Enrichment Of Ag Research Articles

Mineralogical and geochemical characteristics and ore-forming mechanism of hydrothermal sediments in the middle and southern Okinawa Trough

In this study, analysis of mineralogy and geochemistry of fifteen surface sediment samples from four hydrothermal fields in the middle and southern Okinawa Trough is presented. Sediment samples can be divided into two types: (1) Metalliferous group (MS group) containing large amounts of sulfides and sulfate are enriched in Pb, Zn, Cu, Fe, Au, Ag, Ba, As, Hg, Se, Sb, Mo, slightly enriched in U, V, and have rare earth elements (REE) patterns similar to those of hydrothermal vent fluids and sulfides, indicating formation by a complex combination of wasting and erosion primary massive sulfide deposits and plume fallout of sulfides and sulfate. The occurrence of sphalerite with high contents of Fe and of co-existing pyrrhotite as major Fe-sulfide indicate that these minerals are formed at high temperature with low-sulfur fugacity in the Clam and Jade hydrothermal sites. The enrichment of Pb, Zn, Cu, Au, Ag, Ba, As, Hg, Se, Sb, and Mo is related to the presence of galena, sphalerite, Cu-sulfides, stibnite, and realgar in the sediments. (2) Non-metalliferous group (non-MS group) containing small amounts of pyrite are slightly enriched in Pb, Zn, Cu, Au, Ag, As, Hg, Se, Sb, and Mo relative to the East China Sea (ECS) continental shelf sediments, with REE exhibiting a “shale-like flat” patterns and close to Taiwan sediments in a REE discrimination plot, indicating formation by a large amount of terrigenous materials originated from Taiwan Island and a small amount of particles of sulfides in the hydrothermal nonbuoyant plume. The slight enrichment of Pb, Zn, Cu, Au, Ag, As, Hg, Se, Sb, and Mo maybe caused by co-precipitation with the fine-grained sulfides settling from the nonbuoyant plume. The positive relationships between the HREE fractionation index (Gd/Yb)N, heavy mineral proportion, and δEu suggest that (Gd/Yb)N can be used as a sensitive indicator for reflecting the effect of hydrothermal activity on the sediments.

Green methanol synthesis by catalytic CO2 hydrogenation, deciphering the role of metal-metal interaction

The current work deals with the synthesis, characterization and activity studies of zeolite based Ag–Cu bimetallic catalysts for CO2 hydrogenation to methanol. To probe the effect of Ag–Cu weight ratio, Ag–Cu with 1:9, 2:8, 4:6 and 1:1 wt ratios were synthesized by impregnation method. Thermo-gravimetric analysis revealed that catalysts stability was improved by Ag enrichment to the zeolite based Ag–Cu bimetallic catalysts. X-ray diffraction studies showed that zeolite structure has been modified by the incorporation of Ag–Cu metals to the bare zeolite. Nitrogen adsorption desorption studies manifested that BET surface area, pore size and pore volume were less affected by variation in Ag–Cu weight ratio. Formation of nano-sized Ag–Cu bimetallic catalysts with high dispersion was illuminated by Field Emission Electron Microscopy (FESEM). X-ray Photoelectron Spectroscopy (XPS) findings revealed greater metal-metal chemical interaction as a consequent of Ag addition to the zeolite based Ag–Cu bimetallic catalysts. Activity studies of zeolite based Ag–Cu bimetallic catalysts exhibited the promoting role of Ag in CO2 hydrogenation to methanol. The structure activity studies observed Ag–Cu metal-metal chemical interaction as the key factor controlling the rate of methanol synthesis.

Silver Metal Extraction from Refractory Silver Ore Using Chloride-Hypochlorite and Hydrochloric Acid Media Under High Pressure

The mobility of gold and silver metals from refractory ores is very low due to free metal ions in their bodies that bind the transportable and free metal molecules or they are encapsulated in minerals such as sulfides, arsenosulfides, carbonaceous, and clayey materials which make it difficult to extract them. As known from the literature, the enrichment of oxide refractory gold, silver ores, Ag, and Au-rich flotation concentrated from sulfur refractory ores can be leached in the chloride-hypochlorite solutions. In this work, the leaching approach was studied to extract silver ions from refractory ores in the presence of hypochlorite media under high pressure. The mineralogical and scanning electron microscopy analysis of the sample indicated that the silver was encapsulated in barite and quartz minerals in fine sizes. In order to obtain the optimum leaching conditions for the silver ore, the effects of several parameters, namely, temperature, leaching time, NaCl and NaOCl concentration, solid ratio, and particle size on the leaching recovery were investigated in detail. The leaching experiments showed that the highest silver recovery of 62.35% was obtained under the following conditions: temperature of 150 °C, oxygen pressure of 1800 kPa, leaching time of 2 h, concentrations of 2 mol/dm3 and 0.4 mol/dm3 for NaCl and NaOCl, respectively, the solid ratio of 30%, and particle size (d80) 15 μm. The results obtained from this study indicated that the enrichment of refractory silver ores to extract the silver encapsulated in barite and quartz minerals could be possible in the chlorite-hypochlorite under high pressure, a relatively shorter leaching time compared to conventional cyanide leaching.

