Results of gravity and ground magnetic survey

PROCEEDINGS, Kenya Geothermal Conference 2011 Kenyatta International Conference Centre, Nairobi, November 21-22, 2011

RESULTS OF GRAVITY AND GROUND MAGNETIC SURVEY OF MENENGAI GEOTHERMAL FIELD,KENYA.
Kemei J.K., Langat G.K., Ambusso W. and Okumu J. Kenyatta University, Physics Department. P.O Box 43844, Nairobi, Kenya. kemeijosphat10@yahoo.com ABSTRACT Geothermal energy is increasinglybecoming an important source of electricity generation in Kenya. It is estimated that more than 7000MW of electricity can be generated from geothermal prospects in Kenya. Identifying and delineating thisresource can be done using geophysical methods. Currently Geothermal Development Company (GDC) has commenced drilling geothermal exploration wells in Menengai area and from the first well the resultsshowed very good results. Gravity and Ground magnetic survey was carried out in Menengai area to map the subsurface structure. The Gravity measurements and total magnetic field intensity was taken witha station spacing of approximately 1km apart. Data reductions has been done and used to plot contour maps of the study area. Both data sets indicate that the northern part of the geothermal field isdemagnetized indicating a zone of possible higher temperature and higher degree of hydrothermal alteration and intruded with high density bodies in the upper crust. Key words: Ground magnetic survey,Gravity, Bouguer anomaly, Total magnetic field

INTRODUCTION Menengai geothermal field is in the Kenyan segment of the East African Rift system and extends from Lake Turkana in the north to thenorth of Tanzania near Lake Natron as shown in figure 1. Menengai is a shield volcano with highest peak at an elevation of 2278 m.a.s.l. Previous work at Menengai was by Kenya Electricity GeneratingCompany. Geology of Menengai The following presentation is based on the reports of Omenda (2007), Leat (1984) and Baker (1958). The geological activity in the Kenya Rift began about 30 million years ago...