Silver Deposition Research Articles

Modelling and Impact of 3D Print Inaccuracies on the Performance of Circular Waveguide Hybrid Coupler

Circular waveguide hybrid coupler operating over a frequency range of ISM 57-64 GHz, additively printed and metal plated using electroless technique is introduced. Effects of orientation of print and thickness of intricate structures on the performance of circular waveguide hybrid coupler are presented. The structure is printed using commercially available stereolithographic (SLA) printer. Circulatory system operated by a peristaltic pump is used for selective silver deposition of the hybrid coupler.

On the timing and metallogenic implications of the sediment-hosted stratiform copper–silver mineralization in the Creston Formation (Belt-Purcell Supergroup), British Columbia, Canada

Sediment-hosted stratiform copper–silver mineralization is common in Middle Creston strata of southeastern British Columbia, a correlative lithostratigraphic unit of the Ravalli Group of western Montana. The Ravalli Group hosts the largest sediment-hosted stratiform copper–silver deposits of the Belt-Purcell Supergroup. Strata of the Belt-Purcell Supergroup accumulated between ~1540 and 1300 Ma in a pericratonic rift basin (Belt-Purcell basin) constructed over Archean and Paleoproterozoic blocks of Laurentia. The basin underwent several events of deformation and metamorphism at ~1380–1325 Ma (East Kootenay orogeny), ~1200–1000 Ma (Grenvillian), and 900–800 Ma (Goat River orogeny) prior to Meso-Cenozoic Cordilleran tectonism. U–Pb geochronology of detrital zircons from Middle Creston rocks define a maximum age of deposition of ~1470 Ma, in agreement with the established age range for the Belt-Purcell Supergroup in southeastern British Columbia. Molybdenite is locally part of the sediment-hosted stratiform copper–silver mineralization in the region, either as isolated grains within mineralized strata or in paragenetic sequence with the cupriferous sulfides. Re–Os geochronology on molybdenite reveals repetitive episodes of fluid flow through Middle Creston strata in the study area, with principal events at 1170–1140 and 1043–990 Ma. Paragenetically constrained molybdenite, in growth sequence with bornite and chalcocite, yields an age of 1043 ± 6 Ma. Hence, the fluid responsible for the sediment-hosted stratiform copper–silver mineralization in southeastern British Columbia permeated the host sequence ~440 m.yr. after its deposition, coincident with the Grenville-age metamorphic event at ~1200–1000 Ma. Such tectono-thermal activity extended along the western margin of Laurentia beyond the limits of the Belt-Purcell basin, and was a far-field response to orogen-scale collisions taking place off Laurentia during Rodinia assembly.

Effect of pH on the photocatalytic removal of silver ions by β-MnO2 particles

The presence of silver ions (Ag(I)) in wastewater has a detrimental effect on living organisms. Removal of soluble silver, especially at low concentrations, is challenging. This paper presents the use of β-MnO2 particles as a photocatalyst to remove Ag(I) ions selectively from aqueous solution at various pH levels. Inductively coupled plasma mass spectrometry (ICP-MS), X-ray diffraction (XRD), field emission electron microscope (FESEM), transmission electron microscopy (TEM), and X-ray photoelectron microscopy (XPS) were employed to determine the removal efficiency and to characterize the deposition of silver onto the surface of β-MnO2 particles. The optimum pH for the removal of Ag(I) ions was at pH 4 with 99% removal efficiency under 1 h of visible light irradiation. This phenomenon can be attributed to the electrostatic attraction between β-MnO2 particles and Ag(I) ions as well as the suppression of electron-hole recombination in the presence of H+ ions.

Dual-Modal Immunosensor with Functionalized Gold Nanoparticles for Ultrasensitive Detection of Chloroacetamide Herbicides

Convenient and ultrasensitive detection of pesticides is demanded for healthcare and environmental monitoring, which can be realized with a dual-modal strategy. In this paper, based on a biotin-labeled IgG-modified gold nanoparticle (AuNP@IgG-bio) probe, a dual-modal immunosensor was proposed for detecting chloroacetamide herbicides. This platform is relied on the dephosphorylation of ascorbic acid 2-phosphate (AA2P) by alkaline phosphatase (ALP). In addition to this process, ascorbic acid (AA)-triggered deposition of silver on gold nanostars (AuNSs) and the fluorogenic reaction of dehydrogenated AA and o-phenylenediamine (OPD) occur sequentially. Thus, the dual readout of the color change of red-green-blue (RGB) and fluorescence generation in situ induced by crystal growth can be used. The limits of detection (LODs) were as low as 1.20 ng/mL of acetochlor (ATC), 0.89 ng/mL of metolachlor, 1.22 ng/mL of propisochlor, and 0.99 ng/mL of their mixture by a smartphone and 0.44 ng/mL of ATC, 1.59 ng/mL of metolachlor, 2.80 ng/mL of propisochlor, and 0.72 ng/mL of their mixture by a spectrofluorometer. The recoveries from corn were 91.4-105.1% of the colorimetric mode and 92.4-106.2% of the fluorescent mode. Due to its simple observation mode and good performance, this dual-modal immunosensor possesses considerable application prospects.

Harvesting Waste Thermal Energy Using a Surface-Modified Carbon Fiber-Based Thermo-Electrochemical Cell

An important direction in the development of energy saving policy is harvesting and conversion into electricity of low-grade waste heat. The present paper is devoted to the improvement of the efficiency of thermo-electrochemical cells based on carbon fiber electrodes and potassium ferri-/ferrocyanide redox electrolyte. The influence of the carbon fiber electrode surface modification (magnetron deposition of silver and titanium or infiltration implantation of nanoscale titanium oxide) on the output power and parameters of the impedance equivalent scheme of a thermo-electrochemical cell has been studied. Two kinds of cell designs (a conventional electrochemical cell with a salt bridge and a coin cell-type body) were investigated. It was found that the nature of the surface modification of electrodes can change the internal resistance of the cell by three orders of magnitude. The dependence of the equivalent scheme parameters and output power density of the thermoelectric cell on the type of electrode materials was presented. It was observed that the maximum power for carbon fiber modified with titanium metal and titanium oxide was 25.2 mW/m2 and the efficiency was 1.37%.

The Lavrion Mines: A Unique Site of Geological and Mineralogical Heritage

The Lavrion area corresponds to the western part of the Attic-Cycladic metamorphic belt, in the back-arc region of the active Hellenic subduction zone. Between the Eocene and the Miocene, metamorphic rocks (mainly marbles and schists) underwent several stages of metamorphism and deformation due to collision and collapse of the Cycladic belt. Exhumation during the Miocene was accommodated by the movement of a large-scale detachment fault system, which also enhanced emplacement of magmatic rocks, leading to the formation of the famous Lavrion silver deposits. The area around the mines shows the stacking of nappes, with ore deposition mainly localized within the marbles, at marble-schist contacts, below, within, or above the detachment. The Lavrion deposit comprises five genetically-related but different styles of mineralization, a feature never observed in another ore deposit elsewhere, containing the highest number of different elements of any known mining district. The local geology, tectonic, and magmatic activity were fundamental factors in determining how and when the mineralization formed. Other key factors, such as the rise and the fall of sea level, which resulted from climate change over the last million years, were also of major importance for the subsequent surface oxidation at Lavrion that created an unmatched diversity of secondary minerals. As a result, the Lavrion deposit contains 638 minerals of which Lavrion is type-locality for 23 of them, which is nearly 12% of all known species. Apart from being famous for its silver exploitation, this mining district contains more minerals than any other district on Earth. The unique geological, mineralogical, and educational (mining, archaeological, and environmental) features suggest that it is highly suitable to be developed as a future UNESCO Global Geopark.

Cold spray (CS) deposition of a durable silver coating with high infrared reflectivity for radiation energy saving in the polysilicon CVD reactor

The radiative energy loss accounts for roughly 70% of the energy loss in the polysilicon chemical vapor deposition (CVD) reactors and therefore takes up to about 25% cost in the production of polysilicon used for solar cells. In this work, cold spray (CS) process was used to deposit Ag coating with ultra-high infrared reflectance on inner wall of the CVD reactor to minimize the radiative losses. To solve the bond strength problem of depositing soft coatings on hard substrate by CS, a Ni buffer layer with medium hardness was introduced. Results show that Ag coating can be successfully deposited with a porosity lower than 0.1%. Even the as-sprayed Ag coating has a high near-infrared reflectivity of 92% which was much higher than that of a well-polished substrate surface (65%) suggesting an excellent radiation energy saving capacity. The bond strength of the Ag coating is significantly increased from 3.7 MPa to 35.4 MPa and the thermal shock resistance is improved from 22 ± 3 to over 150 cycles by the Ni buffer layer. The scientific methodology demonstrated here can be a cost effective approach to reduce the radiation energy losses in the polysilicon-CVD industry.

Antibacterial Properties of Plasma-Activated Perfluorinated Substrates with Silver Nanoclusters Deposition

This article is focused on the evaluation of surface properties of polytetrafluoroethylene (PTFE) nanotextile and a tetrafluoroethylene-perfluoro(alkoxy vinyl ether) (PFA) film and their surface activation with argon plasma treatment followed with silver nanoclusters deposition. Samples were subjected to plasma modification for a different time exposure, silver deposition for different time periods, or their combination. As an alternative approach, the foils were coated with poly-L-lactic acid (PLLA) and silver. The following methods were used to study the surface properties of the polymers: goniometry, atomic force microscopy, and X-ray photoelectron microscopy. By combining the aforementioned methods for material surface modification, substrates with antibacterial properties eliminating the growth of Gram-positive and Gram-negative bacteria were prepared. Studies of antimicrobial activity showed that PTFE plasma-modified samples coated with PLLA and deposited with a thin layer of Ag had a strong antimicrobial effect, which was also observed for the PFA material against the bacterial strain of S. aureus. Significant antibacterial effect against S. aureus, Proteus sp. and E. coli has been demonstrated on PTFE nanotextile plasma-treated for 240 s, coated with PLLA, and subsequently sputtered with thin Ag layer.

Yakutia as One of the Richest in Natural Resources Regions of the Russian Federation

The paper presents the analysis of the territory study on the presence of minerals in Yakutia. The purpose of this analysis was to summarize the data on the main deposits located in different geographic regions of the republic. The article provides a scientific review of the current state of the mineral resource base of Yakutia, including general information about the region, geological structure, and the largest mineral deposits. In addition, statistical data on the number of deposits and their reserves are given. The problem of the natural resources usage, as well as the subsoil distribution and rent income, is touched upon. The Republic of Sakha (Yakutia) is one of the largest regions of the Russian Federation, more than half of which is located beyond the Arctic Circle. Despite the harsh climate, significant reserves of various minerals are concentrated in Yakutia. There are large reserves of oil, natural gas, coal, diamonds, gold, silver, tin, niobium, uranium ore and other mineral resources. A number of deposits are unique and large. They include Chayandinskoye oil and gas condensate field, Deputatskoye and Terekhtyakhskoye tin-bearing deposits, Agylkinskoye tungsten deposit, Nezhdaninskoye gold ore deposit, Sarylakhskoye and Sentachanskoye gold-antimony deposits and other deposits of silver, rare metals, uranium and other minerals. Of the 35 explored hydrocarbon deposits, 15 are oil and gas condensates, 11 are gas condensates, 2 are oil and gas deposits, and 7 are gas ones. Explored reserves of diamonds in the Yakutian diamondiferous province account for 73.5% (150 deposits) of the Russian Federation reserves, gold - 12.3% (815 deposits). Mining forms about half of the gross regional product of Yakutia. At the same time the republic ranks 7th in the country, while the life quality of the local population takes about 70th place.

New data concerning the age and composition of intrusion complexes of the northern part of Balygychan-Sugoi rift depression (North-Eastern Russia)

The Balagychan-Sugoi (Omsukchan) riftogeneous depression is described by different authors both as a part of Okhotsk-Chukotka volcanic belt (OCVB) and as a separate structure. The unique Dukat gold and silver deposit and a lot of others ore deposits including rare-metal, such as Arylah, Lunnoe, Askold, Mechta, Tidid, Krasin, are associated with this structure. All mentioned objects are located in the south part of the depression and from this point of view are connected with OCVB structure. Evolution of the Balygychan-Sugoi depression is closely related to the stages of magmatic evolution of the region. In the article, these stages are characterized based on the data form intrusion bodies located in the northern part (Naygain depression). This part is the most outlying from the OCVB and less investigated. For the first time, the U-Pb zircon and baddeleyite dating and the description of petrographic and geochemical composition have been carried out for Mandychan gabbro-diorite and Nayahan gabbro leucogranite intrusion complexes from the northern part of the depression and for Omsukchan leucogranite complex. The Late Jurassic – Early Cretaceous intrusions of the Mandychansk complex dated as 143-139 Ma mark the beginning of the rift depression formation. Intrusion of granitoids of the Nayahan and Omsukchan complexes dated as 84-85 Ma and 81-82 Ma correspondently is related with new stage of magmatic activity, synchronous to OCVB formation. The petrographic and geochemical compositions of these granitoids indicate their belonging to the I-type granites, which are typical for extension environments, whereas leucogranites of the Omsukchan complex have some features corresponding to the A-type granites.

Natural Rubber Films Incorporated with Red Propolis and Silver Nanoparticles Aimed for Occlusive Dressing Application

Abstract In this work, NRL films were enriched with red propolis and silver nanoparticles with the aim of obtaining dressings with bactericide properties. To improve the properties of these materials, plasma treatment was also applied to the films. Cytotoxic effects were evaluated by MTT and agar diffusion assays on secondary and stem cells. Determination of cell behavior on the films were assessed by EDS and FEG-SEM. In general, the plasma modified NRL films presented hydrophilic character, favorable condition for biomedical applications. RBS results showed that silver is probably in nanoparticulate form. MTT assays revealed that non-cytotoxic effects were observed for all the samples extracts. Either the plasma treatment or silver deposition were effective in sterilizing the samples and modifying their surfaces. It was demonstrated in this in vitro study that ADSCs associated with NRL films enriched with propolis should be considered promising for application in the healing of occlusive wounds.

Electrodeposition of Silver–Graphene Films for Electronic Connectors in Succinimide Solutions

Silver is electroplated on the surface of connectors as a protective barrier layer in order to improve the corrosion resistance and to increase the durability of the connector. In this work, silver-graphene films were electrodeposited on copper–zinc alloy substrates from a succinimide silver-plating system in Hull-cell alkaline solutions by the addition of 0.4 g L–1 graphene oxide. The crystallographic structure and microstructure of the formed films were determined by X-ray diffraction and scanning electron microscopy, respectively. The corrosion resistance of the films was measured by a potentiodynamic polarization test. The results show that a low amount of graphene was incorporated into a silver deposit. The addition of graphene oxide could not influence the deposition rate and the crystallographic structure of the film, but resulted in a decrease in the size of aggregates or particles, compared with those of a pure silver film. The optimal current density was found to be 0.5 ~ 1.0 A dm–2, the surface of the films had a homogeneous close-packed fine-crystalline structure. The films were uniform, dense, and adherent to the substrate, without any evidence of delamination. At the same time, the addition of graphene oxide improved the corrosion resistance of silver films to a certain extent.

Flower-like gold nanoparticles labeled and silver deposition rapid vertical flow technology for highly sensitive detection of Brucella antibodies.

To prevent the transmission of brucellosis, rapid vertical flow technology (RVFT) was developed to detect brucellosis antibodies. To improve the sensitivity of the technique, lipopolysaccharides (LPS) were purified and used to detect brucellosis antibodies. To improve the sensitivity of serum antibody detection, a single multifunctional buffer was established in whole blood and other biological samples, and the advantages of the lateral flow immunoassay were retained. Flower-like gold nanoparticles were applied to RVFT for the first time. In this study, silver ions were catalyzed by flower-like gold nanoparticles into metal silver deposited on the surface of gold nanoparticles for the first time, which not only increased the particle size of gold nanoparticles, but also showed a more distinguishable black color on the test zone, further improving the sensitivity of RVFT. Standard Brucella-positive serum (containing Brucella antibody at 4000 IU mL-1) could be detected in this system even for a dilution factor of 2 × 10-3. The detection limit was 2 IU mL-1. RVFT can effectively avoid the false negative phenomenon in lateral flow immunoassay. RVFT is simple to operate, with a short reaction time, 2-3 minutes visible to the naked eye, without any equipment. Because it is very important to control the brucellosis epidemic, this approach has great application prospects in basic medical units and for veterinarians.

Magmatic-hydrothermal silver deposits, argentiferous provinces and the main controlling factors of formation

Magmatic-hydrothermal silver deposits, argentiferous provinces and the main controlling factors of formation

Preparation of micron–sized polystyrene/silver core–shell microspheres by ultrasonic assisted electroless plating

In the study, PS/Ag composite microspheres with polystyrene (PS) core and silver shell were synthesized by ultrasonic electroless plating. The samples were characterized by SEM, FTIR and XRD. The effects of times of sensitization and silver plating, mass ratio of AgNO3 to PS microspheres and stirring method on the preparation and dispersion of PS/Ag microspheres were studied. The results show that the more times of sensitization and silver plating, the more uniform the silver deposition on the surface of microspheres. When the mass ratio of AgNO3 to PS microspheres is 2: 1, it can promote the uniform coating of silver shell and reduce the content of free silver. Ultrasonic assisted electroless plating for 10 min can prevent PS/Ag microspheres from agglomerating and improve the speed of electroless plating. The thickness of the silver shell on the surface of the PS microsphere is about 200 nm.

Age and Genesis of the Pokrovskoe Gold–Silver Deposit (Russian Far East)

Abstract ––We present results of geochronological studies of rocks from different igneous complexes and of hydrothermally altered volcanics with Au–Ag mineralization from the Pokrovskoe deposit. The age of the ore-hosting granites of the Sergeevsky pluton of the Upper Amur complex is estimated at ~129 Ma. The primary age of dacites of a sill-like body is within 128–125 Ma and is close to the age of volcanics of the Taldan complex. Propylitization processes superposed on these dacites are dated at ~122–119 Ma. Taking into account the commercial contents of gold and silver in these rocks, we believe that the age of the hosted orebodies is in the same interval. The period 122–119 Ma is also the time of formation of the Gal’ka volcanic complex in the Umlekan volcanic zone, which was accompanied by granitoid magmatism. This suggests that the formation of the Pokrovskoe deposit was associated with the accumulation of the Gal’ka complex.

Plasma-Assisted Silver Deposition on Titanium Surface: Biocompatibility and Bactericidal Effect

Abstract Dental implants are especially susceptible to bacterial adhesion and so microbial contamination. Several techniques have been explored in order to obtain implant surfaces enriched with silver (Ag). The main challenge is to obtain a bactericidal effect keeping the surface biocompatible. In this regard plasma-assisted deposition is a very attractive technique due to its versatility and low environmental impact. Thus, the present work aimed at evaluating the chemical stability, antibacterial activity, and biocompatibility of a commercially pure titanium (cp-Ti) surface containing very low amounts of plasma-deposited Ag. Ag deposition obtained by 10 minutes sputtering was able to promote antibacterial action (around 30%) on a clearly cytocompatible Ti/Ag surface with no apparent impact on biocompatibility. Taken together these results indicate that the proposed deposition process has a great potential for dental implant application with the advantage of using very small amounts of silver to achieve efficacy.

Origin of Qinxi Silver Polymetallic Deposit in Southeast Coast, China: Evidences from H–O–S–Pb Isotopes and Mineral Rb–Sr Geochronology

The Qinxi silver deposit is located in eastern Fujian Province, South China. It is hosted in the late Jurassic Nanyuan volcanic unit and controlled spatially by structural alteration zone. The origins of the deposit are understood poorly. In this study, systematic field geology, precise sulfide geochronology, and H–O–S–Pb isotope analyses were carried out. The symbiotic minerals and ore assemblages are interpreted as evidence that Qinxi ore is a typical middle to low temperature hydrothermal deposit. Galena and sphalerite from the ore yield a Rb–Sr isochronal age of 130 ± 2.0 Ma (MSWD = 1.7), and single galena samples yield a Rb–Sr isochronal age of 130 ± 7.1 Ma (MSWD = 2) and are evidence that the ore was formed in the early Cretaceous period. The silver-bearing quartz vein has O:H and 18O:16O ratios intermediately between magmatic and meteoric water (δ18 Owater-smow from −2.50‰ to −0.1‰ and δDv-smow from −73.6‰ to −60.7‰). The δ34 S values of metal sulfide are close to the primitive mantle sulfur values (δ34S = −1.7 to 7.1‰, avg. = 0.92‰). The Pb isotopic compositions from the ore are similar to those of the hosted volcanic unit, with a value between the upper crust and mantle isotope composition (206Pb/204Pb = 18.421~18.605, 207Pb/204Pb = 15.580~15.772, 208Pb/204Pb = 38.591~39.183). Lead–zinc sulfides have mature crustal-derived Sr isotopic features ((87Sr/86Sr)i = 0.7103). Thus, the metallogenic source materials mainly came from the crust. Moreover, regional geological studies suggest that the Qinxi ore deposit was likely formed in an extensional terrane.

