| Abstract |
Recent research provides an expanded understanding of the thermal state of the crust and the potential for geothermal energy resources in Yukon, Canada. This paper presents an overview of heat flow, Curie point depth mapping, crustal-scale thermal modelling, and new heat generation data which all suggest that south-central Yukon is characterized by relatively higher temperatures in the mid- to shallow crust compared to the northern and southeastern portions of the territory. Heat flow data in Yukon are sparse, but previous measurements show anomalously high heat flow values in the Yukon portion of the northern Canadian Cordillera (i.e. south-central Yukon) having values as high as 105±22 mW/m2. This compares with an average heat flow for all of Canada of 64±16 mW/m2. Curie point depth (CPD) mapping is a technique which estimates the depth in the Earth’s crust to the Curie point temperature (~580 °C) where magnetization in rocks disappears. Recent work by us and others suggests that the CPD for south-central Yukon is relatively shallow and has the range 12-27 km. These CPD results agree well with an 18-23 km depth to Curie point we estimate using a two-layer thermal model of the crust for southern Yukon. The regions with shallow CPD estimates in Yukon generally correspond to areas with elevated heat flow measurements. Geologically, the regions with shallower CPD values correspond to the Cordillera, while deeper CPD areas in the north and southeast portions of Yukon appear to be co-located with continental platform rocks of Ancestral North America that exhibit lower heat flow. In addition, a new compilation of geochemical data reveals numerous localities across southern Yukon with anomalously high values of heat production in Cretaceous and younger granitoid plutons. We assessed geochemical data from ~560 samples and calculated heat production for each sample, then mapped the results across the territory. A large number of samples yielded anomalously high heat production values of 3-10 μW/m3. A smaller number of samples gave even higher heat production values more than 10 μW/m3. This compares to a heat production value of ~2.5-2.8 μW/m3 for typical granite. In general, Cretaceous plutons in southern Yukon show higher heat production values compared to Tertiary plutons. Overall, south-central Yukon is a large region (~250,000 km2) which appears to be broadly characterized by elevated temperatures in both the mid- and shallow crust. In addition, anomalously high heat production measured in granitoid rocks in southern Yukon appear to be abundant and provide yet another source of heat for geothermal resources. If adequate subsurface permeability can be found in the region, relatively small, low-enthalpy geothermal reservoirs may be numerous across south-central Yukon. Two regions of potential deep crustal permeability in south-central Yukon are the Denali and the Tintina fault zones. Both are crustal-scale, strike slip faults that cut northwest across the entire Yukon territory. Successful identification and exploitation of geothermal resources in Yukon would be particularly beneficial due to the cold northern climate and could help supply heat and power to off-grid, fossil-fuel powered entities in Yukon such as mining operations and remote communities. |