Surface energy of fayalite and its effect on Fe-Si-O oxygen buffers and the olivine-spinel transition

Lilova, Kristina; DeAngelis, Michael T.; Anovitz, Lawrence M.; Navrotsky, Alexandra

doi:10.2138/am-2018-6531

Cited by 6 publications

(7 citation statements)

References 23 publications

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“…The surface energy of olivine crystals is taken from Lilova et al. (2018). A ratio between solid‐solid and solid‐liquid interface energies is chosen as r sl = 1.5.…”

Section: Numerical Resultsmentioning

confidence: 99%

Phase‐Field Simulation of Texture Evolution in Magmatic Rocks

2023

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Physical chemistry is used to quantify the reading of the rock record to decipher processes that took place in and on the Earth. Thermodynamic analysis of complex chemical systems that correspond to bulk chemistry of diverse igneous and metamorphic rock types is now commonplace. Such analyses predict the stable mineral assemblages as well as the modal abundance and composition of the minerals as a function of intensive thermodynamic variables such as pressure, temperature, and fugacities of various species (e.g.,). Petrological attributes of the rock record also include textural and microstructural characteristics, but a quantitative thermodynamically consistent approach to handle that is not yet available.The situation is analogous to kinetic analysis. Studies of processes such as diffusion, nucleation, or crystal growth address these processes in individual mineral systems, or populations of crystals in some cases (e.g., nucleation and growth in molten systems), but in a manner that is generally decoupled from quantitative thermodynamic phase relations. In the best of cases, modeling efforts include alternating updates of thermodynamic and kinetic parameters, but without a means of ensuring physico-chemical consistency between these. Previous models for the simulation of texture evolution during crystallization processes in rocks were stochastic approaches, which were developed to validate theoretical models of the crystal size distribution with constant growth rates and an exponential nucleation rate (

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“…The surface energy of olivine crystals is taken from Lilova et al. (2018). A ratio between solid‐solid and solid‐liquid interface energies is chosen as r sl = 1.5.…”

Section: Numerical Resultsmentioning

confidence: 99%

Phase‐Field Simulation of Texture Evolution in Magmatic Rocks

2023

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“…where R is the gas constant, V m , is a molar volume T E m is the melting temperature of an end-member, X L E and X S E are the liquid and solid equilibrium molar fraction of the end-member at a temperature T . The surface energy of olivine crystals is taken from Lilova et al (2018). A ratio between solid-solid and solid-liquid interface energies is chosen as r sl = 1.5.…”

Section: Olivine -Melt Systemmentioning

confidence: 99%

Phase-field simulation of texture evolution in magmatic rocks

Kundin

Steinbach

Chakraborty

2023

Preprint

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The tool of phase-field modeling for the prediction of chemical as well as microstructural evolution during crystallization from a melt in a mineralogical system has been developed in this work. We provide a compact theoretical background and introduce new aspects such as the treatment of anisotropic surface energies that are essential for modeling mineralogical systems. These are then applied to two simple model systems - the binary olivine-melt and plagioclase-melt systems - to illustrate the application of the developed tools. In one case crystallization is modeled at a constant temperature and undercooling while in the other the process of crystallization is tracked for a constant cooling rate. These two examples serve to illustrate the capabilities of the modeling tool. The results are analyzed in terms of crystal size distributions (CSD) and with a view toward applications in diffusion chronometry; future possibilities are discussed. The modeling results demonstrate that growth at constant rates may be expected only for limited extents of crystallization, that breaks in slopes of CSD-plots should be common, and that the lifetime of a given crystal of a phase is different from the lifetime of this phase in a magmatic system. The last aspect imposes an inherent limit to timescales that may be accessed by diffusion chronometry. Most significantly, this tool provides a bridge between CSD analysis and diffusion chronometry - two common tools that are used to study timescales of magmatic processes.

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“…Moreover, some magnetotactic bacteria produce only nanocrystalline greigite (between 30 and 70 nm diameter), which does not convert to pyrite even in the presence of excess H 2 S (25). Thus, it is possible that the small surface energy of the sulfide spinel extends its stability field relative to pyrite in the Fe-S system, analogous to effects seen with magnetite in the Fe-O and Fe-O-SiO 2 systems (10,11). To quantify this possible effect, and analogous effects on the pyrrhotite-greigite equilibrium, one would need to know the surface energy of pyrite and pyrrhotite.…”

Section: Significancementioning

confidence: 99%

“…The change of mineral properties with particle size has been recognized as a critical aspect of geochemical and biochemical reactions in natural systems (9). An important question is whether greigite, a sulfide spinel, has a relatively low surface energy analogous to that of magnetite and other oxide spinels (10,11). If the surface energy of greigite is lower than that of other sulfides in the Fe-S system, its stability at the nanoscale may be enhanced.…”

mentioning

confidence: 99%

“…If the surface energy of greigite is lower than that of other sulfides in the Fe-S system, its stability at the nanoscale may be enhanced. Particle-size decrease also results in shift to lower oxygen fugacity of the Fe-Si-O oxygen buffers (11). The sulfur and oxygen fugacities are directly linked and control the partitioning of metals between sulfide and oxide phases.…”

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confidence: 99%

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Greigite (Fe ₃ S ₄ ) is thermodynamically stable: Implications for its terrestrial and planetary occurrence

Subramani

Lilova

Abramchuk

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Iron sulfide minerals are widespread on Earth and likely in planetary bodies in and beyond our solar system. Using measured enthalpies of formation for three magnetic iron sulfide phases: bulk and nanophase Fe3S4 spinel (greigite), and its high-pressure monoclinic phase, we show that greigite is a stable phase in the Fe–S phase diagram at ambient temperature. The thermodynamic stability and low surface energy of greigite supports the common occurrence of fine-grained Fe3S4 in many anoxic terrestrial settings. The high-pressure monoclinic phase, thermodynamically metastable below about 3 GPa, shows a calculated negative P-T slope for its formation from the spinel. The stability of these three phases suggests their potential existence on Mercury and their magnetism may contribute to its present magnetic field.

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Surface energy of fayalite and its effect on Fe-Si-O oxygen buffers and the olivine-spinel transition

Cited by 6 publications

References 23 publications

Phase‐Field Simulation of Texture Evolution in Magmatic Rocks

Phase‐Field Simulation of Texture Evolution in Magmatic Rocks

Phase-field simulation of texture evolution in magmatic rocks

Greigite (Fe ₃ S ₄ ) is thermodynamically stable: Implications for its terrestrial and planetary occurrence

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Surface energy of fayalite and its effect on Fe-Si-O oxygen buffers and the olivine-spinel transition

Cited by 6 publications

References 23 publications

Phase‐Field Simulation of Texture Evolution in Magmatic Rocks

Phase‐Field Simulation of Texture Evolution in Magmatic Rocks

Phase-field simulation of texture evolution in magmatic rocks

Greigite (Fe 3 S 4 ) is thermodynamically stable: Implications for its terrestrial and planetary occurrence

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Greigite (Fe ₃ S ₄ ) is thermodynamically stable: Implications for its terrestrial and planetary occurrence