How to Measure the Oxidation State of Multivalent Elements in Minerals, Glasses, and Melts?

Neuville, Daniel R.; Cicconi, Maria Rita; Losq, Charles Le

doi:10.1002/9781119473206.ch13

Cited by 5 publications

(2 citation statements)

References 125 publications

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“…Figure 12 shows the SCFe005.0 sample pre-edge peak with 3 fitted Gaussian peakssimilar fits were used for all samples. K-edge XANES data is only qualitative in providing average Fe-O coordination numbers for the glasses [61,79]. This is comparable to what can be concluded regarding Fe-O coordination from the Mössbauer data, with both techniques consistent with iron being present in all glasses as only Fe 3+ , and with an average Fe 3+ -O coordination number between 4 and 5.…”

Section: Fe K-edge Xanessupporting

confidence: 80%

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Structural Changes in Borosilicate Glasses as a Function of Fe2o3 Content: A Multi-Technique Approach

Eales¹,

Bell

Cutforth

et al. 2023

Preprint

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Section: Fe K-edge Xanessupporting

confidence: 80%

“…6), it is highly unlikely that the HAFe samples contain measurable levels of Fe 2+ . In light of this, and the known accuracy of determining iron redox using Mossbauer spectroscopy compared with XANES [79], our Mössbauer data will be given greater weight when discussing the iron chemistry of the HAFe glass series.…”

Section: Fe K-edge Xanesmentioning

confidence: 99%

Structural Changes in Borosilicate Glasses as a Function of Fe2o3 Content: A Multi-Technique Approach

Eales¹,

Bell

Cutforth

et al. 2023

Preprint

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Redox Equilibria

Moretti

Neuville

2021

Magma Redox Geochemistry

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The basic aspects of redox geochemistry are reviewed to provide a useful compendium to appreciate the redox connection between the aqueous-hydrothermal and igneous realms of Earth. The different ways to treat and visualize the oxidation state of elements dissolved in a medium are discussed, showing how E-pH, E-pO 2-, and logfO 2 -pH diagrams are equivalent tools to readily identify redox-sensitive species and their reactions. The redox description of a system is intimately coupled to the knowledge of acid-base properties of the solvent in which redox exchanges take place. For magmas, and then silicate melts, approaches reporting the redox state have so far been centered around the sole concept of oxygen fugacity, fO 2 . Based on relevant solid-gas buffers that involve iron in its different oxidation within minerals, the fO 2 concept has provided a reference scale for all igneous processes at the planetary scale and has become one of the main variables to explain Earth's evolution. Mastering the concept of fO 2 in experimental and observational petrology was the key to constrain the processes behind the very large range of relative oxygen fugacity observed on Earth, particularly in its shallow portion. Nevertheless, current descriptions of silicate melts and magma thermodynamic properties are mainly based on oxides or mineral-like molecular components, disregarding the actual melt reactivity. This poses many limits in our understanding of the true chemical exchanges involving oxygen, iron, and the other redox-sensitive elements. Because silicate melts, unlike aqueous solutions or molten salts, lack a full acid-base description, compositional dependencies are solved by means of empirical treatments based on oxides and their combinations. These in turn can bias the interpretation of chemical exchanges that are recorded in analyzed samples and used to identify the physical and chemical gradients imposed by the several processes (e.g., batch or fractional crystallization, elemental recycling, degassing, deep fluid infiltration) that characterize magma evolution and its geodynamic environment. This short redox compendium aims at stimulating the quest for a comprehensive and unifying picture of the acid-base properties of melts from which we could extrinsic the reactivity of all compounds in magmas, in a way similar to aqueous solutions and molten salts. GENERAL ASPECTS AND RATIONALE Oxidation Number, Electron Transfer, and Half-ReactionsOxidation-reduction (redox) geochemistry studies those natural reactions occurring on Earth in which the transfer of electrons determines a change in the oxidation number

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Ionic Syntax and Equilibrium Approach to Redox Exchanges in Melts

Moretti

2021

Geophysical Monograph Series

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How to Measure the Oxidation State of Multivalent Elements in Minerals, Glasses, and Melts?

Cited by 5 publications

References 125 publications

Structural Changes in Borosilicate Glasses as a Function of Fe2o3 Content: A Multi-Technique Approach

Structural Changes in Borosilicate Glasses as a Function of Fe2o3 Content: A Multi-Technique Approach

Redox Equilibria

Ionic Syntax and Equilibrium Approach to Redox Exchanges in Melts

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