Silicic volcanism in Iceland: Composition and distribution within the active volcanic zones

Jónasson, Kristján

doi:10.1016/j.jog.2006.09.004

Cited by 95 publications

(77 citation statements)

References 66 publications

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“…Some felsite veins have euhedral zircon crystals up to 2 mm in length. Rock of rhyolitic compositions, although common in other Icelandic volcanic centers such as Krafla (e.g., Jónasson, 2007), have not been observed previously at Reykjanes.…”

Section: Primary Lithologymentioning

confidence: 70%

The Iceland Deep Drilling Project 4.5 km deep well, IDDP-2, in the seawater-recharged Reykjanes geothermal field in SW Iceland has successfully reached its supercritical target

Friðleifsson¹,

Elders

Zierenberg

et al. 2017

Sci. Dril.

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Abstract. The Iceland Deep Drilling Project research well RN-15/IDDP-2 at Reykjanes, Iceland, reached its target of supercritical conditions at a depth of 4.5 km in January 2017. After only 6 days of heating, the measured bottom hole temperature was 426 °C, and the fluid pressure was 34 MPa. The southern tip of the Reykjanes peninsula is the landward extension of the Mid-Atlantic Ridge in Iceland. Reykjanes is unique among Icelandic geothermal systems in that it is recharged by seawater, which has a critical point of 406 °C at 29.8 MPa. The geologic setting and fluid characteristics at Reykjanes provide a geochemical analog that allows us to investigate the roots of a mid-ocean ridge submarine black smoker hydrothermal system. Drilling began with deepening an existing 2.5 km deep vertical production well (RN-15) to 3 km depth, followed by inclined drilling directed towards the main upflow zone of the system, for a total slant depth of 4659 m ( ∼  4.5 km vertical depth). Total circulation losses of drilling fluid were encountered below 2.5 km, which could not be cured using lost circulation blocking materials or multiple cement jobs. Accordingly, drilling continued to the total depth without return of drill cuttings. Thirteen spot coring attempts were made below 3 km depth. Rocks in the cores are basalts and dolerites with alteration ranging from upper greenschist facies to amphibolite facies, suggesting that formation temperatures at depth exceed 450 °C. High-permeability circulation-fluid loss zones (feed points or feed zones) were detected at multiple depth levels below 3 km depth to bottom. The largest circulation losses (most permeable zones) occurred between the bottom of the casing and 3.4 km depth. Permeable zones encountered below 3.4 km accepted less than 5 % of the injected water. Currently, the project is attempting soft stimulation to increase deep permeability. While it is too early to speculate on the energy potential of this well and its economics, the IDDP-2 is a milestone in the development of geothermal resources and the study of hydrothermal systems. It is the first well that successfully encountered supercritical hydrothermal conditions, with potential high-power output, and in which on-going hydrothermal metamorphism at amphibolite facies conditions can be observed. The next step will be to carry out flow testing and fluid sampling to determine the chemical and thermodynamic properties of the formation fluids.

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Section: Primary Lithologymentioning

confidence: 70%

The Iceland Deep Drilling Project 4.5 km deep well, IDDP-2, in the seawater-recharged Reykjanes geothermal field in SW Iceland has successfully reached its supercritical target

Friðleifsson¹,

Elders

Zierenberg

et al. 2017

Sci. Dril.

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“…The lapilli and ash products have been normalized to primitive mantle [Lyubetskaya and Korenaga, 2007]. The 2010 Eyjafjallajökull data are compared to the available data on southeastern volcanic zone lavas and tephras [Jónasson, 2007;Sverrisdottir, 2007]. All data are compared to oceanic sediments [Ben Othman et al, 1989] and global subducted sediments (GLOSS) [Plank and Langmuir, 1998].…”

