tectonic control on geothermal sites with specific reference to the

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TECTONIC CONTROL ON GEOTHERMAL SITES WITH TECTONIC CONTROL ON GEOTHERMAL SITES WITH SPECIFIC REFERENCE TO THE ALBERTINE GRABENSPECIFIC REFERENCE TO THE ALBERTINE GRABEN

DozithDozith AbeinomugishaAbeinomugisha

Structural GeologistStructural Geologist

Petroleum Exploration and Production Department,Petroleum Exploration and Production Department,

At theAt the

SECOND AFRICAN RIFT GEOTHERMAL CONFERENCE

Imperial resort Beach Hotel 24Imperial resort Beach Hotel 24thth –– 2525thth November 2008.November 2008.

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TOPICS TO COVER.

1.1. INTRODUCTIONINTRODUCTION

2.2. REGIONAL SETTING OF THE EARSREGIONAL SETTING OF THE EARS

3.3. GEOTHERMAL POTENTIAL OF UGANDAGEOTHERMAL POTENTIAL OF UGANDA

4.4. CONCLUSIONSCONCLUSIONS

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1. INTRODUCTION: Location of Geothermal Sites1. INTRODUCTION: Location of Geothermal Sites

Geothermal Sites influenced by Plate Boundaries

•Divergent-Extension

•Convergent-Compression

•Conservative -Strike Slip

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Convection of the mantle is the major drive for plate tectonics and thinning of the crust

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1.1. INTRODUCTIONINTRODUCTION Source of Geothermal EnergySource of Geothermal Energy

Geothermal fields Associated with active plate boundaries

•Convergent Zones

•Divergent Zones

•Strike slip Zones

Water circulation along deep seated faults

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1. INTRODUCTION: Surface expression of Geothermal Energy1. INTRODUCTION: Surface expression of Geothermal Energy

Deildartunguhver, Iceland: the highest flow hot spring in Europe

Common Surface Expression of Geothermal energy are Hot springs, Geysers, fumaroles

A hot spring is a spring that is produced by the emergence of geothermally heated ground water from the earth's crust.

Source of heat: from the Earth’s interior

•Tectonically active areas; Through deep seated faults

•Volcanic areas; Contact with Magma

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Tectonic setting of Gila hot springs region, New Mexico, USA.

•Springs associated with deep seated extensional faults

GHC Bulletin, December 2002

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Geologic cross section across Gila hot springs. The hot springs are associated with deep seated faults

GHC Bulletin, December 2002

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Tertiary rift

Rifting avoided the stable Cratons. Utilised the mobile belts.

Pre-Cambrian fabric influenced rift geometry

Extension direction is nearly E-W

Albertine graben forms the northern most termination of the Western branch of EARS

Source of map: ftp://e0srp01u.ecs.nasa.gov/

Legend

2. TECTONIC SETTING OF EARS2. TECTONIC SETTING OF EARS

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Albertine Graben

Malawi Rift

East Africa DEM

Ethiopian rift

Tanzania craton

2.2. TECTONIC SETTING OF EARSTECTONIC SETTING OF EARS

Tanganyika Rift

Kenya Rift

Red Sea

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Deep Seated Faults

General Trends

Northern trends in a NNE-SSWCentral trends in a NE-SWSouthern trends in a NNE-SSW

Highly segmented faults

Limited volcanism from the southern Limited volcanism from the southern partpart

3. GEOTHERMAL POTENTIAL OF UGANDA: structural setting of Albert 3. GEOTHERMAL POTENTIAL OF UGANDA: structural setting of Albert RiftRift

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3. GEOTHERMAL POTENTIAL OF UGANDA: Hot spring occurrence3. GEOTHERMAL POTENTIAL OF UGANDA: Hot spring occurrence

Hot Springs aligned along the AlbertineGraben

Over 40 hot springs studied

Three with highest potential

•Katwe - Kikorongo•Buranga

•Kibiro

Courtesy: Godfrey Bahati

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3.3. GEOTHERMAL POTENTIAL OF UGANDA: GEOTHERMAL POTENTIAL OF UGANDA: KatweKatwe AreaArea

Katwe -Kikorongo and Bunyaruguruvolcanic provinces

Volcanic line trend same as the basin margin faults

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KitagataHotspringsKatwe-kikorongoarea

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The Katwe KikorongoGeothermal Potential related to a thinned crust

The thinned crust responsible for the volcanic province

Located in the Accommodation zone of the Lake Edward and Semlki basins

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Muhokya Hot springs

Eastern flanks of the Rwenzori Mountains

The tufa limestone deposits in the area related to hot springs along the NNE –SSW trending faults

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3.3. GEOTHERMAL POTENTIAL OF UGANDA: GEOTHERMAL POTENTIAL OF UGANDA: SempayaSempaya AreaArea

Buranga Hot Springs

Highest surface temperature

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3.03.0 GEOTHERMAL POTENTIAL OF UGANDA: GEOTHERMAL POTENTIAL OF UGANDA: SempayaSempaya AreaArea

5 km

Rwenzori nose underneath Semliki Basin

•Probably Volcanic intrusion

•Gas Chimney above the structuring

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0.00

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1.00

1.50

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2.50

3.00

2km

Buranga Hot springs could be associated with deep seated faults

Rw

enzo

rino

se3.03.0 GEOTHERMAL POTENTIAL OF UGANDA: GEOTHERMAL POTENTIAL OF UGANDA: SempayaSempaya AreaArea

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Turaco wells drilled in Semlikibasin encountered Carbon Dioxide

•Probably from a volcanic body

Geothermal Gradient 30oC –40oC

3.03.0 GEOTHERMAL POTENTIAL OF UGANDA: GEOTHERMAL POTENTIAL OF UGANDA: SempayaSempaya AreaArea

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3.3. GEOTHERMAL POTENTIAL OF UGANDA: GEOTHERMAL POTENTIAL OF UGANDA: KibiroKibiro AreaArea

Kibiro hot springs associated with deep seated faults

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Deep seated faults close to Kibiro

3.03.0 GEOTHERMAL POTENTIAL OF UGANDA: GEOTHERMAL POTENTIAL OF UGANDA: KibiroKibiro AreaArea

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An Oil Drilling Rig at Taitai, a few km north of Kibiro

•Geothermal Gradient in the Butiaba – Wanseko area: 60oC –70oC

3.03.0 GEOTHERMAL POTENTIAL OF UGANDA: GEOTHERMAL POTENTIAL OF UGANDA: KibiroKibiro AreaArea

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4. CONCLUSIONS

Geothermal potential manifested by presence of hot springs

Source of heat is the mantle due to a thinned crust

Water circulation through deep seated faults

Accommodation zones have indicated high potential. Therefore wanseko area with high geothermal gradient needs follow up

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Diversity of wildlife in the Albertine Graben

tectonic control on geothermal sites with specific reference to the

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