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- Krmicek, Lukas, et al.
(author)
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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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In: Czech Polar Reports. - : Masaryk University Press. - 1805-0689 .- 1805-0697. ; 13:2, s. 257-270
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Journal article (peer-reviewed)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. |
- Pokorný, Richard, et al.
(author)
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Driftwood in the Eemian interglacial lacustrine unit from the Faroe Islands and its possible source areas : palaeobotanical and ichnological analysis
- 2018
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In: Boreas. - : Wiley. - 0300-9483. ; 47:4, s. 1230-1243
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Journal article (peer-reviewed)abstract
- The coastal cliffs in Klaksvík (Borðoyar Bay) are the only known locality with Eemian sediments in the Faroe Islands. Previous studies carried out there focused on the sedimentology, tephra chemistry, paleoecology including aquatic environment, or the age of the deposits. In the lacustrine, clayey to silty gyttja we collected scattered wood fragments, identified as Larix sp., Pinus sp., Taxus sp. and Betulaceae? In addition, these wood remains contain numerous trace fossils, made by marine wood-boring bivalves (Teredolites longissimus), which together with a discussion about the areal extent of the identified tree species leads us to conclude that they are non-native, i.e. driftwood. Northern Siberia is usually regarded as the most likely source area for driftwood in the eastern North Atlantic region. We combined the approximate transport distance from the areal extent of the wood with the main directions of marine currents in the relevant section of the North Atlantic. Adding the known average marine current velocities during the penultimate interglacial resulted in 130–200 days for transport from North America and 350–1100 days from Siberia. Comparing this with the maximal buoyancy period for the identified tree species, we conclude that the Faroese driftwood may originate not only from Siberia, but also from the eastern coast of North America, especially from the region around the Great Lakes, as well as from western Europe.
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