The mechanism of oxidation of a basaltic glass: Chemical diffusion of network-modifying cations

Cooper, R. F.; Fanselow, John B.; Poker, D. B.

doi:10.1016/0016-7037(96)00160-3

Cited by 133 publications

(124 citation statements)

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“…These mechanisms were observed for experimental timescales of a few seconds or minutes (Cooper et al, 1996b;Everman and Cooper, 2003) or in the glass region (Cooper et al, 1996a;Cook and Cooper, 2000). As discussed before, at the timescale of our experiments (i.e.…”

Section: Redox Dynamicssupporting

confidence: 73%

“…For example, in a basaltic melt at 1300°C, Muehlenbachs and Kushiro (1974) and Lesher et al (1996) measured oxygen diffusivities (D*) of ~4.10 -12 m²/s and 6.10 -12 m²/s, respectively. This result questions the assumption of Cooper et al (1996a, b) that c O2-D O2-(and c O2 D O2 ) < c modifier cations D modifier cations , c x being the concentration of x.…”

Section: Previous Workmentioning

confidence: 66%

“…Oxygen self and chemical diffusion studies performed on synthetic (Sasabe and Goto, 1974;Dunn, 1982;Schreiber et al, 1986;Cook et al, 1990;Cook and Cooper, 2000;Reid et al, 2001) and natural silicate melts (Dunn, 1983;Canil and Muehlenbachs, 1990;Wendlandt, 1991;Cooper et al, 1996a) have demonstrated the dependence of both kind of diffusion mechanisms on the melt structure. This was also confirmed by other studies of iron redox reactions (e.g.…”

Section: Previous Workmentioning

confidence: 99%

“…Schreiber et al, 1986 and references therein). In H-bearing and H-free basaltic systems, reduction/oxidation reactions are commonly associated with the development of redox reaction fronts and are diffusion-limited (Wendlandt, 1991;Cooper et al, 1996a, b;Everman and Cooper, 2003;Gaillard et al, 2003a). For H-bearing systems, Gaillard et al (2003b) calculated that H 2 mobility should rate-limit redox changes in basalts.…”

Section: Previous Workmentioning

confidence: 99%

“…Both n oxygen and n total are determined by mass balance calculations. As in Cooper et al (1996a), the flux of electron holes (j h. ) was calculated using the charge neutrality condition:…”

Section: Redox Dynamicsmentioning

confidence: 99%

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Time-dependent changes of the electrical conductivity of basaltic melts with redox state

Pommier

Gaillard

Pichavant

2010

Geochimica et Cosmochimica Acta

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. Time-dependent changes of the electrical conductivity of basaltic melts with redox state. Geochimica et Cosmochimica Acta, Elsevier, 2010, 74 (5) Abstract 300 better)The electrical conductivity of basaltic melts has been measured in real-time after fO 2 stepchanges in order to investigate redox kinetics. Experimental investigations were performed at 1 atm in a vertical furnace between 1200°C and 1400°C using air, pure CO 2 or CO/CO 2 gas mixtures to buffer oxygen fugacity in the range 10 -8 to 0.2 bars. Ferric/ferrous ratios were determined by wet chemical titrations. A small but detectable effect of fO 2 on the electrical conductivity is observed. The more reduced the melt, the higher the conductivity. A modifiedArrhenian equation accounts for both T and fO 2 effects on the electrical conductivity. We show that time-dependent changes in electrical conductivity following fO 2 step-changes monitor the rate of Fe 2+ /Fe 3+ changes. The conductivity change with time corresponds to a diffusion-limited process in the case of reduction in CO-CO 2 gas mixtures and oxidation in air. However, a reaction at the gas-melt interface probably rate limits oxidation of the melt under pure CO 2 .Reduction and oxidation rates are similar and both increase with temperature. Those rates range from 10 -9 to 10 -8 m²/s for the temperature interval 1200-1400°C and show activation energy of about 200kJ/mol. The redox mechanism that best explains our results involves a cooperative motion of cations and oxygen, allowing such fast oxidation-reduction rates.

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Section: Redox Dynamicssupporting

confidence: 73%

Section: Previous Workmentioning

confidence: 66%

Section: Previous Workmentioning

confidence: 99%

Section: Previous Workmentioning

confidence: 99%

“…Both n oxygen and n total are determined by mass balance calculations. As in Cooper et al (1996a), the flux of electron holes (j h. ) was calculated using the charge neutrality condition:…”

Section: Redox Dynamicsmentioning

confidence: 99%

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Time-dependent changes of the electrical conductivity of basaltic melts with redox state

Pommier

Gaillard

Pichavant

2010

Geochimica et Cosmochimica Acta

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

Neuville¹,

Cicconi²,

Losq³

2021

Geophysical Monograph Series

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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The mechanism of oxidation of a basaltic glass: Chemical diffusion of network-modifying cations

Cited by 133 publications

References 29 publications

Time-dependent changes of the electrical conductivity of basaltic melts with redox state

Time-dependent changes of the electrical conductivity of basaltic melts with redox state

Redox Equilibria

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

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