Geothermal measurements in Newfoundland

Abstract

We report heat flow values for ten holes at five sites in Newfoundland. The average observed heat flow is 43 ± 4 mW m−2. Corrected for Pleistocene surface temperature variations, the average becomes 50 ± 4 mW m−2, with a range from 38–82 mW m−2. The Dunnage zone (a vestige of the Iapetus Ocean) exhibits a heat flow lower than normal for Paleozoic orogenic belts. The highest heat flow is associated with the Carboniferous St. Lawrence granite intrusion. Heat production measurements were made at three of the sites. Those in the Dunnage zone are low (< 0.8 μW m−3), as expected for former oceanic rocks, while that for the St. Lawrence granite is high (4.9 μW m−3). A plot of heat flow versus heat production for these data and the data of Hyndman et al. for the Maritime Provinces demonstrates that Newfoundland belongs to the same heat flow province as the Maritimes and the eastern United States. The reduced heat flow for the Canadian Atlantic Provinces data is 32 ± 3 mW m−2, uncorrected, and 40 ± 3 mW m−2 when corrected for Pleistocene temperature effects. Computed geotherms for heat flows and heat productions corresponding to the upper and lower observed limits of the data yield temperatures at 30 km depth of about 575 and 475 °C respectively.