Heat flow in the western superior province of the Canadian shield

Abstract

We present new heat flow measurements from deep boreholes at 9 sites, northwest of Lake Superior, in Ontario. The new measurements drastically change the heat flow map in the Western Superior Province of the Canadian Shield. Previous maps relied heavily on shallow (2.5 m) measurements in sediments beneath small lakes and exhibited high heat flow anomalies (>60 mW m-2). The new heat flow values between 31 and 56 mW m-2 are well within the range of values in the eastern part of the Superior and in other Archean provinces. Without the shallow lake data, the mean heat flow from borehole measurements, including 9 previously published values, is 42 ± 8 mW m-2, which is close to the mean of other provinces in the Canadian Shield.