Metal Concentrations and Metal Deposition in Deep Geothermal Wells at the Reykjanes High-temperature Area, Iceland

Hardardóttir, Vigdís; Hannington, Mark D.; Hedenquist, Jeffrey W.

doi:10.1016/j.proeps.2013.03.159

Cited by 7 publications

(3 citation statements)

References 5 publications

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“…(Palgan et al, 2017). The chemical composition of the Reykjanes geothermal fluids is similar to those of black smokers and the fluids precipitate base-metal sulfide deposits similar to black smoker chimneys (Harðardóttir et al, 2012(Harðardóttir et al, , 2013. The most significant difference between typical black smoker vents and the Reykjanes geothermal system is the pressure difference at the surface, which results in subsurface boiling and deposition of metals at Reykjanes in contrast to chimney formation by cooling during mixing with seawater on the seafloor.…”

Section: Introductionmentioning

confidence: 99%

The Iceland Deep Drilling Project at Reykjanes: Drilling into the root zone of a black smoker analog

Friðleifsson¹,

Elders

Zierenberg

et al. 2020

Journal of Volcanology and Geothermal Research

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The aim of the Iceland Deep Drilling Project is to drill into supercritical geothermal systems and examine their economic potential. The exploratory well IDDP-2 was drilled in the Reykjanes geothermal field in SW Iceland, on the landward extension of the Mid-Atlantic Ridge. The Reykjanes geothermal field produces from a b300°C reservoir at 1 to 2.5 km depth and is unusual because it is recharged by seawater. The well was cased to 3000 m depth, and then angled towards the main up-flow zone of the system, to a total slant depth of 4659 m (~4500 m vertical depth). Based on alteration mineral assemblages, joint inversion of wireline logging, and rate of heating measurements, the bottom hole temperature is estimated to be about 535°C. The major problem encountered during drilling was the total loss of circulation below 3 km depth and continuing to the final depth. Drilling continued without recovering drill cuttings, consequently spot coring provided the only deep rock samples from the well. These cores are characteristic of a basaltic sheeted dike complex, with hydrothermal alteration mineral assemblages that range from greenschist to amphibolite facies, hornblende hornfels, and pyroxene hornfels, allowing the opportunity to investigate water-rock interaction in the active roots of an analog of a submarine hydrothermal system. As they have not yet been sampled, the composition of the deep fluids at Reykjanes is unknown at present. Cold water is currently being injected with the aim of enhancing permeability at depth, before allowing the well to heat up prior to flow tests planned for early 2019. The well has at least two fluid feed zones, a dominant one at 3.4 km depth and a second smaller one at 4.5 km. Extensive geophysical surveys of the Reykjanes Peninsula completed recently allow correlation of geophysical signals with rocks properties and in-situ conditions in the subsurface. Earthquake activity monitored with a local seismic network during drilling the IDDP-2 drilling detected abundant small earthquakes (M L ≤ 2) within the depth range of 3-5 km. A zone at 3-5 km depth below the producing geothermal field that was generally aseismic prior to drilling, but became seismically active during the drilling. The drilling of the IDDP-2 has achieved number of scientific and engineering firsts. It is the deepest and hottest drill hole so far sited on an active mid-ocean spreading center. It penetrated an active supercritical hydrothermal environment at depths analogous to those postulated as the high temperature reaction zones feeding black smoker systems.

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Section: Introductionmentioning

confidence: 99%

The Iceland Deep Drilling Project at Reykjanes: Drilling into the root zone of a black smoker analog

Friðleifsson¹,

Elders

Zierenberg

et al. 2020

Journal of Volcanology and Geothermal Research

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“…Thus, seawater dominated geothermal systems in Iceland, such as Reykjanes and Svartsengi, serve as valuable analogues for hydrothermal vent systems on the seafloor, in terms of authigenic mineralization, geothermal solutions and primary lithologies (Hannington et al, 2005;Hardardóttir et al, 2009;Hardardóttir et al, 2013;Kadko et al, 2007;Kleine et al, 2020;Kleine et al, 2018;Marks et al, 2011;Marks et al, 2015;Michard et al, 1984;Mottl and Holland, 1978). Surtsey volcano is located in the southern offshore extension of the Icelandic eastern rift zone (Einarsson, 2008;Jakobsson et al, 2009;Thorarinsson et al, 1964) (Fig.…”

