HR: 0800h
AN: T41B-1204    [Abstracts]
TI: Geophysical and Petrological Consequences of the `Slab Water Cycle'
AU: * Robin, C M
EM: cath.robin@utoronto.ca
AF: Robin, Catherine, Department of Physics University of Toronto, Toronto, ON M5S 1A7 Canada
AU: Robin, P F
EM: py.robin@geology.utoronto.ca
AF: Robin, Pierre-Yves, Department of Geology University of Toronto, Toronto, ON M5S 3B1 Canada
AB: Water released at the bottom of the transition zone within a plunging lithospheric slab and percolating upward through that slab accounts for several phenomena observed within and around subduction zones. The pressure of that water as it rises permits brittle faulting, and therefore deep-focus earthquakes, anywhere from the bottom of the transition zone upward. Water percolating upward above the transition zone also explains the lower of the paired seismic zones observed at intermediate depths, either through its own pressure, or by dehydration of lithospheric mantle serpentinized by it. Eventually, water that does not rise through the hot mantle wedge may be rising in serpentine seamounts. Incompatible elements, and perhaps carbon, should follow the water in that cycle and therefore become progressively concentrated in the subducting slab. When the slab becomes deflected and thrust horizontally along the base of the transition zone, its eventual foundering releases water, which must then rise through normal mantle rather than the slab. What is not dissolved in the transition zone may account for some kimberlites and other `wet spot rocks' far away from the subduction zone. Similarly, a detached slab has to release its water within upwelling mantle and may thus contribute to late arc magmatism that is more abundant and geochemically different than before detachment.
DE: 8120 Dynamics of lithosphere and mantle--general
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting