Equilibrium indium isotope fractionation in chloride-rich aqueous solutions using first-principles calculations

IF 4.5 1区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Geochimica et Cosmochimica Acta Pub Date : 2025-03-15 DOI:10.1016/j.gca.2025.01.026

Haochen Duan , Fang Huang

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引用次数: 0

Abstract

Aqueous indium (In) speciation and isotope fractionation factors are important to understand the origin and transport of indium during magmatic-hydrothermal and atmosphere-hydrosphere processes. Here, we investigate indium speciation in chloride-rich aqueous solutions and explore their reduced partition function ratios (10³lnβ) using first-principles calculations. The simulations with initial configurations of InCl(H₂O)₅²⁺, InCl₂(H₂O)₄⁺, InCl₃(H₂O)₃, InCl₄(H₂O)₂⁻ and InCl₅(H₂O)²⁻ were performed at 400 and 600 K, respectively. The results show that InCl(H₂O)₅²⁺, InCl₂(H₂O)₄⁺, InCl₃(H₂O)_2.4, InCl₄⁻ and InCl₅²⁻ are the stable In³⁺ species at 400 K, and their 10³lnβ decreases from 1.00 ‰, 0.89 ‰, 0.83 ‰, 0.75 ‰ to 0.66 ‰. At 600 K, the stable In³⁺ species are composed of InCl(H₂O)₅²⁺, InCl₂(H₂O)_3.7⁺, InCl₃(H₂O)_1.7, InCl₄⁻ and InCl₅²⁻ with their 10³lnβ decreasing from 0.46 ‰, 0.42 ‰, 0.39 ‰, 0.35 ‰ to 0.31 ‰. These results indicate that 10³lnβ is negatively correlated with the coordination number and bond length of chlorine ligands in aqueous In³⁺ species. Meanwhile, water molecules are gradually removed from the first hydration shell gradually with increasing temperature, such as InCl₂(H₂O)₄⁺ and InCl₄(H₂O)₂⁻ to InCl₂(H₂O)_3.7⁺ and InCl₄⁻, indicating that stable In³⁺ species changes with temperature. Hence, estimating the 10³lnβ of aqueous liquids at different temperatures should consider the potential structure transition of cation species. The calculations of equilibrium indium isotope fractionation factors provide important insights into the mechanism of isotope fractionation in aqueous liquids, and show the potential application of indium isotopes in the geological and supergene processes of indium.

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来源期刊

Geochimica et Cosmochimica Acta 地学-地球化学与地球物理

CiteScore

9.60

自引率

14.00%

发文量

437

审稿时长

6 months

期刊介绍： Geochimica et Cosmochimica Acta publishes research papers in a wide range of subjects in terrestrial geochemistry, meteoritics, and planetary geochemistry. The scope of the journal includes: 1). Physical chemistry of gases, aqueous solutions, glasses, and crystalline solids 2). Igneous and metamorphic petrology 3). Chemical processes in the atmosphere, hydrosphere, biosphere, and lithosphere of the Earth 4). Organic geochemistry 5). Isotope geochemistry 6). Meteoritics and meteorite impacts 7). Lunar science; and 8). Planetary geochemistry.