Teleseismic studies of the lithosphere below the Abitibi-Grenville Lithoprobe transect

In the past decade, the Abitibi-Grenville Lithoprobe transect has been the site of numerous geological and geophysical surveys oriented towards unders tanding the lithospheric evolution of the southeastern Superior and adjoini ng Grenville provinces. Among the different geophysical methods that have b een employed, earthquake seismology provides the widest range of informatio n on the deep structures of the upper mantle. This paper presents a review of studies, both complete and ongoing, involving teleseismic datasets that were collected in 1994 and 1996 along the transect. A complete shear-wave s plitting analysis has been performed on the 1994 dataset as part of a compa rative study on electrical and seismic anisotropies. Results suggest a corr elation between the two anisotropies (supported by xenolith data) and favou r a lithospheric origin for the seismic anisotropy. The two anisotropies ar e believed to represent the fossilized remnants of Archean strain fields in the lithospheric roots of the Canadian Shield. Preliminary splitting resul ts for the 1996 experiment suggest that the S-wave azimuthal anisotropy may be depth dependent and laterally varying. Ongoing receiver function analys is and traveltime inversion studies provide velocity models of the crust an d upper mantle beneath the study area. Preliminary receiver function result s reveal the presence of an S-velocity increase at similar to 90-100 km dep th which appears to be laterally continuous over 200 km. Traveltime inversi on models indicate the presence of an elongate, low-velocity anomaly beneat h the southern portion of the 1996 array which strikes obliquely to major g eological structures at the surface (e.g., Grenville Front). Preliminary in terpretation relates this anomaly to the same process (e.g., fixed mantle p lume, continental rifting) responsible for the emplacement of the Monteregi an Hills igneous province.