A track record of Au–Ag nanomelt generation during fluid-mineral interactions

Domínguez-Carretero, Diego; Gonzáléz-Jiménez, José María; Proenza, Joaquín A.; Villanova-de-Benavent, Cristina; Llovet, Xavier; García-Casco, Antonio

doi:10.1038/s41598-023-35066-y

Cited by 4 publications

(1 citation statement)

References 29 publications

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“…These authors stressed that compared to the original pyrite used in their experiments, the surface area and pore volume of the roasted products, especially the meso-and micro-porosity, increased by one order of magnitude when roasting was carried out at 500-600 • C. But the surface area and porosity significantly decreased when the temperature increased up to 700 • C, meaning that particle sintering occurred during roasting. Natural observations and heating experiments of pyrite-type matrices suggest that such sintering of precious metal particles may be the result of both solid-state diffusion and Au-bearing nanomelt migration and accumulation when high-porosity channels are produced during desulfurization-oxidation of sulfides experiencing thermal input [62][63][64][65]. In the case of Au, migration and coarsening aided by nanomelt formation should be favored by the lower melting point of metal nanoparticles than their bulk counterparts (e.g., Au particles of <4 nm melt at 370 • C instead of 1064 • C of the bulk; Ref.…”

Section: Genesis Of the "Morrongos" During Pyrite Roasting And Later ...mentioning

confidence: 99%

Unveiling High-Tech Metals in Roasted Pyrite Wastes from the Iberian Pyrite Belt, SW Spain

et al. 2023

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The Iberian Pyrite Belt (IPB), in the southwestern Iberian Peninsula, is a large metallogenic province exploited since ancient times. As a result of historical and current mining activity, a vast volume of metallic mineral waste, mainly derived from the processing of pyrite, is still in situ and polluting the environment. A specific mine waste residuum locally known in the area as “morrongos”, which was produced during pyrite roasting mainly in the 19th century, is evaluated here in order to unravel untapped resources of high-tech metals commonly used in high-tech devices. Applying a combination of whole-rock geochemical (ICP-AES, ICPMS, FA-AAS) and single-grain mineralogical techniques (EPMA, LA-ICP-MS, FESEM, and FIB-HRTEM) on the “morrongos”, we unhide the still-present remarkable concentrations of Au, Ag, Pb, Zn, and Cu in them. The mineralogical expressions for these economic metals include oxides (hematite, magnetite, and hercynite), arsenates, sulfates of the jarosite group, native metals, and, to a lesser extent, relictic sulfides. This first-ever estimation of these economic metals in this type of residue allows their revalorization, highlighting them as suitable sources for the exploitation and recovery of metals necessary for the clean energy transition.

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Section: Genesis Of the "Morrongos" During Pyrite Roasting And Later ...mentioning

confidence: 99%

Unveiling High-Tech Metals in Roasted Pyrite Wastes from the Iberian Pyrite Belt, SW Spain

et al. 2023

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Nanomaterial accumulation in boiling brines enhances epithermal bonanzas

Cano,

González-Jiménez,

Camprubí

et al. 2023

Sci Rep

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Epithermal bonanza-type ores, characterized by weight-percent contents of e.g., gold and silver in a few mm to cm, are generated by mixtures of magmatic-derived hydrothermal brines and external fluids (e.g., meteoric) that transport a variety of metals to the site of deposition. However, the low solubilities of precious metals in hydrothermal fluids cannot justify the high concentrations necessary to produce such type of hyper-enriched metal ore. Here we show that boiling metal-bearing brines can produce, aggregate, and accumulate metal nanomaterials, ultimately leading to focused gold + silver ± copper over-enrichments. We found direct nano-scale evidence of nanoparticulate gold- and/or silver-bearing ores formed via nonclassical growth (i.e., nanomaterial attachment) during boiling in an intermediate-sulfidation epithermal bonanza. The documented processes may explain the generation of bonanzas in metal-rich brines from a range of mineral deposit types.

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Behavior of Gold Nanoparticles at the Interphase Boundary of Quartz–Selenide Copper and Iron at a Temperature of 450 °C and Different Selenium Activity

Akimov,

Babkin,

Belozerova

2024

Russian Geology and Geophysics

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—In this work, based on structural and phase analysis data, we consider the behavior of Au nanoparticles (NP) during the formation of interphase boundaries between quartz and copper and iron selenides upon annealing at 450 °C and different selenium activities: lgfSe2=−2.4 with a melted selenium buffer and lgfSe2=−3.15 according to the indications of the indicator mineral mixture γ–Fe1–xSe and δ–Fe1–xSe. In two series of experiments, contrasting textural features (nano- and microstates) of the initial metal phases were used, which made it possible to construct 2D and 3D models of interphase boundaries. In the first case, thin layers of gold NPs (~30 nm thick), iron (~50 nm thick), and copper (~50 nm thick) were deposited onto quartz crystals less than 40 μm in size by magnetron sputtering, i.e., all metals were in a nanosized state. In the second case, iron, copper, and selenium (in eskebornite stoichiometry – CuFeSe2) were introduced into the system in the form of micron-sized powder materials (1–10 microns). Gold still remained in the form of NPs on the quartz surface. The thermal annealing products were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses, and X-ray photoelectron spectroscopy (XPS). The study showed that, regardless of the activity of selenium, annealing of Au NPs leads to partial enlargement of particles (up to submicron sizes) based on the self-assembly mechanism (the size distribution of Au particles corresponds to a lognormal law with a maximum shifted towards smaller sizes), and gold remains in the metallic state. The 2D model of the interphase boundary is a mineral mixture of copper selenides (Cu2Se), iron (γ–Fe1–xSe) and islands of submicron gold particles formed on the surface of quartz. The 3D model of the interphase boundary is characterized by the fact that Au particles are concentrated mainly in eskebornite, and not on the quartz surface. Moreover, NPs are localized in the pores of mesoporous eskebornite, and submicron particles with a size of ~ 200 nm or more are displaced to the surface of eskebornite particles. Based on the data obtained, typomorphic features of the presence of Au NPs in the ore-forming processes of the formation and development of gold ore deposits are formulated.

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A track record of Au–Ag nanomelt generation during fluid-mineral interactions

Cited by 4 publications

References 29 publications

Unveiling High-Tech Metals in Roasted Pyrite Wastes from the Iberian Pyrite Belt, SW Spain

Unveiling High-Tech Metals in Roasted Pyrite Wastes from the Iberian Pyrite Belt, SW Spain

Nanomaterial accumulation in boiling brines enhances epithermal bonanzas

Behavior of Gold Nanoparticles at the Interphase Boundary of Quartz–Selenide Copper and Iron at a Temperature of 450 °C and Different Selenium Activity

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