Terrestrial heat flow in east and southern Africa and the thermal structure of Precambrian lithosphere

I report 26 new heat flow determinations from Tanzania, Zambia, and Zimbabwe which, together with previous heat flow measurements, define a common first-order heat flow pattern in east and southern Africa, a pattern characterized by lower heat flow in the Archean cratons than in the Proterozoic mobile belts surrounding the cratons. This common heat flow pattern suggests that the gross thermal structure of the largely Precambrian lithosphere beneath east and southern Africa is similar.;A previous study, using thermal models which employed a parameterized convection algorithm to calculate heat transfer in the sub-lithospheric mantle, attributed this first-order heat flow pattern to the greater thermal resistance of thicker lithosphere beneath the cratons. I test this interpretation by comparing thermal models constructed using parameterized and full thermal convection algorithms. The models yield similar surface heat flow, and therefore I conclude that the earlier interpretation is robust because surface heat flow appears to be insensitive to the details of how mantle heat is delivered to the base of the lithosphere.;Superimposed on the common first-order heat flow pattern are two second-order differences in heat flow between east and southern Africa which suggest that the thermal structure of the lithosphere differs somewhat between these regions. I examine these second-order heat flow differences and show that their interpretation is not easy because available constraints on crustal heat production, crustal structure, lithospheric thickness and mantle temperatures are insufficient to discriminate between the possible explanations.;Analyses of heat flow from Precambrian terrains worldwide reveal two global heat flow patterns; (1) a heat flow-tectonic age relationship, and (2) a spatial pattern between heat flow and the proximity of Archean cratons. The latter pattern is characterized by heat flow in Archean cratons and Proterozoic terrains adjacent to cratonic margins that is lower than in Proterozoic terrains more than a few hundred kilometers from a cratonic margin. I attribute both heat flow patterns to the greater thermal resistance of thick underlying Archean lithosphere. This interpretation suggests a temporal relationship between heat flow and the age of lithospheric stabilization. Theoretical and numerical studies provide a simple explanation for why heat flow in Precambrian terrains varies with the age of lithospheric stabilization.