FACTORS CONTROLLING THERMAL SPRINGS IN THE CANADIAN CORDILLERA

Thermal springs in the Canadian Cordillera are dominated by deep circulation of crustal fluids. Isotopic analyses have revealed that these springs discharge meteoric water. Structural geology is often the defining factor in the formation of these springs rather that heat flow. Examination of a large number of these springs has revealed no obvious relationship to crustal heat flow. Most springs are found on large-scale faults. Thermal springs appear to develop where regional flow systems are restricted by closely spaced faults. Numerical modeling indicates that the effective permeability of geological units in the hanging wall also appears to be a major factor. Where effective permeability is low, groundwater recharge is insufficient to feed fluid flow along these fault systems. The lack of relationship with crustal heat flow has implications to the viability of thermal springs as an exploration tool for geothermal energy projects. At the same time, the need for enhanced fluid flow in the hanging wall suggests that there are lessons to be learned from thermal springs in areas near unconventional oil and gas development.