Fault-hosted geothermal systems in southeastern British Columbia

• Author / Creator

  Finley, Theron

• Geothermal energy is a low-carbon, base-load, renewable energy resource that should form part of the future global energy portfolio as we seek to reduce carbon emissions and mitigate climate change. In Canada, geothermal resources are underdeveloped and require further investigation to facilitate their development. This thesis applies structural geology, petrology, and geophysics to investigate potential geothermal resources in southeastern British Columbia with a focus on thermal springs. These resources are spatially coincident with major fault systems – the Southern Rocky Mountain Trench (SRMT) fault, Purcell Trench fault, and Columbia River fault – that likely allow for the deep circulation and heating of meteoric water in the crust.
  Field investigations and structural analyses presented in Chapter 2 reveal a previously undocumented post-Eocene phase of right-lateral strike-slip accommodated across multiple fault structures in southeastern British Columbia. These kinematics are consistent with earthquake focal mechanisms and maximum stress directions in the region, which suggests that neotectonic strain plays an important role in controlling the location of thermal springs. When viewed in this context, it is apparent that thermal springs are localized by zones of stress concentration such as fault tips, intersections, and step-overs. On a broader scale, thermal springs are spatially associated with clusters of seismicity. Thus, structural geology and seismology may allow for predictive mapping of hidden geothermal systems elsewhere in the Canadian Cordillera.
  Structural cross-sections and petrographic analyses presented in Chapter 3 reveal strong structural and microstructural anisotropy in rocks near the Valemount geothermal prospect, which is located along the SRMT fault. Understanding the structural anisotropy is key to interpreting magnetotelluric (MT) surveys conducted in the area. At map scale (over tens of kilometers), several subparallel brittle and ductile fault structures represent numerous phases of deformation from the Jurassic to late Cenozoic. Some of these faults may act as permeable conduits for thermal fluid. At microscopic scale (microns to millimeters), highly metamorphosed rocks of the Yellowjacket Gneiss contain conductive minerals including graphite and sulfides, which are aligned and partially connected along cleavage planes. Observations at both scales indicate that anisotropic MT inversions are more appropriate for geothermal exploration in highly deformed regions.

• Subjects / Keywords

  • geothermal
  • canada
  • structural geology
  • british columbia
  • earthquakes
  • magnetotellurics
  • hot spring
  • renewable
  • anisotropy
  • energy
  • fault

• Graduation date

  Fall 2020

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-r87x-jt83

• License

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