| Title | Preliminary Results from a Magnetotelluric Study of the Garibaldi Volcanic Belt Geothermal System, British Columbia, Canada |
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| Authors | James A. CRAVEN, Steve GRASBY, Victoria TSCHIRHART, Seyedmasoud ANSARI, Dariush MOTAZEDIAN and Fateme HORMOZZADE |
| Year | 2020 |
| Conference | World Geothermal Congress |
| Keywords | geothermal, magnetotelluric, geophysics, permeability, conductivity, alteration |
| Abstract | New magnetotelluric (MT) soundings have been conducted at Mount Meager in the Garibaldi volcanic belt (GVB) situated in southwestern British Columbia, Canada approximately 150 km north of Vancouver. Mount Meager is one of a chain of young ( less than 11 k yr) stratovolcanoes in the GVB. Fluids near the surface have temperatures greater than 250 °C, the highest such temperature of any potential geothermal resource in Canada. The new MT data complement two earlier datasets provided by Frontier Geosciences and NRCan. The data have been analyzed to determine the 3D electrical conductivity structure of this portion of the belt in order to elucidate the local and regional controls on permeability thought to be a primary control on the potential of the area sustain fluid production rates at elevated temperatures. Previous studies had demonstrated correlations between increased temperature gradients and conductivity in addition to a 2D model that demonstrated a zone of enhanced electrical conductivity thought to be due to a montmorillonite-dominated cap atop a more resistive zone related to chlorite and sericite alteration. The limited bandwidth and aperture of the prior work could not map out the full lateral extent of the zones, nor could it detect or rule out the presence of any channels between the conductive and resistive areas. The precise boundaries and depths of these features, plus their relationship to permeability controls within the GVB have been modelled using standard 3D finite difference methods using rectilinear meshes. Soon, a novel finite element 3D method recently developed to handle the complex structure and topography expected in this area will be utilized. The new data and enhanced modelling techniques will map and image reliably the fundamental fluid conduits within the potential reservoir, and provide an enhanced understanding of the complex fluid and alteration regimes controlling permeability within this portion of the GVB. |