A geochemical reconnaissance of the Alid volcaniccenter and geothermal system, Danakil depression, Eritrea

Lowenstern, Jacob B.; Janik, C.J.; Fournier, Robert O.; Tesfai, Theoderos; Duffield, Wendell A.; Clynne, Michael A.; Smith, J. G.; Woldegiorgis, L.; Weldemariam, Kidane; Kahsai, Gabreab

doi:10.1016/s0375-6505(99)00002-4

Cited by 19 publications

(5 citation statements)

References 27 publications

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“…The depleted d 18 O values of the steam could be explained in part by fractionation between H 2 O and (Vuataz and Goff 1986) or, in unusual circumstances, between H 2 O and rock (Lowenstern et al 1999); however, these fractionation processes do not explain the dD variations in Sierra Negra steam, which mimic those observed in local meteoric waters. The Mina Azufral fumaroles do not contain any isotopically discernible component of magmatic water.…”

Section: Isotopes Of Background Waters and Fumarole Condensates Siermentioning

confidence: 75%

Contrasting hydrothermal activity at Sierra Negra and Alcedo volcanoes, Galapagos Archipelago, Ecuador

Goff

McMurtry

Counce

et al. 2000

Bulletin of Volcanology

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Sierra Negra and Alcedo volcanoes are adjacent tholeiitic shields with summit calderas located on Isabela Island in the Galapagos Archipelago. Although basaltic eruptions have characterized the evolution of these volcanoes, Alcedo has produced minor volumes of rhyolite lavas and tephras dated at approximately 100 ka. Fumaroles and ephemeral acidsulfate seeps occur within the calderas of both volcanoes, whereas neutral-chloride and diluted steamheated hot springs are absent. Fumarolic activity inside Sierra Negra (Mina Azufral) is fault controlled along the west margin of a horst and discharge temperatures are^210 C (January to February 1995). Water content of the total gas is approximately 75 mol.%, and noncondensible gases consist of approximately 97 mol.% CO 2 and approximately 85% SO 2 of the total sulfur gas. Relative amounts of He, Ar, and N 2 show a distinct hot-spot signature ( 3 He/ 4 He=17.4 0.3 R A ). The d 13 C±CO 2 is approximately ± 3.6½ and d 34 S T is approximately +3.3½. The dD/ d 18 O of fumarole H 2 O indicates steam separation from local meteoric waters whose estimated minimum mean residence time from 3 H analyses is^40 years. Fumarolic activity at Alcedo is controlled by a caldera-margin fault containing at least seven hydrothermal explosion craters, and by an intracaldera rhyolite vent. Two explosion craters which formed in 1993±1994 produce approximately 15 m 3 /s of steam, yet discharge temperatures are^97 C. Water content of the total gas is 95±97 mol.%, noncondensible gas is 92±98 mol.% CO 2 , and sulfur gas is dominated by H 2 S. Relative amounts of He, Ar, and N 2 show extensive mixing between hot spot and air or air-saturated meteoric water components but the average > 3 He/ 4 He=15.5 0.4 R A . The d 13 C±CO 2 is approximately ± 3.5½ and d 34 S T is approximately ± 0.8½. The dD/ d 18 O of fumarole steam indicates separation from a homogeneous reservoir that is enriched 3±5½ in 18 O compared with local meteoric water. 3 H indicates that this reservoir water has a maximum mean residence time of approximately 400 years and empirical gas geothermometry indicates a reservoir temperature of 260±320 C. The intracaldera hydrothermal reservoir in Alcedo is probably capable of producing up to 150 MW; however, environmental concerns as well as lack of infrastructure and power users will limit the development of this resource.

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Section: Isotopes Of Background Waters and Fumarole Condensates Siermentioning

confidence: 75%

Contrasting hydrothermal activity at Sierra Negra and Alcedo volcanoes, Galapagos Archipelago, Ecuador

Goff

McMurtry

Counce

et al. 2000

Bulletin of Volcanology

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“…For example, in the greater rift valley region, in Ethiopia, Kenya and Tanzania heat from geothermal activity and carbon dioxide influx from deeper earth accelerate the dissolution of the otherwise less soluble volcanic rocks and result in high salinity groundwaters (Darling et al, 1996). Geothermal induced salinization of groundwater is commonly observed, for example, in Ethiopia (Darling et al, 1996), Kenya (Darling et al, 1996), Tanzania, Djibouti (Awaleh et al, 2017) and Eritrea (Lowenstern et al, 1999). Groundwater residence time controls the degree to which groundwater salinity increases due to rock dissolution.…”

