Au Deposits Research Articles

Characteristics, geochronology, and formation conditions of W mineralization and its relationship with Au mineralization in the Zhaishang gold deposit, West Qinling Orogen, China

The West Qinling Orogen is an important Au-W ore belt; however, the spatio-temporal and genetic relationships of W and Au ores remain unclear. This study takes the Zhaishang deposit, one of the largest Au-W deposits in the West Qinling Orogen, to trace their connections. The geological observation reveals that high-grade W ores are commonly characterized by extensional hydrothermal veins. In contrast, high-grade Au ores are hosted by breccia zones, which cut the W ore-controlling structures, even though the W and Au ores overlap locally. The mineral assemblages of W ores associated with carbonatization and silicification consist of scheelite and pyrite with few polymetallic sulfides, in contrast to the abundance of polymetallic sulfides and native gold in Au ores linked with silicification. Textural and in situ trace element analyses reveal that the scheelites show a decrease in Na, U, Mo, Nd, and calculated Eu anomaly values and an increase of Th concentrations and Ce anomaly values from early- to late-generation scheelites. This finding, in conjunction with mineral assemblages and previous thermodynamic modeling, suggests a decrease in salinity and oxygen fugacity (fO2) of the oxidized ore-forming fluids of W mineralization, as opposed to the reduced fluids of Au mineralization. The plots of scheelite at Zhaishang in the ternary LREE-MREE-HREE diagram are compatible with those of W deposits related to magmatic-hydrothermal fluids. In situ U-Pb dating of scheelite from W ores constrains the precise timing of W mineralization at ca. 227.9 ± 2.3 and 225.6 ± 3.0 Ma in a collisional orogenic setting. The unequivocal crosscutting relationship, contrasting mineral assemblages, and physiochemical conditions suggest that the W and Au mineralization at Zhaishang are due to two separate mineralization events. The identification of overlapped W and Au mineralization events at Zhaishang is crucial for guiding the regional exploration of W and Au deposits.

Investigation by simulation of the highest sensitivity interferometric pressure sensor at the end of a micro-structured optical fiber

One of the most prevalent techniques used in the construction of optical fiber-based pressure sensors is Fabry–Perot interferometry. This work presents a variety of interferometric sensors based on this feature. To achieve this, we used chemical etching (HF) to create conical cavities at the ends of the optical fibers single mode fiber (SMF) and graded index (GRIN) fiber, where the first gold (Au) deposition allows us to create half-mirrors. So the interface (core/Au) represents the first reflective surface. After filling each micro-cavity with a quantity of polydimethylsiloxane (PDMS) type polymer to form a flexible micro-lens, and proceeding to a second deposition of gold (Au), we got the second reflective surface (PDMS/Au). The sensor with the highest sensitivity to pressure and temperature, namely 0.065 nm/KPa and 0.24 nm/°C, was obtained for a micro-cavity length of 35 μm, a diameter of 60 μm, and a micro-lens thickness of 20 μm, respectively. Analysis and simulation were performed using COMSOL Multiphysics to develop the sensor.

Ore genesis of the Laguhe Au deposit, West Qinling, China: Evidence from sulfide geochemistry and machine learning

The precious metal Au has a wide range of utilization in various fields, and the Au deposits in China are hosted mostly within the West Qinling Orogen and Jiaodong Peninsula. The Laguhe deposit is a newly discovered medium–size Au deposit in the West Qinling Orogen. Previous studies focused mainly on the nature of Au mineralization in this deposit during different exploration stages, so its genesis and ore–forming physico–chemical conditions and processes remain enigmatic. Here, we present major and trace element analyses of Au–bearing pyrite and arsenopyrite from the Laguhe Au deposit, in combination with machine learning to explore its origin and ore–forming processes. The early and late stages of arsenopyrite show As contents of 40.69–46.22 wt% and 39.12–43.22 wt%, respectively, which constrain corresponding ore–forming temperatures at 320–370 °C and 270–340 °C, respectively. The sulfur fugacities in the two stages range from 10–13.2 to 10–8.4. The arsenopyrite has high Co and Ni contents of 0.02–0.28 wt% and 0.02–0.27 wt%, respectively, which suggest that a deep source mafic magmatic water participated in the Au mineralization. The Fe/(S + As) ratios in pyrite vary from 0.838 to 0.869, which indicate that the Laguhe deposit formed at a moderate to deep ore–forming depth (1.5–8.0 km). Most of the Co/Ni ratios (1–5) and the negative correlation (–0.47) between Fe and As contents in pyrite suggest that the ore–forming hydrothermal fluids in the Laguhe deposit were moderately acidic. Based on the heterogeneous Au contents and the lack of correlation between Fe and Au in pyrite and arsenopyrite, most of Au are suggested to likely exist as nanoparticles, with few as lattice Au in pyrite and arsenopyrite. Machine learning results based on the geochemistry of arsenopyrite and pyrite and geochemical features of arsenopyrite and pyrite classified the Laguhe deposit as a Carlin–like type Au deposit. The Au in the Laguhe deposit migrated mainly in the forms of Au(HS)2– and AuH3SiO4 in hydrothermal fluids, which then precipitated as a result of water–rock reaction, fluid immiscibility and fluid boiling at and around plutons and along faults.

