EG15: Magnetotelluric Imaging of the Tendaho Geothermal Field in the Afar Depression, Northeastern Ethiopia

Tendaho geothermal field is a high-enthalpy geothermal area located within the Afar Depression in northeastern Ethiopia. High subsurface temperatures exceeding 270 °C were measured from deep geothermal wells in the Ayrobera and Dubti areas in the Tendaho Graben. Results from well logs and geophysical studies confirmed a shallow liquid-dominated permeable zone in the uppermost sedimentary layer, whereas the deeper Afar Stratoid basaltic sequence contains a deeper reservoir. In this study, we generate a 3D resistivity model using magnetotelluric data acquired since the early 2000s from the Ayrobera and Dubti fields. This work aims to examine the geothermal system in the region and map a shallow and possibly a deeper larger magma in the lower crust that drives the hydrothermal activities in the region. The resulting resistivity model successfully images a conductive clay alteration (zeolite alteration) at shallower depths and potential permeable resistive zones overlaying the shallow conductive layer. Below the 8 km depth, the 3D resistivity model shows a conductive zone possibly associated with a partial melt, as suggested in geochemical and seismic investigations.