| 1. |
- Andrén, Margareta, et al.
(författare)
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Coupling between mineral reactions, chemical changes in groundwater, and earthquakes in Iceland
- 2016
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Ingår i: Journal of Geophysical Research - Solid Earth. - 2169-9313 .- 2169-9356. ; 121:4, s. 2315-2337
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Tidskriftsartikel (refereegranskat)abstract
- Chemical analysis of groundwater samples collected from a borehole at Hafralækur, northernIceland, from October 2008 to June 2015 revealed (1) a long-term decrease in concentration of Si and Naand (2) an abrupt increase in concentration of Na before each of two consecutive M > 5 earthquakes whichoccurred in 2012 and 2013, both 76 km from Hafralækur. Based on a geochemical (major elements and stableisotopes), petrological, and mineralogical study of drill cuttings taken from an adjacent borehole, we areable to show that (1) the long-term decrease in concentration of Si and Na was caused by constant volumereplacement of labradorite by analcime coupled with precipitation of zeolites in vesicles and along fracturesand (2) the abrupt increase of Na concentration before the first earthquake records a switchover tononstoichiometric dissolution of analcime with preferential release of Na into groundwater. We attributedecay of the Na peaks, which followed and coincided with each earthquake to uptake of Na along fracturedor porous boundaries between labradorite and analcime crystals. Possible causes of these Na peaks are anincrease of reactive surface area caused by fracturing or a shift from chemical equilibrium caused by mixingbetween groundwater components. Both could have been triggered by preseismic dilation, which was alsoinferred in a previous study by Skelton et al. (2014). The mechanism behind preseismic dilation so far from thefocus of an earthquake remains unknown.
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| 2. |
- Barbieri, Maurizio, et al.
(författare)
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Changes in groundwater trace element concentrations before seismic and volcanic activities in Iceland during 2010-2018
- 2021
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 793
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Tidskriftsartikel (refereegranskat)abstract
- We analysed temporal variations of trace element concentrations in groundwater from a 101 m-deep borehole (HA01) in northern Iceland during 2010–2018 and compared them with seismic and volcanic events that occurred in the same period to identify potential hydrogeochemical precursors. An increase of B, Al, V, Li and Mo concentrations started from eight months to one month before the 2014 Bárðarbunga eruption (~115 km from HA01), a major rifting event in central Iceland, while Ga and V concentrations began to increase one day and one month after the onset of the event, respectively. We also found that concentrations of some trace elements (Li, B, Ga, Mo, Sr, Rb and Fe) significantly increased before an Mw 5.0 earthquake that occurred ~80 km from the borehole in 2018. However, other notable hydrogeochemical changes were detected during the monitoring period without apparent correlation with the seismic and volcanic events in the region. This study shows that the systematic long-term hydrogeochemical monitoring in seismic and volcanic areas is critical to advance the science of seismic and eruptive precursors. Furthermore, the use of statistical tools, such as Principal Component Analysis (PCA) and Change Point (CP) detection can help identify the most useful chemical elements and validate the trend variability of those elements in the time series, reducing arbitrary choices of pre-seismic and pre-volcanic hydrogeochemical anomalies as potential precursors.
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| 3. |
- Boschetti, Tiziano, et al.
(författare)
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Geothermometry and water-rock interaction modelling at Hafralækur : Possible implications of temperature and CO2 on hydrogeochemical changes previously linked to earthquakes in northern Iceland
- 2022
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Ingår i: Geothermics. - : Elsevier BV. - 0375-6505 .- 1879-3576. ; 105
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Tidskriftsartikel (refereegranskat)abstract
- The low enthalpy (T < 150 °C) groundwater in the HA01 borehole at Hafralækur has a long time series (2008–2018) of chemical and isotopic data. In the previous studies, the variations in chemical and isotope parameters were statistically related to seismic activity. However, the possible effect of temperature has not yet been evaluated. To fill this gap, the results obtained from the classical geothermometric equations (silica solid phases, Na/K, Na-K-Ca) were compared. However, considering that the use of classical geothermometry using the Na/K ratio or silica solid phases solubility is limited by the presence of clay minerals and alkaline conditions (i.e., the presence of pH-dependant silicate anions), new equilibria reactions between labradorite, zeolites (analcime, stilbite) and the activity of the dissolved species in the fluid are presented to overcome this problem. In addition, kinetic reaction path models are presented to trace the possible role of both temperature and CO2 during the most evident chemical variations during earthquakes.
