| Title | 2D Inversion of MT Data to Delineate the Resistivity Structure of Kibiro Geothermal Prospect. |
|---|---|
| Authors | Eriya Kahwa, Geraldine P. Babirye, Nelson R. Birungi and Joseph Nyago |
| Year | 2016 |
| Conference | ARGeo |
| Keywords | Magnetotelluric, electromagnetic, resistivity |
| Abstract | The first geophysical surveys in the Kibiro geothermal prospect were carried out in 2004. The aim of the study was to delineate the areal extent of the geothermal reservoir and come up with a geophysical conceptual model of the area. The Kibiro geothermal prospect is located in the western arm of the East African Rift system in Hoima District, Western Uganda. The prospect is traversed by the Bunyoro-Tooro fault/escarpment with crystalline basement rocks comprising granites, gneisses and amphibolite intrusives on the eastern side and younger Pleistocene sediments on the western side. The geothermal surface manifestations are hot springs with a maximum surface temperature of 86.5˚C and are located on the contact between the crystalline basement rock and the sediments. TEM resistivity surveys carried out in 2004 revealed low resistivity anomalous areas in the crystalline basement which were tested with shallow temperature gradient drilling and found not to be related to the geothermal activity at Kibiro. Recent resistivity investigations aimed at delineating the geothermal resource at Kibiro acquired 65 MT and 44 TEM soundings. The data was analysed using the WinGLink program for static shift correction and 2D inversion of MT. The results of the 2D inversion; cross-sections and iso-resistivity maps suggested very high conductivity anomalies in the crystalline basement rocks east of the Escarpment. A low-resistivity anomaly was traced within the sedimentary basin between the escarpment and the Lake Albert and possibly extending under the Lake. In the context of sediment-hosted geothermal reservoir, the unusually low resistivity clay in Kibiro indicates the extent of sediments affected by hydrothermal alteration. The low resistivity is more likely associated with alteration from an outflow rather than from upflow, except closer to the North Toro Bunyoro (TNB) fault. |