Integrated 3D geological model of the East African Rift basins and upper crust in SW Tanzania – Implications for geothermal resources

Assessing the geothermal resource potential of sedimentary aquifers and basement rocks in a major active continental rift system such as the East African Rift requires a complete understanding of the subsurface structure, specifically the depth to the basement, the thickness of sedimentary rocks and fault architecture of sedimentary basins and the underlying upper crust. These parameters are fundamental to estimating heat flow, reservoir size, and the overall geothermal potential of an area. To constrain these critical parameters, which are currently not well constrained in the study region, located in the southwestern Tanzania, particularly in the Songwe Basin and Runge Volcanic Province, we applied a 3D geological modelling approach integrating all available data, including seismic data, geological sections, geological maps, and satellite-based gravity data. Our findings revealed basement depths ranging from 2 km above sea level to 3.4 km below sea level in the Songwe Basin and RVP, and the total sedimentary thickness for the entire region reached up to 11 km in the Rukwa Basin. The border faults are characterised by a steeper gradient at the end of fault length-displacement profiles, with maximum displacement of up to 11 km and an estimated damage zone width of up to 675 m, indicating possible fault interaction zones. The occurrence of hydrothermal outflow and elevated heat flow along these zones suggests that the border faults control the basin geometry, sediment accommodation, and fluid pathways in the region. Our findings contribute to a better understanding of extensional basin evolution, fluid migration pathways, and the prediction of subsurface temperature distribution. This information aids geothermal resource calculation and identification of potential targets for geothermal exploration and development. • Integration of seismic, geological and gravity data into a unified 3D geological model of the SW Tanzania. • The greatest sediment thickness uncovers a long period of fault activity and subsidence associated with rift propagation. • Variations of basement depth, sediment and volcanic thickness reveal complex geological processes and structural dynamics. • The strain localization along border faults controls basin geometry and sediment accommodation. • The study highlights the impact of fault interactions on hydrothermal outflow in the SW Tanzania