WCSB GEOTHERMAL; WHERE IT IS HOT AND WHERE IT IS NOT- A REVIEW OF GEOTHERMAL STATE OF THE FORELAND BASIN

Temperature (T) at depth and geothermal gradient (grad (T)) of the sedimentary succession of the WCSB have been mapped based on a large industrial thermal database (BHTs, DSTs, annual tests) ever since pioneering work of Anglin and Beck (1965). Few (4) high precision heat flow (HF) measurements starting with first determinations of Garland and Lennox of 1962 done for the wells in areas with modest grad(T ) show modest HF 60+/-10 mW/m², however, it is on the average 20+/- higher than in the exposed Canadian Shield. Recent first high precision Q measurements in deep granitic section in NE Alberta (Majorowicz et al. 2014), heat production (HP) with depth and accounting for paleoclimatic influence shows HF at surface 50mW/m² and 60mW/m² at 2.2km. HF estimates have been done over decades and in our recent mapping. These are based on less precise industrial temperatures and measured/net rock estimates of thermal conductivity of the Phanerozoic sediments. Northern HF high in areas spreading through large part of the foreland basin and especially in the forefront of the Mackenzie Mnt. (90-100mW/m²) discovered by Majorowicz et. al, (1992) has been confirmed by more numerous recent data. Few tens of estimates expanded over decades to over 100 thousand. These new and larger data base shows northward HF increase along the forefront of the disturbed belt. Over-thrusted sedimentary units are heated from below by HF from old crust (20-80 mW/m²) and some 20 +/-5 mW/m² mantle contribution. Heat flow in the deep part of the basin varies from 40 mW/m² in the south to high 100 mW/m² in the north. We have low mantle HF below 2E09 years old crust, no observed heat flow vs. heat generation statistical relationship and general lack of correlation of HF patterns with other potential fields. To account for this we would need to assume that high HP layer of the upper-mid crust varies in thickness as much as factor of two or more or measured HG at top of Pc basement is not representative.

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Majorowicz J., Chan J., Crowell J., Gosnold W., Heaman L., Kück, J., Nieuwenhuis G., Schmitt D., Unsworth M., Walsh N., & Weides S., 2014. Geophysical Journal International, 197, 731–747