Geochemistry of Fe-Ti oxide and sulfide minerals in gabbroic rocks and magnetitite of the Archean Mayurbhanj mafic complex (eastern India): Magma fractionation, thermometry and oxygen fugacity of re-equilibration, and implications for Ni-Cu mineralization

The Archean Mayurbhanj mafic complex in the Singhbhum Craton (eastern India) contains a magmatic Fe-Ti-(V) oxide ore deposit within a gabbro-norite-anorthosite suite of rocks. Immediate country rocks belong to the early Archean Gorumahisani greenstone belt and 3.1 Ga granitic complex. The gabbro-noritic rocks of the Mayurbhanj complex consist of plagioclase (An26−69), clinopyroxene (En42−54Fs4−36Wo22−42), and orthopyroxene (En67−81Fs15−28Wo4−5) as cumulus phases with Fe-Ti-oxides (magnetite and ilmenite) and sulfides (pyrite, pyrrhotite, chalcopyrite) as disseminated phases. Two-pyroxene thermometry yields temperatures of 1199 °C − 956 °C which are close to the primary liquidus temperature of pyroxene from a fractionated basaltic magma. The co-existing magnetite and ilmenite pairs in gabbro and magnetitite yield equilibrium temperatures of 498–797 °C and oxygen fugacities of 11.38–27.1 (log fO2) reflecting various stages of cooling and subsolidus re-equilibration of the mineral phases. Disseminated sulfides are mainly present along the grain boundaries of accessory Fe-Ti oxide grains, within interstitial spaces of silicate minerals, as inclusions within the silicate minerals and along altered fracture zones of the silicate host whereas the magnetitite bodies are devoid of such sulfide mineralization. In-situ trace element analysis of oxide and sulfide minerals from the gabbro-noritic rocks and magnetitite ores reveals a higher concentration of Cr (22301–67433 ppm) and Ni (896–3880 ppm) in the magnetite of gabbro than in the magnetitite bodies. This is due to early fractionation of the accessory magnetite in the gabbro from a Fe-rich basaltic magma. The lower concentration of V (30211–34608 ppm) in the accessory magnetite of the gabbro-noritic rocks than in the magnetitite (48534–64855 ppm) suggests partitioning of vanadium into clinopyroxene within the gabbroic rocks. Higher chalcophile element (Pb ≈ 2–11 ppm, Zn ≈ 6773–8139 ppm, Mo ≈ 25–68 ppm) concentrations in magnetite of the gabbro-noritic rocks indicate equilibration with co-magmatic sulfide mineral assemblages. The partitioning behavior of HFSE (Zr, Hf, Ta, Nb) in the magnetite and ilmenite is mainly dependent on the Ti4+ content of the minerals. The rim of iron-oxide minerals around sulfide grains and negative Ni anomaly in the trace element pattern of pyrite suggest that these pyrite grains have formed after pyrrhotite which is magmatic in origin. Enrichment of Pb (≈ 27–3120 ppm), Ag (≈ 8–15 ppm), Bi (≈ 0.2–9 ppm), As (≈ 48–6561 ppm), and Sb (≈ 0.4–18 ppm) in a few pyrites suggests hydrothermal alteration of primary magmatic pyrite grains.

Super-enrichment mechanisms of precious metals by low-melting point copper-philic element (LMCE) melts

