HR: 1340h
AN: T33A-1326    [Abstracts]
TI: Mantle Fabric Beneath Ontario: Results From the CNSN, FEDNOR and POLARIS Arrays
AU: * Frederiksen, A W
EM: frederik@cc.umanitoba.ca
AF: University of Manitoba, Department of Geological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2 Canada
AU: Miong, S
EM: ummiongs@cc.umanitoba.ca
AF: University of Manitoba, Department of Geological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2 Canada
AU: Eaton, D W
EM: deaton@uwo.ca
AF: University of Western Ontario, Department of Earth Sciences, University of Western Ontario, London, ON N6A 5B7 Canada
AB: The basement of the province of Ontario is Precambrian, consisting of the Archean Superior Province in the north and west, which abuts on the Proterozoic Grenville Orogen. The Grenville, which forms the southeastern edge of the Canadian Shield, is the result of extensive crustal shortening and deformation during the interval 1.3-0.98 Ga. The degree to which this crustal deformation is reflected in the underlying mantle is uncertain, though LITHOPROBE detection of a preserved subduction zone (Calvert et al., 1995) in the Superior indicates that relict Precambrian features are preserved below the crust. A number of permanent CNSN stations (e.g., SADO, GAC, KGNO, etc.) are located on or near the Grenville, and have large archives of teleseismic data available; the deployment of the dense POLARIS network on the Grenville in southern Ontario provides higher-resolution constraints, and has more recently been extended by FEDNOR stations in the Superior province. We present preliminary analyses of the FEDNOR data for SKS splitting and crustal thickness, along with a more detailed examination of receiver functions in the Grenville for upper-mantle structure. The SKS results for the Superior Province show fast directions to be largely in-line with absolute plate motion, in contrast with previously-presented results for the Grenville; receiver functions on a transect across Southern Ontario indicate ubiquitous fine anisotropic layering which varies laterally over distance scales of less than 200 km.
DE: 9350 North America
DE: 8110 Continental tectonics--general (0905)
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting