Geothermal Exploration of the Kenya Central Rift Segment: Case Study of the Otutu Rift Segment

Abstract

Otutu is part of the larger Kenya Central Rift and lies in between the Eburru and Elmenteita volcanic field, within the larger Kenya Rift Valley. The area covers a longer portion of the rift floor thus becomes a good representative of the active rift segment. Geological and geochemical surface exploration studies were undertaken in the area, an area outside the normal central volcanoes so as to understand the areas’ geothermal relevance: volcanology, surface mineralogical and chemical characteristics of the volcanic lavas within the study area. This study gives us a better understanding of the behaviour of a rift segment. During fieldwork, several geological structures were mapped and several samples collected for further analysis. A wide variety of lava rocks were identified and these included alkali olivine basalts, trachytes and abundant. The petrochemical results from both ICP-MS and ICP-AES included the rock composition in terms of major oxides, trace and rare earth elements. These results were used to plot various diagrams that included the variation diagrams (for both major oxides, trace elements), Total Alkali-Silica diagram, the AFM diagram, CIPW Norm Classification and also normalized Rare Earth Elements plots. These results provided a complete view of the various kind of liquids emitted during the last million years along this active segment of the rift. It can, therefore, be concluded that the Otutu rift is an important heat release area. It possibly has a shallow underlying anomalous mantle along the rift axis, where successive magma rejuvenations have taken place. This is supported by the steam vents that are aligned along open fissures and faults synchronous and post-dating the volcanic events. These results are of interest for the future geothermal development of the area. However, further studies are recommended on the area.