Abstract
The tectonic lineaments and thermal structure of Lake Magadi, southern Kenyan rift system, were investigated using ASTER data and geophysical methods. Five N-S faults close to known hot springs were identified for geoelectric ground investigation. Aeromagnetic data were employed to further probe faults at greater depths and determine the Curie-point depth. Results indicate a funnel-shaped fluid-filled (mostly saline hydrothermal) zone with relatively low resistivity values of less than 1 Ω-m, separated by resistive structures to the west and east, to a depth of 75 m along the resistivity profiles. There was evidence of saline hydrothermal fluid flow toward the surface through the fault splays. The observed faults extend from the surface to a depth of 7.5 km and are probably the ones that bound the graben laterally. They serve as major conduits for the upward heat flux in the study area. The aeromagnetics spectral analysis also revealed heat source emplacement at a depth of about 12 km. The relative shallowness implies a high geothermal gradient evidenced in the surface manifestations of hot springs along the lake margins. Correlation of the heat source with the hypocenters showed that the seismogenetic zone exists directly above the magmatic intrusion, forming the commencement of geodynamic activities.
Highlights
Uprising of magma during rifting process often results in various geodynamic activities such as the surface expressions of tectonic lineaments, earthquakes, and manifestations of geothermal resources
Unlike some other geothermal regions where the reservoirs containing hot fluids have to be penetrated during exploitation, geothermal resources around Lake Magadi are clearly manifested on the surface in the form of hot springs and trona deposit along the Lake Margin and in the lake, respectively
The Kenya rift, called the Gregory rift, is the eastern branch of the continental East African rift system (EARS) which extends to about 3000 km from Afar triangle to southern Mozambique [14, 19] (Figure 2)
Summary
Uprising of magma during rifting process often results in various geodynamic activities such as the surface expressions of tectonic lineaments, earthquakes, and manifestations of geothermal resources. Unlike some other geothermal regions where the reservoirs containing hot fluids have to be penetrated during exploitation, geothermal resources around Lake Magadi are clearly manifested on the surface in the form of hot springs and trona deposit along the Lake Margin and in the lake, respectively These surface manifestations of the hot springs have been attributed to the continuous tectonic activities and the presence of various faulting systems in the area [10, 11]. This study employs the use of integrated remote sensing and geophysical methods, geared towards delineating the heat source as well as understanding the influence of active tectonic lineaments on the hydrothermal fluids around Lake Magadi, and with a view to unveiling the geothermal potentials of the area and the cause of tectonic activities
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