Correlation of lithology, hydrothermal alteration with temperarures on Olkaria domes, Kenya

Abstract

The Kenyan Rift which forms part of the great Eastern African rift is a graben.Its formation started about 5 million years ago followed by fissure eruptions in the axis of the Rift to form flood lava by about 2 to 1 million years ago. During the last 2 million years ago the volcanic activity became more intense in the axis of the Rift and as a result, large shield volcanoes which form the geothermal prospects (figure 1) were developed. The case study of this report is Olkaria domes which forms part of the Olkaria complex –one of the 14 geothermal prospects (figure1).Using the enormous data collected in this area by various peoples such as Lagat 2010 on lithology, measured and interpreted hydrothermal alteration minerals temperatures the thermal conditions of the geothermal field can be studied by correlating the three parameters. The Olkaria complex geothermal field is in the southern part of Kenyan rift. It is located south of Lake Naivasha approximately120km NW of Nairobi city. In a geothermal fields heat from the underground is carried to the surface by rocks through conduction or by fluids through convection to the surface of the earth. The introduced high temperatures in collaboration with other factors causes the primary minerals of heated rocks to alter to secondary minerals which are at stable or metastable conditions (Lagat, 2010).With the knowledge of stability temperatures of various secondary minerals in Olkaria dome measured temperatures in a borehole at the appearance of these minerals convey information about the temporal changes in the field.