Geoelectric structure of the Proterozoic Wopmay Orogen and adjacent terranes, Northwest Territories, Canada
Wu, X., I.J. Ferguson and A.G. Jones
Magnetotelluric (MT) soundings were made along a transect in northern Canada crossing the Proterozoic
Wopmay Orogen, Fort Simpson basin, and adjacent parts of the Slave craton and the Nahanni terrane. The results are
used to define the geoelectric structure and constrain the crustal and lithospheric structure and evolution. Across the
Wopmay Orogen, geoelectric strikes at crustal depths average N34°E and are interpreted to be related to transcurrent
faulting that occurred during late distal collisions at the western margin of the orogen. Weak two-dimensionality in the
Fort Simpson basin is interpreted to be due to the sedimentary rocks in the basin. At longer periods, geoelectric strikes
across the Wopmay Orogen rotate from N43°E at uppermost mantle penetration to N62°E at a depth of 100 km.
The uppermost mantle strikes are interpreted to be due to ductile shearing linked to the transcurrent faulting in the
overlying crust. The deeper strikes may be caused by shearing at the base of the present-day lithosphere. Within the
Wopmay Orogen, the MT results image a conductor at the margin of the Fort Simpson and Hottah terranes interpreted
to be related to the collision of these terranes. Conductive crust beneath the western margin of the Great Bear magmatic
arc suggests correlative rocks of the Coronation margin extend south of the Slave craton. Lastly, decreased resistivity in
the Hottah terrane at mantle depths is interpreted to be caused by the introduction of graphitic or sulphidic rocks during
subduction prior to the Hottah–Slave and Fort Simpson – Hottah collisions.
Canadian Journal of Earth Sciences, 42, 955-981, 2005.
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Alan G Jones / 21 April 2006 /