| Title | Geothermal Exploration in Western Canada Using Magnetotelluric Data |
|---|---|
| Authors | Cedar Hanneson, Martyn Unsworth, James Craven |
| Year | 2026 |
| Conference | World Geothermal Congress |
| Keywords | |
| Abstract | The magnetotelluric (MT) method is used to image subsurface electrical resistivity. This is a useful physical property to measure during geothermal exploration because it is sensitive to the presence of fluids such as brines and partially molten rocks, as well as clay minerals formed by hydrothermal alteration. These substances have low electrical resistivity, compared with dry, unaltered host rocks. The MT method is a passive source EM geophysical method. It uses naturally occurring radio waves as the source and frequency as a proxy for depth. High frequencies are measured in the audiomagnetotelluric (AMT) band, and they are used to image shallow structures. Lower frequencies are used in broadband magnetotelluric (BBMT) data collection, and they can image structures throughout the crust. BBMT data were collected near Mount Meager, southwestern BC, in 2019-2020. They were used to image the magmatic and geothermal systems beneath this Holocene volcanic centre. A 3-D electrical resistivity model revealed a magma body at 5-15 km below sea level, as well as fluid pathways from this magma body to the surface near active fumaroles. Geochemical and petrological information was used to infer physical properties of the magma body. AMT and BBMT data were collected in southwestern Yukon in 2021-2023. AMT data measured near Haines Junction were used to image the uppermost 3-4 km of the subsurface. BBMT data measured near Whitehorse and Carmacks were used to image the upper 30-60 km. Three 3-D resistivity models facilitated investigations of crustal structure in southwestern Yukon and interpretations regarding geothermal potential. |