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| 4. |
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| 5. |
- Liljebladh, Bengt, 1959, et al.
(författare)
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De döda vikingarna i Ikkafjorden
- 2022
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Ingår i: Havsutsikt. ; :1, s. 4-7
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 6. |
- Melero-Asensio, I., et al.
(författare)
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Geophysical signature of Malingen, the minor crater of the Lockne-Malingen doublet impact structure
- 2018
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Ingår i: Meteoritics & Planetary Science. - : Wiley. - 1086-9379 .- 1945-5100. ; 53:7, s. 1456-1475
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Tidskriftsartikel (refereegranskat)abstract
- Malingen is the 0.7km wide minor crater associated to the 10 times larger Lockne crater in the unique Lockne-Malingen doublet. The craters formed at 458Ma by the impact of a binary asteroid related to the well-known 470Ma Main Belt breakup event responsible for a large number of Ordovician craters and fossil meteorites. The binary asteroid struck a target sequence including similar to 500m of sea water, similar to 80m of limestone, similar to 30m of dark mud, and a peneplainized Precambrian crystalline basement. Although the Lockne crater has been extensively studied by core drillings and geophysics, little is known about the subsurface morphology of Malingen. We performed magnetic susceptibility and remanence, as well as density, measurements combined with gravity, and magnetic field surveys over the crater and its close vicinity as a base for forward magnetic and gravity modeling. The interior of the crater shows a general magnetic low of 90-100nT broken by a clustered set of high-amplitude, short wavelength anomalies caused by bodies of mafic rock in the target below the crater and as allogenic blocks in the crater infill. The gravity shows a general -1.4mgal anomaly over the crater caused by low-density breccia infill and fractured crystalline rocks below the crater floor. The modeling also revealed a slightly asymmetrical shape of the crater that together with the irregular ejecta distribution supports an oblique impact from the east, which is consistent with the direction of impact suggested for the Lockne crater.
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| 7. |
- Seaman, Paul, et al.
(författare)
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New multibeam mapping of the unique Ikaite columns in Ikka Fjord, SW Greenland
- 2022
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Ingår i: Marine Geology. - : Elsevier BV. - 0025-3227 .- 1872-6151. ; 444
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Tidskriftsartikel (refereegranskat)abstract
- Ikka Fjord in SW Greenland is world famous for its submarine, cold-water craving ikaite (CaCO3·6H2O) tufa columns. Due to the uniqueness of the columns, Ikka Fjord is declared a protected area by the Greenlandic authorities. In the summers of 2018–19, multibeam sonar bathymetry and aerial drone photogrammetric surveys were made in Ikka Fjord mapping and counting the columns and comparing the results to data from geophysical surveys of the fjord in 1995–96. The new surveys provide highly detailed maps of the fjord bathymetry and its columns, their height and position, and several hitherto unknown pockmarks in the seabed. A total of 938 individual columns and structures ranging 0.5–20 m in height from the sea floor were identified: a number surpassing the 678 taller columns (> 1 m) known from previous mapping. Our results support previous observations that the columns are restricted to the spatial extents of the Grønnedal-Íka igneous complex. The new survey data show that column distribution exhibits lineations and variable density over the fjord floor, notably that the innermost central deep part is free of columns. The tallest columns are observed to grow up to the halocline at approximately 2–4 m water depth. The majority of columns have reached only 15–50% of their growth potential. The ~60 columns of maximum growth stand in clusters, interpreted as representing exceptionally favourable growth settings. New seawater data collected in 2019 shows a worrying increase in temperature since the previous measurements in 1995 and 2007–2009, which could potentially affect the stability of the delicate columns of Ikka Fjord.
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| 8. |
- Skelton, Alasdair, et al.
