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The 1-D steady state temperature structure of part of Chad sedimentary basin has been determined using one layer-model. The solution to the Fourier one dimensional heat flow equation was used to generate subsurface temperature. The thermal conductivity, radiogenic heat production and surface heat flow were varied for the generation of different geotherms. The computed geotherms increase linearly with depth from earth surface to the base of the sediment. Comparison between the computed and measured temperatures from some wells shows a very good match. The internal parameters of the basin controlling the thermal structure are thermal conductivity and radiogenic heat production. [ABSTRACT FROM AUTHOR]

The velocity of the short period compressional waves propagating in the top of the earth's upper mantle is the seismic Pn velocity, and the variations of the Pn velocity as observed in various regions of the earth provide some insightS into the physical state and composition of material in the upper mantle. The paucity of seismic Pn velocity data in Africa necessitated the computation of seismic Pn velocities from crustal P-waves obtained from selected earth models and available data from existing observations in Africa. The results show that the computed Pn velocities are less than the field measured seismic Pn velocities just by a small margin of about 0.03-0.06%. Seismic Pn velocity and heat generation are inversely related; based on this observation, a quantitative relationship between seismic Pn velocity and moho temperature, Pn=7.84+4.979×10-4T(moho), and between seismic Pn velocity and surface heat flow, Pn=7.625+6.087'10-3Q0, was established using regression equation with 95% confidence limit. These relationships come in handy when we are unable to obtain some of such data directly from field measurements. [ABSTRACT FROM AUTHOR]

Data from the Earth Gravitational Model (EGM2008) and the Earth Magnetic Anomaly Grid (EMAG2) were used to develop a continental scale crustal thickness model for Africa, and to estimate the depth to the bottom of the magnetic layer (DBML) and the geothermal gradient and heat flow. The results are: (1) the estimated DBML from the magnetic data varies from ~23.0 to ~37.2 km. The shallowest DBML values are located in the northern, eastern, and western parts of the continent, whereas the deepest values are observed in the central and southern regions. (2) The estimated crustal thickness based on gravity data varies from ~29.9 km in the northern and western parts of Africa to ~48.0 km in its southern regions, with an average thickness of 35.1 km for the whole continent. (3) The estimated heat flow varies between high values of 46–59 mW/m2, observed in the northern, eastern, and western regions to low values of ~< 41 mW/m2, observed in the central and southern parts of the continent. (4) The geothermal gradient values vary between 14.5 and 23.6 °C/km (5) The East African rift zone is underlain by shallow DBML characterized by high heat flow values that vary between 42 and 59 mW/m2 (6) The heat flow anomalies in Egypt and Libya may be associated with the zone of the Pelusium megashear system, and it shows heat flow values that vary between 36.3 and 59.0 mW/m2. The current study has taken advantage of the availability of the EGM2008 and EMAG2 datasets to map crustal thickness variations and DBML beneath the continental landmass of Africa. • Mapping crustal thickness variations beneath Africa using gravity data. • Determination of the depth to the bottom of the magnetic layer in Africa using magnetic data. • Calculation of the geothermal gradient and heat flow in Africa. [ABSTRACT FROM AUTHOR]

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. • 1813 geothermal gradients and 1237 heat flows have been compiled over Africa. • These have been corrected to a standard thermal conductivity model. • Significant positive heat anomalies in Northern Africa. • Two controls identified, age of basin and mantle activity. • Mantle heat contribution more important than generally realised. [ABSTRACT FROM AUTHOR]