HR: 09:30h
AN: T31B-07    [PDF]
TI: Lateral Variation in Upper Mantle Viscosity: Role of Water
AU: * Dixon, J E
EM: jdixon@rsmas.miami.edu
AF: Univ. of Miami/RSMAS, 4600 Rickenbacker Cswy., Miami, FL 33149 United States
AU: Dixon, T
EM: tdixon@rsmas.miami.edu
AF: Univ. of Miami/RSMAS, 4600 Rickenbacker Cswy., Miami, FL 33149 United States
AU: Malservisi, R
EM: rmalservisi@rsmas.miami.edu
AF: Univ. of Miami/RSMAS, 4600 Rickenbacker Cswy., Miami, FL 33149 United States
AU: Bell, D
EM: david.r.bell@asu.edu
AF: Arizona State Univ., Dept. of Geol., Tempe, AZ 85287 United States
AB: Differences in the viscosity of the earth's upper mantle beneath the western US (~10$^{17}$-10$^{19}$ Pa-s) and global average values based on glacial isostatic adjustment and other data (~10$^{20}$-10$^{21}$ Pa-s) are generally ascribed to differences in temperature. We compile geochemical data on the water contents of western US lavas and mantle xenoliths, together with calculations of water solubility in olivine and its influence on effective viscosity using a power law creep rheological model, and suggest that the low viscosities for the western US upper mantle reflect the combined effect of high water concentration (essentially at or near the saturation value for olivine) and moderately elevated temperature. The high water contents of the western US upper mantle may reflect the long history of Farallon plate subduction, including flat slab subduction, which effectively advected water into the upper mantle as far inland as the Colorado Plateau.
DE: 3672 Planetary mineralogy and petrology (5410)
DE: 7207 Core and mantle
DE: 8124 Earth's interior--composition and state (old 8105)
DE: 8180 Tomography
SC: Tectonophysics [T]
MN: 2003 Fall Meeting