Gravity measurement to probe the depth of African-continental crust over a north-south profile: theory and modeling

Based upon gravity measurements and calculations, the depth of the African continental crust is estimated. Taking as constraints the mass and radius of earth, and measured gravity, this theoretical method explores the use of gravitational potential to calculate the absolute gravity at three locations in Africa (e.g., Cape Town at latitude -34^o, central Africa at latitude 0, and Benghazi at latitude 32^o). The computational method uses as input a continental crust density ρ₁ = 2.65–2.75 g/cm³ while compromising the oceanic crust density ρ₂ to maintain the average crust density of the planet fixed at <ρ₁₂> = 2.60 g/cm³. Crustal depth is assumed uniform around the earth and kept as a free parameter to adjust for the best fitting of gravity but using values of less than 100 km. A solid angle α_o is a solid angle whose vertex is at the center of earth used to separate continental and oceanic crusts (α_o = 10^o, 20^o, 35^o). The results obtained for the continental crust were H = 36 km near continental edges at both Benghazi and Cape Town, whereas H = 44.4 km at the center of continent. These results are in excellent agreement with those reported by Tedla and coworkers (H = 39 ± 5 km) using an Euler deconvolution method. Our theoretical results from the developed code are also corroborated by results of numerical forward modeling supporting our code's reliability for further geoscience explorations.