Gold Nanoparticle‐Coated Bioceramics for Plasmonically Enhanced Molecule Detection via Surface‐Enhanced Raman Scattering

Herein, feasibility of plasmonically enhanced molecule detection via surface‐enhanced Raman scattering for ceramics that are commonly used as bone or tooth replacement materials is evaluated. Open cell foams of Bioglass 45S5, the commercial hydroxyapatite‐based product Bio‐Oss, and bioinert zirconia‐toughened‐alumina (ZTA) are coated with Au nanoparticles via colloidal deposition to introduce plasmonic effects. Depending on the pore size, gold‐functionalized plasmonic porous Bioglass shows effective Raman enhancement factor (eEF) up to , while depositing gold nanoparticles on Bio‐Oss and porous ZTA resulted in eEF of and respectively. The performance of the plasmonic porous bioceramics under simulated biological conditions is examined in situ in the biological medium fetal bovine serum (FBS) and during extended incubation in mineralizing simulated body fluid (SBF). Most notably, the plasmonic porous Bioglass still delivered an eEF around after 28 days of incubation in SBF, indicating promising stability in simulated biological conditions without significant difference in SBF bioactivity before and after Au deposition. Accordingly, the plasmonically enhanced porous bioceramics offer the possibility for real‐time and sensitive molecule detection at SBF and FBS conditions and can be further developed for sensing of specific biomarkers, for example, in the context of osseointegration of bone replacement materials.

Epitaxially Grown Silicon Nanowires with a Gold Molecular Adhesion Layer for Core/Shell Structures with Compact Mie and Plasmon Resonances.

Noble-metal plasmonic nanostructures have attracted much attention because they can support deep-subwavelength optical resonances, yet their performance tends to be limited by high Ohmic absorption losses. In comparison, high-index dielectric materials can support low-loss optical resonances but do not tend to yield the same subwavelength optical confinement. Here, we combine these two approaches and examine the dielectric-plasmonic resonances in dielectric/metal core/shell nanowires. Si nanowires were grown epitaxially from (111) substrates, and direct deposition of Au on these structures by physical vapor deposition yielded nonconformal Au islands. However, by introduction of a molecular adhesion layer prior to deposition, cylindrical Si/Au core/shell nanostructures with conformal metal shells were successfully fabricated. Examining these structures as optical cavities using both optical simulations and experimental extinction measurements, we found that the structures support Mie resonances with quality factors enhanced up to ∼30 times compared with pure dielectric structures and plasmon resonances with optical confinement enhanced up to ∼5 times compared with pure metallic structures. Interestingly, extinction spectra of both Mie and plasmon resonances yield Fano line shapes, whose manifestation can be attributed to the combination of high quality factor resonances, Mie-plasmon coupling, and phase delay of the background optical field. This work demonstrates a bottom-up synthetic method for the production of freestanding, cylindrically symmetric semiconductor/metal core/shell nanowires that enables the efficient trapping of light on deep-subwavelength length scales for varied applications in photonics and optoelectronics.

Structural controls on formation of the Xiayu vein-hosted Ag–Pb–Zn–Au orefield during intracontinental extension along the southern margin of the North China Craton

The Xiayu Ag–Pb–Zn–Au deposit, situated in the Early Cretaceous Xiong’er shan area on the southern edge of the North China Craton, comprises the Haopinggou, Shagou, Tieluping, and Houzhanggou deposits, making it the largest Ag producer in the southern North China Craton. Despite significant research efforts, the connection between extensional faults and vein–hosted Ag–Pb–Zn–Au deposits in this area is still not well understood. To address this issue, we introduce new structural data, fault–slip data analysis, and information on epithermal Ag–Pb–Zn–Au mineralization. Two separate paleo–stress inversion methods were applied to determine that the region was affected by two discrete stress fields: E–W transtension and NW–SE transtension. Our palaeostress reconstruction indicates that transtensional tectonics would have affected the emplacement of fault–fill veins (stage I) and extensional veins (stage II). Both types of geometric veins show two distinct stages of formation. The first stage (I) involves the development of quartz–pyrite within hydraulic breccia, transitioning into crack–seal laminated shear veins. These likely formed during a period of regional extension in an east–west direction. The second stage (II) features the deposition of undeformed quartz–sphalerite–galena within pre–existing dilational sites near newly formed normal faults or stage I veins. This second stage likely occurred during a regional extension in a northwest–southeast direction.

