The Geochemistry of Arus and Bogoria Geothermal Prospects

Abstract

Arus and Bogoria prospects encompasses several features of geological significance that are considered indicators of possible geothermal potential. These include surface manifestations, such as, intense fumarolic activity (Arus), the vigorous geysers and hot springs (L. Bogoria. Loboi, Maji Moto areas). Anomalous hot ground water boreholes (Mugurin, Emining area) and some carbon dioxide emitting holes in the Esageri area. The springs and boreholes have been sampled and their chemical composition determined and evaluated. The geysers of Lake Bogoria discharge mixed fluid of different proportions of lake water, deep geothermal fluid, and shallow ground water. High flows of discharging fluids were recorded around Lake Bogoria and Maji Moto springs. Reservoir temperature estimates using Quartz geothermometer temperature range from 115 to 425 deg C, while the Na/K geothermometer temperature range from 122 to 377 deg C.

Three hundred and thirty-eight (338) random radon and soil gas sampling points were established. The radon-220 distribution, indicate high counts above 3000 cpm in the western and south western areas of the prospects. These areas include, Arus steam jets, Molo Sirwe and the area to the north of Mugurin. The rest of the area has moderate to low radon-220 counts. The radon-222 distribution indicate high counts in the area between the Arus steam jets and Molo Sirwe. The rest of the prospect’s area has low counts of less than 500 cpm. The four areas with high concentration of Rn-222, are indicative of areas of high permeability and high heat flow. The ground temperature distribution at 0.7 m depth in the Arus and Bogoria Prospects was determined. The areas around the Lelen swamp, Maji Moto, the southern part of Lake Bogoria, and the area north of Arus. They have anomalous ground temperatures in excess of 38°C. High carbon dioxide concentration in the soil gas, was observed around Arus, Molo Sirwe, Noiwet, and the area south of Lomollo. The areas above coincide with deep-seated faults or fractures where the source may be from a magmatic body.

A geothermal resource exists in Arus and Bogoria prospects. The upflow may be located in the area close to the Arus steam jets and the area north of Mugurin. Both areas have high radon and ground temperature. The proposed first exploration well is sited near the Arus steam jets. The proposed second exploration well is sited north of Mugurin and east of Arus steam jets (coordinates 170000 E, 17500 N).The paragraphs should not have line breaks between them – the Normal style will space the paragraphs automatically.