HR: 0830h
AN: S21E-0352    [PDF]
TI: Mineralogical Models of Subduction Zone Tomography
AU: * Yu, T
EM: tony.yu@sunysb.edu
AF: Department of Geosciences, State University of New York at Stony Brook, Stony Brook, NY 11794-2100 United States
AU: Weidner, D
EM: donald.weidner@sunysb.edu
AF: Department of Geosciences, State University of New York at Stony Brook, Stony Brook, NY 11794-2100 United States
AB: Subduction zones have long been recognized by their significant role in the Earth's dynamics and plate tectonics. Mantle seismicity and volcanoes highlight their importance. Seismic tomographic studies and thermal models have been built. Here we model the seismic velocity and density of subduction zones using different thermal profile models, mantle chemical composition models, laboratory phase diagrams, and elasticity data from previous studies. With these we calculate the velocity and density impact and the buoyancy in the subducting slab region. This allows us to understand the effect of different physical and chemical parameters on the distribution of mineral phases in this area. Two major discontinuities have been globally observed at average depths 410km and 660km respectively by seismic wave data study. The 410 discontinuity occurs at a shallower depth within the colder subducting slab compared to the warmer surrounding ambient mantle. This phenomenon agrees well with seismic models based on deep earthquake velocity observations (Krishna \& Kaila, 1995). The generally known discontinuity at 660km is shifted deeper down to 700km in our model. Similar results were presented by previous seismology studies (Thirot et al., 1998). By considering different mantle chemical models, the P-wave velocity jump at 410km in the middle region of the subducting slab is considerably larger for a harzburgite composition than for a pyrolite one. We also find a significant signature of the ilmenite forming reaction within the slab.
DE: 1025 Composition of the mantle
DE: 1212 Earth's interior--composition and state (8105)
DE: 3900 MINERAL PHYSICS
SC: Seismology [S]
MN: 2003 Fall Meeting