Influence of hydrophobic layer of Bis-EMA with different ethoxilations on adhesive's bonding efficacy and mechanical properties

ObjectivesThe aim of this study was to evaluate the effects of a hydrophobic layer of Bis-EMA 4 (B4, 4 ethoxilations), Bis-EMA 10 (B10, 10 ethoxilations) or Bis-EMA 30 (B30, 30 ethoxilations) on dentin adhesion and mechanical properties of a universal adhesive. Materials and methodsExtracted human molars were cut and restored using self-etching mode of Ambar Universal (AU, FGM) adhesive and divided according to the hydrophobic layer employed (n = 8): only AU (Control), SBMP (Scotchbond Multi-Purpose adhesive, 3 M, Commercial Control), B4, B10 and B30. Microtensile bond strength (μTBS) and nanoleakage tests were performed after 24h and 6 months water storage. Interface micro-permeability was surveyed by confocal microscopy. Dynamic-mechanical analysis (DMA) of each adhesive combination (50 wt% Ambar + 50 wt% BisEMA or 100% Ambar) were assessed. The data were statistically analyzed using two-way ANOVA and Tukey's test (p < 0.05). ResultsSBMP achieved the highest μTBS, followed by B4, B10 and Control, whilst B30 presented significantly lowest μTBS when compared with further groups (p < 0.001). After ageing, the only group depicting significant μTBS reduction was Control (p = 0,009). B4 and SBMP were almost devoid of silver deposits and did not show any signs of gaps, even after ageing. B4 presented the lowest micropermeability and the best mechanical behavior on DMA, showing the highest rubbery zone and increased glass transition temperature. ConclusionsBis-EMA-4 might be a suitable monomer for a hydrophobic layer in adhesive strategy, reducing hydrolytic degradation and increasing the durability and mechanical properties of adhesive interfaces.

Trace element characteristics of magnetite: Constraints on the genesis of the Lengshuikeng Ag–Pb–Zn deposit, China

Magnetite occurs as an ore mineral in many types of deposits and its trace element characteristics can be used to fingerprint various types of mineral deposits and distinguish different ore forming processes. The Lengshuikeng Ag–Pb–Zn deposit (LSKD) is one of the largest silver deposits in China, but the ore forming processes involved in its formation are still unclear. In this study, magnetites from six representative samples of different mineralization types were examined. Their trace element contents were analyzed using in situ laser ablation inductively coupled plasma mass spectrometry (LA–ICP–MS), to better understand the genesis and evolution of the ore-forming fluids responsible for Ag–Pb–Zn mineralization. The studied magnetites were divided into two types based on their spatial occurrence, associated minerals and distinctive textures. Type A magnetites are large, display subhedral to euhedral forms and appear inclusion-free. They coexist with siderites and formed early, preceding the formation of surrounding sulphides. Type B magnetites are small, exhibit irregular and anhedral forms that feature as wall-rock alterations, and were formed during the main mineralization stage. They coexist with main-stage sulphides and Fe-Mn-bearing carbonate minerals, in which Mn content increases corresponding to the evolution of the mineralization process. Generally, magnetites from the LSKD contain low amounts of Ti and V, and widely variable Al and Mn contents, which resulted from multiple influxes of low-temperature hydrothermal fluid. Type A magnetites are inferred to have formed paragenetically early at relatively high temperatures without coeval precipitation of base-metals. Conversely, Type B magnetites are interpreted to have formed during the early (B1, stage 1) and main (B2, stage 2) stages of Ag–Pb–Zn mineralization under alteration and dissolution–reprecipitation processes (DRP) from the later ore-forming hydrothermal fluids. Trace element characteristics of magnetite suggest the late hydrothermal fluid was characterized by low temperatures, and was enriched of Cl and Mn. The wide range of contents of trace elements (e.g. Ga, Mo and Sn) in magnetite that underwent DRP can be explained by different wall-rock types and water/rock ratios. Characteristics of the late hydrothermal fluids, including those from detailed microscopic observations, indicate that the ingress of Ag, Pb and Zn occurred as metal–Cl complexes, and that dissolution of early Fe, Pb, and Zn sulphides supplied the S required for the final precipitation of silver.