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Online-Ressource

Schlussbericht : Förderzeitraum: 01.07.2016-30.06.2019 (2019)

Klemme, Stephan ; Wilke, Max 1966- ; Westfälische Wilhelms-Universität Münster

[Münster] : Westfälische Wilhelms-Universität Münster

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Schlagwort(e): Forschungsbericht ; PETRA ; Röntgenfluoreszenzspektroskopie ; Hydrothermale Phase ; Transportprozess

Materialart: Online-Ressource

Seiten: 1 Online-Ressource (11 Seiten, 9,48 MB) , Illustrationen, Diagramme

URL: https://doi.org/10.2314/KXP:173388324X

DOI: 10.2314/KXP:173388324X

Sprache: Deutsch

Anmerkung: Förderkennzeichen BMBF 05K16PMA , Unterschiede zwischen dem gedruckten Dokument und der elektronischen Ressource können nicht ausgeschlossen werden

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Determination of the iron oxidation state in Earth materials using XANES pre-edge information (2001)

Petit, Pierre Emmanuel ; Farges, François ; Wilke, Max ; [weitere]

Chester : International Union of Crystallography (IUCr)

Journal of synchrotron radiation 8 (2001), S. 952-954

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ISSN: 1600-5775

Quelle: Crystallography Journals Online : IUCR Backfile Archive 1948-2001

Thema: Geologie und Paläontologie , Physik

Notizen: Fe K-edge XANES spectra have been measured in more than 35 Fe(II) and Fe(III)-bearing minerals. The separation between the average pre-edge centroid positions for Fe(II) and Fe(III) is 1.4 ± 0.1 eV. Examination of calculated pre-edge features of mechanical mixtures of phases containing different proportions of Fe(II) and Fe(III) reveals that different trends of pre-edge position vs. pre-edge intensity can be observed, depending on the coordination environment. Both pre-edge parameters have been used to estimate the ferric/ferrous ratio in 12 natural minerals.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1107/S0909049500021063

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3

Digitale Medien

Water and the density of silicate glasses (2000)

Richet, Pascal ; Whittington, Alan ; Holtz, François ; [weitere]

Springer

Contributions to mineralogy and petrology 138 (2000), S. 337-347

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ISSN: 1432-0967

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie

Notizen: Abstract A review of published and newly measured densities for 40 hydrous silicate glasses indicates that the room-temperature partial molar volume of water is 12.0 ± 0.5 cm3/mol. This value holds for simple or mineral compositions as well as for complex natural glasses, from rhyolite to tephrite compositions, prepared up to 10–20 kbar pressures and containing up to 7 wt% H2O. This volume does not vary either with the molar volume of the water-free silicate phase, with its degree of polymerization or with water speciation. Over a wide range of compositions, this constant value implies that the volume change for the reaction between hydroxyl ions and molecular water is zero and that, at least in glasses, speciation does not depend on pressure. Consistent with data from Ochs and Lange (1997, 1999), systematics in volume expansion for SiO2–M2O systems (M=H, Li, Na, K) suggests that the partial molar thermal expansion coefficient of H2O is about 4 × 10−5 K−1 in silicate glasses.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s004100050567

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The dependence of the partitioning of iron and europium between plagioclase and hydrous tonalitic melt on oxygen fugacity (1999)

