Gold Sulfide Research Articles

Catalysis of chalcopyrite on thiourea oxidation by Fe3+ and the advantage of oxalate during thiourea leaching of gold

Thiourea is a low-toxicity gold lixiviant that has promise to replace the highly toxic cyanide for gold extraction. Chalcopyrite is an important gold-bearing sulfide mineral, and thus investigation of its influence on gold leaching is important to maximize the utilization of refractory copper sulfide gold ore. In this paper, the effect of chalcopyrite on thiourea leaching of gold and the role of oxalate were studied through a series of leaching experiments, surface characterization and DFT calculation. Results showed that the presence of chalcopyrite severely hindered thiourea leaching of gold demonstrated as the greatly decreased in gold dissolution and thiourea stability. The detrimental effect of chalcopyrite was inferred to be the catalysis of chalcopyrite on thiourea oxidation by Fe3+, leading to the much-increased thiourea consumption, and thus deteriorated the gold dissolution. Oxalate as an additive was used to improve gold dissolution and thiourea stability. Oxalate not only weakens the interaction between Fe3+ and thiourea through complexing with Fe3+, but also competes with thiourea to adsorb on the chalcopyrite surface, decreasing thiourea adsorption. Besides, the formation of Fe-oxalate complexes, as the terminal acceptor of electron, significantly reduced the oxidizability of Fe3+, thus relieving the catalysis of chalcopyrite on thiourea oxidation.

Porphyry and Epithermal Au-Cu Systems of the Southern Caucasus and Northern Iran

This article presents tangible geological evidence for coexistence of porphyry copper and epithermal gold systems within single polygenic deposits and provides a paleothermophysical model for their origins. Brief metallogenic analysis of the Southern Caucasus and Northern Iran has shown that such deposits are confined to long-living calc-alkaline island arcs and were formed during their orogenesis. Examples of complex Sonajil (Iran), Gharta, and Merisi (Georgia) deposits are considered. Investigation has shown that for combined porphyry and epithermal ore formation some preconditions are suggested to exist: (i) Source of anomalous energy, which exceeds thermodynamics of the enclosing environment; (ii) Existence of temperature gradient, which determines conventional flows of fluids composed of endogenous and meteoric constituents (proven by rhythmical zoning of ore lodes); (iii) Stability of such conditions for a period of sulfide ore formation. However, such a process of sulfide ore formation cannot explain formation of high sulfidation gold deposits. Mass precipitation of free gold requires phreatic collapse in the ore conduit channel already after formation of hydrothermally altered rocks, and this event results in creation of either hydrothermal breccias, often with jigsaw-fit texture or brecciated vuggy silica where host rocks and hydrothermally altered rocks are cemented by a gold-bearing quartz matrix.

Superimposed Gold Mineralization Events in the Tuanshanbei Orogenic Gold Deposit, Central Jiangnan Orogen, South China

Abstract The Jiangnan orogen, one of the largest gold-producing areas in China, has experienced multiple orogenic events with complex structural overprinting that is marked by multiple stages of magmatism, deformation, metamorphism, and orogenic gold mineralization. Different orogenic events have been recognized in the Neoproterozoic, mid-Paleozoic, Triassic, and Early Cretaceous, reflecting collisions and intracontinental orogenic episodes. The age of gold deposition in the Jiangnan orogen, however, has been poorly constrained owing to the absence of suitable dating minerals. Field studies in the orogen indicate the Tuanshanbei gold deposit includes two generations of auriferous quartz-ankerite-pyrite-arsenopyrite veins (Q2 and Q3), with the latter of the two notable for containing more abundant ankerite and base metal sulfides. The Q2 veins were formed throughout the near S-N–directed shortening associated with D1 deformation and along resulting subhorizontal to low-angle-dipping EW- to WNW-striking transpressive faults. The Q3 veins, containing about 70% of the total gold resource, were primarily localized in moderately to steeply dipping NW-striking tensional/tensional shear faults and moderately dipping NE- to NNE-striking transpressive faults that were products of NW-SE–directed shortening during D2 deformation. Both vein generations are temporally younger than the 437.2 ± 4.2 Ma Tuanshanbei granodiorite host, and both are crosscut by postgold ca. 225 Ma diabase dikes. Hydrothermal monazite coexists with native gold and gold-bearing metal sulfides in the Q2 and Q3 veins. The Q2 monazite yielded a Tera-Wasserburg lower intercept age of 415.1 ± 2.1 Ma, consistent within error with an ankerite Sm-Nd isochron age of 410 ± 15 Ma and a laser ablation-inductively coupled plasma-mass spectrometry hydrothermal zircon 206Pb/238U age of 411.2 ± 4.0 Ma. The Q3 monazite yielded a Tera-Wasserburg lower intercept age of 234.3 ± 1.1 Ma. These new ages suggest that the Early Devonian gold event was overprinted by hydrothermal activity along the same structural system almost 200 m.y. later such that the gold resource must be a product of two temporally distinct events. Geologic and structural evidence, coupled with existing published geochemical data, suggests both ore-forming events were related to crustal metamorphism typical of most orogenic gold deposits. Fluids would have been derived from Neoproterozoic metasedimentary basement rocks, most likely from metamorphic devolatilization of the Neoproterozoic Cangxiyan Group greenschist-amphibolite facies metasediments. There is no evidence suggesting any type of magmatic contribution to the ore-forming process at either time. The data are best interpreted to suggest that various parts of the basement were metamorphosed near the greenschist-amphibolite boundary at different times, but during both times, the gold-bearing metamorphic fluids eventually migrated into the same structural conduits.