Review on the development of multi- and hyperspectral remote sensing technology for exploration of copper–gold deposits

Most Copper (Cu) and Gold (Au) deposits are accompanied by hydrothermal alteration, generally related to ore-forming hydrothermal fluids. Multispectral and hyper-spectral Remote Sensing (RS) technology is essential for Cu-Au mineral prospecting. This paper provides an overview of RS data and the research situation and development tendencies of RS exploration technologies related to Cu-Au deposits. Initially, RS geologists applied the Band Ratio (BR) and Principal Component Analysis (PCA) to extract hydroxyl and iron anomalies from Landsat RS data to characterize the hydrothermal alterations associated with Cu-Au deposits. In the era of advanced spaceborne thermal emission and reflection radiometry (ASTER), clay minerals, sulfate minerals, carbonate minerals, silica minerals, and iron minerals can be identified because of three Visible and near-infrared bands (VNIR), six shortwave infrared bands (SWIR), and five Thermal Infrared bands (TIR). Alteration of mineral assemblages can be carried out to map alteration zones, which are essential for calibrating Cu-Au alteration zones, such as the typical alteration zoning characteristics of Porphyry Copper Deposits (PCD). Because of its high spectral resolution, Satellite hyperspectral RS can quantitatively map surface alteration minerals to indicate the exploration of Cu-Au deposits. RS geologists have extensively researched matching libraries and field spectra for Alteration Mineral Mapping (AMM). However, subpixel mineral information caused by low spatial resolution and atmospheric factors has an unavoidable influence on satellite hyperspectral RS AMM, and it is essential to use low-altitude unmanned aerial vehicle (UAV) hyperspectral RS. UAV hyperspectral AMM combined with geochemistry and geophysics is a means of prospecting and exploring Cu-Au deposits.

Core-shell metallic nanotube arrays for highly sensitive surface-enhanced Raman scattering (SERS) detection

Here, we demonstrate the application of highly ordered, periodic Ag/Au core-shell triangle nanotube arrays as an ultrasensitive and low-cost surface-enhanced Raman scattering (SERS) substrate for the first time. The arrays of core-shell nanotube, with an outer diameter of 1.5 μm, were fabricated using top-down wafer-scale lithography followed by sequential sputter deposition of Ag and Au. The SERS activity of various combinations of core-shell structures was evaluated. It was found that Ag-core nanotubes overlaid with the Au-shell resulted in the highest Raman intensity, where the enhancement factor for R6G as a probe molecule is determined to be 1.38 × 107. Meanwhile, the limit of detections for R6G and ketoprofen analytes was evaluated to be 10−10 and 10−6 M, respectively. Linear correlations between the SERS signal intensities and logarithmical scale of both analytes in different concentrations were also established, ranging 10−4–10−10 and 10−2–10−6 M for R6G and ketoprofen, respectively. The Raman R6G peak intensity mapping suggests our metal nanotube arrays act as effective plasmonic hotspots and, thus, are useful for SERS sensing applications.

Rutile U-Pb dating reveals the Oligocene age of the Dashuigou Te-Bi deposit and a contemporaneity with regional alkaline magmatism in Sanjiang region

The Dashuigou deposit, located in the transitional zone between the Yangtze craton to the east and the Songpan-Ganze orogen to the west, is the world’s only known deposit where tellurium and bismuth are exploited as primary products. The Te-Bi orebodies mainly occur as the dolomite-tetradymite and Te-bearing pyrrhotite veins in Triassic low-grade metamorphic rocks. The ore minerals mainly consist of tetradymite, tsumoite, tellurobismuthite, pyrrhotite, and chalcopyrite. While mineralogy and geochemistry of the ores in the Dashuigou deposit have been well documented in the past decades, the age of the Te-Bi mineralization in the Dashuigou district is not well defined due to lack of both suitable dating mineral and chronometer, and thereby impedes further understanding on its ore genesis.Hydrothermal rutile coeval with tetradymite has been identified in this study from a high-grade dolomite-tetradymite vein in the Dashuigou deposit. This rutile is closely associated with tetradymite, tsumoite, Te-bearing pyrrhotite, and contains many tiny tetradymite inclusions. Here, we present the first in situ trace element compositions and U-Pb age of these rutile crystals using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). The rutile is enriched in V, Nb, Ta, Sn, and Cr, but has low contents of As, Sb, and W, indicating a magmatic origin. U-Pb dating on rutile demonstrates a well-constrained age of 32.4 ± 3 Ma, which is interpreted as the timing of Te-Bi mineralization for the Dashuigou deposit. This new age provides the first evidence suggesting that the Dashuigou deposit is contemporary with regional Eocene-Oligocene alkaline magmatism and related metallogenic event in Sanjiang region. Compared with the Beiya Te-Bi-bearing porphyry Cu-Au and Yao’an Au deposits in the alkaline magmatic belt, we propose that the Dashuigou Te-Bi deposit was likely product of a concealed alkaline magmatic-hydrothermal system. This study also demonstrates the rutile U-Pb geochronology being a powerful tool for dating unusual ore systems.

Middle Devonian Evandale porphyry Cu-Mo (Au) deposit, southwestern New Brunswick, Canada: Analysis of petrogenesis to potential as a source for distal intrusion-related epithermal gold mineralization

The 391.2 ± 3.2 Ma (U-Pb on zircon) Evandale Granodiorite of southwestern New Brunswick is quite a unique intrusive rock in the southern part of the northeastern Appalachians. This research examines the relationship between the porphyry Cu-Mo-(Au) and epithermal systems with Evandale Granodiorite and environs. This Middle Devonian multi-phase I-type granite intrudes along the northern boundary of the deformed Silurian sedimentary and mafic volcanic rocks of the Mascarene Basin. This granitoid is identified as an oxidized I-type system with adakitic geochemical signatures and associated porphyry Cu-Mo-(Au) mineralization, possibly linked to slab failure sourced from decompression melting of the lower crust caused by post-collisional uplift, similar to the Magaguadavic Granite to the southwest. The Evandale adakitic intrusion is divided into two phases that consist of (1) a calc-alkalic coarser phase ranging from medium- to coarse-grained, seriate to porphyritic granodiorite to monzogranite with metaluminous to peraluminous features, and (2) the later stage alkali-calcic fine-grained (to aplitic) locally porphyritic phase ranging from a monzogranite to syeno-granite with peraluminous characteristics. The primary mineralogy of the intrusive rocks consists of K-feldspar + albite + plagioclase + quartz + biotite + hornblende + apatite ± muscovite ± zircon, along with several alteration phases, such as biotite, chlorite, sericite, and calcite. Geochemical analyses (using INAA, ICP-MS, and XRF) indicate that both phases of the Evandale granodiorite show a high concentration of Cu (108 ppm) and Au (33 ppb) associated with the presence of pyrite, chalcopyrite, and arsenopyrite in the fine-grained dyke samples. Up to 6 ppm Mo was contained within the granitic phase, whereas lesser amounts of Mo were confined to the fine grained to aplite phases. Microprobe analyses of primary biotite as both phenocrysts and groundmass shows 0.55 avg. wt.% Cl and 0.21 avg. wt.% F, which are relatively concentrated compared to other high-grade porphyry deposits. Hydrothermally altered rocks, veins, and sulfides associated with the porphyritic suite result from buoyant magmatic-hydrothermal fluids from a deeper intrusion exsolving fluids (quenched porphyry related), depressurizing, and reacting with the host coarser grained granodiorite and even some of the dykes locally. Based on the geothermometry and geobarometry of amphibole (actinolite-magnesiohornblende), the crystallization temperature and pressure of the Evandale coarse-grained granite and aplite are 674–755 °C, 0.2–0.7 kbar (20–70 MPa) and 838 °C, 0.42–1.4 kbar (42–140 MPa), respectively. This is consistent with biotite formation at temperatures ranging from 670° to 760 °C, based on Ti-in-biotite thermometry. Also, zircon saturation temperatures of the earlier coarse-grained porphyritic granites and later fine-grained porphyry to aplitic dykes are 736 °C and 787 °C, respectively. Spatially and temporally associated gold deposits beside Evandale and within this region of southwestern New Brunswick suggests that these oxidized I-type intrusions are a potential source for distal, low sulfidation epithermal gold deposits in the region.

