Publication 102
Electromagnetic images of the Trans-Hudson orogen: The North American Central Plains anomaly revealed
Jones, A.G., J. Ledo and I.J. Ferguson
Abstract
Magnetotelluric studies of the Trans-Hudson orogen over the last two decades, prompted by the discovery of
a significant conductivity anomaly beneath the North American Central Plains (NACP), from over 300 sites yield an
extensive database for interrogation and enable three-dimensional information to be obtained about the geometry of the
orogen from southern North Dakota to northern Saskatchewan. The NACP anomaly is remarkable in its continuity
along strike, testimony to along-strike similarity of orogenic processes. Where bedrock is exposed, the anomaly can be
associated with sulphides that were metamorphosed during subduction and compression and penetratively emplaced
deep within the crust of the internides of the orogen to the boundary of the Hearne margin. A new result from this
compilation is the discovery of an anomaly within the upper mantle beginning at depths of approx. 80�100 km. This
lithospheric mantle conductor has electrical properties similar to those for the central Slave craton mantle conductor,
which lies directly beneath the major diamond-producing Lac de Gras kimberlite field. While the Saskatchewan mantle
conductor does not directly underlie the Fort � la Corne kimberlite, which is associated with the Sask craton, the spatial
correspondence is close.
Source
Canadian Journal of Earth Sciences, 42, 457-478, 2005.
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Alan G Jones / 21 April 2006 /
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