Section: Introductionmentioning

confidence: 99%

The Surtsey volcano geothermal system: An analogue for seawater-oceanic crust interaction with implications for the elemental budget of the oceanic crust

et al. 2020

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Surtsey is a young volcanic island in the offshore extension of Iceland's southeast rift zone that grew from the seafloor during explosive and effusive eruptions in 1963-1967. In 1979, a cored borehole (SE-1) was drilled to 181 m depth and in 2017 three cored boreholes (SE-2a, SE-2b and SE-3) were drilled to successively greater depths. The basaltic deposits host a low-temperature (40-141 °C) seawater-dominated geothermal system. Surtsey provides an ideal environment to study water-rock interaction processes in a young seawater geothermal system. Elemental concentrations (SiO2, B, Na, Ca, Mg, F, dissolved inorganic carbon, SO4, Cl) and isotope contents (δD, δ 18 O) in borehole fluids indicate that associated geothermal waters in submarine deposits originated from seawater modified by reactions with the surrounding basalt. These processes produce authigenic minerals in the basaltic lapilli tuff and a corresponding depletion of certain elements in the residual waters. Coupling of measured and modeled concentrations investigates the effect of temperature and associated abundance of authigenic minerals on chemical fluxes from and to the igneous oceanic crust during lowtemperature alteration. The annual chemical fluxes calculated at 50-150 °C range from-0.01 to +0.1×10 12 mol yr-1 for SiO2, +0.2 to +129×10 12 mol yr-1 for Ca,-129 to-0.8×10 12 mol yr-1 for Mg and-21 to +0.4×10 12 mol yr-1 for SO4 where negative values indicate chemical fluxes from the ocean into the oceanic crust and positive values indicate fluxes from the oceanic crust to the oceans. These flux calculations reveal that water-rock interaction at varying water-rock ratios and temperatures produces authigenic minerals that serve as important sinks of seawaterderived SiO2, Mg and SO4. In contrast, water-rock interaction accompanied by dissolution of 2 basaltic glass and primary crystal fragments, provides a significant source of Ca. Such lowtemperature alteration could effectively influence the elemental budget of the oceanic igneous crust and ocean waters. The modelling provides insights into water chemistries and chemical fluxes in low-temperature MOR recharge zones. Surtsey also provides a valuable young analogue for assessing the chemical evolution of fluid discharge over the life cycles of seamounts in ridge flank systems.

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“…As a result of the elevated salinity of the present-day geothermal fluid, the in-situ pH (i.e., at reservoir temperatures) is about 5.5, which is lower than is typically the case in other geothermal fields in Iceland (Arnórsson, 1978;Henley and Ellis, 1983). The fluid chemistry of the Reykjanes geothermal system has been documented extensively in Arnórsson (1978Arnórsson ( , 1995, Ólafsson and Riley (1978), Lonker et al (1993), Hardardóttir et al (2009Hardardóttir et al ( , 2013, Seward (2014), Kaasalainen et al (2015), Óskarsson et al (2015), Libbey and Williams-Jones (2016-supplementary material), and Hannington et al (2016).…”

Section: The Reykjanes Geothermal Systemmentioning

confidence: 99%

Compositions of hydrothermal silicates and carbonates as indicators of physicochemical conditions in the Reykjanes geothermal system, Iceland

Libbey

Williams‐Jones

2016

Geothermics

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Metal Concentrations and Metal Deposition in Deep Geothermal Wells at the Reykjanes High-temperature Area, Iceland

Cited by 7 publications

References 5 publications

The Iceland Deep Drilling Project at Reykjanes: Drilling into the root zone of a black smoker analog

The Iceland Deep Drilling Project at Reykjanes: Drilling into the root zone of a black smoker analog

The Surtsey volcano geothermal system: An analogue for seawater-oceanic crust interaction with implications for the elemental budget of the oceanic crust

Compositions of hydrothermal silicates and carbonates as indicators of physicochemical conditions in the Reykjanes geothermal system, Iceland

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