Geochemistry of Fumarole Discharges and Borehole Waters of Korosi-Chepchuk Geothermal Prospect, Kenya

Abstract

Korosi-Chepchuk geothermal prospect is situated immediately to the north of Lake Baringo and south of Paka in the Kenyan Rift. This paper aims at discussing chemical characteristics of the borehole waters, and uses the fumarole gas discharge in the determination of subsurface temperatures and establish the source of water feeding the hydrothermal system using stable isotopes. Korosi volcanic complex and Chepchuk ridges have an active and exploitable geothermal resource with estimated reservoir temperatures in excess of 240°C as deduced from gas geothermometers. Korosi Chepchuk fumaroles show a trend where ?2H and ?18O are onsiderably depleted. The source of the fumarole discharge is the local meteoric waters. Two boreholes; Nyaunyau and Loruk have the highest measured temperatures and plot differently from the others, implying they could be representing waters with geothermal input unlike the others. From Na-K-Mg ternary diagram it is observed that none of the borehole waters have attained equilibrium with aquifer rocks and therefore are not suitable for use to estimate reservoir temperature, except the Loruk and Nyaunyau borehole waters that are close to partial equilibrium and could be suitable for solute geothermometry.