231-3 Thermodynamic Model For the Incorporation of Fe into ZnS (Sphalerite)

Session: Critical Mineral Resources and Recovery in the Americas: Emerging Methods in Exploration and Sustainable Extraction (Posters)

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Sphalerite (ZnS) plays a critical role in both geology and material science as it is the world’s primary source of zinc extracted from hydrothermal ore deposits, has been identified in atmospheres of high-temperature exoplanets and may also possibly serve as a geothermometer. In nature, it typically forms as a solid solution incorporating predominantly Fe but also other elements such as Cd. While prior studies have examined temperature dependent solubility, structural changes and vibrational effects of the FeS-ZnS solid solution, a comprehensive thermodynamically based and phase diagram verified model to predict Fe incorporation into sphalerite is not readily available for thermodynamic modelling. Such a model is especially crucial to predict Fe incorporation at low temperatures where kinetic effects hinder experimental studies and extreme environments such as high temperature and pressures not easily accessible by experimental setups. 

Thus, this study aims to provide an extensive experimental dataset on the thermodynamic properties of the FeS-ZnS solid solution in the sphalerite structure. For this, samples along the solid solution were synthesized via solid-state synthesis, phase purity was confirmed by x-ray diffraction (XRD), and enthalpic values were obtained through high temperature oxide melt drop solution calorimetry. Heat capacity measurements will be performed by a physical property measurement system (PPMS). The thermodynamic data for the hypothetical FeS endmember is extrapolated from the solid solution data and compared to existing computationally obtained values. The experimental thermodynamics enables thermodynamic modelling of ore deposits which can prove crucial for further exploration. 

The resulting thermodynamic model provides a robust framework for accurately predicting Fe incorporation in sphalerite, bridging a critical gap between experimental data, computational predictions, and phase equilibria essential for geologic and material science applications.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7969

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