Fumarole Gas Geochemistry of Paka Geothermal Prospect, North Rift, Kenya

Abstract

Intense and widespread geothermal surface activity manifested in the form of fumaroles, hot grounds and hydrothermally altered rocks characterize Paka geothermal prospect. Geochemical investigation entailing sampling and analysis of steam discharges from selected fumaroles was carried out. Chemical results of fumarole discharges were used to predict the chemical characteristics of the geothermal reservoir as well as estimate subsurface temperatures. The fumarolic gases are CO2-dominated with significant H2 and CH4 concentrations present. H2S may have been lost during ascent of the fluids to the surface or possibly due to the generally low H2S concentrations in the Kenya Rift. Reservoir temperatures in excess of 300?C are estimated from gas geothermometers based on the fumarole gas compositions. The main origin of the water feeding the geothermal reservoir in Paka is meteoric as evidenced by stable isotope data.