Assessment of Modified Culture Conditions for Fungal Bio-Oxidation of Sulfidic Gold Ores Performed at Circumneutral pH

The significant neutralization of waste streams required after the acidic bio-oxidation of sulfidic gold ores could be avoided by performing a novel treatment at circumneutral pH with an in situ neutralization. For the first time, the white-rot fungus Phanerochaete chrysosporium was incubated in a modified culture medium containing corn steep, an industrial waste product, to support microbial activity and, subsequently, the oxidation of a sulfidic ore at an initial circumneutral pH environment. In this investigation, the concentration of the native culture medium ingredients was first evaluated with response surface methodology to attain maximum sulfide oxidation. The statistical analysis proposed a modified culture medium composed of 12.86 g/L glucose, 2.20 g/L malt extract, 1.67 g/L yeast extract, and 0.49 g/L MgSO4·7H2O to reach a maximum of 28.7% sulfide oxidation after 14 d-bio-oxidation. pH-controlled batch cultures showed that an increase in initial pH in the range of 5.8 to 7.0 reduced the microbial activity, affecting sulfide oxidation. In addition, the modified culture medium at which yeast extract was substituted with 1.67 g/L corn steep produced comparable microbial activity and sulfide oxidation after 14 d, attaining 21.6% at 5% w/v with a maximum 39 U/L lignin peroxidase and 116 U/L manganese peroxidase. A 40.6% sulfide oxidation and 43.8% gold recovery were obtained after 42 d three-cycle replenishing bio-oxidation and 24 h cyanidation, respectively. Overall, corn steep waste showed the potential to substitute more expensive culture medium ingredients, supporting microbial activity and oxidation of sulfidic gold ores at an initial circumneutral pH and contributing to circularity of waste management.

Effect of mechanical activation on biooxidation and gold extraction of a high-grade flotation concentrate using mesophilic and moderately thermophilic microorganisms

The effect of mechanical activation and biooxidation on the gold extraction from a high-grade (168 g/t) gold sulfide concentrate was investigated using a mixed culture of iron- and sulfur-oxidizing microorganisms. The influence of mechanical activation pretreatment, the nutrient medium type (Norris and 9K), initial pH, and microbial culture type was investigated on the biooxidation ability of mixed cultures of mesophilic and moderately thermophilic microorganisms. Results showed that gold extraction from the non-activated non-biooxidized concentrate was 83.9%, while after biooxidation, it reached 98.8%. The gold recovery from the mechanically activated non-biooxidized concentrate was 77.3%, which reached 97.6% after biooxidation. Therefore, biooxidation was found to have a significant positive effect on gold extraction, but mechanical activation had a negative effect on it in both abiotic and biotic media. The characterization of solid residues was performed by SEM/EDS and chemical analyses. Jarosite and gypsum were the main precipitates formed during biooxidation, especially in 9K nutrient medium. It was found that mechanical activation reduced the efficiency of biooxidation process mainly as a result of overcoming negative effects such as weak bacteria-mineral attachment, the release of toxic species, increasing pulp viscosity, and the coating of gold grains by less soluble solids on the positive effects such as the enhancing of surface area and the disordering of the crystal structure of refractory sulfide phases.

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

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

Combining flipped class sessions with traditional lectures in a non-computational upper level economic geology class

Flipped classrooms have been shown to be useful in both introductory and advanced computational Earth Science courses. However, to date they have not been implemented in advanced level non-computational courses. Here we assess a three-year study into the use of flipped classroom techniques in a fourth year undergraduate Mineral Deposits class. One to two flipped classrooms were used to teach porphyry deposits, iron oxide copper gold and/or volcanogenic massive sulfide deposits. The effectiveness of the technique was assessed using a combination of student feedback forms, comparison of students’ ability to answer exam questions from topics taught by flipped classroom versus other topics taught by traditional methods, and interviews with students 6 to 36 months after completion of the course. The students’ ability to answer lecture exam questions was slightly higher in topics taught as flipped classrooms compared to traditional techniques. Whereas the students’ ability to answer laboratory exam questions was slightly lower between topics taught as flipped classrooms. However, most students did think that the flipped classrooms were useful and aided in their learning of the material. The use of video lectures was particularly appreciated by some who found that it increased their flexibility and ability to absorb the material at their own pace. As such we determined that flipped classrooms are an effective technique for teaching upper-level non-computational Earth Science courses and they increased behavioral, emotional, and cognitive engagement.

Native Gold and Unique Gold–Brannerite Nuggets from the Placer of the Kamenny Stream, Ozerninsky Ore Cluster (Western Transbakalia, Russia) and Possible Sources

We carried out a comprehensive study of native gold (morphology, composition, intergrowths, and microinclusions) from alluvial deposits of the Kamenny stream (Ozerninsky ore cluster, Western Transbaikalia, Russia). The study showed that there were four types of native gold, which differed significantly in their characteristics and probably had different primary sources from which placers were formed: gold–quartz, oxidized gold–sulfide, gold–silver, and zones of listvenites with copper–gold and gold–brannerite (Elkon-type). Particular attention was paid to the study of unique, both in size and in composition, gold–brannerite nuggets of the Kamenny stream. It was established that the gold in the gold–brannerite nuggets (GBNs) had wide variations in chemical composition and mineral features. According to them, there were five different fineness types of native gold: 750–800‰; 850–880‰; 880–920‰; 930–960‰; and 980–1000‰. The data obtained indicated a multistage, possibly polygenic, and probably polychronous formation of GBN gold–uranium mineralization. The first stage was the formation of early quartz–nasturanium–gold–W–rutile–magnetite association (Middle–Late Paleozoic age). The second was the crystallization of brannerite and the replacement of an earlier pitchblende with brannerite (Late Triassic (T3)–Early Jurassic (J1) age). The third was the formation of the hematite–barite–rutile–gold association as a result of deformation–hydrothermal processes, which was associated with the appearance of zones of alteration in brannerite in contact with native gold with 8–15 wt.% Ag. The fourth was hypergene or the low-temperature hydrothermal alteration of minerals of early stages with the development of iron hydroxides (goethite) with impurities of manganese, tellurium, arsenic, phosphorus, and other elements. The carbon isotopic composition of an organic substance indicates the involvement of a biogenic carbon source. In the OOC area, there were signs that the composition of the GBNs and the quartz–chlorite–K–feldspar-containing rocks corresponded to Elkon-type deposits.

Age and mineralization origin of the Zhongshangou Au deposit, Zhangjiakou goldfield, North China: Constraints from molybdenite Re-Os age and sulfides S-Pb isotopes

The Zhangjiakou goldfield, located in the northern North China Craton (NCC) margin, is a typical gold mineral province in China, containing over 67 gold deposits with 260 t gold reserve. However, gold mineralization age in this district has not been well constrained. Here, we integrate mineral paragenesis, molybdenite Re-Os age and in situ sulfides S and Pb isotopes from the Zhongshangou Te-rich Au deposit to constrain the timing and origin of gold and tellurium mineralization. Molybdenite Re-Os dating yielded a weighted average age of 381.7 ± 2.0 Ma (2σ, MSWD = 0.37, n = 7). Molybdenite has similar δ34S value (-12.9 to −8.5‰, n = 10) to other sulfide minerals (23 pyrite, 2 chalcopyrite and 2 bornite, δ34S = -13.6 to −5.6‰). Lead isotope compositions also show no difference among these sulfide minerals. Considering the mineral paragenesis and S-Pb isotopes, we suggest that molybdenite coprecipitated with gold, tellurides and other types of sulfides from the ore-forming fluids, and that the molybdenite Re-Os data could represent the timing of Zhongshangou gold and tellurium mineralization. New and published age data define a ca. 380 Ma Au-Te mineralization event for the Zhangjiakou goldfield. These Au deposits were genetically associated with the Devonian alkaline magmatism.

ON THE SEDIMENTS FORMATION DURING AUTOCLAVE OXIDATIVE LEACHING OF REFRACTORY SULFIDE GOLD-BEARING ORES CONCENTRATES

The processes occurring during autoclave oxidative leaching of refractory sulfide gold ores concentrates are discussed, as a result of which difficult-to-remove deposits (sediments) are formed on all internal surfaces of autoclaves, reducing equipment performance. It is shown that the phase composition of the sediments varies across autoclave sections and that the main component of the sediments is potassium jarosite KFe3(SO4)2(OH)6. The mechanism of sediments formation is analyzed and possible ways to prevent appearance them are discussed.

The Brehov volcanogenic and stratabound base metal and gold deposit (Eastern Slovakia): Position and genetic relations in the Internal Carpathian–Alpine Cenozoic metallogenetic belt

The Brehov ore deposit, near the village of Brehov, is located in the East Slovakian Basin 15 km south-east of the Trebišov town. A progressive development of Middle Badenian to Middle Sarmatian sedimentation and volcanism in the Brehov hydrothermally mineralized area is manifested in the article. The volcanogenic, stratabound, polymetallic (Zn, Pb, Cu) and gold sulphide deposit within the Brehov–Sirník interpreted resurgent caldera occurs in the volcanosedimentary sequence. Mineralization in the deposit, consisting of the fine-grained aggregate of sulphides, is interpreted to be of shallow water origin. It is placed mostly in the rhyodacite volcaniclastics and partly in calcareous claystone, altered and brecciated. Three types of ores – the stringer (keiko), yellow and black ore – were distinguished near the Brehov village on the basis of ore composition, being formed by successive mineralization stages. The stringer ore, consisting of the sulphide minerals, dominates in the quartz-dioritic (siliceous) rocks. The yellow ore is represented primarily by pyrite, but contains also minor chalcopyrite and quartz. The black ore is an intimate mixture of sphalerite, galena, sometimes barite and minor pyrite and chalcopyrite. Tetrahedrite and marcasite occur sporadically. The ore in all cases is fine-grained. The ore bodies are almost everywhere enclosed by clay, composed of montmorillonite, sericite and chlorite. The ore bearing fluids were probably colloids of hydrothermal origin. Textures are considered to indicate that the colloids replaced the country rocks, rather than merely filled open spaces in the rhyodacite pyroclastics and epiclastics. Despite the precious metals (mostly gold) are economically important commodity in many Kuroko type deposits, in the Brehov ore deposit they occur in volumetrically minor amounts. Visible gold is present as inclusions of native gold in major sulphide minerals, whereas silver occurs in Ag-sulphides and sulphosalts, e.g. tetrahedrite and ferberite.

A clean and efficient innovative technology for refractory sulfide gold ore: In situ gold extraction via self-generated thiosulfate

Green non-toxic extracting gold from refractory sulfide gold ore using thiosulfate is an essential guarantee for the sustainable development of the gold industry. However, there are many bottlenecks, including environmental pollution from traditional pretreatment of sulfide gold ore and high consumption of chemical thiosulfate. Herein, a clean and efficient innovative technology for the comprehensive utilization of refractory sulfide gold ore (high sulfur and high arsenic) was first proposed. For high arsenic sulfide gold ore, a sufficient sulfur source (addition of pyrite or sulfur) could be supplemented, and then thermal activation pretreatment for thiosulfate generation. This alternative technology can prevent the volatilization of hazardous gases (SO2 and As2O3) and instead collect them as less harmful solids (S8 and As2S3). Moreover, thermal activation pretreatment of this sulfide gold ore significantly enhances the oxidation capacity and results in the generation of sufficient thiosulfate (286 mM). The pretreatment also breaks down the sulfide inclusions to expose the encapsulated gold, which can be in situ extracted via self-generated thiosulfate. As a result, a gold extraction rate of 80.2% was achieved for this refractory sulfide gold ore without the addition of chemical thiosulfate. This innovative technology is of high academic and industrial interest, addressing the high thiosulfate consumption and promoting the industrialization of green gold extraction from refractory sulfide gold ore.

On the Formation of Deposits during Autoclave Oxidative Leaching of Concentrates of Refractory Sulfide Gold Ores

On the Formation of Deposits during Autoclave Oxidative Leaching of Concentrates of Refractory Sulfide Gold Ores

Formation Model of the Gold-Sulfide Deposits of the Western Kalba and Its Main Forecast and Search Criteria

The West Kalba Gold ore Belt (WKB), located within the Greater Altai, is a unique gold ore province on a global scale. It contains about 500 known gold occurrences and deposits. The main industrial type for the WKGB are gold-bearing sulfide deposits. The article presents a model for the formation of gold sulfide deposits in West Kalba. The main predictive-search criteria are considered, which make it possible to assess the prospects of areas for the presence of potential gold-sulfide objects within the described territory. The aim of the work is to clarify the main predictive and prospecting criteria specific to the considered field model. The given data is highlighted using descriptive analytics methods.

Overcoming stereological Bias: A workflow for 3D mineral characterization of particles using X-ray micro-computed tomography

Mineral separation processes operate on properties of individual particle, which can currently be quantified with 2D characterization techniques, namely 2D automated mineralogy. While 2D automated mineralogy data have driven significant developments in particle-based separation models, this data inherently correspond to 2D slices of 3D objects, which leads to stereological bias in the quantification of geometric particle properties. X-ray micro-computed tomography (µCT) is a 3D imaging technique that can quantify particle geometry. However, µCT only collects limited information regarding material composition, making mineral identification quantification a challenge. To overcome this challenge, we present a workflow that utilizes individual particle histograms and corrects image artefacts caused by µCT measurements, such as partial volume effect. We demonstrate the application of the workflow to perform 3D mineral characterisation of a sulfidic gold ore, where mineral phases that are commonly mistaken with µCT could be distinguished: pyrite and chalcopyrite, gold, and galena. Results were verified by comparison with inductively coupled plasma mass spectrometry and 2D automated mineralogy. As a result, the workflow provides the user with a detailed 3D particle dataset containing the modal mineralogy and surface compositions, size, and geometrical properties of each particle in a sample – essential data for modelling mineral separation processes.

Improving the technology of copper-zinc ore beneficiation of a Uralian-type pyrite deposit

Introduction and research objective. Copper-zinc ore of pyrite deposits of the Uralian type are refractory. Difficulties in beneficiation are due to their material composition: fine coarseness and emulsion impregnation of ore minerals in each other, a large amount of flotation-active pyrite, a high content of finely dispersed and submicroscopic gold in sulfides, etc. In the course of pyrite ore processing at dressing mills, 83–91% of copper and 10–45% of gold are extracted into copper concentrates, and 46–78% of zinc and 5–15% of gold are extracted into zinc concentrates. Increasing the process performance of pyrite deposit ore processing is a promising and urgent task. Methods of research included copper-zinc pyrite ore material composition study through quantitative chemical analysis, chemical phase analysis for the forms of copper, zinc, gold and silver compounds, and mineralogical analysis. Technological studies were carried out by flotation and gravity methods using a centrifugal concentrator and a concentration table. Conclusions. In the course of pyrite deposit copper-zinc ore beneficiation at the dressing mill, the effect of circulating concentration of gold in the coarse copper concentrate regrinding cycle was established. The results of studies on the centrifugal concentration of gold in a centrifugal concentrator with further secondary cleaning of its heavy fraction on a concentration table show the possibility of obtaining a gravity product with a mass fraction of gold up to 200 g/t under its operational extraction up to 29%. It was noted that the integrated flotation-gravity technology for copper-zinc ore beneficiation will increase the through extraction of gold into marketable mineral products by more than 1.5%. The use of a combination of butyl potassium xanthate and FRIM-2920 reagent-collector in the copper-zinc pyrite ore flotation technology contributes to increased extraction of copper and gold into copper concentrate by 0.87% and 3.22%, respectively, and zinc into zinc concentrate by 0,4%. Increasing the pulp temperature in the zinc flotation cycle to 40–45 °C and returning the control zinc flotation concentrate and tailings from the first cleaning flotation of zinc to the II main zinc flotation allows increasing the mass fraction of zinc in the zinc concentrate from 48.5 to 51.1% under a simultaneous increase in the extraction of zinc into zinc concentrate from 62.6 to 65.6%.

