Heat flow in the Kenya rift zone

Wheildon, J.; Morgan, Paul; Williamson, K.H.; Evans, T.R.; Swanberg, C.A.

doi:10.1016/0040-1951(94)90173-2

Cited by 57 publications

(36 citation statements)

References 26 publications

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“…Heat flow values from the Kenya Rift are highly variable, generally ranging between 40 and 110 mW/m 2 , with geothermal gradients between 2.5 and 6.6 8C/100 m (Wheildon, Morgan, Williamson, Evans, & Swanberg, 1994). The Loperot-1 well indicates that the Lokichar Basin today lies in the middle range of the data, however, during the active rifting and volcanic phase, it is quite likely that heat flow, and thus temperatures, were higher.…”

Section: Basin Temperaturementioning

confidence: 86%

Hydrocarbon potential of the Meso-Cenozoic Turkana Depression, northern Kenya. II. Source rocks: quality, maturation, depositional environments and structural control

Talbot

Morley

Tiercelin

et al. 2004

Marine and Petroleum Geology

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Section: Basin Temperaturementioning

confidence: 86%

Hydrocarbon potential of the Meso-Cenozoic Turkana Depression, northern Kenya. II. Source rocks: quality, maturation, depositional environments and structural control

Talbot

Morley

Tiercelin

et al. 2004

Marine and Petroleum Geology

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“…The ensemble of heat-×ow data from East Africa (Nyblade et al, 1990;Nyblade, 1997;Wheildon et al, 1994), when compared to the global distribution of heat ×ow in tectonically undisturbed Precambrian terrains of similar age, indicates that heat ×ow from areas of East Africa outside of the rift valleys is not elevated. Heat ×ow from within the rift valleys, although probably elevated, is not well determined by observations.…”

Section: Upper Mantle Structurementioning

confidence: 97%

Crust and upper mantle structure in East Africa: Implications for the origin of Cenozoic rifting and volcanism and the formation of magmatic rifted margins

Nyblade

2002

Volcanic Rifted Margins

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Crust and upper mantle structure in East Africa, together with the tectonic history of the region, is used to evaluate geodynamic processes commonly associated with the formation of magmatic rifted margins. Cenozoic rifting and volcanism in East Africa represent the earliest stage in the development of a rifted continental margin, and East Africa is one of the few places where geodynamic processes may be active that could lead to the development of a magmatic rifted margin. The Precambrian tectonic framework of East Africa is characterized by an Archean craton (Tanzania Craton) surrounded by Proterozoic mobile belts. An extensive nonmagmatic rift system associated with the separation of Madagascar from Africa developed in the mobile belts during the Permian-Cretaceous. In the Cenozoic, two rift branches (Western Rift and Eastern Rift) formed in the mobile belts. Volcanism is present in both branches, but most of it is concentrated in the Eastern Rift. Crustal structure away from the Cenozoic rifts is typical for Precambrian crust. Similarly, uppermost mantle structure across East Africa does not appear to have been altered, except beneath the rift valleys. Deeper in the upper mantle a thick (~200 km) lithospheric keel is found under the Tanzania Craton, and a broad (200-400 km wide) thermal anomaly extending to a depth of at least 400 km is beneath the Eastern Rift. Several models cannot fully account for the tectonic history of East Africa and/or the structure of the crust and upper mantle, including edge ×ow in the convecting mantle around the keels of Archean cratons, broad (> 500 km wide) thermal upwellings originating in the lower mantle, a relatively stationary plume head, and a plume head that ×ows outward along topography on the underside of the lithosphere. Consequently, these models are not strong candidates for the origin of volcanism and rifting in East Africa. Models with two or more plume heads, however, can explain the relevant observations, and therefore a multiple plume head explanation for the rifting and volcanism in East Africa is favored. These µndings further call into question the viability of nonplume models for the formation of magmatic rifted margins, particularly models invoking edge ×ow in the convecting mantle around cratonic keels.

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“…Comparisons with measured temperatures show that areas with the highest bottom hole temperatures and heat flow values >200 mWm -2 are directly above the deeper gaps. (Wheildon et al, 1994).…”

Section: Exploration and Reservoir Evaluationmentioning

confidence: 99%

A Comprehensive Study of Fracture Patterns and Densities in The Geysers Geothermal Reservoir Using Microearthquake Shear-Wave Splitting Tomography

Malin¹,

Shalev²,

Lou³

et al. 2004

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In this project we developed a method for using seismic S-wave data to map the patterns and densities of sub-surface fractures in the NW Geysers Geothermal Field. 1) This project adds to both the general methods needed to characterize the geothermal production fractures that supply steam for power generation and to the specific knowledge of these in the Geysers area. 2) By locating zones of high fracture density it will be possible to reduce the cost of geothermal power development with the targeting of high production geothermal wells.3) The results of the project having been transferred to both US based and international geothermal research and exploration agencies and concerns by several published papers and meeting presentations, and through the distribution of the data handling and other software codes we developed.Our project extended over a 3 year time period. It included extensive compilation of data from existing and past seismic networks surrounding the Geysers Geothermal area. The study focused on identifying, measuring, modeling, and interpreting the effects of fractures on seismic S-waves at this site, specifically the North West Geysers. Computer codes to handle and process such observations were developed. The last year of our project included a DOE guided, scientific and collaborative exchange with Dr. Silas Simiyu of the Kenya Electric Power Generating Company, Inc., the national power company of the Government of Kenya.As part of our collaboration with industry and other exploration groups, we provided a training course on S-wave splitting tomography. The notes from this course are included in this Final Report, as are compressed versions of the publications resulting from from our work.A further benefit to both the geothermal research community and geothermal industry resulted from our collaboration with KenGen: after hearing our presentation of our results on this project at the World Geothermal Congress in Japan, we were approached by the World Bank and United Nations Environmental Program to begin a similar project in the East African Rift Region. Comparison of the Accomplishments with Goals and ObjectivesFor this project our original Goals and Objectives were:1. S-wave splitting identification and processing of microearthquake recordings from geothermal exploration and production areas. Application of this identification and processing approach to the NW Geysers 2. Determining the crack orientations around the seismic networks, past and present, in the NW Geysers.3. Complete a 3-D inversion for the crack density distribution in the NW Geysers.4. Develop further the computational methods for forward modeling of anisotropic wave propagation.5. Develop a software package that can handle all of the steps above.The Accomplishments in each of these areas of our project were:1. We both tested the S-wave splitting analysis approaches of the University of Edinburgh group (S. Crampin, PI) and developed our own method. The new methods are summarized in Lou et al. (1997), a copy of which is attached t...

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Heat flow in the Kenya rift zone

Cited by 57 publications

References 26 publications

Hydrocarbon potential of the Meso-Cenozoic Turkana Depression, northern Kenya. II. Source rocks: quality, maturation, depositional environments and structural control

Hydrocarbon potential of the Meso-Cenozoic Turkana Depression, northern Kenya. II. Source rocks: quality, maturation, depositional environments and structural control

Crust and upper mantle structure in East Africa: Implications for the origin of Cenozoic rifting and volcanism and the formation of magmatic rifted margins

A Comprehensive Study of Fracture Patterns and Densities in The Geysers Geothermal Reservoir Using Microearthquake Shear-Wave Splitting Tomography

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