Mapping subsurface lineaments beneath the Ethiopian plateaus and the adjoining Ethiopian rifts using gravity data: Implications for tectonic evolution of the underlying crust

The aim of this study is to map subsurface lineaments beneath the Ethiopian plateaus and the rifts (the Afar Depression, the main Ethiopian rift, and the southern Ethiopian rift) using aero gravity data. Linear structures of the earth known as geological lineaments, may serve as indicators of key tectonic units in the crust that are linked to mineral deposits, active faults, groundwater controls, earthquakes, and geomorphology. Lineament distributions are directly related to mineralization in regions where ore fluid migration forms mineral deposits and may be used to find new locations for exploration. A series of subsurface lineament maps at different depth slices were created from upward-continued Bouguer gravity grids. The derived subsurface lineaments were generally oriented in a northwesterly direction in contrast to the dominant northeasterly orientations of the surface lineaments mapped by previous studies. Through the use of upward continuation and the depth slices of a residual Bouguer gravity anomaly map, the depths to subsurface lineaments were calculated which ranged between 0 – 50 km. The number and density of the lineaments decrease with depth while their lengths show inconsistent behavior with depth. The study further demonstrated the eastward younging of the Arabian Nubian Shield in Ethiopia based on the depth-dependent westward shifting of significant subsurface lineaments discovered beneath the plateau in the northwest Ethiopia.