Multiple stages of Au mobilization in the Changshagou Au deposit, Eastern Tianshan, NW China: Insights from mineral chemistry and fluid inclusions

Gold deposits involving multiple stages of mineralization have received considerable attention, but the relationship between these Au enrichment episodes remains enigmatic. The Changshagou Au deposit in the Chinese Tianshan Orogenic Belt exhibits two contrasting styles of mineralization. Early stockwork disseminated sulfide mineralization is associated with potassic alteration and acid magmatic fluids (log fO2 = -30 to -25, pH = 3 to 6), whereas late auriferous vein mineralization is associated with silicification and weakly alkaline hydrothermal fluids (log fO2 = -35 to -32, pH = 4 to 8). Early mineralization (average Au grade = 1.8 g/t) is dominated by invisible gold in sulfides, whereas late mineralization (average grade = 3.7 g/t) contains abundant native gold (fineness = 799 to 872). Fluids with high Au solubilities (∼104 ppb) from the late-stage mineralization remobilized pre-existing Au and formed As-enriched overgrowth bands on pyrite, with the core of these pyrite containing up to 1800 ppm Au, but little As, and their rim containing up to 4300 ppm As, but little Au. Subsequent fluid boiling accompanied with the escape of CO2 and H2S elevated the pH and redox state of the fluid (log fO2 = -32 to -28, pH >8), which caused a decrease in Au solubilities and precipitation of native gold (average grade = 28.6 g/t). In summary, we suggest the Changshagou Au deposit formed as a result of three key processes — pre-enrichment, re-mobilization, and re-enrichment — all of which are important to the formation of Au deposits characterized by multiple stages of mineralization.

TWO STAGES OF MINERALIZATION IN THE SOUTHERN TIEN SHAN Au-W METALLOGENIC BELT: ISOTOPIC U-Pb DATING (LA-ICP-MS METHOD) OF ZIRCON FROM INTRUSIVE ROCKS AT THE JILAU W-Au DEPOSIT (TAJIKISTAN)

The paper presents new isotopic U–Pb zircon data (LA–ICP–MS method) on the intrusive rocks from the Chinorsai massif, which is spatially and probably genetically related to the large Jilau tungsten-gold deposit. This deposit, together with the other large Au deposits (Muruntau, Zarmitan, Kumtor, etc.) is part of the largest Au (Au–W) metallogenic belt of Tien Shan. The deposit is represented by small zones of scheelite-bearing skarn and later (overprinting) large stockwork of veins and veinlets with scheelite-gold mineralization that occurs within and near the intrusion. The concordant isotopic zircon U-Pb data (301.0 ± 2.6 Ma; MSWD = 2.6) are older than the isotopic zircon U–Pb data previously reported (about 288 Ma). This indicates a substantial extent of the magma emplacement and crystallization process that probably corresponded to several intrusive events or phases, which is a prerequisite for the formation of associated intrusive-related Au deposits. Also, the isotopic age determined highlights the earlier formation of gold-polymetallic-tungsten deposits as compared to Mo–W and Sn-W deposits in the region, which are related to the later Early Permian intrusions. In addition, zircon xenocrysts with much older age (from ca. 970 Ma to ca. 2200 Ma) have been identified; they probably represent the age of the orogenic basement including that of the basement terranes of the Tarim and Karakum cratons.

Interfacial adsorption of gold nanoparticles on arsenian pyrite: New insights for the transport and deposition of gold nanoparticles

Gold nanoparticles (AuNPs) are found extensively in the near-surface Earth system. The transport, aggregation, and deposition of AuNPs have been potentially recognized as an important process and even a fundamental intermediary step both in formation of high-grade gold deposits and in the dispersion of gold into the Earth's surface environment. The interfacial adsorption between AuNPs and sulfide minerals is a long-recognized process regulating transport and deposition of gold in hydrothermal fluids, and the occurance of Au and As in pyrite are often observed in various hydrothermal Au deposits. However, the adsorption behavior of AuNPs on sulfide minerals and the fundamental chemical mechanism for the AuAs relationship remain enigmatic. In this work, we selected citrate as a surrogate for typical natural organic compounds abundantly found in lower-temperature hydrothermal systems and Earth's surface environment, and experimentally investigated the adsorption of negatively charged AuNPs on pyrite and arsenian pyrite under anaerobic conditions. We demonstrate that pyrite and nanoparticle surface properties, and solution chemistry, control the adsorption process. Negligible adsorption of AuNPs on pyrite (absent of As) was verified under all experimental conditions likely due to high electrostatic repulsion. However, we observed AuNPs adsorption on arsenian pyrite and suggest that this interaction is due to negative charge-assisted hydrogen bonds ((−)CAHBs) between hydroxyl/oxyl groups on the surface of arsenian pyrite and carboxyl groups on the citrate capping agent of AuNPs. Also, the lower negative charge density of arsenian pyrite surfaces significantly reduces electrostatic repulsion between both negatively charged AuNPs and arsenian pyrite. The solution pH, coexisting organics (citrate) concentration, and ionic strength are demonstrated to play substantial roles in the adsorption of AuNPs on arsenian pyrite. However, the solution pH appears to be an overriding factor controlling the adsorption of AuNPs which decreases with the increase of pH. With respect to citrate concentration, the adsorption rates of AuNPs onto arsenian pyrite initially decreases, but only slightly, and then increases. Increased ionic strength also promotes the adsorption of AuNPs. Our findings highlight a potentially important role of AuNPs in transport and deposition processes of gold in aqueous mediums, and provide new insights on the geochemical behavior of metal nanoparticles in the hydrothermal systems and Earth's surface environment.