Section: Trace Elements In the Matrix Glassesmentioning

confidence: 99%

Processes controlling the 2010 Eyjafjallajökull explosive eruption

Borisova¹,

Toutain²,

Stefánsson³

et al. 2012

J. Geophys. Res.

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[1] To constrain the temporal evolution of the fluid-magma system responsible for the 2010 Eyjafjallajökull eruption (20 March to 20 May, 2010, Southern Iceland), we investigated the volatile, major, trace element, and Sr-Nd-Pb isotopic compositions of bulk lapilli and ash samples representing different stages of the eruption. In addition, we analyzed ash leachates and volcanic plume-derived aerosols sampled over Southern Europe in early May 2010. Available remote-sensing data for the total mass of SO 2 liberated in the 2010 eruption, together with data obtained in this study, suggest that the high explosivity of the 2010 sub-plinian Eyjafjallajökull eruption was caused by saturation of the pre-eruptive hybrid trachyandesitic magma with aqueous fluid. We hypothesize that the bulk of the aqueous fluid had been dissolved in the trachydacitic melt at least since the eruption of 1821-1823. The trachydacitic melt was enriched in volatiles, large-ion lithophile elements, and high field strength elements, a composition similar to that of oceanic sediments. The Sr-Nd-Pb isotopic data obtained in this study, combined with existing O isotopic data on bulk 2010 Eyjafjallajökull lapilli and ashes, demonstrate that this melt enrichment was due to its primary source being hydrous oceanic lithosphere entrained in a deep mantle plume rather than shallow hydrothermally altered crust. The hypothesized strong crystal fractionation of plume-derived mafic melts (crystallized fraction >90%) from an enriched mantle source can explain the observed high explosivity of silicic and hybrid Icelandic magmas, especially those of the southeastern volcanic zone (Eyjafjallajökull, Katla, and Hekla).

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“…Rhyolitic domes and ridges near the caldera rim suggest that magma chambers existed in the past beneath the volcano, because these rhyolites were likely generated at the sides of an active magma chamber [Jónasson , 2007]. Whether the drilled melt in IDDP-1 is part of a large magma chamber has not been fully determined.…”

Section: Introductionmentioning

confidence: 99%

Focal mechanisms and size distribution of earthquakes beneath the Krafla central volcano, NE Iceland

et al. 2016

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Seismicity was monitored beneath the Krafla central volcano, NE Iceland, between 2009 and 2012 during a period of volcanic quiescence, when most earthquakes occurred within the shallow geothermal field. The highest concentration of earthquakes is located close to the rock‐melt transition zone as the Iceland Deep Drilling Project‐1 (IDDP‐1) wellbore suggests and decays quickly at greater depths. We recorded multiple swarms of microearthquakes, which coincide often with periods of changes in geothermal field operations, and found that about one third of the total number of earthquakes are repeating events. The event size distribution, evaluated within the central caldera, indicates average crustal values with b = 0.79 ± 0.04. No significant spatial b value contrasts are resolved within the geothermal field nor in the vicinity of the drilled melt. Besides the seismicity analysis, focal mechanisms are calculated for 342 events. Most of these short‐period events have source radiation patterns consistent with double‐couple (DC) mechanisms. A few events are attributed to non‐shear‐faulting mechanisms with geothermal fluids likely playing an important role in their source processes. Diverse faulting styles are inferred from DC events, but normal faulting prevails in the central caldera. The best fitting compressional and tensional axes of DC mechanisms are interpreted in terms of the principal stress or deformation rate orientations across the plate boundary rift. Maximum compressive stress directions are near‐vertically aligned in different study volumes, as expected in an extensional tectonic setting. Beneath the natural geothermal fields, the least compressive stress axis is found to align with the regional spreading direction. In the main geothermal field both horizontal stresses appear to have similar magnitudes causing a diversity of focal mechanisms.

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Silicic volcanism in Iceland: Composition and distribution within the active volcanic zones

Cited by 95 publications

References 66 publications

The Iceland Deep Drilling Project 4.5 km deep well, IDDP-2, in the seawater-recharged Reykjanes geothermal field in SW Iceland has successfully reached its supercritical target

The Iceland Deep Drilling Project 4.5 km deep well, IDDP-2, in the seawater-recharged Reykjanes geothermal field in SW Iceland has successfully reached its supercritical target

Processes controlling the 2010 Eyjafjallajökull explosive eruption

Focal mechanisms and size distribution of earthquakes beneath the Krafla central volcano, NE Iceland

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Silicic volcanism in Iceland: Composition and distribution within the active volcanic zones

Cited by 95 publications

References 66 publications

The Iceland Deep Drilling Project 4.5 km deep well, IDDP-2, in the seawater-recharged Reykjanes geothermal field in SW Iceland has successfully reached its supercritical target

The Iceland Deep Drilling Project 4.5 km deep well, IDDP-2, in the seawater-recharged Reykjanes geothermal field in SW Iceland has successfully reached its supercritical target

Processes controlling the 2010 Eyjafjallajökull explosive eruption

Focal mechanisms and size distribution of earthquakes beneath the Krafla central volcano, NE Iceland

Contact Info

Product

Resources

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The Iceland Deep Drilling Project 4.5 km deep well, IDDP-2, in the seawater-recharged Reykjanes geothermal field in SW Iceland has successfully reached its supercritical target

The Iceland Deep Drilling Project 4.5 km deep well, IDDP-2, in the seawater-recharged Reykjanes geothermal field in SW Iceland has successfully reached its supercritical target