Silicic volcanic complexes in the Main Ethiopian Rift (MER) system host long-lived
shallow magma reservoirs that provide heat needed to drive geothermal systems. Some
of these geothermal systems in Ethiopia appear to be suitable for green and sustainable
electricity generation. One such prospect is located at the Corbetti volcanic complex
near the city of Awassa. High-resolution imaging of the subsurface below Corbetti
is of imminent importance, not only because of its geothermal potential, but also
due to reported evidence for an ongoing magmatic intrusion. In this study, we present
a new subsurface 3-D electrical conductivity model of Corbetti obtained through the
inversion of 120 magnetotelluric stations. The model elucidates a magmatic system
under Corbetti and reveals that it is linked to a magma ponding zone in the lower
crust. Magma is transported through the crust and accumulates in a shallow reservoir
in form of a magmatic mush at a depth of (sic) 4 kmb.s.l. below the caldera. The imaged
extent and depth of the shallow magma reservoir is in agreement with previous geodetic
and gravimetric studies that proposed an ongoing magmatic intrusion. Interpreting
our model with laboratory-based conductivity models for basaltic and rhyolitic melt
compositions suggests that Corbetti is seemingly in a non-eruptible state with similar
to 6-16 vol. per cent basaltic melt in the lower crust and similar to 20-35 vol. per
cent rhyolitic melt in the upper crust. With these observations, Corbetti's magmatic
system shares common characteristics with volcanic complexes found in the central
MER. Specifically, these volcanic complexes are transcrustal two-stage magmatic systems
with magma storage in the lower and upper crust that supply heat for volcano-hosted
high-temperature geothermal systems above them. According to the presented subsurface
model, a cross-rift volcano-tectonic lineament exerts first-order controls on the
magma emplacement and hydrothermal convection at Corbetti. Our study depicts hydrothermal
convection pathways in unprecedented detail for this system and helps identify prospective
regions for future geothermal exploration. 3-D imaging of both the Corbetti's magmatic
and associated geothermal systems provides key information for the quantitative evaluation
of Corbetti's geothermal energy potential and for the assessment of potential volcanic
risks.
