Three dimensional conductivity model of the Tendaho High Enthalpy Geothermal Field, NE Ethiopia

Didana, Yohannes Lemma; Thiel, Stephan; Heinson, Graham

doi:10.1016/j.jvolgeores.2014.11.013

Cited by 20 publications

(9 citation statements)

References 23 publications

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“…From the dimensionality analysis and very small tipper values, we conclude that there are no indicators for off-profile conductors in the data, so we consider the absence of a conductive anomaly at the proposed depth of the magma chamber as a robust feature in our model and not an MT resolution issue. This is in stark contrast to the situation elsewhere in the MER and Afar, where the presence of magma is associated with an electrically conducting subsurface (e.g., Didana et al, 2015;Johnson et al, 2015;Whaler & Hautot, 2006). This first order contradiction between our MT results and other geophysical and geochemical observations gives new insights into the storage of melt under an on-axis volcano in the CMER.…”

Section: Melt Storage Under Alutocontrasting

confidence: 96%

The Electrical Structure of the Central Main Ethiopian Rift as Imaged by Magnetotellurics: Implications for Magma Storage and Pathways

2018

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The Main Ethiopian Rift is part of the East African Rift with its unique geological setting as an active continental breakup zone. The Main Ethiopian Rift includes a number of understudied active volcanoes with potentially high risks for this densely populated part of Ethiopia. Using newly recorded (2016) magnetotelluric data along a 110 km long transect crossing the whole rift, we present a regional 2‐D model of electrical resistivity of the crust. The derived model endorses a previous study that drew the surprising conclusion that there was no highly conductive region associated with a magma chamber directly under the central rift volcano Aluto. This has implications for the estimation of the amount of magma present, its water content, and the storage conditions, as the volcano is actively deforming and results from seismicity and CO2 degassing studies all indicate magma storage at about 5 km depth. Additionally, the existence of a strong conductor under the Silti Debre Zeyt Fault Zone approximately 40 km to the northwest of the rift center is confirmed. It is located with a slight offset to the Butajira volcanic field, which hosts a number of scoria cones at the boundary between the NW plateau and the rift. The magnetotelluric model reveals different electrical structures below the eastern and western rift shoulders. The western border is characterized by a sharp lateral contrast between the resistive plateau and the more conductive rift bottom, whereas the eastern flank shows a subhorizontal layered sequence of volcanic deposits and a smooth transition toward the shoulder.

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Section: Melt Storage Under Alutocontrasting

confidence: 96%

The Electrical Structure of the Central Main Ethiopian Rift as Imaged by Magnetotellurics: Implications for Magma Storage and Pathways

2018

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“…Active deformation processes in the Afar depression provide important clues (e.g., Keir et al, ; Pagli et al, ). Constraints on crustal structure primarily come from teleseismic receiver function studies (Ayele et al, ; Dugda et al, ; Hammond et al, ; Stuart et al, ), wide‐angle seismic surveys (Berckhemer et al, ; Maguire et al, ; Makris & Ginzburg, ), gravity (Lewi et al, ; Redfield et al, ; Tessema & Antoine, ; Tiberi et al, ), and MT studies (Desissa et al, ; Didana et al, , ; Johnson et al, ; Van Ngoc et al, ). A primary focus is to address the links between crustal thinning, magma intrusion, and subsidence to address a long‐standing debate in plate tectonics: When does seafloor spreading start?…”

Section: Late Stage Continental Breakup and Initiation Of Seafloor Spmentioning

confidence: 99%

“…models of MT and gravity data through the Boset volcano in the northern MER; Whaler & Hautot, ; Cornwell et al, (), section 4.2). Didana et al (, ) imaged an upper crustal zone of extensive partial melt fraction (up to 0.13) beneath the Tendaho Graben geothermal prospect to the east of the southern MHR axis, connected to a large intrusive magmatic body underlying the TG and MHR, fed by a mantle source.…”

Section: Late Stage Continental Breakup and Initiation Of Seafloor Spmentioning

confidence: 99%

“…This agreement between MT and gravity results is reminiscent of that found for the location of dense subsurface bodies, interpreted as gabbroic, and conductors across the northern MER through Boset volcano. Didana et al (, ) have modeled several MT profiles across the TG geothermal prospect to the southeast of the profile of Johnson et al () and to the east of the southern MHR axis. Seismic surface wave (Guidarelli et al, ), Pn (Stork et al, ), and body wave tomography (Hammond et al, ) studies image slow upper mantle velocities throughout the MHR rift segment, with the most extreme reductions centered on the recently active northern part.…”

Section: Late Stage Continental Breakup and Initiation Of Seafloor Spmentioning

confidence: 99%

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Crustal Structure of Active Deformation Zones in Africa: Implications for Global Crustal Processes

et al. 2017

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The Cenozoic East African rift (EAR), Cameroon Volcanic Line (CVL), and Atlas Mountains formed on the slow‐moving African continent, which last experienced orogeny during the Pan‐African. We synthesize primarily geophysical data to evaluate the role of magmatism in shaping Africa's crust. In young magmatic rift zones, melt and volatiles migrate from the asthenosphere to gas‐rich magma reservoirs at the Moho, altering crustal composition and reducing strength. Within the southernmost Eastern rift, the crust comprises ~20% new magmatic material ponded in the lower crust and intruded as sills and dikes at shallower depths. In the Main Ethiopian Rift, intrusions comprise 30% of the crust below axial zones of dike‐dominated extension. In the incipient rupture zones of the Afar rift, magma intrusions fed from crustal magma chambers beneath segment centers create new columns of mafic crust, as along slow‐spreading ridges. Our comparisons suggest that transitional crust, including seaward dipping sequences, is created as progressively smaller screens of continental crust are heated and weakened by magma intrusion into 15–20 km thick crust. In the 30 Ma Recent CVL, which lacks a hot spot age progression, extensional forces are small, inhibiting the creation and rise of magma into the crust. In the Atlas orogen, localized magmatism follows the strike of the Atlas Mountains from the Canary Islands hot spot toward the Alboran Sea. CVL and Atlas magmatism has had minimal impact on crustal structure. Our syntheses show that magma and volatiles are migrating from the asthenosphere through the plates, modifying rheology, and contributing significantly to global carbon and water fluxes.

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“…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. Apart from these areas, there are several other promising places along the MER that are still in a preliminary exploration phase (Purschel et al, 2013).…”

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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Three dimensional conductivity model of the Tendaho High Enthalpy Geothermal Field, NE Ethiopia

Cited by 20 publications

References 23 publications

The Electrical Structure of the Central Main Ethiopian Rift as Imaged by Magnetotellurics: Implications for Magma Storage and Pathways

The Electrical Structure of the Central Main Ethiopian Rift as Imaged by Magnetotellurics: Implications for Magma Storage and Pathways

Crustal Structure of Active Deformation Zones in Africa: Implications for Global Crustal Processes

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

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