Hydrothermal Deposits Research Articles

Ru Nanoparticle Assemblies Modified with Single Mo Atoms for Hydrogen Evolution Reactions in Seawater Electrocatalysis

Ru-based catalysts manifest unparalleled hydrogen evolution reaction (HER) performance, but the hydrolysis of Ru species and the accumulation of corresponding reaction intermediates greatly limit HER activity and stability. Herein, Ru nanoparticle assemblies modified with single Mo atoms and supported on N-incorporated graphene (referred to as MoRu-NG) are compounded via hydrothermal and chemical vapor deposition (CVD) methods. The incorporation of single Mo atoms into Ru lattices modifies the local atomic milieu around Ru centers, significantly improving HER catalytic behavior and stability. More specifically, MoRu-NG achieves overpotentials of 53 mV and 28 mV at 10 mA cm−2, with exceptional stability in acidic and alkaline seawater solutions, respectively. In MoRu-NG, Ru atoms have a special electronic structure and thus possess optimal hydrogen adsorption energy, which indicates that excellent HER activity mainly hinges upon Ru centers. To be specific, the d-electron orbitals of Ru atoms are close to half full, giving Ru atoms moderate bond energy for the assimilation and release of hydrogen, which is beneficial for the conversion of reaction intermediates. Moreover, the incorporation of single Mo atoms facilitates the formation of O and O’-bidentate ligands, significantly enhancing the structural stability of MoRu-NG in universal-pH seawater electrolysis. This work advances a feasible construction method of hexagonal octahedral configuration (Ru-O-Mo-N-C) and provides a route to synthesize an efficient and stable catalyst for electrocatalytic HER in universal-pH seawater.

Geological Characteristics and Preliminary Genesis Exploration of the Sakay Gold Deposit in Vientiane, Laos

The Sakay gold deposit in Vientiane, Laos, is located in the Indochina landmass of the southeastern segment of the Tethys orogenic belt, specifically within the Vientiane-Pakse micro-landmass and the Vientiane-Pakse metallogenic belt. This area is regionally significant for the concentration of minerals such as gold, copper, and tin. The host rocks of the deposit are intermediate volcanic lavas and volcanic tuffs, occurring in near-east-west brittle shear structural fractures through hydrothermal filling and metasomatism. The ore exhibits granular texture, subhedral texture, porphyritic texture, and oriented polycrystalline texture, with structural features such as disseminated, vein-like, and cataclastic breccia. The main ore minerals are pyrite, sphalerite, galena, and chalcopyrite, while the gangue minerals are primarily quartz, calcite, and dolomite. Gold is mainly present as included gold or fissure gold within the crystal lattices and microfractures of minerals such as pyrite and sphalerite. Based on mineral assemblages and generation timing, the mineralization can be divided into three stages: arsenopyrite-pyrite-dolomite-quartz (I), sphalerite-galena-chalcopyrite-calcite (II), and siderite (III), with the latter stages often overlaying the former, showing evident cross-cutting and metasomatic phenomena. The surrounding rocks in the mining area are altered, mainly showing silicification, carbonatization, limonitization, sericitization, and chloritization. Preliminary studies suggest that this deposit is a low-temperature hydrothermal gold deposit within a brittle shear zone.

Flotation of a mineralized structure to decrease arsenic content in gold concentrate

Arsenic is a penalty element in flotation concentrates, thus decreasing their quality. Consequently, the present investigation is developed with the objective of carrying out the flotation of a mineralized structure to reduce the content of arsenic “As” in the gold concentrate “Au”. For this purpose, sampling was carried out in a vetiform hydrothermal deposit taking 2 kg for Au-As chemical and mineralogical analysis and two flotation tests in a Rougher stage with the same entry conditions, i.e. Au grade equal to 11.46 g/t and As 1.81%. The results indicate that in test 1 the As content in the concentrate was 4.57%, while in test 2 the As grade in the concentrate was 4.86%, considering that in the latter, in addition to the reagents used in test 1, copper sulfate was applied as an activator, where no sulfide depression was evidenced. Finally, it is concluded that with the experimentation developed, the mineral presented a positive response to the flotation process, achieving the expected result with trial 1, also taking into account the dosage of the reagents used.