低熔点亲铜元素（LMCE）As、Sb、Bi、Hg、Pb、Se、Te、Tl、Sn等，均具有亲铜性、低熔点、半金属的特性，在成矿过程中可以形成LMCE熔体，并对Au、Ag、PGE等贵金属的高效富集沉淀起到一种重要的桥梁作用。作者对前人研究资料与LMCE热力学相图进行了分析，并结合浅成低温热液型、造山型、卡林-类卡林型、碱性-偏碱性侵入岩型金矿床的研究成果，探讨了LMCE熔体形成、类型及其对Au、Ag、PGE等贵金属富集成矿的机理，并提出了LMCE熔体参与成矿的矿物组合与结构特征标志。LMCE熔体可以在岩浆过程、（岩浆）热液过程及变质过程中形成，是贵金属矿床重要的成矿机制之一。LMCE熔体中存在大量原子团簇，团簇间的聚集生长会使熔体难以达到相平衡，形成许多非平衡矿物组合，如包含LMCE的自然元素、金属互化物及含LMCE的多相矿物。Au在LMCE熔体中也可以团簇存在，金团簇聚集形成球状或片状，并形成巨富的金矿体。LMCE熔体形成的矿物常以浑圆状、近浑圆状、不规则状的单个或群体组合的乳滴、珠滴、气泡的微粒包体产在硫化物、硒化物、碲化物、氧化物和硅酸盐矿物内或沿矿物裂隙线形排列，这些LMCE微粒包体是熔体扰动导致熔-熔或熔-液间发生乳化所致，流体沸腾是引起熔体扰动的主要机制。LMCE熔体不能快速淬火结晶，通常在低温下缓慢冷却达到相平衡，形成复杂的矿物组合，该特点即使在微米到纳米级的矿物微粒中也显著存在。熔体-流体包裹体是LMCE熔体参与成矿作用最为直接的证据。固溶体分解结构、熔体退火结构、矿物-熔体二面角结构、溶解-再沉淀结构等也是LMCE熔体参与成矿的标志性结构。;The low-melting point chalcophile elements (LMCE), including As, Sb, Bi, Hg, Pb, Se, Te, Tl, Sn and so on, have characteristics of chalcophile behavior, low melting point and semi-metallic properties, which can form LMCE melt during mineralization process and play an important role for the efficient enrichment and precipitation of Au, Ag, PGE and other precious metals. In this paper, the previous research data and the LMCE thermodynamic phase diagrams were analyzed. Combining research results of epithermal, orogenic, Carlin to Carlin-like and alkaline to meta-alkaline intrusion-related gold deposits, the authors discussed the formation and type of LMCE melts and their mechanisms for the enrichment of Au, Ag, PGE and other precious metals, and summarized mineral compositions and characteristic textures of mineralization that benefited by LMCE melts. The LMCE melts can be formed during magmatic, (magmatic-) hydrothermal and metamorphic processes, and belong to one of the important metallogenic mechanisms for precious metal deposits. There are many ion clusters in the LMCE melts, and aggregation between the clusters precludes the melt to reach phase equilibrium, which results in many non-equilibrium mineral combinations, including the coexistence of native LMCE, intermetallic compounds and multiphase minerals containing LMCE. Gold could also exist as ion clusters in the LMCE melt that gather to form spherical or flakes native gold, and form the super-rich ore bodies. The minerals formed by LMCE melt often exist as single or group combinations of emulsion droplets, beads, and bubbles in round, nearly round, and irregular particle inclusions in sulfides, selenides, tellurides, oxides and silicates, or distribute along fractures of minerals. These LMCE micro-inclusions are derived from melt disturbance that result in melt-melt or melt-liquid emulsification. Fluid boiling should be the main mechanism that causes the melt disturbance since the LMCE melt cannot be quenched and crystallized quickly at this process. It is usually cooled slowly at low temperature to achieve phase equilibrium and form complex mineral compositions. This feature is significant even in micro-to nano-scale mineral particles. Melt-fluid inclusions are the most direct evidence for the involvement of LMCE melts during mineralization. Solid solution decomposition texture, melt annealing texture, mineral-melt dihedral texture, dissolution-reprecipitation texture are also characteristic textures of LMCE melts involved in mineralization.

Selective enrichment and separation of Ag(I) from electronic waste leachate by chemically modified persimmon tannin

A 2,5-dimercapto-1,3,4-thiadiazole (DMTD)-immobilized and persimmon tannin (PT)-based biosorbent, DMTD-PT, was synthesized via a one-pot method and used for selective enrichment of Ag(I) from electronic waste (e-waste) leachate. Batch adsorption revealed that both PT and DMTD-PT had a weaker affinity for co-existing metal cations. However, DMTD-PT and PT adsorbed 98.7% and 20.7% of Ag(I), respectively, with a dose of 5.0 g L−1 each at pH 3.0 from e-waste leachate that contained 117.3 mg L−1 of Ag(I) at room temperature. These observations indicate that the selectivity of DMTD-PT is superior to that of PT. The column adsorption further proved that DMTD-PT can be used to separate Ag(I) from e-waste leachate. The adsorption of Ag(I) on DMTD-PT fit the Langmuir isotherm well with a maximum adsorptive capacity of 50.7 mg g−1. A thermodynamics study further indicated that the adsorption was spontaneous and was dominated by chemisorption. The two mass transfer models of homogeneous solid diffusion model (HSDM) and a Linear Driving Force (LDF) model were used to study the kinetics and generally well fitted the experimental data. Analyses of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) of fresh and Ag(I)-adsorbed DMTD-PT further revealed that the plausible adsorption mechanism was principally attributable to the complexation of N and S on the diazole ring. Also, DMTD-PT exhibited better reusability and qualified durability without a distinct decrease in Ag(I) adsorption even after 5 repeated cycles.

Late Cretaceous black shales from the Tuscan Sedimentary Succession (northern Tuscany, Italy): geochemistry and ore mineralogy

We report on the first geochemical and mineralogical study of the Late Cretaceous black shales and black phyllites occurring within the basal portion of the “Scaglia toscana” and “Scisti sericitici” formations, respectively (Northern Apennines, northern Tuscany, Italy). The black shales occurring within the “Scaglia toscana” Formation are interbedded with red and greenish shales and form cm-thick layers; in some localities they are characterized by the occurrence of cm- sized pyrite nodules. Black phyllites and meta-cherts in the “Scisti sericitici” Formation are associated with Cu ores and with a small pyrite-molybdenite mineralization. These rocks are made of variable amounts of quartz, “chlorite”, illite/muscovite, pyrite ± calcite ± albite plus accessory amounts of baryte, apatite, sulfides and sulfosalts. In addition, they contain abundant carbonaceous matter (2-12 wt% total organic carbon). Whole-rock analyses by ICP-MS reveal a marked enrichment of Cd, Ag, Zn, Sb, Cu, Mo, V, Pb, and Tl with respect to the average marine shale and to the more typical shales of the “Scaglia toscana” fm. The distribution of these elements in the studied samples is compatible with a strongly anoxic and euxinic depositional environment. The hyper-enrichment of Cd, Ag, Zn, Sb and Cu strongly suggests that besides from seawater these elements were extracted from additional sources, most likely hydrothermal vents.

Distribution of trace elements in sulfides from Deyin hydrothermal field, Mid-Atlantic Ridge – Implications for its mineralizing processes

Knowledge about the trace element distribution in sulfides is the key for understanding the trace metal inventory during the formation of the volcanic massive sulfide deposits on the seafloor. The distribution of trace metals in sulfides reflects changes in the physicochemical conditions and precipitation processes during precipitation. Hydrothermal black smoker samples of this study originate from the southern Mid-Atlantic (TVG02, TVG06) and can be classified into two types: (1) (Fe-Zn) sulfides consisting predominantly of pyrite and sphalerite, with minor chalcopyrite, isocubanite, and galena and (2) (Fe-Cu) sulfides, which contain mainly pyrite and chalcopyrite, with rare isocubanite and sphalerite. The sulfide samples were analyzed by electron microprobe for major elements, and by laser ablation inductively coupled plasma mass spectrometry, focused ion beam technique and transmission electron microscopy for in situ trace elements. The data reveal complex hydrothermal processes in high- and low- temperature fluids. Colloform and dendritic pyrite from (Fe-Zn) sulfides are enriched in Mn, Tl, As, V, Pb, and Zn, indicating precipitating from a rapid mixture of low temperature fluids (100–250 °C) with seawater. A continuous enrichment of incompatible elements (Pb and Zn) at the interface of growing pyrite with fluid finally leads to the nucleation and precipitation of sphalerite and galena, and results in the enrichment of As, Hg, Pb, Au, Ag, and Cd in sphalerite micro-inclusions which are hosted in colloform pyrite at low temperature. Galena inclusions occur in the pores and the interstices of sphalerite grains and formed by the enrichment of Pb in the hydrothermal fluid at low-temperature (<250 °C). High Cu, As, Ag, Au, and Sb concentrations in colloform sphalerite indicate a medium to low formation temperature (350–200 °C). Copper, Sb, Se, and Sn enrichments in coarse-grained sphalerite indicate medium temperature hydrothermal fluids. Idiomorphic pyrite and chalcopyrite have high Se and Co contents and indicate precipitaion from high-temperature (>300 °C) fluids.

Paragenetic relationships between low- and high-grade gold mineralization in the Cripple Creek Au-Te deposit, Colorado: Trace element studies of pyrite

The Cripple Creek alkaline igneous rock-related low-sulfidation epithermal gold telluride deposit is hosted in a 10 km wide Oligocene alkaline volcanic diatreme in Proterozoic rocks. Periods of phreatic eruptions and progressively more mafic alkaline magma emplacement created the diatreme and breccias that host the gold ore, followed by breccia pipe creation, and later by the emplacement of phonolite and later lamprophyre dikes throughout the diatreme. Pervasive potassic alteration affected much of the diatreme, and is spatially related to the late-stage veins containing native gold and precious metal tellurides. Previous studies have mainly focused on the high-grade gold veins primarily located toward the center of the diatreme. The current study evaluates the mineralogy and paragenesis of low-grade mineralization in the currently mined Wild Horse Extension (WHEX), Globe Hill, and Schist Island pits, and the Galena Embayment along the margin of the diatreme next to the WHEX pit, as well as high-grade mineralization in the WHEX and Cresson pits. Given the variable paragenesis of mineralizing stages in different locations in the Cripple Creek deposit, a simplified three stage paragenesis (stages 1, 2, and 3) is recognized here involving low- and high-grade gold mineralization.Scanning electron microscopy, electron microprobe, and laser ablation-inductively coupled plasma-mass spectrometry analyses are used to compare the trace element compositions of pyrite in low- and high-grade gold mineralization. These analyses reveal a complex trace element pattern with variability in Ag, As, Au, Co, Ni, Sb, and Te in the rims, cores, and zones (area between the core and the rim) of stages 2 (Py2) and 3 pyrite (Py3) and spatially between the pits currently being mined. Trace element concentrations in stage 1 pyrite (Py1) are lower than those in Py2 and Py3 and the patterns are uniform. Trace elements reside within the lattice structure of pyrite and as micro- and nano-inclusions (e.g., up to 48,220 ppm As, 6983 ppm Co, 12,250 ppm Ni, and 10,860 ppm Sb). The trace element patterns from the final stage of pyrite growth in high-grade gold telluride veins indicate enrichment in Ag, As, Au, Cu, Pb, Sb, and Te.The paragenesis and compositional zoning of pyrite associated with high-grade ore contrast with those associated with pyrite from low-grade ore, which preceded the formation of high-grade gold telluride veins. This suggests that metallic mineralization occurred in multiple episodes and that low-grade ore did not form from the same hydrothermal fluids that precipitated the high-grade ore. Early pyrite formed under passive, non-boiling conditions, followed by a transition to vigorous boiling in Py2 and Py3, ending with non-boiling conditions recorded in the Au and As-rich rims of Py3. This enrichment in Au and As on the rims of pyrite is consistent with other alkaline igneous rock-related epithermal Au deposits, as are the concentrations of trace elements throughout the pyrite grains. The presence of As, Ag, Co, Cu, Mo, Ni, Sb, Te, and Tl in pyrite are considered vectors to high-grade Au ore in the Cripple Creek deposit.

Ultrahigh-Temperature Sphalerite from Zn-Cd-Se-Rich Combustion Metamorphic Marbles, Daba Complex, Central Jordan: Paragenesis, Chemistry, and Structure

Minerals of the Zn-Cd-S-Se system that formed by moderately reduced ~800–850 °C combustion metamorphic (CM) alteration of marly sediments were found in marbles from central Jordan. Their precursor sediments contain Se- and Ni-enriched authigenic pyrite and ZnS modifications with high Cd enrichment (up to ~10 wt%) and elevated concentrations of Cu, Sb, Ag, Mo, and Pb. The marbles are composed of calcite, carbonate-fluorapatite, spurrite, and brownmillerite and characterized by high P, Zn, Cd, U, and elevated Se, Ni, V, and Mo contents. Main accessories are either Zn-bearing oxides or sphalerite, greenockite, and Ca-Fe-Ni-Cu-O-S-Se oxychalcogenides. CM alteration lead to compositional homogenization of metamorphic sphalerite, for which trace-element suites become less diverse than in the authigenic ZnS. The CM sphalerites contain up to ~14 wt% Cd and ~6.7 wt% Se but are poor in Fe (means 1.4–2.2 wt%), and bear 100–250 ppm Co, Ni, and Hg. Sphalerite (Zn,Cd,Fe)(S,O,Se)cub is a homogeneous solid solution with a unit cell smaller than in ZnScub as a result of S2− → O2− substitution (a = 5.40852(12) Å, V = 158.211(6) Å3). The amount of lattice-bound oxygen in the CM sphalerite is within the range for synthetic ZnS1−xOx crystals (0 &lt; x ≤ 0.05) growing at 900 °C.

Analysis of silver coins from colonial Brazil by hand held XRF and micro-XRF

In this work, 960 réis coins from the period when Brazil was a colony of Portugal were analyzed using the x-ray fluorescence (XRF) spectrometry. The history of these coins, dated between the end of the 17th century and the beginning of the 19th century, had a great influence on the immigration of the Portuguese Prince Regent D. João to Brazil, who arrived in 1808. Bearing in mind the need to expand the timid Brazilian monetary system, the Portuguese crown decided to collect Spanish silver pesos of 8 reales, recoined with a value of 960 réis. The recoinage procedure was carried out using a stamp; therefore, in many cases, it is possible to check the base currency. In this work, were investigated 17 samples of 960 réis coins by XRF, in which the base coin was 8 reales manufactured with raw materials from Mexican mines. In addition to characterizing the elemental composition of the coins, the XRF data were evaluated using multivariate statistical method of Robust Principal Component Analysis (ROBPCA), which was used to classify the coins based on their elemental composition. However, with XRF, elementary information is obtained for a depth of only a few micrometers. One of the essential issues in Ag–Cu metal alloys is the Ag enrichment, which can cause changes to the elemental composition of the surface. Therefore, initially, a study was carried out to verify whether the surface compositions of the coins were altered by the Ag enrichment.

Apportionment of some chemical elements in soils around the coal mining area in northern Bangladesh and associated health risk assessment

In this work, fifteen chemical elements viz., Pb, Cd, Cr, As, Ag, Mn, Fe, Co, Ni, Cu, Zn, Na, K, Ca, and Mg were estimated in the coal mine-impacted soil samples sourced from Barapukuria coal mine area of Bangladesh using atomic absorption spectrometer and flame photometer for assessing their contamination levels with an implication to human health and environment. The level of considered elements was found to be lower compared to their corresponding world normal limit, except for Zn. Physicochemical properties of soils such as pH, oxidation-reduction potential, and electrical conductivity, as measured using a multiparameter meter in aqueous solution, indicated the acidic nature of soils with the presence of considerable oxidizing and ionic substances. Principal component, cluster, and correlation analyses ascertained the probabilistic anthropogenic sources of elemental contaminations and significant inter-parameter associations. These analyses suggest that Zn, Cu, Ni, Co, Cd, Mn, and As in soil originated from anthropogenic activities, particularly from the adjacent coal mining operations, indicating a common source of origin. Enrichment factor (EF), geo-accumulation index (Igeo), contamination factor (CF), pollution load index (PLI), ecological risk factor (Er), potential ecological risk index (RI), and human health risk assessment of chemical elements were employed for evaluating the impact of potentially hazardous elements in soils on surrounding environment and local residents. EF values suggest a significant enrichment of Ag, As, Zn, Cd, Pb, Co, Ni, Mn, and Cu in soils having anthropogenic origin while K, Cr, Ca, Na, and Mg originated from geogenic sources. The Igeo and CF data indicate a considerable accumulation of Cd, As, Ag, and Zn in the soil. A moderate risk potential was manifested by the Er and RI indices posing a threat to the soil environment. The non-carcinogenic threat was observed mostly among the children cohort due to the preponderance of these elemental concentrations.

Pressure leaching of selenium and tellurium from scrap copper anode slimes in sulfuric acid-oxygen media

Copper anode slimes are essential secondary resources from which valuable metals, such as Cu, Se, Te, Au, and Ag, may be recovered. Herein, oxidation pressure leaching is proposed for the pretreatment of copper anode slimes to realize efficient extraction of Cu, Se, and Te and enrichment of Au and Ag in the leaching residue. Detailed investigations were conducted to determine the effects of sulfuric acid concentration, liquid-to-solid ratio, oxygen partial pressure, and reaction temperature on the recovery of Cu, Se, and Te. Results of thermodynamic analyses indicate that high pH values enhanced the transformation of insoluble Se2− into soluble HSeO3−, whereas low pH environments favored the presence of soluble Te(OH)3+. During the first stage of oxygen pressure leaching in H2SO4 (0.5 mol/L) with a liquid-to-solid ratio of 10 mL/g, the leaching ratios of Cu, Se, and Te were 99.54%, 96.95%, and 68.54%, respectively. The results of the SEM-EDS and MLA analyses of the first-stage pressure leaching residue indicate that the remaining Se and Te existed as Ag2Se and TeO2 phases, which were further dissolved in a H2SO4 solution (1 mol/L) with a liquid-to-solid ratio of 20 mL/g to obtain Se and Te leaching ratios of 99.5% and 98.6%, respectively.

Effect of thermal oxidation on surface chemistry and elemental segregation of Al-Cu-Li alloy

The thermal stability of Al-Cu-Li alloys is critical for the extreme working conditions in the aircraft industry. The initial stages of thermal oxidation of an industrial AA 2050-T8 Al-Cu-Li alloy were investigated by in situ XPS and ToF-SIMS.Annealing the sample at 200 °C leads to a surface enrichment in metallic Li and Ag. When exposed to oxygen at low pressure (PO2 < 10−6 mbar) a mixed Li-Al oxide layer is formed. Photoemission intensities (recorded at 45° and 90° relative to the surface) are consistent with the formation of a continuous oxide layer for oxygen exposure from 0 to 5000 langmuirs (L). Assuming a homogeneous composition of the oxide layer, its thickness was 9 ± 1 Å at 5000 L. The relative content of Li and Al in the oxide layer evolves from an initial value of 50% to stabilize at 70% of Li above 100 L of oxygen exposure. Simultaneously, the content of Li at the alloy substrate surface is reduced from 10% to 0%. Moreover, specific segregation sites are evidenced by ToF-SIMS three-dimensional chemical mapping. For Li, a homogenous surface distribution while for Mg the accumulation at the grain boundaries were observed. The segregation of Ag at the oxide/alloy interface was confirmed by ToF-SIMS ion depth profiles.

Application of an ordinary kriging–artificial neural network for elemental distribution in Kahang porphyry deposit, Central Iran

Estimation of elemental distribution with minimum estimation errors is crucial in mineral exploration. This study aims to estimate Cu, Mo, Ag, and Au distribution in a local scale. To do this, the application of an ordinary kriging–artificial neural network (OK-ANN) model is proposed for elemental distribution based on lithogeochemical data in Kahang porphyry deposit, Central Iran. In addition, ordinary kriging (OK) method is applied and the result will be compared with the suggested method. Following this, the proposed estimation model has less error in comparison with the OK. To ensure the validity of proposed OK-ANN, the results were correlated with lithological, faults, and alteration maps in the studied region using a logratio matrix. As a result, main parts of Ag and Au enrichment are associated with faults and argillic alteration with high values of overall accuracies (OAs) in the western part of the deposit. Furthermore, Cu values estimated by the OK-ANN are connected with potassic alteration zone in the central part of deposit. In addition, the Cu-, Mo-, Au-, and Ag-enriched anomalous parts are associated with the existing faults, major alterations, and Eocene sub-volcanic rocks as well as porphyritic quartz diorites, monzodiorite–monzogranite, and dacitic units. Correlation coefficient between raw data and the results obtained by the proposed estimator is more than 84%, meaning that the proposed technique can be utilized for estimation of geochemical data in porphyry deposits.

Mineralogy and Metallogenesis of the Sanbao Mn–Ag (Zn-Pb) Deposit in the Laojunshan Ore District, SE Yunnan Province, China

The Sanbao Mn–Ag (Zn-Pb) deposit located in the Laojunshan ore district is one of the most important deposits that has produced most Ag and Mn metals in southeastern Yunnan Province, China. Few studies are available concerning the distribution and mineralization of Ag, restricting further resource exploration. In this study, detailed mineralogy, chronology, and geochemistry are examined with the aim of revealing Ag occurrence and its associated primary base-metal and supergene mineralization. Results show that manganite and romanèchite are the major Ag-bearing minerals. Cassiterite from the Mn–Ag ores yielded a U–Pb age of 436 ± 17 Ma, consistent with the Caledonian age of the Nanwenhe granitic pluton. Combined with other geochemical proxies (Zn-Pb-Cu-Sn), the Sanbao Mn–Ag deposit may originally be of magmatic hydrothermal origin, rather than sedimentary. The Ag-rich (Zn-Pb (Sn)-bearing) ore-forming fluids generated during the intrusion of the granite flowed through fractures and overprinted the earlier Mn mineralization. Secondary Ag (and possibly other base-metals) enrichment occurred through later supergene weathering and oxidation.

Characterization of Weathering Processes of the Giant Copper Deposit of Tizert (Igherm Inlier, Anti-Atlas, Morocco)

The giant Tizert copper deposit is considered as the largest copper resource in the western Anti-Atlas (Morocco). The site is characterized by Cu mineralization carried by malachite, chalcocite, covellite, bornite and chalcopyrite; azurite is not observed. The host rocks are mainly limestones (Formation of Tamjout Dolomite) and sandstones/siltstones (Basal Series) of the Ediacaran/Cambrian transition. The supergene enrichment is most likely related to episodes of uplift/doming (last event since 30 Ma), which triggered the exhumation of primary/hypogene mineralization (chalcopyrite, pyrite, galena, chalcocite I and bornite I), generating their oxidation and the precipitation of secondary/supergene sulfides, carbonates and Fe-oxyhydroxides. The Tizert supergene deposit mainly consists of (i) a residual patchwork of laterite rich in Fe-oxyhydroxides; (ii) a saprolite rich in malachite, or “green oxide zone” where primary structures such as stratification are preserved; (iii) a cementation zone containing secondary sulfides (covellite, chalcocite II and bornite II). The abundance of Cu carbonates results from the rapid neutralization of acidic meteoric fluids, due to oxidation of primary sulfides, by carbonate host rocks. Chlorite is also involved in the neutralization processes in the sandstones/siltstones of the Basal Series, in which supergene clays, such as kaolinite and smectites, subsequently precipitated. At Tizert, as can be highlighted in other supergene Cu-deposits around the world, azurite is absent due to low pCO2 and relatively high pH conditions. In addition to copper, Ag enrichment is also observed in weathered rocks; Fe-oxyhydroxides contain high Zn, As, and Pb contents. However, these secondary enrichments are quite low compared to Cu in the whole Tizert site, which is therefore, considered as relatively homogeneous.

