Regional variations in geothermal gradient and heat flow across the African plate

1813 geothermal gradient measurements from deep wells have been accessed across the African plate. Thermal conductivities based largely on North African sampling and publications have been used to either directly estimate heat flow from these or to calibrate other author's figures to form a standardised dataset. Variations seen in geothermal gradient can be due to lateral changes in lithology and thermal conductivity. The thermal regime of West Africa is shown to be consistent and featureless, with the exception of high heat flows over some igneous-influenced areas such as Senegal/Mauritania. Southern Africa is consistently thermally cold. More tectonically active regions in eastern and northern Africa show far more variation and generally higher heat flows. Two main controls are identified, namely time elapsed from rifting/break-up and an igneous related input of heat from the mantle. Plots of heat flow against age of basin show support for McKenzie models of exponential thermal decline. The Red Sea is therefore a valid analogue for the past thermal regime of many current passive margins. Extinct magmatic margins are colder than their amagmatic counterparts. The regions of highest heat flow show a correlation with those of young mantle-derived igneous activity and those of anomalous upper mantle seismic velocities, indicative of partial melting.