre magmatism. Lavas are mainly basaltic andesites and andesites although a few basalt and dacite have also been dated. All of them are characterized by low MgO values ($<$ 6 %), tholeiitic to calc-alkaline REE chondrite-normalized patterns and are of both low K and medium K affinity. Lavas display geochemical characteristics similar to that of the central islands of the Lesser Antilles arc. Within Basse Terre, geochemical characteristics are relatively constant through time, indicating no major change of volcanic processes during the whole subaerial activity. Finally the detailed chronological framework now available provides new constraints for estimating rates of edification and destruction at the island scale and, more generally, to help better understand the evolution of the still active Guadeloupe island Soufriere volcano.
DE: 1749 Volcanology, geochemistry, and petrology
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting