A controlled-source, time-domain electromagnetic survey over an upthrust section of Archean crust in the Kapuskasing Structural Zone

SUMMARY A pilot controlled source electromagnetic survey was conducted in the Kapuskasing Structural Zone to test the application of the UTEM technique for determining the electrical conductivity structure of the Earth's crust to depths of up to 10 km. In general, the data are consistent with the results of an earlier broadband magnetotelluric (MT) survey and indicate a quasi-layered earth below a variable overburden zone with conductances between 0.1 and 0.5 S. At some depth below 10 km, conductivity appears to increase in agreement with the MT interpretation and provides confidence that the static shift of the MT data was corrected. A weakly conductive layer, located at depths greater than 2 km, is possibly associated with a feature of the Ivanhoe Lake Cataclastic Zone (ILCZ), a major fault zone along which up to 30 km of the Earth's crust has been thrust to the surface. There was no clear evidence in the UTEM data for a conductive zone extending to the proposed surface strike location of the ILCZ. A conductive anomaly at depths of 1–2 km may extend east of the present survey area and suggested that a subsequent UTEM survey must expand the coverage to the east.

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