HR: 14:10h
AN: V12G-03 INVITED     [PDF]
TI: Simultaneous Submarine and Subaerial Volcanic Activity on the Flanks of the Western Canary Islands La Palma and El Hierro
AU: * Hansteen, T H
EM: thansteen@geomar.de
AF: GEOMAR, Vulkanologie und Petrologie, Kiel, 24148 Germany
AU: Schmincke, H U
EM: hschmincke@geomar.de
AF: GEOMAR, Vulkanologie und Petrologie, Kiel, 24148 Germany
AU: Kl\"{u}gel, A
EM: akluegel@uni-bremen.de
AF: Universit\"{a}t Bremen, Fachbereich Geowissenschaften, Bremen, 28334 Germany
AU: Abratis, M
EM: abratis@geo.uni-jena.de
AF: Universit\"{a}t Jena, Institut f\"{u}r Geowissenschaften, Jena, 07749 Germany
AB: The westernmost and youngest Canary Islands La Palma (2.0 Ma) and El Hierro (1.1 Ma) are presently in their shield stages. The subaerial and submarine morphology of both islands is characterized by one or three elongated ridges, respectively, commonly interpreted as volcanic rift zones. Our investgations indicate that young submarine volcanic activity off the islands is not confined to the extensions of these rift zones, but is also dispersed along the island flanks. Fresh basaltic rocks dredged along these flanks (RV "Poseidon" cruise 270 in 2001, and RV "Meteor" cruise M43 in 1998) comprise basanites to tephrites and alkali basalts. Remarkably, the dredged lavas are geochemically more diverse than those of the Holocene subaerial ridges. Fresh basalts have been recovered from 21 young volcanoes on the submarine flanks of El Hierro at depths from 800 to 2300 m. Another 25 volcanic cones can be tentatively identified from morphologies similar to the dreged ones. These submarine volcanoes off El Hierro occur in a dispersed manner on the blunt noses representing the extensions of the postulated suabearial northeast and northwest rift zones but also off the rift axes. Young volcanoes also occur within the Las Playas and El Julan landslide scars, testifying to renewed volcanic activity following large landslides. On the east flank of La Palma, we recovered basaltic rocks from 8 volcanic cones at depths between 850 and 2200 m and at a distance of up to 30 km off the rift axis, recognizing another 20 possible volcanoes in the same area from high-resolution bathymetric data. Remarkably, young submarine volcanoes are comparatively rare on the western flank and the submarine extension of the Cumbre Vieja rift zone. The high density of apparently young volcanoes on the NE and NW slopes of El Hierro suggests that submarine volcanism is volumetrically important during subaerial growth stages of the Canary Islands. Our results indicate that a broad melting anomaly involving distinct sources must occur in the mantle beneath La Palma and El Hierro.
DE: 1040 Isotopic composition/chemistry
DE: 3640 Igneous petrology
DE: 3670 Minor and trace element composition
DE: 8434 Magma migration
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting