The oxidation state of europium in silicate melts as a function of oxygen fugacity, composition and temperature

A. D. Burnham; A. J. Berry; H. R. Halse; P. F. Schofield; G. Cibin; J. F.W. Mosselmans

doi:10.1016/j.chemgeo.2015.07.002

The oxidation state of europium in silicate melts as a function of oxygen fugacity, composition and temperature

A. D. Burnham^*, A. J. Berry, H. R. Halse, P. F. Schofield, G. Cibin, J. F.W. Mosselmans

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

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Abstract

Europium L_III-edge X-ray absorption near edge structure (XANES) spectra were recorded for a series of synthetic glasses and melts equilibrated over a range of oxygen fugacities (fO₂s, from -14 to +6 logarithmic units relative to the quartz-fayalite-magnetite, QFM, buffer) and temperatures (1250-1500°C). Eu³⁺/σEu (where σEu=Eu²⁺+Eu³⁺) values were determined from the spectra with a precision of ±0.015. Eu³⁺/σEu varies systematically with fO₂ from 0 to 1 over the range studied, increases with decreasing melt polymerisation and temperature, and can be described by the empirical equation: Eu3+/σEu=11+10-0.25logfO2-6410T-14.2Λ-10.1, where Λ is the optical basicity of the melt and T is the temperature in K. Eu³⁺/σEu in glasses and melts equilibrated at the same conditions are in excellent agreement for Fe-free systems. For Fe-bearing compositions the reaction Eu²⁺+Fe³⁺=Eu³⁺+Fe²⁺ occurs during quenching to a glass and the high temperature value of Eu³⁺/σEu is not preserved on cooling; in situ measurements are essential for determining Eu³⁺/σEu in natural melts.

Original language	English
Pages (from-to)	248-259
Number of pages	12
Journal	Chemical Geology
Volume	411
DOIs	https://doi.org/10.1016/j.chemgeo.2015.07.002
Publication status	Published - 4 Sept 2015

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@article{02f44879ca53490bb573c75c9dee25ff,

title = "The oxidation state of europium in silicate melts as a function of oxygen fugacity, composition and temperature",

abstract = "Europium LIII-edge X-ray absorption near edge structure (XANES) spectra were recorded for a series of synthetic glasses and melts equilibrated over a range of oxygen fugacities (fO2s, from -14 to +6 logarithmic units relative to the quartz-fayalite-magnetite, QFM, buffer) and temperatures (1250-1500°C). Eu3+/σEu (where σEu=Eu2++Eu3+) values were determined from the spectra with a precision of ±0.015. Eu3+/σEu varies systematically with fO2 from 0 to 1 over the range studied, increases with decreasing melt polymerisation and temperature, and can be described by the empirical equation: Eu3+/σEu=11+10-0.25logfO2-6410T-14.2Λ-10.1, where Λ is the optical basicity of the melt and T is the temperature in K. Eu3+/σEu in glasses and melts equilibrated at the same conditions are in excellent agreement for Fe-free systems. For Fe-bearing compositions the reaction Eu2++Fe3+=Eu3++Fe2+ occurs during quenching to a glass and the high temperature value of Eu3+/σEu is not preserved on cooling; in situ measurements are essential for determining Eu3+/σEu in natural melts.",

keywords = "Eu/Eu, In situ, MORB, Rare earth element, Redox, Silicate glass, XANES",

author = "Burnham, {A. D.} and Berry, {A. J.} and Halse, {H. R.} and Schofield, {P. F.} and G. Cibin and Mosselmans, {J. F.W.}",

note = "Publisher Copyright: {\textcopyright} 2015 Elsevier B.V..",

year = "2015",

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doi = "10.1016/j.chemgeo.2015.07.002",

language = "English",

volume = "411",

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T1 - The oxidation state of europium in silicate melts as a function of oxygen fugacity, composition and temperature

AU - Burnham, A. D.

AU - Berry, A. J.

AU - Halse, H. R.

AU - Schofield, P. F.

AU - Cibin, G.

AU - Mosselmans, J. F.W.

PY - 2015/9/4

Y1 - 2015/9/4

N2 - Europium LIII-edge X-ray absorption near edge structure (XANES) spectra were recorded for a series of synthetic glasses and melts equilibrated over a range of oxygen fugacities (fO2s, from -14 to +6 logarithmic units relative to the quartz-fayalite-magnetite, QFM, buffer) and temperatures (1250-1500°C). Eu3+/σEu (where σEu=Eu2++Eu3+) values were determined from the spectra with a precision of ±0.015. Eu3+/σEu varies systematically with fO2 from 0 to 1 over the range studied, increases with decreasing melt polymerisation and temperature, and can be described by the empirical equation: Eu3+/σEu=11+10-0.25logfO2-6410T-14.2Λ-10.1, where Λ is the optical basicity of the melt and T is the temperature in K. Eu3+/σEu in glasses and melts equilibrated at the same conditions are in excellent agreement for Fe-free systems. For Fe-bearing compositions the reaction Eu2++Fe3+=Eu3++Fe2+ occurs during quenching to a glass and the high temperature value of Eu3+/σEu is not preserved on cooling; in situ measurements are essential for determining Eu3+/σEu in natural melts.

AB - Europium LIII-edge X-ray absorption near edge structure (XANES) spectra were recorded for a series of synthetic glasses and melts equilibrated over a range of oxygen fugacities (fO2s, from -14 to +6 logarithmic units relative to the quartz-fayalite-magnetite, QFM, buffer) and temperatures (1250-1500°C). Eu3+/σEu (where σEu=Eu2++Eu3+) values were determined from the spectra with a precision of ±0.015. Eu3+/σEu varies systematically with fO2 from 0 to 1 over the range studied, increases with decreasing melt polymerisation and temperature, and can be described by the empirical equation: Eu3+/σEu=11+10-0.25logfO2-6410T-14.2Λ-10.1, where Λ is the optical basicity of the melt and T is the temperature in K. Eu3+/σEu in glasses and melts equilibrated at the same conditions are in excellent agreement for Fe-free systems. For Fe-bearing compositions the reaction Eu2++Fe3+=Eu3++Fe2+ occurs during quenching to a glass and the high temperature value of Eu3+/σEu is not preserved on cooling; in situ measurements are essential for determining Eu3+/σEu in natural melts.

KW - Eu/Eu

KW - In situ

KW - MORB

KW - Rare earth element

KW - Redox

KW - Silicate glass

KW - XANES

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U2 - 10.1016/j.chemgeo.2015.07.002

DO - 10.1016/j.chemgeo.2015.07.002

M3 - Article

SN - 0009-2541

VL - 411

SP - 248

EP - 259

JO - Chemical Geology

JF - Chemical Geology

ER -

The oxidation state of europium in silicate melts as a function of oxygen fugacity, composition and temperature

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