HR: 0800h
AN: T41B-1174    [Abstracts]
TI: Observational evidence for serpentinization of the uppermost mantle caused by bending related normal faulting offshore Middle America
AU: Grevemeyer, I
EM: igrevemeyer@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz Institute for Marine Sciences, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Flueh, E R
AF: IFM-GEOMAR, Leibniz Institute for Marine Sciences, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: * Ranero, C R
EM: cranero@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz Institute for Marine Sciences, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Klaeschen, D
AF: IFM-GEOMAR, Leibniz Institute for Marine Sciences, Wischhofstrasse 1-3, Kiel, 24148 Germany
AU: Villinger, H
AF: University of Bremen, Klagenfurter Strasse, Bremen, 28359 Germany
AB: Offshore Nicaragua new heat flow data show a profound deficiency in lithospheric heat loss seaward of the deep sea trench. Heat flow values decrease toward the axis. The decreasing values correspond to an increasing number of faults and fault throw of normal faults on the incoming plate as the plate approaches the trench axis. These faults are created while the ridgid lithosphere is forced and bended into the Middle America trench. We suggest that these faults support a vigorous hydrothermal circulation system in the incoming plate. In this area, new seismic refraction data suggest that both crustal and upper mantle velocities are clearly reduced with respect to the velocity structure of mature oceanic lithosphere. Reduced velocities in the crust are interpreted to be realted to crustal cracks and fissures caused by bending related faulting. Reduced upper mantle velocities are in accordance with upper mantle rocks which contain 5-10 percent serpentinites. Thus, in addition to pore and chemically bound water in the sediment and crust, altered upper mantle is an important agent to facilitate the flux of water into the deep subduction zone.
DE: 8010 Fractures and faults
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 7218 Lithosphere and upper mantle
DE: 3000 MARINE GEOLOGY AND GEOPHYSICS
DE: 3015 Heat flow (benthic) and hydrothermal processes
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting