Gold Deposits Research Articles

Gold Deposits of Central and North Asia

Gold Deposits of Central and North Asia

The Jerooy Gold Deposit (Northern Tien Shan, Kyrgyzstan): U-Pb SIMS Geochronology of Intrusive Complexes, Hydrothermal Alteration, and Model of Ore Formation

The Jerooy Gold Deposit (Northern Tien Shan, Kyrgyzstan): U-Pb SIMS Geochronology of Intrusive Complexes, Hydrothermal Alteration, and Model of Ore Formation

Development of nanocrystallized magnetoelastic sensors with self-biased effect and improved mass sensitivity

The growing demand for cost-effective and wireless sensing technologies requires the development of simple, efficient and optimized sensors able to accurately detecting external agents. Magnetoelastic resonators represent an alternative to the traditional sensing systems, able to combine all the previously cited factors. Several studies have focused on increasing their sensitivity, in order to make it closer to the market. The present study explores thermal treatments as a novel approach to enhance the sensitivity of magnetoelastic resonators, focusing on the positive impact of crystallization processes induced in magnetoelastic platforms. The experimental results confirm an enhancement of resonant frequency and quality factor of the magnetoelastic platforms as treatment temperature increases. Particularly, the sensor annealed at 550 °C shows an increase of the resonant frequency value of 45 % with respect to the as-quenched platform, being that increase of around 1700 % for the quality factor. In addition, the nanocrystallization induction leads to a self-biased resonance, consequence of the intrinsic magnetization resulting from the crystallization in Fe2B and FeCo phases. Further, the study shows the importance of stability in resonant frequency, emphasizing the potential of the 550 °C-annealed platform for mass sensor applications. Gold deposition experiments reveal the enhanced sensitivity of the sensor annealed at 550 °C of 40 % compared to the as-quenched sensor, as well as an increase of 38 % on its accuracy. These findings represent a significant step forward in the development of magnetoelastic-based mass sensors, highlighting the pivotal role of thermal treatments in optimizing sensitivity for practical and efficient external agents detection systems.

Ecological and geochemical assessment of soils in residential areas of Eastern Transbaikalia

Relevance. Environmental pollution by mining wastes is one of the most urgent environmental problems. Aim. To determine the degree of soil pollution in the residential areas of Eastern Transbaikalia. Objects. Total soil pollution according to the Saet formula (Zc) was studied in 30 settlements of Eastern Transbaikalia, including 14 settlements related to mining. Methods. In order to determine the degree of soil contamination, the settlements were grouped: settlements at gold ore, molybdenum lead-zinc and rare-metal deposits, as well as settlements not related to mining. The factual material was obtained during the research under the basic projects of the Institute of Natural Resources, Ecology and Cryology of the Siberian Branch of the Russian Academy of Sciences from 2000 to 2022. In addition, published data and materials of the territorial geological funds (Chita) were used. The X-ray fluorescence method was used to determine the concentrations of chemical elements in analytical laboratories of the Geological Institute of SB RAS (Ulan-Ude), ISP-MS of ZAO "SGS Vostok Limited" (Chita). Results. Among the considered groups of settlements the following indicators of total soil contamination degree (Zc) were established: mining settlements of lead-zinc deposits – 68.87; gold deposits – 30.67; molybdenum deposits – 32.25; rare-metal deposits – 0.03; settlements not related to mining activity – 0.32. According to the total degree of soil contamination Zс, the settlements of lead-zinc deposits correspond to extremely hazardous, molybdenum deposits – hazardous; gold deposits – moderately hazardous; the settlements of rare-metal deposits and the ones not related to mining activities – low levels of pollution.

Modelo cinemático del control estructural 4D y metalogénesis del distrito auroargentífero Vetas-California (Santander, Colombia)

). The gold and silver deposits of the Vetas-California mining district are hosted in Paleozoic gneisses and Mesozoic granites of the Santander massif in the Eastern Cordillera of Colombia, far from the northern Andean volcanic arc. In the California area, there is ambiguity in defining the epithermal-type metallogenic model with high to intermediate sulfidation due to the presence of Late Triassic-Early Jurassic and Miocene magmatism. The best-known hydrothermal episodes comprise two early porphyritic-style phases: a) characterized by a propylitic alteration with molybdenite of the ~10.1 Ma-old La Mascota breccia, related to granodiorite porphyries and smaller-volume rhyodacitic dykes; and b) attributed to a magmatic-hydrothermal system due to phyllic alteration associated with quartz-pyrite veins with hydrothermal sericite dated at ~3.4 Ma. These two hydrothermal episodes were followed by four epithermal phases related to the development of multiphase hydrothermal breccias and quartz-alunite alteration, defined by bornite, covellite, and chalcopyrite, alongside wolframite, enargite, and sphalerite, with gold and silver mineralization between ~2.6 and ~ 1.6 Ma. To understand the relationship of the emplacement of the porphyries and the subsequent auro-argentiferous enrichments to the deformation front observed in the Pamplona buttress, to the east of the Santander Massif, a 4D structural model of the mineralization is formulated here. This model is based on the spatial analysis of the stresses responsible for the La Baja-Angostura dextral fault in terms of the regional kinematics of the Bucaramanga sinistral fault. It is considered that the SW sector of the deposit area corresponds to a well-defined, tabular, sub-vertical body of the La Mascota breccia. On the other hand, the NE sector in the La Baja-Angostura fault is expressed as a topographically elevated right horsetail splay, which controls the more disseminated distribution of the mineralization by means of veinlet swarms arranged in an ~E-W direction. The disseminated mineralization of Vetas-California was probably favored by late thermal expansion-contraction events in the gneissic sockets, which allowed the accumulation and precipitation of boiling solutions rich in volatiles and elements of economic interest.

Exploration geochemical evidence for the genesis of the Jiaodong gold deposits in eastern China: A case study of the Haiyu gold deposit

Jiaodong is the largest gold province in China and has great potential for further prospecting. It has been confirmed that the enrichment of Au is always accompanied by pyritization in Jiaodong gold deposits, so the genesis of pyritization in gold deposits and the mechanism of Au enrichment associated with pyritization has always been an issue of discussion to the researchers, the relationship between pyritization and Au enrichment is still unclear. In order to solve this problem, this paper studied the occurrence state and transformation characteristics of S in the ore-bearing geological bodies and discussed the mechanism of Au enrichment. 84 samples were collected from the drill hole ZK3006 of the Haiyu gold deposit, the average sampling interval was 15m, and 7 specific elements/analytical indexes were measured (Total sulfur, Reduced sulfur, Na2O,CaO, Sr, Ba, and Au), Burning-iodine quantity method was used to measure the content of Total sulfur, Combustion neutralization method was used to measure the content of Reduced sulfur Inductively coupled plasma-atomic emission spectrometry was used to measure the content of Na2O and CaO, Wavelength dispersive X-Ray fluorescence spectrometry was used to measure the content of Sr and Ba, and Foamed plastic enrichment-inductively coupled plasma-mass spectrometry was used to measure the content of Au.

Optimizing the cut-off grade for tabular gold deposits, considering the South African gold tax and mineral resource royalty regime

The South African mineral resource royalty system, initiated in 2010, employs a hybrid ad valorem approach tied to profitability ratios. This rate is then applied to the total revenue from mineral sales. In this article we explore how the profitability ratio in the mineral resource royalty formulae interacts with the gold tax formula as applied to South African gold mines, devising a strategy for cut-off grade optimization. The study focuses on nine narrow, tabular-reef (Witwatersrand) gold mines. The approach involves a mixed-integer cut-off grade optimizer utilizing Excel Solver, incorporating relevant royalty and income tax formulae. Different mineral resource royalty cost scenarios were examined. Ignoring these costs in the break-even analysis lowers the cut-off grade but slightly boosts profits compared to considering expected costs. The developed optimizer model, recognizing the profitability aspect of the mineral resource royalty and income tax formulae, yielded a 6% lower cut-off grade than the base case. This is significant for increasing mine life. While the profit differences are marginal (0.2% compared to the break-even base case), substantial improvements were noted: a 6% increase in stope tons above cut-off grade, and a 4% rise in total revenue. Enhanced resource utilization (3% extra gold kilograms) reduces necessary development and overall costs, allowing for a reduction in the cut-off grade and ultimately, more profit.

Geochemical Evidence of Ore-Forming Processes in the Shuiyindong Gold Deposit of Southwest Guizhou Province, China.

The Shuiyindong deposit is one of the ultralarge Carlin-type gold deposits in Southwest Guizhou Province, China. Gold mineralization mainly occurs in the Permian Longtan Formation and the early Triassic Yelang Formation. It is controlled by both strata and faults. Detailed studies of the mineralogy and geochemistry characteristics of the Shuiyindong deposit are conducted to investigate the ore-forming process. Arsenian pyrite and arsenopyrite are the main Au-hosting minerals. Three types of pyrite can be recognized, including euhedral and subhedral pyrite, framboidal pyrite, and bioclastic pyrite. The euhedral and subhedral pyrite is the main Au-hosting type. The Au appears as a solid solution (Au+) and natural nanoscale gold (Au0) in the sulfide minerals. The Co/Ni ratios of sulfides (0.07-3.13) reveal that the ore-forming fluids were mainly affected by hydrothermal activity, but magmatic activity cannot be excluded. Organic matter in the ores is abundant (0.11-3.04%), which might provide sulfur for pyrite and favor an increase in the porosity and permeability of the host rocks by releasing organic acids. The REE and trace element results suggest that halogens (F and Cl) were contained in the reducing magmatic hydrothermal fluids. The sulfur isotopic data (from -8.64‰ to 27.17‰) suggest that the source of sulfur is complicated and is probably a combination of a magmatic source, the reduction of marine sulfate, and bacterial sulfate reduction. The Pb isotopic data of the sulfides indicate that Pb is from a mixture of crust and mantle sources. The obvious enrichment zones exist along the boundary faults in the geochemical map of As, implying that As may originate from the deep crust and then move to the strata with basinal fluids. By combining these results, it can be inferred that the ore-forming fluids were a mixture of basinal and deep source fluids. A probable ore-forming model of the Shuiyindong gold deposit is established.

Contribution of bismuth melts to gold endowment in the Baolun gold deposit, Hainan Island, South China

Bismuth (Bi) melts and related polymetallic alloys can efficiently scavenge gold (Au) from Au-unsaturated aqueous solutions, contributing to the Au endowment in many hydrothermal deposits. However, original evidence for Au–Bi melts is often poorly preserved due to post-precipitation alteration. This complicates investigation of the liquid bismuth collector model in hydrothermal Au deposits. Here we present primary evidence for the occurrence of Au–Bi melt in hydrothermal systems through an examination of the Au–Bi phases and textures in the Baolun Au deposit (Hainan Island). This study found that maldonite, native bismuth, Au–Bi symplectite and Au–Bi melt blebs appeared successively following the precipitation of native gold. Notably, large Au–Bi melt blebs were well preserved in natural systems due to the rapid cooling of fluids. The mineral assemblages and their corresponding fluid physiochemical conditions suggest that the evolution of the ore fluids at Baolun was characterized by a continuous reduction in Au and Bi concentrations and Au/Bi ratios alongside decreasing fluid temperatures and sulfur fugacity (fS2). These observations offer direct evidence for Au scavenging by Bi melts in a mesothermal (275–450 °C), low-fS2 and reduced hydrothermal system, aligning well with the Au–Bi binary phase evolution established in metallurgy. As the fluid cooled further, the Au–Bi phases were subsequently overprinted by later Te–S-rich fluids, as evidenced by the formation of bismuthinite, jonassonite, and joséite-A around the Au–Bi phases. Importantly, our study reveals that the Baolun Au deposit ischaracterizedby a Au–Bi–Te hydrothermal system and that the metamorphic country rocks at Baolun are the major source of Au, Bi, and Te.

Spatial Clustering of Primary Geochemical Halos Using Unsupervised Machine Learning in Sari Gunay Gold Deposit, Iran

Spatial Clustering of Primary Geochemical Halos Using Unsupervised Machine Learning in Sari Gunay Gold Deposit, Iran

Genesis and fluid evolution of the Hatu orogenic gold deposit in the West Junggar, Western China

The West Junggar in Xinjiang, western China, represents a significant gold mineralization belt hosting over 200 gold deposits, with the Hatu gold deposit being the largest among them. In this study, ore geology and fluid inclusion assemblages of quartz samples from the Hatu gold deposit were investigated in an effort to clarify the mineralization process and its relationship with the geodynamic settings. The mineralization process is delineated into early (pyrite-albite-quartz veins), middle-a (quartz-ankerite veins), middle-b (quartz-ankerite-sulfide-native gold veins), and late (quartz-calcite veins) stages. The early stage veins suggest a compressional setting while the middle-a and middle-b stage veins suggest a tensional shear setting. The late stage veins are typically filled fissures cutting through earlier veins. Scanning electron microscope-cathodoluminescence (SEM-CL) reveals that early stage quartz (Q1) exhibits concentric CL-oscillatory growth zoning, while middle-a stage quartz (Q2a) displays unidirectional zoning and ranges from CL-bright to CL-dark, middle-b stage quartz (Q2b) is CL-bright and weakly zoned, and late-stage euhedral quartz (Q3) shows sector zoning transitioning from CL-gray to CL-dark. Quartz that formed in these stages developed three types of fluid inclusions: pure CO2 (PC-type), CO2–H2O (C-type), and H2O–NaCl (W-type). The early stage quartz contains C- and W-type fluid inclusions homogenizing at 309–345 °C, while the late stage quartz contains only W-type fluid inclusions with homogenization temperatures of 164–229 °C. Microthermometry of fluid inclusion indicated the evolutionary of the metallogenic fluid from a high-temperature, CO2-rich, and minor CH4 metamorphic fluid to a low-temperature, CO2-poor meteoric fluid. From the early to middle-a stages, fluid boiling caused the unloading of ore-forming elements whereas fluid mixing led to the precipitation of polymetallic sulfides and gold in the middle-b stage. Trapping pressures in the middle-b stage were estimated using C-type inclusions, illustrating that gold mineralization took placed at depth of 8.0 km. We propose classifying the Hatu gold deposit as an orogenic deposit, originating from the collisional orogenesis between the Yili-Kazakhstan and Siberian continents in the Late Carboniferous.

The Xilaokou carbonate-sulfide vein type gold deposit: A distinct mineralization in the giant Jiaodong gold province, North China

The Xilaokou gold deposit with ca. 50 t of gold reserve @ 2.7 g/t represents a novel type (carbonate-sulfide vein type) of gold mineralization within the Jiaodong gold province. However, its mineralization age and metallogenic mechanism remain poorly constrained, hindering a comprehensive understanding of the ore-forming processes in the Jiaodong gold province. In this study, we employ syn-ore stage hydrothermal monazite in situ U-Pb geochronology to determine the ore-forming age of the Xilaokou gold deposit. Additionally, we conduct in situ LA-(MC)-ICP-MS elemental mapping and sulfur isotope analysis in ore-related pyrite to unravel the sulfur source(s) and provide new insights into the ore-forming processes of the Xilaokou gold deposit. Our findings reveal the following key points: (1) U-Pb dating of hydrothermal monazite in Au-bearing pyrite yields an ore-forming age of119.9 ± 3.0 Ma. This age is consistent with the mineralization ages (around 120 ± 5 Ma) of other gold deposits in the region, including Liaoshang-, Jiaojia-, and Linglong-type deposits. (2) Gold in pyrite primarily occurs as micro-grains (5–20 μm) within pyrite fissures associated with sphalerite and galena. (3) Elemental mapping and sulfur isotope analysis indicate that major Au mineralization is linked to elevated concentrations of As, Sb, and Tl, along with heavy sulfur isotope values (δ34S∼24.7 ‰). (4) Early-stage Au mineralization is characterized by enrichment of As, Cu, and Bi, with normal sulfur isotopic composition (δ34S∼8 ‰). We propose that the carbonate-sulfide vein type gold deposits represented by the Liaoshang and Xilaokou gold deposits in the Jiaodong gold province are genetically linked to quartz-sulfide vein and disseminated type deposits. The major ore-forming stage involved the addition of S and Au from a metamorphic massif at slightly lower temperatures. These findings highlight a new exploration direction within the North China Craton. In summary, the Xilaokou gold deposit provides valuable insights into gold mineralization processes in Jiaodong, emphasizing the importance of considering diverse deposit types and their genetic relationships in the region.

Hydrochemical Characteristics, Controlling Factors and Groundwater Sources of Zaozigou Gold Mine

The Zaozigou gold deposit is recognized as one of the largest and most significant independent gold deposits in northwest China, representing a colossal orogenic gold-antimony deposit. It is imperative to delve into the hydrochemical characteristics and controlling factors within the mining area to unveil the groundwater circulation evolution process and enhance water resource management. In 2018, a comprehensive collection of 50 groups of groundwater samples was conducted, alongside 17 groups of surface water and underground mine water samples in 2023. Compositional descriptive analysis, correlation analysis, Piper three-plot, Gibbs map, ion ratio method, hydrogeochemical simulation and PCA methods were employed to reveal the chemical characteristics and evolution process of groundwater in the Zaozigou gold mine. Furthermore, employing water isotopes theory allowed for the identification of recharge sources and circulation conditions within the Zaozigou Gold Mine. The findings indicated a transition from HCO3-Na·Ca type polluted water in 2018 to primarily the SO4-Ca·Mg type and HCO3·SO4-Na·Ca·Mg type groundwater hydrochemistry types by 2023. The hydrochemical characteristics of the study area are closely related to the mining depth and time. The chemical characteristics are influenced by various factors such as rock weathering, mineral dissolution, cation exchange processes, atmospheric precipitation as well as human activities related to pollution from industrial mining activities.

Machine learning on white mica short-wave infrared (SWIR) spectral data in the Tengjia Au deposit, Jiaodong peninsula (Eastern China): A prospecting indicator for lode gold deposits

Lode gold deposits are the primary source of global gold resources and possess significant mineralization potential at depth, necessitating new strategies to locate deep concealed orebodies. The Tengjia Au deposit, a newly-discovered concealed altered rock-type lode gold deposit (50 t @ 3.89 g/t), is located within the Zhaoping metallogenic belt of the illustrious gold-rich Jiaodong peninsula in Eastern China. It is distinguished by pervasive phyllic alteration associated with gold mineralization, making it an ideal target for mineral geochemical exploration in lode gold deposits. The mineralization and alteration at Tengjia unfold across three distinct stages, delineated by mineral assemblages and textural relationships: K-feldspar-quartz (I), quartz-sericite-native gold-sulfide (Ⅱ), quartz-calcite-galena-sphalerite (Ⅲ) stages.Systematic analysis of short wavelength infrared (SWIR) spectra, coupled with petrographic observation, has unveiled an abundance of white micas (montmorillonite, muscovite, illite, paragonite, and phengite) within Stage Ⅱ at Tengjia. The Al-OH absorption feature wavelengths (Pos2200), as well as illite crystallinity (IC) values, exhibit a discernible shift towards longer wavelengths (>2204 nm) and higher values (>1.4) in the vicinity of ore deposition, which likely resulted from intense water–rock interaction between ore-forming fluid and wall rocks. Discriminant analysis of the orthogonal partial least squares method (OPLS-DA) shows that the absorption wavelengths corresponding to Water, –OH, and Al-OH effectively differentiate between ore and wall-rock samples. Additionally, analysis using the random forest algorithm (RF) demonstrates that spectral data from Tengjia white micas can reliably classify orebodies, achieving an accuracy of 83.2 %. Hence, the findings suggest that the unique SWIR spectral features of white micas offer a valuable tool for detecting the concealed Tengjia gold mineralization. This study proposes a novel approach that integrates machine learning technology with SWIR analysis for the identification of concealed lode gold deposits.

Using Airborne Magnetic and Radiometric Data to Unravel Auriferous Prospective Areas in the Pitangui Greenstone Belt, NW of Quadrilátero Ferrífero – MG

The Pitangui Greenstone Belt (PGB), NW of the Quadrilátero Ferrífero, Brazil, is a meta-volcano-sedimentary sequence that hosts some important gold deposits recently discovered. Research has been made in the PGB to understand its gold mineral system, but the information regarding the prospective vectors associated with gold mineralization is still unclear. Here, we show the application of airborne magnetic and radiometric data to find the spatial relation between hydrothermal alteration zones and the structural framework of the PGB region. The results showed that the occurrence of gold deposits is associated with NW-SE structures and hydrothermal alteration zones. This association does not exist with E-W structures, which has direct implications on the relevance of these structures in the prospective modeling. Additionally, the application of radiometric data to map hydrothermal alteration zones showed that the limitations of this technique can generate anomalies not strictly associated with hydrothermal alteration processes. In this case, some anomalies could be linked with secondary processes like weathering, leaching, transportation and accumulation of mobile elements, such as K and U.

3D mineral prospectivity modeling using deep adaptation network transfer learning: A case study of the Xiadian gold deposit, Eastern China

Mineralization distribution is commonly heterogeneous in space due to the various geology and structure conditions or fluid flow and evoluation, causing the possible difference in mineralization distribution regularity between shallow and deep at a deposit. This presents important challenges for three-dimensional mineral prospectivity modeling (3D MPM) for deep zones with the scarcity data conditions. Transfer learning has shown promising generalization performance in tasks involving shifts in data distribution, reducing reliance on labeled samples and enhancing learning capability with limited data. In this study, we propose an approach of 3D MPM, namely DAN-CBAM, based on the deep adaptation network (DAN) augmented with the convolutional block attention module (CBAM). It theoretically can harmonize the distribution of ore-controlling features between shallow and deep zones of deposits while effectively extract critical high-dimensional features and spatial patterns. The Xiadian orogenic gold deposit was selected as a case study to validate the approach. The DAN integrates multi-layer, multi-kernel adaptation at the top layer of the CNN, resulting in improved alignment of marginal distributions across domains. Metrics for distribution similarity such as Wasserstein distance, were reduced by 0.250 and KL divergence decreased by 0.032. Additionally, the inclusion of the CBAM module led to a lower MK-MMD loss and a faster convergence rate. And the DAN-CBAM model achieves superior prediction accuracy (0.85) compared to traditional deep neural network (DNN) models (0.81). These highlight CBAM's effectiveness in enhancing the model's ability to capture spatial similarities in mineralization. Furthermore, the area under the curve (AUC) value of the DAN-CBAM model (0.869) significantly outperforms traditional machine learning methods, including CNN (0.786) and Random Forest (0.703) models, underscoring its superior predictive efficiency in 3D MPM for deep mineralization. Therefore, the proposed DAN-CBAM model is promising to be applied in the 3D MPM, in particular for the deposits with different mineralization distribution regularities in space.

Evaluation of gold mineralisation potential using AHP systems and weighted overlay analysis

The demand for sustainable development goals and the absence of systematic development and organised exploration for gold has prompted this study to integrate magnetic and radiometric datasets with lithology to evaluate the gold mineralisation potential in the Ilesha schist belt. This study considers 3168.72 km2 of the Ilesha schist belt in southwestern Nigeria, a frontier belt for gold deposits. The high-resolution airborne magnetic and radiometric datasets were processed using enhancement techniques, including the analytical signal, lineament density, and K/Th ratio. CET grid analysis, Euler deconvolution, and analytical signal depth estimation methods were used to aid the interpretation. The spatial integration and interpolation were performed using the Analytical Hierarchy Process (AHP) and weighted overlay analytical tools within the ArcGIS environment. The dominant structural controls for potential mineralisation are ENE–WSW and ESE–WNW trends. The depth of the magnetic sources revealed by the analytical signal ranged from 63.17 to 629.47 m, while depths ranging from 47.32 to 457.22 m were obtained from Euler deconvolution. The delineated highly magnetic edge sources, dense lineaments, radiometrically highlighted alteration zones, and lithological hosts for gold mineralisation were integrated to establish the gold mineralisation potential map. The AHP deductions reveal that 10.52% of the study site is within the high mineralisation potential class, a remarkable 60.39% falls within the moderate class, a significant portion (28.86%) falls within the poor class, and 0.23% is considered unfavourable. The result was optimised by validation using known mines, with 94% (i.e., 15 out of 16 mining sites) plotting within the high mineralisation potential class. This assessment provides invaluable insight for stakeholders and policymakers to embark on gold exploration and exploitation and promote sustainable mineral development.

Controlling the growth mode of Au depositing on Au nanobipyramids via ligand coverage for SERS enhancement

Gold deposition on Au nanoparticles is a common method to control the shape and further modify the properties of nanoparticles as their properties have a strong correlation with their nanostructures. For Au nanobipyramid (Au NBP), it has advantages such as the enhancement of electric field and a higher tunability in plasmon wavelength than the Au nanorod and thus owns a greater potential in shape control. In this paper, we demonstrate a scheme of depositing Au on the surface of Au NBP with the presence of a type of ligand 2-mercaptobenzoimidazole-5-carboxylic acid (MBIA) to synthesize Au NBP@Au dimers. The growth mode of Au depositing on Au NBP can be controlled by the coverage of MBIA. As the coverage is low, with a concentration of MBIA below 0.4 mM, the rough core–shell nanostructure is synthesized; However, as the coverage is high, with a concentration of MBIA over 0.8 mM, gold deposition may form islands on the surface of Au NBP. The SERS performance of Au depositing on Au NBP can also be enhanced by growth mode. For the rough-surface core–shell growth mode, the enhancement is more significant as the EF is improved from 3.5 × 105 to 1.06 × 106 than the islands-growing growth mode due to the coupling between core and shell. And our results show that with multiple types of nanosturctures easy to obtained by changing modified ligand coverage, the controlled growth has a great potential in the dimer design and SERS enhancement using Au NBP.