Section: Rock Dissolutionmentioning

confidence: 99%

Assessing groundwater salinity across Africa

Gurmessa

MacAllister

White

et al. 2022

Science of The Total Environment

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“…There, godovikovite commonly forms stalactite or thick crusts in subsurface cavities. Anhydrous alums are less common in volcanic fumaroles: godovikovite has been described in the Phlegrean fields and La Fossa crater on the island of Vulcano (Mindat.org database, 2019), while its hydrated form (Tschermigite) has been found in the thermal fields of Southern Kamchatka Peninsula (Zhitova et al, 2019), East African rift (Lowenstern et al, 1999) and possibly Merapi volcano, Indonesia (Kavalieris, 1994). Steklite, KAl(SO4)2, the K-analogue of godovikovite, has been identified in the fumarole deposits of Tolbachik volcano, Kamchatka (Murashko et a., 2013).…”

Section: Crust Formation Processesmentioning

confidence: 99%

Uptake of gaseous thallium, tellurium, vanadium and molybdenum into anhydrous alum, Lascar volcano fumaroles, Chile

Sainlot

Vlastelić

Moune

et al. 2020

Geochimica et Cosmochimica Acta

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Formation of secondary sulphate minerals during the reaction between volcanic gases and rocks modulates the composition and flux of gaseous emanations. We report on the sub-surface formation of anhydrous alum (M I M III (X VI O4)2 with M I = NH4 + , Na + , K + ; M III = Al 3+ , Fe 3+ and X VI = S 6+) in the 330°C fumaroles of the Lascar volcano (Chile). The alum occurs as a few millimetres thick crust that grew internally by two-way diffusion of reaction gases and diffusive influx of rock cations within the crust. The average growth rate is estimated at ca. 0.3 m/day, based on the 19-year-long activity of the degassing fracture hosting the crust. The growth rate is controlled by the slow migration of the rock cations and decreases towards crust rim. The crust selectively concentrates Tl, V and Te (thousands of g/g) and to a lesser extent Mo (hundreds of g/g). The uptake of gaseous Tl, V and Mo is not due to saturation of the gas with Tl, V and Mo compounds but to the possibility for the elements to enter the crystal structure of alum: Tl + , V 3+ and Mo 6+ might substitute for the M I , M III and X VI ions, respectively. The process of Te uptake remains uncertain, but must be related to the incorporation of Tl and V with which Te tightly correlates. Thallium, V and Te concentrations increase by a factor > 20 from core to rim, where they reach 8760, 8508, and 1687 g/g respectively. This trend correlates with the decrease of crust growth rate. This indicates that the low rate of rock cations supply to the outer edge of the crust favours the substitution of Tl, V and Te in the crystal network. Such surface enrichment does not occur for Mo, because Mo competes with S, another element from the gas. This suggests that the surface of mature alum crust has a high adsorption capacity for those gaseous metals able to compensate for the lack of rockderived cations. Based on the composition of gases escaping from the fracture hosting the crust, it is estimated that the partition coefficients of Tl (3.310 7), V (1.110 7) and Te (0.610 7) between crust surface and gases are two to four orders of magnitude higher than for other volatile metals and metalloids. It follows that gases equilibrating with anhydrous alums lose between 77 and 95% of their initial Tl content, but less than 1% of Pb. Given the Tl emission rate of Lascar volcano (5 g/day), between 17 and 104 g of toxic Tl would deposit every day if all Lascar gases were to equilibrate with anhydrous alums.

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A geochemical reconnaissance of the Alid volcaniccenter and geothermal system, Danakil depression, Eritrea

Cited by 19 publications

References 27 publications

Contrasting hydrothermal activity at Sierra Negra and Alcedo volcanoes, Galapagos Archipelago, Ecuador

Contrasting hydrothermal activity at Sierra Negra and Alcedo volcanoes, Galapagos Archipelago, Ecuador

Assessing groundwater salinity across Africa

Uptake of gaseous thallium, tellurium, vanadium and molybdenum into anhydrous alum, Lascar volcano fumaroles, Chile

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