Magmatic Native Gold: Composition, Texture, Genesis, and Evolution in the Earth’s Crust

Abstract —Here we report results of microforms’ studies of native gold and its alloys in igneous rocks, modified to varying degrees by secondary processes. We discuss the composition and occurrence of both the deep-seated magmatic gold-bearing alloys and the products of their transformation under conditions of the upper Earth’s crust. Gold-bearing Kamchatka adakites and ankaramites, Ildeus massif mafic-ultramafic intrusions and adakites from the Stanovoy fold system as well as dacites from the Bolivian Andes were formed during melting of either the suprasubduction mantle wedge or the subducted oceanic crust. In depleted peridotites from the Avachinsky Volcano in Kamchatka as well as suprasubduction ophiolites from Polar Urals, Eastern Sayan and the Western Mediterranean Betic–Rifean belt, the gold-bearing mantle was hybridized by subduction-related melts and high-temperature fluids. Volcanic rocks associated with the Lesser Khingan Fe–Mn deposits and Zolotaya Gora Au deposit in Southern Urals as well as Taragai ultramafic rocks in the South Khingan Range display subduction-related geochemical characteristics. Gold-bearing trachytes in the Virginian Appalachians (USA) represent felsic differentiates of mafic intraplate magmas. We propose that one of the principal forms of gold transport into the upper crustal environments is represented by Cu–Ag–Au alloys, which precipitated from mantle-derived silicate melt enriched in chalcophile and siderophile elements. Such Cu–Ag–Au alloy-rich magmatic rocks can either constitute primary sources of precious metals in the mantle-crust system or serve as geochemical precursors to the formation of native gold assemblages in epithermal and mesothermal ore deposits. Presence of magmatic gold particles in subduction-related igneous rocks and mantle restites hybridized by subduction-derived melts and high-temperature fluids suggest the existence of gold-rich horizons in the Earth’s mantle at depths comparable to typical depths of generation of primary convergent zone and some within-plate magmas.

Study of the Heat‐Induced Degradation Mechanism in PbI2‐Excess Perovskite Solar Cells

The photodecomposition of PbI2 in the perovskite halide structure has been identified as a primary reason for the rapid degradation of metal halide perovskite solar cells (PSCs) under continuous illumination. In particular, excess PbI2 on the surface of perovskite films reduces the stability of PSCs via several mechanisms that are still unelucidated. Herein, the influence of excess PbI2 on PSCs is investigated by varying the Au deposition rate, which results in different temperatures during the fabrication of PSCs, and then they are compared with stoichiometric PSCs. It is demonstrated that the anion exchange of Br− in perovskite and I− in excess PbI2 occurs at the grain boundary and interface of the perovskite layers induced by the high heating temperature, leading to a photoluminescence peak redshift and lower power conversion efficiency. Light illumination accelerates the exchange of Br− and I− between the perovskite layer and excess PbI2 induced by carrier accumulation at the interface and grain boundary, leading to the poor stability of the PSCs.

Zircon and apatite fingerprints on the magma fertility for the Jurassic igneous rocks in the southern Lhasa subterrane, Tibet

The products of long-lasting magmatism (ca. 170 Myr) related to the northward subduction of the Neo-Tethys Ocean are preserved in the southern Lhasa subterrane (SLT). However, only a few large porphyry Cu–Au deposits related to these igneous rocks have been discovered in the Xiongcun ore concentration area. Here, we present zircon and apatite data on Jurassic fertile suites (FS), barren suites (BS), and recently proposed prospecting target suites (PTS) in the SLT, intending to present a case study of the regional-scale porphyry metallogenic potential. The zircon geochemical data with Rayleigh fractionation modeling show that the zircon geochemical characteristics of the FS and PTS were affected by high proportions of amphibole and titanite crystallization, whereas the zircon geochemistry of the BS displays the effects of plagioclase fractionation or mixing with the least evolved melts. The zircon Ce4+/Ce3+ and Eu/Eu* values cannot be used to trace the oxygen fugacity of the magma due to prior or simultaneous mineral crystallization. However, the zircon Ce/Ce* and Ce/Nd ratios may be used as semiquantitative measures of the magma redox conditions. This result is similar to that calculated by the new magmatic oxybarometer using trace elements in zircon, showing that the FS (ΔFMQ = 1.21 ± 0.42) and PTS (ΔFMQ = 1.29 ± 0.51) have higher oxygen fugacity levels than the BS (ΔFMQ = 0.40 ± 0.88). The melt S contents estimated from magmatic apatites are lower in the FS and PTS than in the BS, which is attributed to prior anhydrite crystallization under high oxygen fugacity and low temperature conditions. The higher Cl in the melt of the FS (average 0.098 wt%) than in the melts of the PTS (average 0.045 wt%) and BS (average 0.04 wt%) shows that elevated Cl contents in melts are likely important for forming porphyry Cu–Au deposits. The combined geochemical characteristics of zircon and apatite suggest that a high oxygen fugacity (ΔFMQ > 1.2), prior or concurrent anhydrite crystallization, and high zircon Eu/Eu* (>0.6), Ce4+/Ce3+, and (Yb/Dy)N values can be used to refine potential porphyry Cu–Au targets on a regional scale in the SLT. High melt Cl contents and apatite MnO and Pb contents can effectively indicate fertile suites at the deposit scale.

