Electromagnetic images of crustal structures in southern and central Canadian Cordillera

Data from more than 400 magnetotelluric soundings, made since the early 1980s in the Canadian Cordillera over a 300 000 km ² area between 40 and 53.5°N, are used to image qualitatively regional three-dimensional crustal variation in electrical conductivity by means of phase maps, phase-frequency sections, and maps of resistivity at depth. The lowest crust has a generally pervasive, low resistivity throughout the Cordillera west of the Foreland Belt. Observed lateral variations in conductivity may result from variations in fracture density, temperature, and the sources of hot fluid, such as the subducting Juan de Fuca plate under the Coast Belt, and mantle upflow under the Omineca Belt. -from Authors