Aluto-langano geothermal field, ethiopian rift valley: physical characteristics and the effects of gas on well performance

Gizaw, Berhanu

doi:10.1016/0375-6505(93)90050-w

Cited by 26 publications

(50 citation statements)

References 5 publications

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“…Aluto has an internally drained central depression (herein referred to as a caldera floor) that has been partially in-filled by alluvium and reworked material from the surrounding surface volcanic deposits. While there are no detailed accounts of the eruptive history of the complex, descriptions of the geology of Aluto are in regional-scale mapping reports (e.g., Dakin and Gibson, 1971;Di Paola, 1972;Kebede et al, 1985); studies of the Ziway-Shala lake basin system (Gasse and Street, 1978;Street, 1979;Le Turdu et al, 1999;Benvenuti et al, 2002;Gibert et al, 2002), and publications related to geothermal development on Aluto (Gebregzabher, 1986;Valori et al, 1992;Gizaw, 1993;Gianelli and Teklemariam, 1993;Teklemariam et al, 1996;Saibi et al, 2012). This work and our own field investigations suggest that the Aluto volcanic complex has undergone several cycles of explosive and effusive volcanism throughout its history and that these eruptive phases have been dominantly silicic in composition.…”

Section: Aluto Volcano-geological Overview and Deep Well Observationsmentioning

confidence: 98%

Structural controls on fluid pathways in an active rift system: A case study of the Aluto volcanic complex

et al. 2015

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In volcanically and seismically active rift systems, preexisting faults may control the rise and eruption of magma, and direct the flow of hydrothermal fluids and gas in the subsurface. Using high-resolution airborne imagery, field observations, and CO 2 degassing data on Aluto, a typical young silicic volcano in the Main Ethiopian Rift, we explore how preexisting tectonic and volcanic structures control fluid pathways and spatial patterns of volcanism, hydrothermal alteration and degassing. A new light detection and ranging (lidar) digital elevation model and evidence from deep geothermal wells show that the Aluto volcanic complex is dissected by rift-related extensional faults with throws of 50-100 m. Mapping of volcanic vent distributions reveals a structural control by either rift-aligned faults or an elliptical caldera ring fracture. Soil-gas CO 2 degassing surveys show elevated fluxes (>>100 g m -2 d -1 ) along major faults and volcanic structures, but significant variations in CO 2 flux along the fault zones reflect differences in near-surface permeability caused by changes in topography and surface lithology. The CO 2 emission from an active geothermal area adjacent to the major fault scarp of Aluto amounted to ~60 t d -1 ; we estimate the total CO 2 emission from Aluto to be 250-500 t d -1 . Preexisting vol canic and tectonic structures have played a key role in the development of the Aluto volcanic complex and continue to facilitate the expulsion of gases and geothermal fluids. This case study emphasizes the importance of structural mapping on active rift volcanoes to understand the geothermal field as well as potential volcanic hazards.

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Section: Aluto Volcano-geological Overview and Deep Well Observationsmentioning

confidence: 98%

Structural controls on fluid pathways in an active rift system: A case study of the Aluto volcanic complex

et al. 2015

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“…These lakes are generally structurally controlled and filled a NNE trending tectonic depressions (Le Turdu et al, 1999). The Lakes region is well known by its geothermal potential (UNDP, 1973;Chernet, 1982;Gizaw, 1993;Gianneli and Teklemariam, 1993). Hydrologically, the basins form separate units but hydrogeologically they form a unique system within the Rift due to the underground interconnection by NE-SW aligned regional faults.…”

Section: Introductionmentioning

confidence: 99%

Hydrogeochemical and lake level changes in the Ethiopian Rift

Alemayehu

Ayenew

Kebede

2006

Journal of Hydrology

104

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“…1). One example is the Aluto-Langano geothermal system in the central part of the Main Ethiopian Rift (MER), where InSar (Interferometric Synthetic Aperture Radar) analysis has identified ongoing surface deformation with cycles of uplift and subsidence (Biggs et al, 2011), and which hosts a welldeveloped hydrothermal reservoir and a productive geothermal field (Gizaw, 1993;Teklemarian et al, 1996;Samrock et al, 2015). Besides Aluto, knowledge of the geothermal potential of other areas in Ethiopia has increased in recent years; examples include i) Tendaho in the Afar depression (Didana et al, 2015), ii) Gedemsa-Sodere and iii) Corbetti (Teklemarian and Kebede, 2010;Kebede, 2014); these latter two are located within the MER.…”

Section: Introductionmentioning

confidence: 99%

Geothermal potential and origin of natural thermal fluids in the northern Lake Abaya area, Main Ethiopian Rift, East Africa

Minissale

Corti

Tassi

et al. 2017

Journal of Volcanology and Geothermal Research

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In this study, the occurrence, chemical composition, origin and geothermal significance of thermal springs and fumaroles naturally discharging in the area located north of the Lake Abaya (western margin of the Main Ethiopian Rift, East Africa) are reviewed in relation with recent tectonics. All thermal springs showed a dominantly Na-HCO 3 composition, consistent with observations dating from at least 1972, and most of them displayed a narrow range of δD and δ 18 O isotopic compositions for water similar to regional meteoric origins. These observations suggest that water-rock interaction processes occur in all aquifers and dominate the contributions of water that actively circulate within thermal fluids, and also suggest a similar elevation of groundwater recharge throughout the study area. Most of the thermal springs are dominated by a CO 2 -rich gas phase and discharge along the active faults bordering the western edge of the Main Ethiopian Rift valley. The δ 13 C values of CO 2 and the 3 He/ 4 He isotopic ratios are consistent with the presence of mantle-derived fluids similar to what is observed in many other areas along the kinematically active African Rift, especially within Ethiopia. The application of geothermometric techniques in the liquid and the gas phases suggests the presence of a deep reservoir in which the fluids equilibrated at a maximum temperature of approximately 180°C. Additionally, the presence of fumaroles at boiling temperatures and water/mud boiling pools in several places suggests that the geothermal reservoir is positioned at a relatively shallow depth and likely located in the western side of the study area. The analysis of data collected throughout time reveals that the waters of Lake Abaya have experienced an increase in salinity of 20% paralleled contemporaneously with a decrease in pH and δ 18 O and δD of water in the last 40 years; these changes do not appear to be related to climate changeinduced increases in temperature or evaporation at the global scale.

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Aluto-langano geothermal field, ethiopian rift valley: physical characteristics and the effects of gas on well performance

Cited by 26 publications

References 5 publications

Structural controls on fluid pathways in an active rift system: A case study of the Aluto volcanic complex

Structural controls on fluid pathways in an active rift system: A case study of the Aluto volcanic complex

Hydrogeochemical and lake level changes in the Ethiopian Rift

Geothermal potential and origin of natural thermal fluids in the northern Lake Abaya area, Main Ethiopian Rift, East Africa

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