Slave Electromagnetic studies

The Archean Slave craton is an ideal natural laboratory for investigating lithosphere formation and evolution processes, and has become an international focus of broad geoscientific investigation following the discovery of economic diamondiferous kimberlite pipes. Four deep-probing electromagnetic surveys, using the nautral-source magnetotelluric (MT) technique, have recently been carried out on the craton using novel acquisition procedures (Figure 1). These surveys have resulted in reconnaissance level 3-D coverage of the craton, with dense spacing along 2-D profiles. The first survey (blue circles on Fig. 1) involved conventional MT acquisition along the only all-weather road on the southwestern extremity of the craton. Fifteen sites are equi-distantly-spaced on the exposed craton, from Tibbit Lake to the east to Rae to the west. The second survey was a three-part series of acquisition along the winter roads with the electrodes lowered through the ice to the lake bottoms and the magnetometers on land. The former ensured low resistance ground contact for electric field measurements, and the latter avoided motion noise in the period range 10-100 s caused by movement of the lake ice. Measurements were made at a total of forty-four locations (blue squares on Fig