Structural Geology of Eburru Volcano and Badlands Geothermal Prospects in Kenya

Abstract

Eburru is a Quaternary volcano situated on the southern segment of Kenya Rift, an arm of the larger EARS,it forms the highest topography within the entire Kenyan rift at an elevation of 2800m, while Badlands lies lower to the North of Eburru massif towards Lake Elementaita. This paper describes the results from examination of existing data and geological exploration by KenGen geology team during structural geological mapping of Eburru and Badlands geothermal prospects. The exercise was carried on May, 2014 with objective to pinpoint the structural setting, map geothermal manifestations and mapping of alteration characteristics and identify the possible location of heat sources. The main structures observed in Eburru area include a series of fault and fracture network system with a general N-S trends and minor E-W, NE-SW and NNE-SSW trending faults, craters and ring structure. These structures play a significant role in controlling the recharge and fluid movement within the geothermal system especially at the intersection of E-W and N-S faults. On mapping Badlands geothermal prospect; distinct N-S trending faults and fractures outlining both the regional and local tectonics with minor NE-SW trending faults were noted, possibly the main control of recharge and fluid movement within the geothermal system in the area. These faults, fractures and fissures form a fissure zone of ≈7-10 km wide. However, within the fissure zone at least one mini-graben was observed (≈2 km wide), which may be of significant geothermal interest. Geologically younger structures were noted in Badlands area. Rock types range from mafic to siliceous rich lavas. Basalt, trachytes, rhyolites and pyroclastics are common in the Eburru area. Obsidian outcrops and pumice cover were noted at hill tops. Basalts with minor obsidian, trachyte, volcanic agglomerates, pyroclastics, tuff and sporadic trachy-andesites are the predominant rock types characterizing the Badlands geothermal prospect.