High-precision determination of iron oxidation state in silicate glasses using XANES

Cottrell, Elizabeth; Kelley, K. A.; Lanzirotti, Antonio; Fischer, R. A.

doi:10.1016/j.chemgeo.2009.08.008

Cited by 194 publications

(186 citation statements)

References 58 publications

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“…Berry et al, 2003, Cottrell et al, 2009. Commensurate with this, the intensity of the peak corresponding to Fe 3+ (at higher energy) grows proportionately larger relative to the intensity of the peak corresponding to Fe 2+ (at lower energy); thus the ratio of peak intensities can also be used to quantify oxidation state , Cottrell et al, 2009). Spectra were collected in fluorescence mode using a 9 element Ge array detector and a silicon channel-cut (311) monochromator at station X26A (bending magnet) at the National Synchrotron Light Source (NSLS), Brookhaven National Lab.…”

Section: Analytical and Experimental Techniquesmentioning

confidence: 90%

“…The area-weighted average energy of the two pre-edge peaks, or centroid, shifts to higher energy as the ratio of ferric to ferrous iron increases, allowing quantification of Fe 3+ /∑Fe in silicate glasses (e.g. Berry et al, 2003, Cottrell et al, 2009. Commensurate with this, the intensity of the peak corresponding to Fe 3+ (at higher energy) grows proportionately larger relative to the intensity of the peak corresponding to Fe 2+ (at lower energy); thus the ratio of peak intensities can also be used to quantify oxidation state , Cottrell et al, 2009).…”

Section: Analytical and Experimental Techniquesmentioning

confidence: 99%

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Spherulite crystallization induces Fe-redox redistribution in silicic melt

et al. 2009

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Rhyolitic obsidians from Krafla volcano, Iceland, record the interaction between mobile hydrous species liberated during crystal growth and the reduction of ferric iron in the silicate melt. We performed synchrotron µ-FTIR and µ-XANES measurements along a transect extending from a spherulite into optically distinct colorless and brown glass zones. Measurements show that the colorless glass is enriched in OH groups and depleted in ferric iron, while the brown glass shows the opposite relationship. The color shift between brown and clear glass is sharp, suggesting that the colorless glass zone was produced by a redox front that originated from the spherulite margin and moved through surrounding melt during crystallization. We conclude that the most likely reducing agent is hydrogen, produced by magnetite crystallization within the spherulite. The Krafla obsidians dramatically capture redox disequilibrium on the micoscale and highlight the importance of hydrous fluid liberation and late-stage crystallization to the redox signature of glassy lavas.

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Section: Analytical and Experimental Techniquesmentioning

confidence: 90%

Section: Analytical and Experimental Techniquesmentioning

confidence: 99%

Spherulite crystallization induces Fe-redox redistribution in silicic melt

et al. 2009

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“…A1). All melt inclusion and seafloor glass spectra were visually inspected and compared to spectra taken on San Carlos olivine and standard glasses from Cottrell et al (2009) in order to screen for crystal contamination. Any spectra demonstrating signs of spectral features similar to those observed in San Carlos olivine were not considered in this study and additional spectra were collected to accommodate for this elimination.…”