Modification of TiO2 template with In2S3 for quasi-epitaxial growth of Sb2S3 thin film solar cells

Abstract Thin film solar cells based on the wide band gap absorber antimony sulfide (Sb2S3) have great application potential and prospect. Typical Sb2S3 thin-film solar cells usually use a low-cost solution method (such as hydrothermal deposition) to prepare the light-absorbing material, and use a toxic CdS film with a narrow band gap (about 2.4 eV) as the electron transport layer (ETL). TiO2, a non-toxic ETL alternative with a wide band gap (3.1–3.4 eV), fulfills the photoelectric needs of the ETL. But when the TiO2 is used as a template for Sb2S3 deposition, it shows an island of uneven growth. Herein, an ion layer adsorption and reaction method was used to modify the surface of TiO2 with an ultra-thin layer of In2S3, thereby improving the nucleation and growth characteristics of Sb2S3 during hydrothermal deposition. In this way, the Sb2S3 film forms a compact and specular state on the TiO2 surface similar to that on the CdS surface, realizing the quasi-epitaxial growth of the Sb2S3 film, which provides a new solution for efficient and environmentally friendly solar cells.

Biogeochemical sulfide mineralization in the volcanic-hosted Tongguan hydrothermal field, southern Mid-Atlantic Ridge

Biogeochemical mineralization is increasingly recognized as a significant factor in the formation of submarine hydrothermal sulfide deposits. While several mechanisms by which hydrothermal organisms may facilitate metal deposition have been documented in many seafloor hydrothermal deposits, the potential involvement of biogenic processes in the mineralization of hydrothermal deposits in the southern Mid-Atlantic Ridge (SMAR) has been largely overlooked until now. In this study, we investigate sulfide chimney sample from the volcanic-hosted Tongguan hydrothermal field on the SMAR and present several lines of evidence for biogeochemical mineralization. Mineralogical analysis infers four types of biogenic pyrite and chalcopyrite structures: macrobiotic-related tube structures, microbial-related quasi-stromatolite, quasi-oncolite and globular structures. These biogenic structures exhibit selective enrichment of elements such as Mn, Pb, and Cu in biogenic pyrite compared to abiotic pyrite. In-situ sulfur isotope studies indicate that biogenic minerals possess lower δ34S values than abiotic minerals. We identified three biomineralization mechanisms: an “active” mineralization process mediated by macro-organism, a “passive” mineralization process associated with microbial mats, and a microbial assimilatory sulfate reduction process. Our research suggests that the role of biogenic processes in SMAR hydrothermal mineralization should be given further consideration.

Titanite and allanite as a record of multistage co-mobility of Ti-REE-Nb-As during metamorphism in the Central Alps

Abstract The high field strength elements (HFSE) Ti, Nb, and rare earth elements (REE) are commonly regarded as immobile during hydrothermal activity and metamorphism, making them important tracers of geological processes. Here, we report a Ti-REE-Nb-As mineralization recently discovered in quartz, feldspar, muscovite ± biotite, fluorapatite, hematite, epidote, and dravite-schorl veins hosted in quartz ± feldspar ± muscovite ± biotite gneisses from the Monte Leone nappe (Switzerland/Italy). The veins formed during prograde metamorphism and were boudinaged and/or folded during peak metamorphism under lower amphibolite facies. The mineralization consists of megacrysts (≫2 cm) of allanite-(Ce) and Nb-REE-rich titanite-(I). Titanite-(I) displays prominent primary oscillatory- and sector-zonings in Y+REE and Nb. Allanite-(Ce) and titanite are also present as metamorphic minerals disseminated in the host-rock. The vein-hosted megacrysts and their host rocks have identical Nd isotope systematics, indicating that the HFSE mineralization results from small-scale remobilization of host-rock components. Localized, fluid-assisted dissolution of vein-hosted allanite-(Ce), epidote, and dravite-schorl during retrograde alpine deuteric alteration resulted in cavities lined with chlorite, muscovite, hematite, and diverse REE minerals. The same fluids caused titanite-(I) to break down into a porous assemblage of acicular niobian rutile with lamellae of crichtonite-group minerals and/or hematite and a suite of REE-Nb-Ti micro-minerals. A few titanite (titanite-II) crystals preserve an intermediate stage of the dissolution-reprecipitation process. Unlike titanite-(I), they display a patchwork-like micro-texture (100 μm sized subgrains with inhomogeneous Nb concentrations); they host lamellae of crichtonite-group minerals within cleavage planes of the parent titanite, as well as secondary Y+Nb+REE oxides and calcite along subgrain boundaries. The occurrence of calcite indicates that CO2-enriched fluids promoted the destabilization of titanite-(I). Highly localized fluid flow accounts for the common occurrence of fresh and altered allanite-(Ce) and titanite in close proximity. The HFSE-enriched veins reveal a complex history of mobility of minor elements (Ti, Nb, REE, As ± B, Be) together with major components (Si, Al, K, Na, Fe) from the host rock, resulting in their early (prograde) concentration within the veins, and their remobilization upon the action of oxidized CO2-bearing fluids during retrograde metamorphism. In general, crystallization of enriched phases during prograde metamorphism may be an important step in determining the fertility of a source rock for hydrothermal HFSE deposits.

Mineral Chemistry and Iron Isotope Characteristics of Magnetites in Pertek Fe-Skarn Deposit (Türkiye)

This study investigates the mineral chemistry and iron isotope composition of the Pertek Fe-skarn deposit in the Eastern Taurides, Turkey, to elucidate skarn formation and ore genesis through chemical and isotopic parameters. The deposit consists of substantial and dispersed magnetite ores formed by the intrusion of a dioritic suite into marbles. Mineral assemblages, including hematite, goethite, andradite garnet, hedenbergite pyroxene, calcite, and quartz, exhibit compositional variations at different depths within the ore body. Magnetite is commonly associated with hematite, goethite, garnet, pyroxene, calcite, and quartz. Extensive LA–ICP–MS analysis of magnetite chemistry reveals elevated trace element concentrations of titanium (Ti), aluminum (Al), vanadium (V), and magnesium (Mg), distinguishing Pertek magnetite from low-temperature hydrothermal deposits. The enrichment of Ti (>300 ppm) and V (>200 ppm), along with the presence of Al and Mg, suggests formation from high-temperature hydrothermal fluids exceeding 300 °C. Discriminant diagrams, such as Al+Mn versus Ti+V, classify Pertek magnetite within the skarn deposit domain, affirming its medium- to high-temperature hydrothermal origin (200–500 °C), characteristic of skarn-type deposits. Magnetite thermometry calculations yield an average formation temperature of 414.53 °C. Geochemical classification diagrams, including Ni/(Cr+Mn) versus Ti+V and TiO2-Al2O3-MgO+MnO, further support the skarn-type genesis of the deposit, distinguishing Pertek magnetite from other iron oxide deposits. The Fe-skarn ore samples display low total REE concentrations, variable Eu anomalies, enrichment in LREEs, and depletion in HREEs, consistent with fluid–rock interactions in a magmatic–hydrothermal system. The δ56Fe values of magnetite range from 0.272‰ to 0.361‰, while the calculated δ56Fe_aq values (0.479‰ to 0.568‰) suggest a magmatic–hydrothermal origin. The δ57Fe values (0.419‰ to 0.530‰) and the calculated 103lnβ value of 0.006397 indicate re-equilibration of the magmatic–hydrothermal fluid during ore formation.

Enhanced stability and catalytic activity of subnanometric platinum cluster by surface doping of zirconium in CeO2

Enhanced stability and catalytic activity of subnanometric platinum cluster by surface doping of zirconium in CeO2

Hydrothermal Deposition of Metal Sulfide Heterojunction Thin Films for Photoelectrochemical Water Splitting.

Metal sulfides represent a broad class of materials with considerable potential for applications in photovoltaic devices and energy technologies. However, the low-temperature synthesis of high-quality metal sulfide thin films remains a formidable challenge. Hydrothermal deposition, known for its versatility and cost-efficiency, has been successfully employed to synthesize a variety of materials, yet its application in the preparation of metal sulfide thin films has not been extensively explored. In this study, we develop a hydrothermal deposition method to synthesize five distinct types of metal sulfide thin films, each with well-defined phases and compositions. As a case study, CdS/Bi2S3 thin film was selected and evaluated as photoanode for photoelectrochemical water splitting. Through O-doping and the modification of an ultrathin MoO3 overlayer, the photocurrent density was significantly enhanced from 1.52 mA cm-2 (CdS/Bi2S3) to 2.27 mA cm-2 (CdS/O-Bi2S3), and further to 2.84 mA cm-2 (CdS/O-Bi2S3/MoO3) at 1.23 V vs. reversible hydrogen electrode under AM 1.5G illumination. This methodology is expected to advance both fundamental and applied research on metal sulfides.

Tailoring Presynthesized Amorphous Sb2S3 Particles Enables High-Efficiency Pure Antimony Sulfide Solar Cells.

At present, hydrothermal deposition techniques are unique to attain high-efficiency antimony sulfide (Sb2S3) solar cells. It is very common that during the mixing of antimony and sulfur sources before the hydrothermal reaction, the solution quickly changes from colorless to yellow due to the formation of amorphous Sb2S3 particles. However, the effect of presynthesized Sb2S3 particles on the deposition kinetics of Sb2S3 absorber layers and the device performance is completely unknown. To pave the pathway toward high-efficiency Sb2S3 solar cells, it is urgent to disclose the mechanism behind such a phenomenon. By accurately controlling the number and size of presynthesized Sb2S3 particles in the hydrothermal precursor solution, it was found that the suspended Sb2S3 particles act as growth centers, facilitating the orderly deposition of the Sb2S3 film on the substrate, which in turn affects the film's thickness, grain size, densification, and crystallinity. Based on this finding, the Sb2S3 solar cell with an efficiency of 7.29% is achieved, which is currently one of the highest fundamental efficiency obtained for Sb2S3 prepared by hydrothermal methods without doping. This study lays the groundwork for investigating the growth mechanism of Sb2S3 produced by hydrothermal deposition techniques and provides guidelines for the preparation of high-efficiency Sb2S3 solar cells.

From Source to Sink: U-Pb Geochronology and Lithochemistry Unraveling the Missing Link Between Mesoarchean Anatexis and Magmatism in the Carajás Province, Brazil

The connection between crustal anatexis and magmatism is key to understanding the mechanisms that drive the evolution of the continental crust. Isotope geology and lithochemistry are important tools for reconstructing links between these processes, as field evidence of their connection is often obliterated by deformation in high-grade terrains. Thus, this study proposes new insights into the connection between the Mesoarchean regional metamorphism, crustal anatexis, and plutonism in the northern sector of the Carajás Province (i.e., Carajás Domain), in the Amazonian Craton, around 2.89 to 2.83 Ga. The widespread crustal anatexis in the Carajás Domain involved the water-fluxed melting of banded orthogneisses of the Xingu Complex and Xicrim-Cateté Orthogranulite (crystallization age at ca. 3.06–2.93 Ga), producing metatexites and diatexites with stromatic, net, schollen, and schlieren morphologies and coeval syntectonic leucosomes with composition similar to tonalites, trondhjemites, and granites. These leucosomes yielded crystallization ages of 2853 ± 5 Ma (MSWD: 0.61), 2862 ± 13 Ma (MSWD: 0.1), and 2867 ± 7 Ma (MSWD: 1.3). Their lithochemical data are similar to those of several diachronous Mesoarchean granitoids of the Carajás Domain in terms of major, minor, and trace elements and magmatic affinity. In addition, binary log–log vector diagrams (e.g., La vs. Yb; Rb vs. Yb), Sr/Y vs. Y, and Eu/Eu* vs. Yb plots indicate that plagioclase fractionation preceded melt extraction, establishing evolving source-to-sink trends between leucosomes and granites. These results show that the interplay between high-grade metamorphism, crustal anatexis, and magmatism may have shaped the evolution of the Mesoarchean continental crust in the Carajás Province, developing a petrotectonic assemblage associated with collisional orogens. The Mesoarchean geodynamic setting played a critical role in the development of coeval ca. 2.89 Ga magmatic–hydrothermal copper deposits in the Carajás Province, as well as Neoarchean world-class iron oxide–copper–gold deposits linked to post-orogenic extensional rebound.

The Structure and Near-Bottom Magnetic Anomaly Characteristics of the Daxi Vent Field on the Carlsberg Ridge, Northwestern Indian Ocean

Seafloor hydrothermal vent areas are potential sources of polymetallic sulfide deposits and exhibit distinct mineralization structures under different tectonic settings. The Daxi Vent Field (DVF), located on the Carlsberg Ridge in the northwestern Indian Ocean, represents a basalt-hosted hydrothermal system. To investigate the alteration zone structure of the DVF, high-resolution near-bottom bathymetric and magnetic data were collected during the Chinese DY57 expedition in 2019. Based on the results of magnetic anomaly data processing, including reduction to a level surface and Euler deconvolution, the location and depth of the magnetic sources were identified. In addition, two 2.5D magnetic forward models crossing the active and inactive vent fields were constructed. The results indicate that the range of the alteration zone in the active vent at the DVF extends up to 120 m in width and 80 m in depth, while the hydrothermal deposit at the extinct vent on the northeastern side extends up to 220 m along the ridge axis with a thickness of 30 m.

Potential and Harmful Effects of Titanium Dioxide Nanoparticle on Health: A Brief Note

Titanium dioxide nanoparticles (TiO<sub>2</sub> NPs) are formed in vast amounts worldwide for usage in several applications. They possess excellent photocatalytic properties, high chemical stability, and a wide bandgap, making them highly effective in environmental remediation and solar energy conversion. TiO<sub>2</sub> nanoparticles exhibit biocompatibility, allowing their utilization in biomedical uses, such as molecular imaging, drug delivery, and tissue engineering. Chemical methods, such as hydrothermal, sol-gel, and chemical vapor deposition, provide versatility in controlling nanoparticle size, morphology, and crystallinity. They offer relatively lower production costs, scalability, and the ability to incorporate dopants or functionalize the nanoparticle surface. Their small size and large surface area- to-volume ratio enable enhanced reactivity and surface functionality, facilitating their incorporation into composite materials and surface coatings for improved performance. Regarding the potential toxicity of TiO<sub>2</sub> nanoparticles, the bulk form of TiO<sub>2</sub> is considered safe for human consumption, but the reduced size of nanoparticles raises concerns about their potential adverse effects. TiO<sub>2</sub> nanoparticles strongly depend on factors, such as particle size, surface modifications, exposure route, and duration. Therefore, continued research is essential to gain a comprehensive understanding of the toxicity mechanisms and develop strategies to mitigate any potential adverse effects, ensuring the safe and responsible utilization of TiO<sub>2</sub> nanoparticles in different fields.

Ore geology, mineralogy and geochemistry of a fault-controlled hydrothermal clay-Li deposit hosted by Precambrian metasedimentary rocks in south China

Ore geology, mineralogy and geochemistry of a fault-controlled hydrothermal clay-Li deposit hosted by Precambrian metasedimentary rocks in south China

Polymetallic Te-rich melts contribute to efficient enrichment and precipitation of Au in hydrothermal ore deposits

Polymetallic Te-rich melts contribute to efficient enrichment and precipitation of Au in hydrothermal ore deposits

Applications and implications of monitoring surface hydrothermal deposits at Lastarria Volcano, Chile, using multispectral satellite data and cloud computing

Applications and implications of monitoring surface hydrothermal deposits at Lastarria Volcano, Chile, using multispectral satellite data and cloud computing

Fe/Ru synthesized by hydrothermal deposition on hyper-crosslinked polystyrene as promising Fischer-Tropsch catalyst

Fe/Ru synthesized by hydrothermal deposition on hyper-crosslinked polystyrene as promising Fischer-Tropsch catalyst

A Review of Carboniferous-Triassic Tectonic-Magmatic Evolution of Luang Prabang–Loei Metallogenic Belt in Laos and Thailand and Implications for Gold–Copper Mineralization

