GROUND-BASED GEOPHYSICAL SURVEYS OF GEOTHERMAL SYSTEM AT MOUNT BAKER, WA, USA

Mount Baker has been identified as a primary target for geothermal exploration in the State of Washington, USA, through play fairway analysis. The Mount Baker play is on the lower eastern flank of the active volcano and hosts surface thermal features as well as 48 ^oC bottom-hole well temperature at 140 m. Additionally, the area has existing geothermal leases, paved and gravel road access, and is proximal to existing transmission lines at the Baker Lake Dam, increasing the geothermal favorability of the area.

Detailed geologic mapping of the area has been limited due to dense vegetation and steep topography. LiDAR imagery revealed several NE-trending linear features, some of which are coincident with Baker Hot Springs. These features were investigated through dense ground-based gravity and magnetic surveys conducted between July and September 2016. Among other features, the studies revealed a strong magnetic and gravity gradient beneath Baker Hot Springs and extending ~1.7 km to the SSW. This anomaly is coincident with a linear feature observed in LiDAR and near a mapped fault. Near the hot springs, the pronounced linear anomaly intersects a NE-trending, less well-defined linear anomaly, suggesting a possible permeable pathway associated with the intersection of these linear features. We present several 2-D forward models of gravity and magnetic data as well as a 3-D inversion of magnetic susceptibility to interpret the structural controls of the Mount Baker hydrothermal system.