HR: 1340h
AN: T13A-0429    [Abstracts]
TI: Towards an Integrated Seismic Characterization of the Slave Craton
AU: * Rondenay, S
EM: rondenay@mit.edu
AF: MIT, 77 Massachusetts Ave, 54-512, Cambridge, MA 02139 United States
AU: Snyder, D B
EM: dsnyder@NRCan.gc.ca
AF: Geological Survey of Canada, 615 Booth Street, Ottawa, ON K1A 0E9 Canada
AU: Chen, C
EM: cwchen@mit.edu
AF: MIT, 77 Massachusetts Ave, 54-512, Cambridge, MA 02139 United States
AU: Straub, K M
EM: kmstraub@mit.edu
AF: MIT, 77 Massachusetts Ave, 54-512, Cambridge, MA 02139 United States
AU: Bank, C
EM: bank@geology.utoronto.ca
AF: University of Toronto, Earth Science Center, 22 Russell St., Toronto, ON M5S 3B1 Canada
AU: Bostock, M G
EM: bostock@eos.ubc.ca
AF: University of British Columbia, 2219 Main Mall, Vancouver, BC V6T 1Z4 Canada
AB: Archean cratons form the core of the majority of Earth's continents and offer a unique window into the evolution of continents and plate tectonics over geological time. The dynamics that led to the evolution and stabilization of cratons over one billion years ago, however, remain poorly understood. The Archean Slave province, located in the NW Canadian Shield, is an ideal site to study the formation of cratons due to its high degree of preservation and petrological evidence that its lithosphere possesses a distinct stratification resulting from cratonic assembly. The last decade has witnessed an explosion of seismological work in the region, with more than 45 broadband seismic stations deployed over variable lengths of time by the University of British Columbia, the Geological Survey of Canada, the POLARIS consortium and MIT. These data have been subjected to a wide array of seismic analyses: body- and surface-wave tomographic inversions were applied to the complete dataset, whereas receiver functions and shear-wave splitting were applied to subsets of the data. When considered together, these results yield an unprecedented seismic characterization of the Slave province. The Slave's lithosphere is, on average, 200 km thick and displays seismic velocities that are ~2-3% faster than surrounding Proterozoic orogens and ~2% faster than average cratonic values. At smaller scales, a low velocity anomaly centered to the south of the Lac de Gras kimberlite field is observed between 50-300 km depth. The anomaly has a radius of ~100 km, it exhibits a 2.8% slowness contrast with respect to the surrounding mantle, and may represent post-stabilization alteration of the cratonic lithosphere by processes responsible for kimberlite magmatism. Coherent results from shear-wave splitting and surface-wave analyses show evidence for two layers of anisotropy beneath the Slave craton: one in the uppermost lithosphere that may be associated with crustal structure from the last episode of regional deformation; and another one in the mantle lithosphere and possibly the asthenosphere, with a principal axis aligned with the direction of absolute plate-motion. Receiver functions show evidence of finer-scale anisotropic layering throughout the Slave's lithosphere - a possible sign of cratonic assembly by processes of shallow subduction and underplating. The seismic signature of the Slave craton therefore contains information about the entire evolution of the region, from its initial assembly during the Archean to its current deformation in response to plate motion.
DE: 7218 Lithosphere (1236)
DE: 8103 Continental cratons
DE: 8180 Tomography (6982, 7270)
SC: Tectonophysics [T]
MN: Fall Meeting 2005