Heat production and geotherms for the continental lithosphere

We propose a continental lithosphere heat production model based on the petrology of crust and mantle, heat production measurements of surface and xenolith samples, and tectono-thermal constraints. Continental elevation considered within a thermal isostasy rubric is used to partition crustal heat production into upper crustal and lower crustal contributions. The best-fitting partition model using elevation data from 33 North American tectonic provinces suggests upper crustal heat production on average accounts for ~ 6% of observed surface heat flow. An average heat production for the lower crust of 0.4 μW/m3 is based on measurements from exposed granulite terranes while a lithospheric mantle heat production of 0.02 μW/m3 is based on chemical analyses of mantle xenoliths. Results are relatively insensitive to mantle composition and thickness of the upper crustal heat producing layer. Continental geotherms are computed using the generalized heat production model and incorporating thermal conductivity results from a number of recent laboratory studies. P–T conditions of xenoliths provide further constraints to ensure that our geotherms and hence the heat production model are reasonable. P–T conditions of 10 Precambrian regions are consistent with surface heat flow of 40 mW/m2 and a lithospheric thickness of 200 km. Our generalized model for heat production can serve as a reference model from which anomalies are identified.

Research highlights
► Estimate of lithospheric heat production and temperatures.
► Average upper crustal heat production is estimated at 26% of surface heat flow.
► Geotherm family for the continental lithosphere parameterized in surface heat flow.
► Cratonic regions with xenoliths have average surface heat flow of 40 mW/m2.