Theoretical calculation of equilibrium Mg isotope fractionations between minerals and aqueous solutions

Gao, Caihong; Cao, Xiaobin; Liu, Qi; Yang, Yuhong; Zhang, Siting; He, Yuyang; Tang, Mao; Liu, Yun

doi:10.1016/j.chemgeo.2018.04.005

Cited by 50 publications

(43 citation statements)

References 129 publications

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“…This method was named the "volume variable cluster model method, or VVCM" (Fig. 1) (He and Liu, 2015;He et al, 2016;Gao et al, 2018;Zhang and Liu, 2018).…”

Section: Theory and Calculation Methodsmentioning

confidence: 99%

“…The result of the calculation shows that the position of the virtual charge points can affect the calculation value of RPFRs. The VVCM method can be used to solve systems in which heavy elements have anharmonic effects and minerals with H-bonding and weak interactions, and the method is proven to be efficient by computational simulation (Gao et al, 2018).…”

Section: Theory and Calculation Methodsmentioning

confidence: 99%

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Equilibrium sulfur isotope fractionations of several important sulfides

Zhang

2021

Geochem. J.

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“…This method was named the "volume variable cluster model method, or VVCM" (Fig. 1) (He and Liu, 2015;He et al, 2016;Gao et al, 2018;Zhang and Liu, 2018).…”

Section: Theory and Calculation Methodsmentioning

confidence: 99%

Section: Theory and Calculation Methodsmentioning

confidence: 99%

Equilibrium sulfur isotope fractionations of several important sulfides

Zhang

2021

Geochem. J.

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“…In addition, the precipitation of Mg-carbonate in the playa sediments only affects the isotope ratio but does not significantly lower the total concentration of dissolved Mg which is driven by evaporation, thereby allowing Mg-carbonates to maintain (super)saturation. It is also worth noting that the Rayleigh calculation refers to isotopic composition of the bulk fluid, although changes in chemical speciation due to precipitation most likely affect the isotopic composition of the Mg 2+ (aq) ion (Schott et al, 2016;Gao et al, 2018) 1), so the prevalence of Rayleigh processes in the saturated zone cannot be determined.…”

Section: Formation Of Hydromagnesitementioning

confidence: 99%

Mechanisms controlling the Mg isotope composition of hydromagnesite-magnesite playas near Atlin, British Columbia, Canada

et al. 2021

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The alkaline playas near Atlin, British Columbia, Canada are likely one of the few surface environments on Earth where contemporaneous formation of hydromagnesite and magnesite occurs at temperatures that do not exceed 15 °C. This environment offers a unique opportunity to examine the impact of different formation mechanisms on Mg isotope compositions of Mg-carbonate minerals at low temperature. In this study, we report the Mg isotope composition of ultramafic bedrock, Mg-carbonate sediments, and both surface and ground waters in this geological setting. The composition of hydromagnesite suggests a Rayleigh-type distillation effect on the fluid Mg isotope ratios in unsaturated sediment above the water table. Through this mechanism of formation, hydromagnesite is progressively depleted in 24 Mg obtaining δ 26 Mg values as high as +1.14‰ near the sediment surface. In contrast, magnesite formation is characterized by enrichment of the solid phase in 24 Mg. The apparent Mg isotope fractionation factor during magnesite formation at ~ 10 °C ranges between ~ 0.7±0.1‰ and 1.8±0.1‰. The distinct Mg isotope composition of hydromagnesite in comparison to magnesite supports magnesite formation occurring by precipitation from the fluid, or dissolution-reprecipitation, rather than solid-phase transformation from a hydrous Mg-carbonate precursor. Overall, the results provide insights on low temperature Mgcarbonate mineral formation that has implications for long-term storage of CO2.

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“…Even higher W/R are expected to have been involved in the formation of massive carbonate‐serpentine veins which acted as main fluid paths for fluids interacting with peridotites (de Obeso & Kelemen, 2018; Noël et al., 2018). Secondary minerals from the three steps formed at variable W/R have different aqueous Mg 2+ ‐mineral fractionation properties with silicates expected to become enriched in 26 Mg and carbonates enriched in 24 Mg (e.g., Beinlich et al., 2014; Gao et al., 2018; Liu et al., 2017; Pinilla et al., 2015; Wang et al., 2019; Wimpenny et al., 2014) suggesting that Mg isotopes can be used as tracers of alteration.…”

Section: Geological Background and Sample Selectionmentioning

confidence: 99%

A Mg Isotopic Perspective on the Mobility of Magnesium During Serpentinization and Carbonation of the Oman Ophiolite

et al. 2021

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Alteration of ultramafic rocks is ubiquitous in near-surface environments, both on land and below the seafloor. Mantle olivine and pyroxene are unstable at near-surface conditions and undergo hydration (serpentinization) and carbonation when fluids are present (e.g., Moody, 1976). These reactions result in the formation of serpentine minerals, carbonates, brucite, magnetite, and other Fe-oxides and hydroxides. Serpentinization and carbonation reactions are often nearly isochemical apart from the addition of H 2 O and CO 2 (e.g., Coleman & Keith, 1971). Both observations and thermodynamic modeling suggest that changes in major element ratios such as Si/Mg are minor (e.g., ≤10% for low-temperature reaction with seawater,

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Theoretical calculation of equilibrium Mg isotope fractionations between minerals and aqueous solutions

Cited by 50 publications

References 129 publications

Equilibrium sulfur isotope fractionations of several important sulfides

Equilibrium sulfur isotope fractionations of several important sulfides

Mechanisms controlling the Mg isotope composition of hydromagnesite-magnesite playas near Atlin, British Columbia, Canada

A Mg Isotopic Perspective on the Mobility of Magnesium During Serpentinization and Carbonation of the Oman Ophiolite

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