Wilke, Max ; Behrens, Harald

Springer

Contributions to mineralogy and petrology 137 (1999), S. 102-114

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ISSN: 1432-0967

Quelle: Springer Online Journal Archives 1860-2000

Thema: Geologie und Paläontologie

Notizen: Abstract The dependence of iron and europium partitioning between plagioclase and melt on oxygen fugacity was studied in the system SiO2(Qz)—NaAlSi3O8(Ab)—CaAl2Si2O8(An)—H2O. Experiments were performed at 500 MPa and 850 °C/750 °C under water saturated conditions. The oxygen fugacity was varied in the log f O2-range from −7.27 to −15.78. To work at the most reducing conditions the classical double-capsule technique was modified. The sample and a C—O—H bearing sensor capsule were placed next to each other within a BN jacket to minimise loss of hydrogen to the vessel atmosphere. By this setup redox conditions slightly more reducing than the FeO—Fe3O4 buffer could be maintained even in 96 h runs. Raman spectra showed that the BN was modified by reaction with hydrogen resulting in a low hydrogen permeability. The partition coefficients determined for Eu at 850 °C and 500 MPa vary from 0.095 at conditions of the Cu—Cu2O buffer to 1.81 at the most reducing conditions (C—O—H sensor). In the same f O2 interval the partition coefficient for Fe varies from 0.55 at oxidising conditions to 0.08 at the most reducing conditions. The partitioning of Sm, which was added as a reference for a trivalent REE, does not vary with the oxygen fugacity, yielding an average value for D = 0.07. Lowering the temperature to 750 °C for a given f O2 decreases the partition coefficient of Eu and increases that of Fe. Comparison with published data at 1 atm and at higher temperatures shows that both temperature and composition of the melt have strong effects on the partitioning behaviour. As the change of the partition coefficients in the geologically relevant f O2 range is quite strong, element partitioning of Eu and Fe might be used to estimate redox conditions for the genesis of igneous rocks. Furthermore, by modelling the partitioning data it is possible to extract information about the redox state of the melt. Resulting ferric-ferrous ratios show significant differences from those predicted by empirical models.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/s004100050585

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Confocal μ -XANES as a tool to analyze Fe oxidation state in heterogeneous samples: the case of melt inclusions in olivine from the Hekla volcano (2024)

Botcharnikov, Roman ; Wilke, Max ; Garrevoet, Jan ; [weitere]

Copernicus Publications (EGU)

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Publikationsdatum: 2024-04-03

Beschreibung: Here we present a confocal Fe K-edge μ-XANES method (where XANES stands for X-ray absorption near-edge spectroscopy) for the analysis of Fe oxidation state in heterogeneous and one-side-polished samples. The new technique allows for an analysis of small volumes with high spatial 3D resolution of 〈100 µm3. The probed volume is restricted to that just beneath the surface of the exposed object. This protocol avoids contamination of the signal by the host material and minimizes self-absorption effects. This technique has been tested on a set of experimental glasses with a wide range of Fe3+ ΣFe ratios. The method was applied to the analysis of natural melt inclusions trapped in forsteritic to fayalitic olivine crystals of the Hekla volcano, Iceland. Our measurements reveal changes in Fe3+ ΣFe from 0.17 in basaltic up to 0.45 in dacitic melts, whereas the magnetite–ilmenite equilibrium shows redox conditions with Fe3+ ΣFe ≤0.20 (close to FMQ, fayalite–magnetite–quartz redox equilibrium) along the entire range of Hekla melt compositions. This discrepancy indicates that the oxidized nature of glasses in the melt inclusions could be related to the post-entrapment process of diffusive hydrogen loss from inclusions and associated oxidation of Fe in the melt. The Fe3+ ΣFe ratio in silicic melts is particularly susceptible to this process due to their low FeO content, and it should be critically evaluated before petrological interpretation.

Materialart: Article , PeerReviewed

Format: text

Format: archive

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Oxidising agents in sub-arc mantle melts link slab devolatilisation and arc magmas (2018)

Bénard, Antoine ; Klimm, Kevin ; Woodland, Alan B. ; [weitere]

Nature Publishing Group

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Publikationsdatum: 2022-05-25

Beschreibung: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Nature Communications 9 (2018): 3500, doi:10.1038/s41467-018-05804-2.

Beschreibung: Subduction zone magmas are more oxidised on eruption than those at mid-ocean ridges. This is attributed either to oxidising components, derived from subducted lithosphere (slab) and added to the mantle wedge, or to oxidation processes occurring during magma ascent via differentiation. Here we provide direct evidence for contributions of oxidising slab agents to melts trapped in the sub-arc mantle. Measurements of sulfur (S) valence state in sub-arc mantle peridotites identify sulfate, both as crystalline anhydrite (CaSO4) and dissolved SO42− in spinel-hosted glass (formerly melt) inclusions. Copper-rich sulfide precipitates in the inclusions and increased Fe3+/∑Fe in spinel record a S6+–Fe2+ redox coupling during melt percolation through the sub-arc mantle. Sulfate-rich glass inclusions exhibit high U/Th, Pb/Ce, Sr/Nd and δ34S (+ 7 to + 11‰), indicating the involvement of dehydration products of serpentinised slab rocks in their parental melt sources. These observations provide a link between liberated slab components and oxidised arc magmas.

Beschreibung: We acknowledge financial support by the Australian Research Council (DE120100513 and DP120104240) and the ESRF for beam time (EC1061 and ES238).

Repository-Name: Woods Hole Open Access Server

Materialart: Article

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