303-8 Dimensionality Assessment and Structural Controls on the Ihimbo Geothermal Prospect, Western Branch of the East African Rift System.

Session: Honoring the Late Professor Mohamed Abdelsalam: Outstanding Researcher, Generous Colleague, Legendary Mentor, and Ambassador for the Geosciences In Africa (Posters)

Poster Booth No.: 183

Presenting Author:

Daniel Duah-Boakye

Authors:

Duah-Boakye, Daniel¹, Katumwehe, Andrew², Mickus, Kevin³, Emishaw, Luel⁴, Bibirye, Paula⁵, Halihan, Todd⁶, Vilcáez, Javier⁷

(1) Boone Pickens School of Geology, Oklahoma State University, Stillwater, Oklahoma, USA, (2) Boone Pickens School of Geology, Oklahoma State University, Stillwater, Oklahoma, USA, (3) Missouri State University, Springfield, Missouri, USA, (4) Kleinfelder, Dallas, Texas, USA, (5) Independent Researcher, Broken Arrow, Oklahoma, USA, (6) Boone Pickens School of Geology, Oklahoma State University, Stillwater, Oklahoma, USA, (7) Boone Pickens School of Geology, Oklahoma State University, Stillwater, Oklahoma, USA,

Abstract:

The Ihimbo geothermal prospect, located in the non-volcanic segment of the western branch of the East African Rift System (EARS), offers a unique opportunity to investigate fault-controlled geothermal systems in a tectonically active but amagmatic setting. The site lies along a major NW–SE trending fault zone, parallel to the rift axis, which is believed to enhance meteoric water infiltration and hydrothermal circulation. This study integrates broadband magnetotelluric (MT) soundings with geological and structural data to evaluate the subsurface resistivity architecture and its link to known surface manifestations.

The dimensionality assessment of MT data from 74 sites reveals a general pattern of near-surface 1D structures that transition into more complex 2D geometries at depth beyond 150m. Apparent resistivity curves commonly display overlapping TE and TM modes at short periods (0.01s), suggesting layered conductivity, while divergence at longer periods (above 10s) points to deeper structural variations. Strike analysis highlights two dominant azimuths (90°–120° and 120°–150°), aligning with mapped fault orientations. Elongated Phase tensor ellipses and tipper responses further indicate localized 3D effects, likely tied to intersecting fault zones or deep structural controls.

These results suggest that the Ihimbo system is structurally controlled, with permeability likely governed by deep fault intersections and anisotropic lithologies. The findings provide a foundation for identifying geothermal fluid pathways and targeting future drilling. Ongoing 1D and 2D resistivity inversions will help refine the geothermal model and better constrain reservoir extent within the broader rift tectonic framework.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6535

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