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- Krmicek, Lukas, et al.
(författare)
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The 2023 Litli-Hrútur eruption of the Fagradalsfjall Fires, SW-Iceland : Insights from trace element compositions of olivine
- 2023
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Ingår i: Czech Polar Reports. - : Masaryk University Press. - 1805-0689 .- 1805-0697. ; 13:2, s. 257-270
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Tidskriftsartikel (refereegranskat)abstract
- This study provides data on the trace element composition of olivine from olivine tholeiitic basalts sampled during the July-August 2023 Litli-Hrutur eruption of the Fagradalsfjall Fires in the Reykjanes Volcanic Belt. Chemistry of the Litli-Hrutur olivine is characteristic for volcanic olivine crystals that represent products of magmatic crystallisation. The investigated olivine megacrysts show forsterite (Fo) content in the range of 81 (rims) to 85 (cores) mole percent [defined as Fo = Mg/(Mg + Fe)]. Olivine Ni concentrations (1540-1840 ppm) correlate positively with the Fo contents. In addition, Ca contents show a range from 1890 to 2460 ppm at relatively low Ti concentrations. Olivine from the Litli-Hrutur samples shows an equilibrium with peridotitic mantle melts, yet the data show that the 2023 Litli-Hrutur and the 2022 Meradalir olivine populations crystallised from compositionally more evolved magma batches than olivine crystals from the 2021 Geldingadalir eruption of the Fagradalsfjall Fires. These results imply that magmatic differentiation has taken place between the initial 2021 events and the subsequent 2022 and 2023 eruptions as a result of crystal-liquid fractionation, shifting the overall magma chemistry towards more evolved compositions with time. This implies that fractional crystallisation in sub -alkaline magma reservoirs operates on the scale of years, which is a fundamental advance in our understanding of these common magmatic systems.
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| 3. |
- Krmicek, Lukas, et al.
(författare)
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Trace element composition in olivine from the 2022 Meradalir eruption of the Fagradalsfjall Fires, SW-Iceland
- 2022
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Ingår i: Czech Polar Reports. - : MASARYK UNIV PRESS. - 1805-0689 .- 1805-0697. ; 12:2, s. 222-231
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Tidskriftsartikel (refereegranskat)abstract
- This study focuses on determining the trace element composition in olivine from olivine tholeiitic basalts sampled in Iceland during the 2022 Meradalir eruption of the 2021 -ongoing Fagradalsfjall Fires. The chemistry of Meradalir olivine is characteristic for a volcanic origin where olivine crystals represent the product of crystallisation. Olivine from the Meradalir basalt magma falls within the field characteristic for the melting of a dominantly peridotitic mantle source. However, the data show that the 2022 Meradalir olivine crystalized from a compositionally more evolved magma than olivine from the preceding 2021 Geldingadalir eruption of the Fagradalsfjall Fires.
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- Radu, Ioana-Bogdana, et al.
(författare)
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Water in clinopyroxene from the 2021 Geldingadalir eruption of the Fagradalsfjall Fires, SW-Iceland
- 2023
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Ingår i: Bulletin of Volcanology. - : Springer. - 0258-8900 .- 1432-0819. ; 85:5
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Tidskriftsartikel (refereegranskat)abstract
- Water content plays a significant role in magma genesis, ascent rate, and, ultimately, in the style and intensity of volcanic eruptions, due to its control on the density, viscosity and melting behaviour of silicate melts. A reliable method for determining the pre-eruptive magmatic water content is to use phenocrysts of nominally anhydrous minerals (NAMs) which can preserve water as hydrogen configurations in structural defects. The advantage of this method is that eruptive changes such as water loss during magma degassing may be experimentally reconstructed and analysed by infrared spectroscopy. Applying this to clinopyroxene crystals (n=17) from lava samples (n=7) from April 2021 of the Geldingadalir eruption, SW-Iceland, reveals parental water contents of 0.69 ± 0.07 to 0.86 ± 0.09 wt. % H2O. These values are higher than those expected for typical mid-ocean ridge basalts (MORB 0.3–0.5 wt. % on average) indicating a significant plume (OIB) contribution to the magma source. Moreover, such water concentrations would imply that water saturation in the ascending Geldingadalir magmas was attained only at very shallow levels within the plumbing system. This could explain the at times pulsating behaviour within the uppermost conduit system as being the result of shallow episodic water vapour exsolution in addition to the deep-sourced CO2 flux.
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