Lithospheric geometry of the Wopmay Orogen from a Slave Craton to Bear Province magnetotelluric transect
Jessica E. Spratt, Alan G. Jones, Valerie Jackson, Louise Collins, and Anna Avdeeva
Two-dimensional inversions of lithospheric-probing magnetotelluric (MT) data at a total of twenty sites acquired along
an approximately east-west 300-km-long profile across the Wopmay Orogen in the Northwest Territories, Canada,
provide electrical resistivity models of the boundary between the Archean Slave craton and the adjacent Proterozoic
Analysis of distortion effects and structural dimensionality indicate that the MT responses are primarily
one-dimensional or only weakly two-dimensional with a depth-independent geoelectric strike angle of N32šE,
consistent with regional structural geology.
The regional-scale model, generated from the longer period responses from all of the sites along the profile,
reveals significant lateral variations in the lithospheric mantle.
Resistive cratonic roots are imaged to depths of ~200 km beneath both the Slave craton and the Hottah terrane of the
These are separated by a less resistive region beneath the Great Bear magmatic zone, which is speculatively interpreted
as a consequence of a decrease in the grain size of olivine in the Wopmay mantle, caused by localized shearing,
compared to its neighboring cratonic roots.
Focused two-dimensional models, from higher frequency responses at sites on specific sections of the profile,
reveal the resistivity structure at crustal depths beneath the region.
These suggest that the root of the Slave craton crosses beneath the Wopmay orogen, and that the Wopmay fault zone
does not penetrate into the lower crust.
A comparison of these results with those obtained during the LITHOPROBE project further south shows striking
along strike variations in the conductivity structure associated with the Wopmay orogen.
Journal of Geophysical Research, volume, pages, 200x.
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Alan G Jones / 13 August 2008 /