Assessment of the Kiejo-Mbaka geothermal field by three-dimensional geophysical modelling

High-resolution magnetotelluric and gravity data have been collected over the Kiejo-Mbaka geothermal field, located along NW–SE trending Mabka fault, in Karonga Rift basin (East Africa System). Such resolution allowed to reconstruct field structure with unprecedented detail. Resistivity modelling has obtained by three-dimensional finite-differences inversion of MT data, while density accomplished surface-oriented data. Geophysical identified two sedimentary sub-basins separated Mbaka fault ridge, exposing basement; these previously unknown fills a maximum thickness ca. 1.5 km. The estimation clay cation exchange capacity (CEC) from magnetotellurics identifies layer low-temperature smectite alteration south-western sub-basin sediments, interpreted as cap. resulting updated conceptual model system is therefore fault-controlled lateral leakage into expectably implying larger reservoir volume than estimated.