Metallogenic model of the Lykling ophiolite-hosted lode Au deposit, Scandinavian Caledonides: Insight from fluid inclusions, mineral chemistry and stable isotope geochemistry

The Lykling lode Au deposit represents a unique example of gold mineralization in the Upper Allochthone of the Scandinavian Caledonides. The mineralization is hosted by the Early Ordovician Lykling Ophiolite Complex and the intruding trondhjemite unit and spatially associated with two generations of mafic dykes that crosscut both the ophiolitic complex and trondhjemite. Field observations indicate that the mafic dykes did not play an active role in the emplacement of Au at Lykling, however their contacts with the immediate host rocks (i.e., gabbro and trondhjemite) may have focused ore-forming fluids.Three main stages in the evolution of the hydrothermal system in the Lykling area are documented by two generations of auriferous quartz veins: 1) older quartz-carbonate veins hosted by moderately angled brittle-ductile shear zones and 2) younger quartz-sulfide veins that fill steeply dipping brittle faults. Stage 1 resulted in deposition of barren quartz and gold-free pyrite from moderately saline NaCl-CaCl2-H2O ± CO2 fluids at temperatures between ∼310–330 °C and pressures in the range from 2.7 to 3.5 kbars. Under the given physicochemical conditions Au was mobile in the form of its chloride complexes. Stage 2 is associated with multiple episodes of ductile deformation punctuated by concomitant brecciation reflecting brittle-ductile transition processes. Fluid inclusion data reveals a decrease in temperature and pressure that may result in the formation of stable Au-bisulfide complexes and making the hydrothermal mobility of Au sensitive to changes in pressure. Consequently, the fluctuation in pressure controlled by the development of brittle-ductile structures likely resulted in the precipitation of native gold in quartz veins. Stage 3 represents a pure brittle event which is accompanied by a significant decrease in the fCO2/fS2 ratio. Mixing of higher-temperature and moderate-salinity fluids with cooler fluids has been recognized as the principal trigger for deposition of sulfides and a paragenetically late phase of native gold in the Lykling hydrothermal system.The Lykling ophiolite-hosted lode Au deposit shows numerous similarities with orogenic gold deposits elsewhere, including structural controls during mineralizing events, deposition from moderately to low salinity CO2-bearing aqueous solutions, deposition from a focused fluid flow along trans-crustal fault zones with a mixed brittle-ductile character and the spatial association with regionally metamorphosed terranes. In contrast to the great majority of the known orogenic gold deposits, the Lykling ophiolite-hosted lode Au deposit records a magmatic origin of volatiles. Therefore, taking into consideration field relationships and the regional setting of the Lykling deposit, we argue that its formation is concomitant with emplacement of the Sunnhordland Batholith during post-collisional thinning of the crust and associated localized uplift within the Lykling Ophiolite Complex.

Growth Mediated Disassembly of Cucurbit[8]uril Cross‐linked Static Cubic Self‐assembly of Silver Nanoparticles

AbstractStatic self‐assembly resides in thermodynamically stable global minima of the energy landscape, whereas dynamic self‐assembly occupies local minima of the energy profile and remains in the ordered state for a limited time via dissipation of energy to surroundings. This makes the spatiotemporal control over the assembly and disassembly mechanism easily controllable in the case of dynamic self‐assembly. However, due to the higher thermal stability of static self‐assembly, it is very challenging to perform reverse engineering on these types of systems. Herein we report growth reaction‐based reversal of static silver cubes obtained via cucurbit[8]uril (CB[8]) crosslinked self‐assembly of silver nanoparticles (AgNP). The AgNP building units with variable CB[8] surface coverage have been used as seeds onto which deposition of gold via growth reaction has been performed. The disassembly of supracube structure has been controlled by the formation of [AuCl4]−–CB[8] complex and successive reduction of [AuCl4]− to Au0 on the surface of the seed. The resulting monodispersed isotropic nanoparticles, formed from the CB[8] based cubic self‐assembly after growth, exhibit Au−Ag bimetallic nature. Quenching of the fluorogenic response from the hydrophobic dye coumarin‐7, added after growth, suggests direct interaction with the metallic nanoparticle surface after disassembly and thereby confirms successful growth reaction mediated reversal of self‐assembly.