MSc defence by Samuel Munyiri
Samuel Munyiri, MSc Fellow in Geology at the University of Iceland will give a lecture on his MSc project on Friday 27th May, 2016 at 14:00 at University of Iceland, venue not confirmed yet.
The title of the project is:
Structural Mapping of Olkaria Domes Geothermal Field using Geochemical Soil Gas Surveys, Remote Sensing and GIS
Samuel's supervisors are:
Dr. Björn S. Harðarson Gunnlaugur M. Einarsson from ISOR and Prof. Þorvaldur Þórðarson from University of Iceland.
The external examiner will be Kristján Saemundsson Senior Geologist at ISOR.
Everyone's welcome to attend.
Abstract
Olkaria Geothermal field is a high temperature geothermal system located on the eastern arm of the East African Rift System. It is placed within the Central Kenyan Rift Valley and is dominated by late Quaternary rhyolitic volcanism. Basalts, tuffs and trachytes occupy the subsurface with the latter forming the reservoir rock. The Volcanic Complex has no clear caldera association but it’s bounded by an arcuate ring of volcanic domes in the east, south and southwest (ring structure) has been used to invoke the presence of a buried caldera. The geothermal license area is subdivided into seven fields for geothermal development purposes namely; Olkaria East, Olkaria Northeast, Olkaria Central, Olkaria Northwest, Olkaria Southwest, Olkaria Southeast and Olkaria Domes field (study area). Normal faulting is prominent in the Domes field with dips ranging from 20° to 80° to the west and the east. Fault strikes vary from North-South, Northwest-Southeast, Northeast-Southwest and East-West. The oldest faults strike Northwest and coincide with the initiation of the Kenyan rift system while the youngest are the North striking and are thought to have formed during a distinct period of dyking that took place along the Ol Njorowa Gorge about 2.5 Ma. East-West striking faults were discovered to the east of Domes field and are inferred to be formed during a period of transform faulting. Thrust faulting is rare throughout the field but portrays brief periods of crustal compression. Geothermal manifestations were observed as key indicators of permeable zones that gave indication of faults and fractures which may have been obscured by recent pyroclastic deposits. Soil gas surveys indicate an E-W orientation of CO2 soil gas anomalies along the south of Domes field, especially in the vicinity of the ring structure (i.e. Olkaria caldera fault zone). The Central Kenyan rift shows sudden change in the stress regime which caused fault orientation changes from Northwest to Northeast. Digital Elevation Models (DEM) show step normal faulting to be dominant forming steep shoulder faults along the rift margins. Regional faults exhibit near vertical dips to the east and west, forming a graben which is approximately 45km wide. Transform faulting is evidenced along the Central Kenyan rift and may have been responsible for sudden changes in the strike of the rift faults.