| 1. |
- Andrén, Margareta, et al.
(författare)
-
Coupling between mineral reactions, chemical changes in groundwater, and earthquakes in Iceland
- 2016
-
Ingår i: Journal of Geophysical Research - Solid Earth. - 2169-9313 .- 2169-9356. ; 121:4, s. 2315-2337
-
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.
|
|
| 2. |
|
|
| 3. |
- Budd, David, 1985-, et al.
(författare)
-
Persistent multitiered magma plumbing beneath Katla volcano, Iceland
- 2016
-
Ingår i: Geochemistry Geophysics Geosystems. - : American Geophysical Union (AGU). - 1525-2027. ; 17:3, s. 966-980
-
Tidskriftsartikel (refereegranskat)abstract
- Recent seismic unrest and a persistent Holocene eruption record at Katla volcano, Iceland indicate that a near-future eruption is possible. Previous petrological investigations suggest that Katla is supplied by a simple plumbing system that delivers magma directly from depth, while seismic and geodetic data also point toward the existence of upper-crustal magma storage. To characterize Katla's recent plumbing system, we established mineral-melt equilibrium crystallization pressures from four age-constrained Katla tephras spanning from 8 kyr BP to 1918. The results point to persistent shallow- (≤8 km depth) as well as deep-crustal (ca. 10 – 25 km depth) magma storage beneath Katla throughout the last 8 kyr. The presence of multiple magma storage regions implies that mafic magma from the deeper reservoir system may become gas-rich during ascent and storage in the shallow crust and erupt explosively. Alternatively, it might intersect evolved magma pockets in the shallow-level storage region, and so increase the potential for explosive mixed-magma ash eruptions.
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Dahrén, Börje, 1984-
(författare)
-
Magma plumbing architecture in Indonesia and the North Atlantic Igneous Province
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Magma plumbing systems represent the physical framework of magma transport and storage from the source region in the mantle, through the crust, until reaching the surface in a volcanic eruption. Characterising the different aspects of magma plumbing, in particular the distribution of magma storage zones throughout the crust, is of key importance to better understand the behaviour of individual volcanoes. In particular, shallow crustal magma storage and associated magma-crust interaction processes could potentially explain some of the worlds most unpredictable and explosive volcanoes. This thesis studies magma plumbing architecture in the Sunda Arc (Indonesia), and the North Atlantic Igneous Province, based on elemental and isotope geochemistry, and derived petrological modelling.In this study, I have employed petrological models, so called geothermobarometers, to calculate pressures and temperatures (P-T) of crustal magma storage. Geothermobarometers are calibrated thermodynamic formulations based on the composition of magmatic minerals and their co-existing melt as a function of the P-T conditions of crystallisation. Using the calculated P-T estimates, I was able to derive the depth of magma storage, and thereby reconstruct the architecture of magma storage systems. A number of different geothermobarometers based on different mineral phases, including plagioclase, clinopyroxene and olivine, were used for this purpose,The geothermobarometric modelling was combined with additional elemental and isotope geochemical analyses, as well as collaborations with geophysical investigations. These additional approaches were used to corroborate the findings of the geothermobarometric modelling, and also to model and quantify magma-crust interaction processes that take place during crustal magma storage, such as assimilation of crustal lithologies into the magmatic system.The findings of this thesis build upon the growing body of evidence in support of the prevalence of shallow magma storage in different volcanic settings worldwide. This realisation is relevant to volcano monitoring and hazard mitigation worldwide.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Dahrén, Börje, fil.dr, 1984-, et al.
(författare)
-
Transformation or consolidation : Evaluating transformative agreements at Uppsala University with an eye to the future
- 2021
-
Konferensbidrag (refereegranskat)abstract
- In the last few years, we have seen how publishing agreements have become increasingly common across Europe. At Uppsala University, the traditional subscription agreements now represent a minority of our agreements with the publishers and we suspect they will be phased out. Currently, our most common type of publishing agreements are the transformative agreements negotiated on the national level by the Bibsam consortia and offered to all Swedish higher education institutions. These transformative agreements currently cover most major international publishers and could be considered the new normal.Uppsala University is one of the largest and oldest universities in northern Europe. We are a truly multidisciplinary university, covering the humanities, social sciences, medicine, science and technology. This means that the university library should ideally be able to provide the same level of publishing support for theologists as well as geologists. With that in mind, the library was tasked to evaluate our portfolio of publishing agreements, with a special focus on the impact of the transformative ones. We wanted specifically to look at these new agreements in regards to 1) the impact for the individual researchers 2) economic aspects on various levels, and 3) the paradigm shift towards open science that is taking place in scholarly communication.–We have identified a few key effects and aspects of the transformative agreements:• They remove thresholds and provide a smooth transition to OA publishing• They are arguably very expensive. Are these just the latest iteration of the “Big Deals”?• The coverage is not equal for all parts of the university. Great coverage for STEM, not so much for the arts and humanities.• Other publishing actors are unfairly and disproportionally disadvantaged. Non-commercial OA publishers, diamond OA and small scale society publishing lose much of their advantage on the already dysfunctional publishing market.–What to do next?• A local strategy for publishing agreements is needed to complement what is provided by national consortia.• Libraries should divert more energy towards support for DIY publishing and other researcher-led initiatives.• The time for OA advocacy is in the past. It is time for global and holistic open science perspectives.In conclusion, our view is that transformative agreements are highly useful for us at this point in time, but need to be managed and complemented. It is essential that we keep monitoring the costs, provide alternatives and develop our services portfolio. Above all, we need to recognise that these agreements are a stepping stone on the path towards open science. They are, however, not the final solution.
|
|
| 10. |
- Jamshidi, K., et al.
(författare)
-
Magma storage and plumbing of adakite-type post-ophiolite intrusions in the Sabzevar ophiolitic zone, northeast Iran
- 2015
-
Ingår i: Solid Earth. - : Copernicus GmbH. - 1869-9510 .- 1869-9529. ; 6:1, s. 49-72
-
Tidskriftsartikel (refereegranskat)abstract
- Subduction-related adakite-type intrusive rocks emplaced into the late Cretaceous-Paleocene Sabzevar ophiolite zone, northeast Iran, range from Mg-andesite to rhyodacite in composition. Here we investigate the magma supply system to these subvolcanic intrusive rocks by applying thermobarometric mineral and mineral-melt equilibrium models, including amphibole thermobarometry, plagioclase-melt thermobarometry and clinopyroxene-melt barometry. Based on the results of these thermobarometric models, plagioclase crystallized dominantly at pressures of similar to 350 (130 to 468) MPa, while amphiboles record both low pressures (similar to 300 MPa) and very high pressures (> 700 MPa) of crystallization. The latter is supported by the calculated pressures for clinopyroxene crystallization (550 to 730 MPa). The association of amphibole with clinopyroxene and no plagioclase in the most primitive samples (Mg-andesites) is consistent with amphibole fractionation from very hydrous magmas at deep crustal levels of the plumbing system, which may have been a key process in intensifying adakite-type affinities in this rock suite. Barometry, combined with frequent disequilibrium features such as oscillatory-zoned and sieve-textured plagioclase crystals with An-rich overgrowths in more evolved samples, implies that final magma differentiation occurred in an open upper crustal magma system that developed progressively stronger compositional modifications during high-level magma storage.
|
|
