Publication 95

Electrical resistivity structure of the Yellowknife River Fault Zone and surrounding region.

A.G. Jones and X. Garcia


EXTECH-III magnetotelluric (MT) data acquired across the Yellowknife River Fault Zone (YRFZ), combined with LITHOPROBE MT and geomagnetic transfer function (GTF) regional data from a 130-km-long profile centred on Yellowknife, yield information about the geometries of subsurface structures as reflected by changes in electrical resistivity. Analyses of the MT data show that they can be validly interpreted in terms of two-dimensional (2-D) structures with an average dominant strike direction of approximately north-south, consistent with exposed geology and particularly the YRFZ and coincident Proterozoic faults. Models of the MT and GTF data, obtained using objective inversion, show conducting features within the fault zone that penetrate to deep crustal levels and a broad diffusive less resistive zone in the upper mantle beneath the surface trace of the YRFZ. Within the fault zone the structures have an electrical resistivity of 1000 ohm.m or less. One site, on Walsh Lake, exhibits highly anomalous responses, indicative of a significant conductor at a depth of some 250 m below the surface, that are taken to be the graphitic argillites of the Walsh Lake Formation. The crust outside the fault zone is highly resistive throughout its whole extent, with resistivity of greater than 10,000 ohm.m. The upper mantle beneath the crust is around 4,000 ohm.m, except below the fault where it is 1,000-2,000 ohm.m.


EXTECH-III GAC Special Issue, , accepted, 13 May, 2004. Gold in the Yellowknife Greenstone Belt, Northwest Territories: Results of the EXTECH III Multidisciplinary Research Project, published by Geological Association of Canada, Mineral Deposits Division, Special Publication No. 3, Chapter 10, 126-141.

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Alan G Jones / 02 May 2006 /