HR: 0800h
AN: T11B-0568    [Abstracts]
TI: Shear Wave Splitting Results from the Coast Mountains Batholith, British Columbia
AU: * Frassetto, A
EM: andyf@email.arizona.edu
AF: University of Arizona, Department of Geosciences Gould-Simpson Building #77 1040 E 4th St., Tucson, AZ 85716, United States
AU: Zandt, G
EM: gzandt@email.arizona.edu
AF: University of Arizona, Department of Geosciences Gould-Simpson Building #77 1040 E 4th St., Tucson, AZ 85716, United States
AU: Dueker, K
EM: dueker@uwyo.edu
AF: University of Wyoming, Department of Geology and Geophysics Dept. 3006 1000 University Ave., Laramie, WY 82071, United States
AU: Calkins, J
EM: jcalkins@email.arizona.edu
AF: University of Arizona, Department of Geosciences Gould-Simpson Building #77 1040 E 4th St., Tucson, AZ 85716, United States
AB: The main goal of the interdisciplinary Batholiths continental dynamics project is to understand how the composition, structure, and fabric of the crust and mantle evolved following the emplacement of the Coast Mountains Batholith (CMB). The major issue related to the CMB is determining whether crustal melting and distillation generated an ultramafic root as in the Sierra Nevada and if so, determining the ultimate fate of this material. A key element of this analysis involves characterizing mantle anisotropy throughout the region. We utilize a dataset of 45 broadband seismometers deployed between June 2005 and September 2006. These stations were deployed along two transects approximately 200 km apart across the Insular superterrane, Coast Shear Zone, CMB, and interior plateau. This study presents new shear wave anisotropy results calculated from teleseismic SKS phases collected across the Batholiths array. At this time we have constraints from the highest quality event, analyzed using the methods from Silver and Chan (1991). Further analysis will include all good quality SKS phases. Previously the only anisotropy measurement is a well constrained null value from permanent station at Bella Bella, BC (BBB) just west of the batholith along the southern seismic transect. Stations to the east of BBB show splits of ~1.5 seconds along an ENE-WSW fast direction. This major increase in SKS anisotropy over a small spatial interval may result from shallow mantle flow beneath the batholith or a frozen fabric within the lithosphere. Stations along the northern transect show a somewhat smaller average splitting time of 1.2 s and a clockwise rotation of the fast direction into roughly E-W. We aim to resolve whether our initial anisotropy measurements, which are generally consistent along each seismic transect but comparatively different between transects, result from a regional flow pattern within the asthenosphere or an already established fabric within the lithosphere, including the crust.
DE: 7200 SEISMOLOGY
DE: 7208 Mantle (1212, 1213, 8124)
DE: 8100 TECTONOPHYSICS
DE: 8120 Dynamics of lithosphere and mantle: general (1213)
DE: 8178 Tectonics and magmatism
SC: Tectonophysics [T]
MN: 2007 Fall Meeting