Preliminary Chemical Composition of Fumarolic Gases and Hot Springs of the Barrier
Volcanic Complex Geothermal Prospect- North Rift Kenya
Leakey Ochieng, Jeremiah Kipngok, Sylvia Malimo and Isaac Kanda
lochieng@gdc.co.ke, jkipngok@gdc.co.ke , smalimo@gdc.co.ke and ikanda@gdc.co.ke
Geothermal Development Company
P.O Box 17700 - 20100
Nakuru
The Barrier Volcanic Complex (BVC) is essentially composed of four distinct polygenetic
volcanic edifices; Kaloleyang, Likaiu East, Likaiu West and Kakorinya, which are situated on
the floor of the northern sector of the Kenya rift, immediately south of Lake Turkana. These
volcanic centres are characterised by a wide spectrum of superposed lava. Geothermal
manifestations occur in the form of fumaroles, silica sinters, Logipi hot springs and
hydrothermally altered rocks characterised by argillic alteration deposits of alunite, kaolinite, and
other clay minerals found in the areas of fumarolic activity in the Kakorinya caldera and its
summit. The caldera is the youngest volcanic centre and has the most promising geothermal
potential. This paper outlines chemical characteristics of the sampled seven Logipi hot springs
and six Kakorinya fumaroles in the BVC. The fumarole gas chemistry indicates CO2 as the
dominant gas coupled with a high atmospheric contamination, which be virtually propelled by
the interconnectivity of the various fissures, fractures and minor faults in the caldera or from
dissolved air in shallow aquifers. The atmospheric contamination predominantly affects the
chemistry of the fumarolic gas species through condensation. The fumaroles mark the outflow of
the system as manifested by the isotopic composition and the chemistry. The Logipi thermal
springs discharge waters of Na-Cl-HCO3 facies suggesting peripheral waters, which indeed
marks the outflow of the geothermal system as confirmed from the Na/K and HCO3/SO4 ratios
as well as the δ18O and δ2H stable isotopes signatures. A high temperature geothermal resource exists
in the BVC with an estimated equilibrium reservoir temperature above 280oC based on the gas
geothermometers.
Key Words: Fumaroles, atmospheric contamination, geothermometer, Outflow, Upflow