AN: S52A-17TI: SNORE 97 - THE SLAVE-NORTHERN CORDILLERA REFRACTION EXPERIMENT IN NORTHWESTERN CANADA
AU: R. ClowesEM: AU: R. EllisEM: AU: P. Hammer
AF: Earth and Ocean Sciences, University of British Columbia, Vancouver,    B.C.
EM: AU: G. SpenceAF: Earth and Ocean Sciences, University of Victoria, Victoria,    B.C.EM: AU: I. AsudehEM: AU: B. RobertsAF: Geological Survey of Canada, 1 Observatory Cr., Ottawa, Ontario,    Canada, K1A 0Y3EM: asudeh@cg.NRCan.gc.caAU: Z. HajnalAF: Geological Sciences, University of Saskatchewan, Saskatoon,    SaskatchewanEM: AU: B. BeaudoinEM: AU: R. SellAF: IRIS/PASSCALEM: AU: Tom BurdetteAF: United States Geological SurveyEM: AB: During August-September 1997, LITHOPROBE conducted a seismic    refraction/wide-angle reflection (R/WAR) survey (SNORE 97) in    northwestern Canada. This experiment is one component of the    Slave-Northern Cordillera Lithospheric Evolution (SNORCLE) Transect, a    multi-disciplinary study of the structure and evolution of the    continental lithosphere in a region where the rock record spans 90\%    of Earth's history. The seismic experiment is designed to determine    the velocity structure of the crust and sub-crustal lithospheric    mantle from Great Slave Lake in the Northwest Territories to the coast    of the Alaska "panhandle". From east to west, the SNORCLE Transect    crosses a series of tectonic elements including the Archean Slave    Province, Early Proterozoic Wopmay Orogen, the southern projection of    the Middle Proterozoic Racklan Orogen (mostly buried beneath    Phanerozoic cover) and the northern Cordillera (which records a    complex history of crustal extension (1.5-0.37 Ga) followed by crustal    accretion (since 0.37 Ga)). The relationships of the velocity    structural models with coincident seismic reflection, magnetotelluric    and other geophysical and geological data will improve our knowledge    of the tectonic structure of these domains and elucidate their past    history. Four R/WAR refraction profiles (lines 11, 21, 22 and 31) were    collected over the transect area. For each line, 600 portable    seismographs were deployed at a station spacing of 0.5 to 1.2 km. A    total of 36 explosive shots were detonated at intervals of about 60 km    along the profiles and also at distant offsets from both ends of line    11 to provide additional upper mantle information. Line 11 in NWT    crosses the Archean and Proterozoic structures extending WSW for about    600 km from east of Yellowknife to about Nahanni Butte. Line 21 in    northern B.C. extends from the western Proterozoic tectonic elements,    including the enigmatic Nahanni terrane, into the authochthonous/parauthochthonous    portion of the northern Canadian Cordillera. Line 22 addresses the    accreted terrane component of the northern Cordillera in B.C.,    including Stikinia (the largest terrane element in the Cordillera),    and ties directly with the previous U.S. ACCRETE project. Seismographs    deployed on lines 21 and 22 also provide broadside coverage over the    crustal-scale Tintina transcurrent fault zone. Line 31 in the Yukon    runs NE-SW for about 300 km from the authochthonous /parauthochthonous    portion of ancestral North America across the Tintina fault and into    the accreted terrane portion of the Cordillera which is dominated by    smaller units of many terranes. Data quality is exceptional. All    profiles display good signal-to-noise ratio on both crustal and upper    mantle arrivals out to about 600 km offset. Strong shear-wave arrivals    are observed along most of the profiles, including prominent upper    mantle arrivals.SC: SDE: 7218DE: 7203DE: 7205MN: 1997 Fall Meeting