Pyroclastic rocks as a tool to evaluate geothermal systems in the Kenyan Rift valley

Abstract

Pyroclastic rocks when studied keenly would be a big boost to identifying the geothermal system of a targeted area and better still a geothermal prospecting tool in potential regions, even before other surface investigations are undertaken. It is such factors as volume and characteristics-both chemical and physical, of these rocks that need to be looked at on a wider scope. Pyroclastics refer to tephra produced by the expansion of magmatic gases and is a collective term for tuffs, ash, and ignimbrites (pumice-rich pyroclasic flows). Among other factors that will be explained later, pyroclastic rocks can be used to estimate the size of their parental chamber, indicate both host rock permeability and existence of water in the thermal system, and reconstruct the host rock lithology and stratigraphy beneath the volcano. This project is aimed at creating more deserved attention on pyroclastics in Kenya’s geothermal- potential areas, most of which happen to occur in the Rift, for detailed analyses in the prospecting stages. Excellent examples of the use of pyroclastic rocks and lithic constituents in exploration for geothermal reservoirs are provided by studies in the Latium volcanic province of Italy, Taupo in New Zealand, and Nisyros in Greece.