Critical and Strategic Minerals in the Russian Federation

Global development and scientific and technological progress are intensifying the use of mineralraw materials (MRMs)—the necessary basis for the production of high-tech products. The advanced producing countries of these products are in dire need of various raw materials, which are critical and, as a rule, are supplied from third countries. Strategic is a mineral raw material, which is of particular importance for ensuring the economic development of the country, its defense and security. Due to the complex structure of extraction, processing and consumption of raw materials, many of its types are in short supply. In the world literature, the concept of “deficient MRMs” in its content most closely corresponds to “critical MRMs,” that is, raw materials that are critically needed for industry and are characterized by a significant risk of their supplies. Most critical raw materials are needed for production promising high-tech industrial products and new materials and, in particular, for “green technologies” in connection with the course of decarbonization of the economy actively pursued by world powers. In the production of such products, the consumption of MRMs is growing rapidly, especially rare-earth elements (REEs), V, Li and platinum-group elements (PGEs). From the list of 61 kinds of MRMs that are strategic for Russia, the extraction of oil, gas, Cu, Au, PGEs, Ni, apatite ores, K salts, and diamonds (as well as nonlisted coals, Fe ores, Na salts, V, B ores, magnesite, and chrysotile asbestos) fully covers their current domestic consumption in the Russian Federation and the achieved level of export. U, Mn, and Cr ores; Zr; high-purity quartz raw materials (SiO2); bauxite (Al); graphite; fluorite and nonstrategic barite; kaolin; and bentonite are deficient; their exploitation only partially provides domestic consumption, which is largely dependent on imports; it is carried out in insufficient volumes in the presence of significant reserves of relatively low quality. The most deficient in this list are Ti, Li, Ta, Nb, and REEs (usually, there are groups of heavy and light rare earths (HREEs and LREEs, respectively)): their domestic consumption is provided mainly by imports with very limited production (despite large reserves, including low quality ores). Re, Be, Nb, Ta, HREEs, Y, Sc, LREEs, Ge, Ga, Li, Hf, and Co, and, of nonstrategic MRMs, Bi and Sr, should be considered critical MRMs in the Russian Federation. The most important source of dispersed/ associated elements is represented by raw materials of mining enterprises of nonferrous metallurgy: Cu and Zn subsectors, In, Ge, Ga, Cd, Tl, Se, Te, Sb, Bi, etc.; Al subsectors, Ga; for Au and Au–Ag deposits, Sb, As, Te, Se, Bi, Tl. An associated source of lithium is represented by brines of gas-condensate fields. The issues of assessing complex raw materials for high-tech industry are considered using the example of pyrite, porphyry, and gold-ore deposits of the Ural folded region, which play an important role in its overall metallogenic potential.

Conditions of Formation of Epithermal Mineralization of the Kyplatap Volcanic Field (Central Chukotka)

