HR: 1340h
AN: T13A-0432    [Abstracts]
TI: Probing the Upper Mantle Beneath Northern and Eastern Ontario
AU: * Darbyshire, F A
EM: fdarbysh@nrcan.gc.ca
AF: Geological Survey of Canada, 615 Booth Street, rm 200, Ottawa, ON K1A0E9 Canada
AU: * Darbyshire, F A
EM: fdarbysh@nrcan.gc.ca
AF: Department of Earth Sciences, University of Western Ontario, 1151 Richmond Street, London, ON N6A5B7 Canada
AU: Snyder, D B
EM: dsnyder@nrcan.gc.ca
AF: Geological Survey of Canada, 615 Booth Street, rm 200, Ottawa, ON K1A0E9 Canada
AB: Analysis of teleseismic data from the POLARIS/FedNor seismograph network across northern and eastern Ontario is providing valuable new information about the structure and properties of the lithosphere beneath the Superior and southwestern Grenville Provinces. Surface wave data from 34 broadband seismograph stations across the region are used to map out lithospheric structure, using two different methods. A two-station analysis technique has been applied to over 80 station pairs to measure path-averaged Rayleigh wave dispersion. The best coverage is for a set of northwest-southeast paths along the `Diamond Corridor' of eastern Ontario, with more sparse coverage in central and western Ontario. In addition, an array analysis method is applied to two arrays of 5-7 stations each, in the Abitibi region of northeast Ontario and in southeast Ontario, resulting in an average Rayleigh wave dispersion curve for each array. Upper mantle structure is modelled from the dispersion curves using a Monte-Carlo method, which provides information on the range of mantle structures that satisfy the data sets. The models show significant variation in the thickness and properties of the continental lithosphere across Ontario. Lithospheric thickness varies from under 140km in the southeast to over 220km in the northeast, with intermediate values across northwestern Ontario. It is known from SKS splitting results that the upper mantle beneath much of Ontario is significantly anisotropic, with the greatest anisotropy beneath the western Superior Province. Rayleigh wave dispersion curves from different azimuths also suggest the presence of lithospheric anisotropy, though constraints on its nature will require a longer period of data collection by the POLARIS/FedNor array.
DE: 7218 Lithosphere (1236)
DE: 7255 Surface waves and free oscillations
DE: 8130 Heat generation and transport
DE: 9350 North America
SC: Tectonophysics [T]
MN: Fall Meeting 2005