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Abstract— <p>This paper reports the thermodynamic analysis of Ni<sub><i>x</i></sub>Fe<sub>1-<i>x</i></sub> oxidation for awaruite, Ni<sub>3</sub>Fe, which is widespread in serpentinized ultrabasic rocks, and other Ni–Fe phases over a wide range of temperatures (400–1873 K) and crustal pressures up to 2 kbar. It was found that the equilibrium γ(Ni<sub><i>x</i></sub>Fe<sub>1 –</sub> <sub><i>x</i></sub>)–Fe oxides constrains oxygen fugacity (<i>f</i>O<sub>2</sub>) at the NNO–IW range. For γ(Ni<sub><i>x</i></sub>Fe<sub>1 –</sub> <sub><i>x</i></sub>) with an iron mole fraction <i>x</i> ≥ 0.5, <i>f</i>O<sub>2</sub> approaches the IW buffer. The reaction of kamacite, α(Ni<sub>0.05</sub>Fe<sub>0.95</sub>), with oxygen is close to the IW–IM buffer reactions. The <i>f</i>O<sub>2</sub> values of awaruite preservation are no higher than ∆QFM = –(7.8–5.2) at <i>T</i> = 400–600 K and increase to ∆QFM = –(2.7–2.0) at <i>T</i> &gt; 1000–1200 K. The obtained approximations of the temperature dependence of <i>f</i>O<sub>2</sub> can be used to estimate the redox conditions in low-sulfide systems containing Ni<sub><i>x</i></sub>Fe<sub>1 –</sub> <sub><i>x</i></sub> under the conditions of the Earth’s crust.</p>

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Thermodynamic Analysis of NixFe1 – x Alloy Oxidation

  • 期刊论文

  • 发表日期：

    2025年3月1日

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  • V. N. Devyatova,
  • A. G. Simakin,
  • A. N. Nekrasov

摘要

Abstract—

This paper reports the thermodynamic analysis of NixFe1-x oxidation for awaruite, Ni3Fe, which is widespread in serpentinized ultrabasic rocks, and other Ni–Fe phases over a wide range of temperatures (400–1873 K) and crustal pressures up to 2 kbar. It was found that the equilibrium γ(NixFe1 – x)–Fe oxides constrains oxygen fugacity (fO2) at the NNO–IW range. For γ(NixFe1 – x) with an iron mole fraction x ≥ 0.5, fO2 approaches the IW buffer. The reaction of kamacite, α(Ni0.05Fe0.95), with oxygen is close to the IW–IM buffer reactions. The fO2 values of awaruite preservation are no higher than ∆QFM = –(7.8–5.2) at T = 400–600 K and increase to ∆QFM = –(2.7–2.0) at T > 1000–1200 K. The obtained approximations of the temperature dependence of fO2 can be used to estimate the redox conditions in low-sulfide systems containing NixFe1 – x under the conditions of the Earth’s crust.