The Luang Prabang (Laos)–Loei (Thailand) metallogenic belt is located on the northwestern margin of the Indochina Block. It is one of the most important gold–copper metallogenic belts in Southeast Asia. This region underwent tectonic and magmatic evolution in the late Paleozoic-Mesozoic period within the Paleo-Tethys realm, resulting in complex metallogenic processes. Consequently, epithermal Au-Ag, porphyry-skarn Au-Cu, and hydrothermal vein-type gold deposits were formed. However, the genetic type of the vein-type gold deposits is still not fully understood. The relationship between the three types of gold deposits and the regional tectonic evolution has not been summarized up until today. We summarize the previous mineralization characteristics and exploration data of commonly known deposits and combine them with new evidence and ore deposit insights from our recent studies on the source and evolution of ore-forming fluids in the region. We confirm that the hydrothermal vein-type gold deposits in the belt are typical orogenic gold deposits. Based on previous regional tectonic-magmatic-metallogenic studies, metallogenic characteristics, and temporal and spatial distribution of three types of typical gold–copper deposits in the belt, we synthesize and establish a regional metallogenic model related to the subduction-closure of the Paleo-Tethys Ocean and subsequent continental–continental collision process, resulting in the formation of epithermal Au-Ag during the late Permian-early Triassic subduction, porphyry-skarn Au-Cu in the early–middle Triassic period during the closure of the ocean, and orogenic Au during the late Triassic collision. Since there are few reports on the geochemical characteristics of gold–copper deposits and their related magmatic rocks, the potential for gold–copper mineralization and their links to the magmatic rocks in the belt still needs further study.

Enhanced Photoelectrochemical Performance by Constructing CdS/CdSe Heterojunction Structure

The growing need for sustainable energy development has become a critical issue due to worsening environmental pollution and climate change. Among the various technologies, the photoelectrochemical technology has been recognized as one of the essential approaches for advancing sustainable energy production. Out of the semiconductor materials used in PEC systems, cadmium sulfide (CdS) and cadmium selenide (CdSe) have been widely studied as promising candidates due to their advantageous properties. CdS, with a bandgap of 2.4 eV and high photoactivity, and CdSe, with a narrower bandgap of 1.9 eV and excellent light absorption characteristics, offer complementary advantages. In this study, we synthesized the CdS and CdSe materials via hydrothermal and chemical bath deposition methods, respectively, to fabricate a CdS/CdSe heterojunction photoanode system. The heterojunction CdS/CdSe photoanode formed a type-II structure, which facilitated efficient charge separation and transfer. Moreover, the CdS/CdSe photoanode exhibited high light absorption properties with very low charge transfer resistance, attributed to the role of CdS particles beneath CdSe as an electron transfer layer and the porous structure of the composite material. As a result, the CdS/CdSe photoanode achieved high photocurrent density of 4.51 mA·cm-2 comparing to their individual cases, representing a 78% improvement in PEC performance compared to the only CdSe photoanode case.

Role of impurities in the semiconducting properties of natural pyrite: Implications for the electrochemical accumulation of visible gold and formation of hydrothermal gold deposits

Abstract Pyrite (FeS2), the most abundant sulfide mineral on Earth, typically contains a host of minor and trace elements, including As, Co, Ni, and Au. It is an important semiconductor with unique structural properties markedly influenced by elemental impurities. However, whether the change in semiconducting properties of natural pyrite is caused by the type and concentration of trace elements or by a non-stoichiometry-related doping mechanism remains uncertain. Moreover, the effect of semiconducting properties on the enrichment mechanism of Au has not been well addressed. Here, we investigate microscopic pyrite crystals from the Heilangou gold field (HGF) in the eastern Jiaodong Peninsula using field emission scanning electron microscopy (SEM), electron probe microanalysis (EPMA), in situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), potential-Seebeck microprobe (PSM), and thermoelectric measurements. The results demonstrate that pyrite grains show either p- or n-type conductivity depending on chemical compositions. Pyrite enriched in As, which typically substitutes for S in the crystal structure, tends to be p-type with a positive Seebeck coefficient, whereas pyrite crystals enriched in Co, Ni, Cu, and Zn, as well as those depleted in As, are typically n-type. Moreover, As shows the strongest influence on the semiconducting properties of natural pyrite crystals and a strong positive correlation with Au. We observed that visible Au grains are preferentially accumulated on individual domains of sulfides (e.g., As-rich pyrite) that act as cathodes, suggesting that electrical p-n junctions in sulfides drive electrochemical reactions with ore-forming fluids, resulting in the deposition of visible Au. The electrochemical precipitation mechanism of Au may account for the formation of other types of hydrothermal Au deposits.