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confidence: 99%

Variations in Fe3+/∑Fe of Mariana Arc Basalts and Mantle Wedge fO2

Brounce

Kelley

Cottrell

2014

Journal of Petrology

221

145

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When collecting Fe-µ-XANES spectra on olivine-hosted melt inclusions, it is important to avoid hitting the olivine crystal with the beam during analysis. Olivine contains several weight percent of Fe 2+ and even a very small amount of olivine interference will "contaminate" the pre-edge structure of Fe-µ-XANES spectra collected for melt inclusions and bias the result towards more reduced values. The region of XANES spectra at higher energies than the Fe-Kα absorption edge contains information related to Fe-coordination and can be used to distinguish glass structure (random and on average, uncoordinated) from olivine signal (strong coordination, Fig. A1). All melt inclusion and seafloor glass spectra were visually inspected and compared to spectra taken on San Carlos olivine and standard glasses from Cottrell et al. (2009) in order to screen for crystal contamination. Any spectra demonstrating signs of spectral features similar to those observed in San Carlos olivine were not considered in this study and additional spectra were collected to accommodate for this elimination. Model liquid lines of descentTo constrain the effects of fractional crystallization on magmatic Fe 3+ /∑Fe ratios, model liquid lines of descent that match the observed major element variations were generated using PetroLog3 (Danyushevsky & Plechov, 2011). The mineral-melt models that most closely replicate the natural data were chosen for each location, resulting in some variation in the models used from volcano to volcano. Individual model parameters

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“…Reference glass LW_0 was monitored continuously during each experimental session to correct for instrumental drift. Further details related to this correction can be found in Cottrell et al [2009]. Spectra were scrutinized for influence from phenocrysts or microphenocrysts in the glass chips.…”

Section: 1002/2016gc006457mentioning

confidence: 99%

“…Fe 31 /Fe Ratios Wafered glass chips were also analyzed in situ for Fe 31 / P Fe ratios via micro x-ray absorption near edge structure (l-XANES) spectroscopy following the methods and techniques of Cottrell et al [2009] at beamline X26A, National Synchrotron Lightsource, Brookhaven National Laboratory. Spectra were collected in fluorescence mode from 7020 to 7220 eV using a 4-element Vortex ME-4 silicon drift diode detector with two single element Vortex-Ex detectors (Hitachi) coupled to an XMap digital spectrometer system, a Si [311] monochromator and a nominal beam size of 9 3 5 mm.…”

Section: 1002/2016gc006457mentioning

confidence: 99%

The Fina Nagu volcanic complex: Unusual submarine arc volcanism in the rapidly deforming southern Mariana margin

Brounce

Kelley

Stern

et al. 2016

Geochem Geophys Geosyst

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In the Mariana convergent margin, large arc volcanoes disappear south of Guam even though the Pacific plate continues to subduct and instead, small cones scatter on the seafloor. These small cones could form either due to decompression melting accompanying back-arc extension or flux melting, as expected for arc volcanoes, or as a result of both processes. Here, we report the major, trace, and volatile element compositions, as well as the oxidation state of Fe, in recently dredged, fresh pillow lavas from the Fina Nagu volcanic chain, an unusual alignment of small, closely spaced submarine calderas and cones southwest of Guam. We show that Fina Nagu magmas are the consequence of mantle melting due to infiltrating aqueous fluids and sediment melts sourced from the subducting Pacific plate into a depleted mantle wedge, similar in extent of melting to accepted models for arc melts. Fina Nagu magmas are not as oxidized as magmas elsewhere along the Mariana arc, suggesting that the subduction component responsible for producing arc magmas is either different or not present in the zone of melt generation for Fina Nagu, and that amphibole or serpentine mineral destabilization reactions are key in producing oxidized arc magmas. Individual Fina Nagu volcanic structures are smaller in volume than Mariana arc volcanoes, although the estimated cumulative volume of the volcanic chain is similar to nearby submarine arc volcanoes. We conclude that melt generation under the Fina Nagu chain occurs by similar mechanisms as under Mariana arc volcanoes, but that complex lithospheric deformation in the region distributes the melts among several small edifices that get younger to the northeast.

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High-precision determination of iron oxidation state in silicate glasses using XANES

Cited by 194 publications

References 58 publications

Spherulite crystallization induces Fe-redox redistribution in silicic melt

Spherulite crystallization induces Fe-redox redistribution in silicic melt

Variations in Fe3+/∑Fe of Mariana Arc Basalts and Mantle Wedge fO2

The Fina Nagu volcanic complex: Unusual submarine arc volcanism in the rapidly deforming southern Mariana margin

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