Heat flow and differences in lithospheric thickness

Abstract

Observations of surface heat flow may be used to constrain the thickness of the lithosphere only in those regions that have approached conductive equilibrium, presumably the oldest continental and oceanic areas. A model is set up to investigate lithospheric thickness differences between old oceans and old continents. The main variable parameters are the surface heat flow, the mean heat production within the continents, and the vertical distribution of the continental heat production. There need be no thickness difference between an old continental region, with a heat flow of 40 mW m -2 and a uniform crustal heat production of 0.5 μW m -3 , and an old oceanic region. Both these values are close to average for old shield areas. Lower surface heat flow, higher mean heat production or exponental distribution of the same heat sources imply a thicker continental lithosphere. In some places old continental lithosphere is probably thicker than that under oceans.