Crystal habit-directed gold deposition on pyrite: Surface chemical interpretation of the pyrite morphology indicative of gold enrichment

Huang, Xian; He, Hongping; Zhu, Jianxi; Du, Runxiang; Wu, Xiao; Hong-mei, Tang; Tan, Wei; Liang, Xiaoliang; Teng, H. Henry

doi:10.1016/j.gca.2019.08.011

Cited by 35 publications

(10 citation statements)

References 55 publications

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“…The PBE + U method 42 (U-J = 1.6 eV) was employed to describe the pyritic surfaces with an energy cutoff of 400 eV for plane wave basis. The feasibility of this method has been confirmed by previous studies on pyritic systems 21,43,44 . All atoms in the considered pyrite models were fully relaxed until the forces dropped below 0.01 eV/Å.…”

Section: Methodssupporting

confidence: 56%

“…Because the partition coefficient of Au(I) between pyrite and the fluid decreases when temperature increases 19,20 , gold nanoparticles exsolved from a solid solution at a relatively high temperature is geologically plausible. A previous experimental study demonstrated that gold ions were readily reduced and deposited as nanoparticles at the pyrite-water interface 21 , hence the gold nanoparticles could also be included in pyrite during crystallization (Fig. 4a).…”

Section: Discussionmentioning

confidence: 92%

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Hyperenrichment of gold in pyrite induced by solid-state transportation

Huang

Zhu

et al. 2022

Commun Earth Environ

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The hyperenrichment of gold is critical for the formation of high-grade gold deposits in orogenic systems, where gold enrichment can reach several percent. However, many details on the nature of the hyperenrichment mechanism remain unclear. Here we show a “self-purification” model that could explain the hyperenrichment of gold from nanoparticles to veinlets in deformed pyrite. The three-dimensional spatial relationship and coexistence of gold nanoparticles and veinlets indicate a direct transformation from the former to the latter in solid-state. Theoretical evaluation reveals that this transformation involves a thermodynamically favorable self-purification process. We thus propose that deformation/thermo drives the transport of gold nanoparticles towards veinlets in pyrite through atomic diffusion. This deformation/thermo-driven model is applicable to any deformed nano-gold-bearing pyrite and explains how solid-state transport can effectively concentrate gold to a very high grade. Similar mechanisms may have broad implications in both ore-forming and beneficiation processes.

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Section: Methodssupporting

confidence: 56%

Section: Discussionmentioning

confidence: 92%

Hyperenrichment of gold in pyrite induced by solid-state transportation

Huang

Zhu

et al. 2022

Commun Earth Environ

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“…The simplified Hubbard U correction (GGA+U) method (Dudarev et al 1998) was employed to describe the 3d electrons of Fe element. The parameter U-J= 1.6 eV was employed, and the feasibility of such a parameter was confirmed by previous studies on pyritic systems (Zhang et al 2012;Xian et al 2019bXian et al , 2019aXian et al , 2021.…”

Section: Density Functional Theory Calculationsmentioning

confidence: 66%

Evaluating the physicochemical conditions for gold occurrences in pyrite

Huang

Zhu

et al. 2023

American Mineralogist

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While noble metals often occur as minor components in host minerals in various ore deposits, little theoretical assessment exists to predict the occurrence of these metals. Here, we probe the fundamental controls responsible for the occurrence of trace elements in host minerals through first-principles calculations. We apply the theoretical model to understanding the debated issues concerning the occurrence of gold (Au) in pyrite, in which the valence of Au is ascribed to either This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.The published version is subject to change. Cite as Authors (Year) Title. American Mineralogist, in press.

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“…3c). Therefore, the oxidation rate of microscopic pyrite {111} facets is greater than that of {100} facets, which is caused by the difference in surface properties between the {100} and {111} facets (Zhu et al, 2018;Xian et al, 2019). Regardless of grain size, the exposed crystal facet controls the reactivity of the framboidal pyrite microcrystals.…”

Section: Resultsmentioning

confidence: 99%

Morphology dominated rapid oxidation of framboidal pyrite

Du¹,

Huang²,

Wu³

et al. 2021

Geochem. Persp. Let.

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The rapid oxidation of framboidal pyrite is conventionally attributed to its fine grain size. However, the effect of the crystal facets of the microcrystals in the framboids on the oxidation process has been overlooked. We synthesised pyrite monocrystals of microscopic size with both {100} and {111} facets, which are two major forms of framboidal pyrite crystals, in order to examine the oxidation behaviour of pyrite framboids. The results showed that the oxidation rate of microcrystals with a greater proportion of {111} facets was approximately 2 times higher than that of those with a greater proportion of {100} facets although the latter's size was smaller. Such a difference makes framboidal pyrite with {111} facets more sensitive to oxidative weathering in geochemical cycles than other forms of pyrite. These findings emphasise the role of crystal anisotropy in controlling the oxidation of framboidal pyrite, thereby suggesting that the shape controlled oxidation of pyrite is a potential indicator of the local redox conditions of the palaeoenvironment where it occurred.

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Crystal habit-directed gold deposition on pyrite: Surface chemical interpretation of the pyrite morphology indicative of gold enrichment

Cited by 35 publications

References 55 publications

Hyperenrichment of gold in pyrite induced by solid-state transportation

Hyperenrichment of gold in pyrite induced by solid-state transportation

Evaluating the physicochemical conditions for gold occurrences in pyrite

Morphology dominated rapid oxidation of framboidal pyrite

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