Aluto-Langano Geothermal Field, Ethiopia: Multiscale Image of Trans-crustal Magmatic System by Combining Local 3D and Regional 2D Magnetotelluric Soundings

Abstract

Geothermal energy has the potential to support Ethiopia in its attempt to overcome energy poverty and provide sustainable energy for all. The formation and distribution of geothermal energy resources in Ethiopia is associated with magmatic activity along the Main Ethiopian Rift (MER). Until now, geothermal exploration mainly concentrated on shallow magmatic-hydrothermal systems underneath volcanoes in the central part of the MER. At the geothermal field of the Aluto volcano local 3-D magnetotelluric (MT) surveys successfully imaged the geothermal reservoir leading to the placement of productive geothermal wells. However, due to the limited aperture (15 km) of the surveys it was not possible to image the lower crustal magmatic plumbing system of the volcano. A regional MT study along a 120 km long profile transecting the rift and Aluto volcano was conducted within the project RiftVolc. They imaged an off-rift axis magmatic system in the Silti-Debre Zeyit Fault Zone (SDFZ) west of the central rift. However, the feeding zone of Aluto’s magmatic system remained enigmatic. In this study we combined the two existing datasets, resulting in a selection of 165 stations located at Aluto and 26 stations along the 120 km long RiftVolc cross-rift profile. The preliminary 3-D model revealed the existence of a deep conductor in about 35 km of depth on the western side of the rift, indicating that partial melt is present.