The article considers the geochemical features and conditions of the formation of substantially silver mineralization of the Kyplatap volcanic field (KVF), of the Chaunsky zone, of the Central Chukchi Sector, of the Okhotsk-Chukchi volcanic belt (OChVB). New data on the composition, distribution and grade of trace elements, including REE in ores, are presented. The noticeable enrichment REE of the studied samples, the predominance of light lanthanides over heavy ones, very low Eu/Sm ratios (\( \ll {\kern 1pt} 1\)), weakly inclined near–chondrite spectra with obvious Eu minima are typical for the epithermal ore-forming system of the KVF. The Ce/Ce* vary from slightly negative to moderately positive values (from 0.81 to 1.38), and the Eu/Eu* vary from 0.28 to 0.7. This combination of Ce/Ce* and Eu/Eu* indicates the oxidative conditions prevailing during ore formation. The results of thermo- and cryometric studies of fluid inclusions in quartz allowed us to establish that the ore-forming fluid contained Na, Mg and K chlorides, epithermal mineralization was deposited by homogeneous hydrothermal fluids with salt concentrations (0.3–6.2 wt. %-eq. NaCl), fluid density – 0.60–0.87 g/cm3, at temperatures from 203 to 343°C, water vapor pressure varied from 40 to 140 bar. The obtained geochemical and thermometric data confirm the assumption put forward earlier – that the studied mineralization of KVF belongs to the intermediate sulfidation epithermal class. These data point to andesite magmas and meteoric waters as the most likely sources of fluids. The information in the article is of practical importance for regional predictive metallogenic constructions, prospecting and evaluation of epithermal Au–Ag deposits.

A LONG-LASTING EVOLUTION OF THE ORE-MAGMATIC SYSTEM AT THE MURUNTAU GOLD DEPOSIT (WESTERN UZBEKISTAN, TIEN SHAN): THE EVIDENCE FROM ISOTOPIC U-PB ZIRCON AGE (LA-ICP-MS METHOD) OF THE GRANITOIDS OF THE SARDARA (SARYKTY) PLUTON

The paper presents the first data of the isotopic zircon U–Pb study (LA–ICP–MS method) on the granodiorite-granite from the Sardara (Sarykty) pluton in the district of the giant Muruntau Au deposit in the Western Tien Shan (Uzbekistan). In a single sample, three age groups of zircon crystals identified, with their concordant U–Pb age being 322.0 ± 3.7 Ma (MSWD = 3.1, 4 zircon grains), 301.6 ± 2.1 Ma (MSWD = 0.17, 11 zircon grains), and 289.1 ± 4.9 Ma (MSWD = 0.98, 2 zircon grains), respectively. The scatter of the isotope age data obtained can be interpreted using the model of subsequent crystallization of various zircon generations in variably-deep magmatic batches, followed by zircon capturing during the magma differentiation and crystallization. Notable is a quite close coincidence of the two (the younger) age intervals to the concordant U–Pb zircon ages, which were published before for the granitoid rocks found directly at the Muruntau deposit. The latter thus can represent the dike “splits” occurred at the respective stages of the magma evolution (progressing differentiation) in the deeper batches of the granitoid magma, with its larger intrusions represented by the Sardara (Sarykty) and other plutons outcropping at some distance from the deposit. Overall, the older isotopic U–Pb zircon data of the Sardara (Sarykty) pluton (in the order of 322 Ма and 302 Ма, respectively) correspond closer to the subduction event, whereas the younger U–Pb zircon data (in the order of 289.5 Ma) are quite relevant to the post-collisional stage occurred in the region. Therefore, the initiation and initial development of the magma batches in the Muruntau deposit district could occur in the subduction environment but the final granitoid magma differentiation and crystallization were completed already at the post-collisional stage.

Cobalt Prospectivity Using a Conceptual Fuzzy Logic Overlay Method Enhanced with the Mineral Systems Approach

AbstractThis paper describes mineral prospectivity research conducted in Finland to predict favorable areas for cobalt exploration using the “fuzzy logic overlay” method in a GIS platform and public geodata of the Geological Survey of Finland. Cobalt occurs infrequently as a core product in mineral deposits. Therefore, we decided to construct separate conceptual mineral prospectivity models within the Northern Fennoscandian Shield, Finland, for four deposit types: (1) “Orthomagmatic Ni–Cu–Co sulfide deposits,” (2) “Outokumpu-type mantle peridotite-associated volcanogenic massive sulfide (VMS)-style Cu–Co–Zn–Ni–Ag–Au deposits,” (3) “Talvivaara black shale-hosted Ni–Zn–Cu–Co-type deposits” and (4) “Kuusamo-type (orogenic gold with atypical metal association) Au–Co–Cu–U–LREE deposits”. In addition, we created a model combining till geochemical data with data derived from bedrock drilling and mineral indications, including boulders and outcrops. The mineral prospectivity models were statistically tested with the “receiver operating characteristics” method using exploration drilling data from known mineral deposits as validation sites. In addition, the predictive performance of the models was evaluated by using success rate curves, where the number of previously identified deposits was compared with the area coverage of the predicted highly favorable areas. These results indicate that the knowledge-driven mineral prospectivity method using parameters derived from mineral systems models is effective in defining favorable exploration target areas at the regional scale. This study's innovation lies in its comprehension of the process of evaluating mineral prospectivity when the commodity of interest is not the primary commodity within the mineral system.