Mineralogy and character of the Liikavaara Östra Cu-(W-Au) deposit, northern Sweden

ABSTRACT The Liikavaara Östra Cu-(W-Au) deposit is situated close to the operating Aitik Cu-Au mine in northern Sweden. It is scheduled for production in 2023. Modern geological descriptions of the deposit are lacking though knowledge of geological and mineralogical details prior to operation is beneficial to avoid surprises. In this study, petrological, mineralogical and geochemical investigations of the wall rocks, host rock and mineralisation, and zircon U-Pb analysis of a footwall granodioritic intrusion were carried out. The mineralisation is hosted by quartz±tourmaline-calcite veins, calcite veins and aplite dykes that cross-cut biotite-amphibole schists and gneisses. The wall rocks to the ore are metavolcaniclastic rocks of basaltic to andesitic composition. A granodiorite intrusion occurs in the footwall. The mineralisation is mainly chalcopyrite, pyrrhotite and pyrite with some sphalerite, galena, scheelite, molybdenite and magnetite. It shows slight enrichments in Au, Ag and Bi. Gold and Ag occur as electrum and Ag also in hessite and an Ag-sulphide. The Bi mineralogy includes native Bi, Bi-tellurides and Bi-sulphides. These minerals are found as inclusions, along the borders of and in cracks in chalcopyrite, pyrite, pyrrhotite, sphalerite, molybdenite and quartz. The footwall granodiorite intrusion was dated at 1.87 Ga. It is suggested here to be the source for ore genesis based on its spatial relation to the mineralisation, as well as on high-salinity fluids and metal composition of the ore. The aplite dykes may have acted as pathways for the magmatic hydrothermal fluids that carried the metals from the intrusion to the host rock.

Non-destructive identification of surface enrichment and trace element fractionation in ancient silver coins

A common issue in non-destructive surface analysis of historical silver coins is depletion of Cu from the near-surface areas, which in turn results in higher Ag content at a coin’s surface. This paper reports a non-destructive analytical strategy using µXRF for identification of Ag and Cu surface enrichments and depletions by comparing peak intensity ratios of Ag Kα/Ag Lα, Cu Kα/Ag Kα and Cu Lα/Ag Lα for coins and Ag-Cu standards of similar composition. Our characterization of coins from different contexts and chronologies shows that a multi-standard approach provides the most reliable identification of surface enrichment of Ag and depletion of Cu. Coins possessing Ag surface enrichment were further analysed with LA-ICP-MS to determine any differences in trace element composition between the cores and surface of the coins. We show that the near-surface regions of these coins are enriched in Au and depleted in Co, Ni, As, and Pt relative to their cores. These systematics allow for a more robust assessment of the degree of silver coin surface alteration critically important in measuring the original composition of historical silver coins.

A novel process for silver enrichment from Kaldo smelting slag of copper anode slime by reduction smelting and vacuum metallurgy

Silver in Kaldo smelting slag of copper anode slime is diffuse and hard to be enriched. In this study, a novel process consisting of reduction smelting and vacuum metallurgy was developed to enrich Ag in Kaldo smelting slag of copper anode slime through laboratory and scale-up experiments. Pb, Bi and Ag in the slag were first enriched in Pb–Bi–Ag alloy by reduction smelting. Results show that when the reduction smelting was conducted for 40min under 1350 °C with the addition of reductant, limestone and iron powder accounting respectively for 10%, 20% and 26% of the raw feed, the recovery of Pb, Bi and Ag was 95.12%, 98.13% and 99.11%, respectively. After the reduction smelting, Ag was separated from Pb and Bi by vacuum distillation based on their difference in vapor pressure. Results show that Pb and Bi in Pb–Bi–Ag alloy were removed under the pressure of 3Pa, distillation temperature of 1000 °C and distillation duration of 2 h. After the vaccum metallurgy process, Ag enrichment ratio is above 9. The scale-up experiment shows that Ag recovery is higher than 98%, and more than 97% of Pb and Bi form Pb–Bi alloy product, which further proves that this novel process is simple but efficient for silver enrichment and separation from Pb and Bi in Kaldo smelting slag of copper anode slime.