Heat flow : heat production studies in Nova Scotia

Abstract

Instruments and techniques were developed to measure heat flow in shallow and deep lakes. For the latter, they are an adaptation of the oceanic method using a lightweight thermogradient probe. Heat flow measured with this instrument is 1.51 ±0.23 μcal/cm 2 sec (63 ±9 mW/m 2 ) in Bras d'Or Lake, N.S. For shallow lakes, temperatures were measured at successive depths in the sediments to determine the thermal gradient. In Chocolate Lake and Card Lake the heat flows are 1.42 ±0.21 μcal/cm 2 sec (59 ±9 mW/m 2 ) and 1.92 ±0.29 μcal/cm 2 sec (82 ±12 mW/m 2 ) respectively. The former compares well with the heat flow in a nearby bore hole at Halifax, N.S. As a heat flow province (q = 1.08 + 9 A0) Nova Scotia appears to be distinct from others, especially the New England States heat flow province. The total heat flux and the components from heat flow provinces (q0 and DA0 ) when averaged for tectonic age decrease with tectonic age. It appears that erosion can account for the long term decay of the crustal component DA0 and a sinking low velocity zone can account for the decay of the mantle component q with age.