(författare)
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Changes in groundwater chemistry before two consecutive earthquakes in Iceland
- 2014
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Ingår i: Nature Geoscience. - 1752-0894 .- 1752-0908. ; 7:10, s. 752-756
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Tidskriftsartikel (refereegranskat)abstract
- Groundwater chemistry has been observed to change before earthquakes and is proposed as a precursor signal. Such changes include variations in radon count rates(1,2), concentrations of dissolved elements(3-5) and stable isotope ratios(4,5). Changes in seismicwave velocities(6), water levels in boreholes(7), micro-seismicity(8) and shear wave splitting(9) are also thought to precede earthquakes. Precursor activity has been attributed to expansion of rock volume(7,10,11). However, most studies of precursory phenomena lack sufficient data to rule out other explanations unrelated to earthquakes(12). For example, reproducibility of a precursor signal has seldom been shown and few precursors have been evaluated statistically. Here we analyse the stable isotope ratios and dissolved element concentrations of groundwater taken from a borehole in northern Iceland between 2008 and 2013. We find that the chemistry of the groundwater changed four to six months before two greater than magnitude 5 earthquakes that occurred in October 2012 and April 2013. Statistical analyses indicate that the changes in groundwater chemistry were associated with the earthquakes. We suggest that the changes were caused by crustal dilation associated with stress build-up before each earthquake, which caused different groundwater components to mix. Although the changes we detect are specific for the site in Iceland, we infer that similar processes may be active elsewhere, and that groundwater chemistry is a promising target for future studies on the predictability of earthquakes.
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| 9. |
- Stockmann, Gabrielle, et al.
(författare)
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Carbon mineral storage in seawater:Ikaite(CaCO3·6H2O)columns in Greenland.
- 2018
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 146, s. 59-67
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Tidskriftsartikel (refereegranskat)abstract
- The marine Ikka Fjord in Greenland is well known for its remarkable submarine columns made of the cold-carbonate ikaite (CaCO3·6H2O). Here, natural processes lead to fast-precipitating ikaite at low temperatures (< 10°C) when carbonate-bearing groundwater seeps through fractures in Ikka Fjord and mixes with seawater. Within an area of 0.75 km2, 678 columns of 1 – 20 meters height have been registered, continuously growing at rates measured at 50 cm per year. Understanding this natural system is of importance for carbon capture and storage efforts as it represents a very efficient method for carbon mineral storage in cold seawater.
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| 10. |
- Stockmann, Gabrielle, et al.
(författare)
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Control of a calcite inhibitor (phosphate) and temperature on ikaite precipitation in Ikka Fjord, southwest Greenland
- 2018
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 89, s. 11-22
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Tidskriftsartikel (refereegranskat)abstract
- Ikaite (CaCO3 center dot 6H(2)O) forms submarine tufa columns in Ikka Fjord, SW Greenland. This unique occurrence is thought to relate to aqueous phosphate concentration and low water temperatures (< 6 degrees C). Phosphate ions are well-known inhibitors of calcite precipitation and Ikka Fjord has a naturally high-phosphate groundwater system that when mixing with seawater leads to the precipitation of ikaite. In the study presented here, experiments simulating conditions of Ikka Fjord show that a) the formation of ikaite is unrelated to the aqueous phosphate concentration (0-263 mu mol/ kg PO43-) in 0.1 M NaHCO3/0.1 M Na2CO3 solutions mixing with seawater at 5 degrees C and pH 9.6-10.6, and b) ikaite forms at temperatures up to 15 degrees C without phosphate and in open beakers exposed to air. Instead, supersaturation of ikaite and the seawater composition are the likely factors causing ikaite to precipitate in Ikka Fjord. This study shows that adding Mg2+ to a NaHCO3/Na2CO3 - CaCl2 mixed solution leads to the formation of ikaite along with hydrated Mg carbonates, which points to the high Mg2+ concentration of seawater, another known inhibitor of calcite, as a key factor promoting ikaite formation. In experiments at 10 and 15 degrees C, increasing amounts of either nesquehonite (Mg(HCO3)(OH)center dot 2H(2)O) or an amorphous phase co-precipitate with ikaite. At 20 degrees C, only the amorphous phase is formed. In warming Arctic seawater, this suggests Mg carbonate precipitation could become dominant over ikaite in the future.
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