Genesis of the Xiaobeigou gold deposit in the Jiapigou gold district, Northeast China: Constraints from fluid inclusions, quartz H–O isotopes, and pyrite in situ sulfur isotope and trace element compositions

The Xiaobeigou gold deposit (>20 t @ 17.36 g/t) is located in the Jiapigou gold district (JGD), Northeast China, representing a large-sized quartz vein-type gold deposit hosted by Neoarchean basement gneiss and is related to Mesozoic intrusions in space and time. Four hydrothermal stages were identified from early to late, namely, (1) barren quartz stage, (2) quartz–pyrite stage, (3) gold–quartz–polymetallic sulfide stage, and (4) quartz–carbonate stage. Three main types of fluid inclusions (FIs) have been identified: water-rich (H2O–NaCl; W-type), mixed aqueous-carbonic (CO2–H2O–NaCl; C-type) and pure carbonic (CO2; PC-type) FIs. The early-stage quartz contains W- and C-type FIs that yield moderate homogenization temperatures (270–379 °C) and moderate-low salinities (4.82–17.87 wt% NaCl equivalent). The main-stage quartz grains contain all three types of FIs that yield medium–low temperature (179–263 °C) and moderate-low salinity (2.82–9.86 wt% NaCl equivalent). Only W-type FIs are recognized in late-stage quartz grains, which have low temperatures (133–183 °C) and low salinities (1.91–7.73 wt% NaCl equivalent). The initial ore-forming fluid of the Xiaobeigou gold deposit was a moderate homogenization temperature and moderate-low salinity CO2–H2O–NaCl ± CH4 ± N2 hydrothermal fluid system. Fluid immiscibility is the main mechanism leading to the precipitation of gold and other metal sulfides. The H–O isotopic values (δ18OH2O = −6.87 to 5.90‰; δD = −102 to −78‰) and composition of the quartz suggest that the initial ore-forming fluids consisted mainly of magmatic water mixed with meteoric water during the late stage of the mineralization process. The S isotope data (δ34S = 3.2 to 4.4‰, avg. 3.6‰) indicate that the ore-forming materials are magmatic sources. EPMA and LA–ICP–MS data show that a large amount of gold mineralization mainly occurs in the main ore-forming stage. The high Co/Ni ratio indicates that the pyrite may be a magmatic–hydrothermal source. Taking into account all available data and regional geological history, we suggest that a magmatic–hydrothermal source for the Xiaobeigou gold deposit in the JGD and the ore formation is related to the subduction of the Paleo-Pacific Plate beneath Eurasia.

Gold–Sulfide Mineralization in the Manitanyrd Region, Polar Urals, Russia

This article describes the characteristics of gold–sulfide–quartz and gold–sulfide (gold–arsenic) ore occurrences in the Manitanyrd region of the Polar Urals. Ore occurrences are confined to NE-trending shear zones and have the common features of a geological structure. The host rocks are metamorphosed volcanic and volcanic–sedimentary rocks. We analyzed the mineral and chemical composition of the ore mineralization in all studied ore occurrences, showing that they belong to the same mineral type—pyrite–arsenopyrite, with a variable ratio of the main minerals. Arsenic pyrite is present in all ore occurrences. Two stages of ore formation were distinguished: early gold–pyrite–arsenopyrite with finely dispersed gold and late gold–galena–chalcopyrite–sphalerite with coarse gold, fahlore, and sulfosalts Pb, Cu, Bi, Sb. Native gold of the first generation, finely dispersed in arsenopyrite and pyrite, had an average to high fineness (800‰–1000‰) with a relatively low dispersion. Native gold of the second generation was larger, and its fineness in ore occurrences varied; in one of them, it varied from 300‰ to 950‰, while in others, it varied from 800‰ to 950‰. The isotope composition of sulfur in sulfides (δ34S) ranged between −0.2‰ and −8.0‰. δ34S values of sulfides in the range of −0.2‰ to −3.5‰ were similar to meteorite, indicating the participation of a single deep magmatic source of sulfur in the ore formation. According to the study of fluid inclusions, the formation of ore quartz veins occurs in the temperature range of 467–109 °C. The similarity of the geological–structural, mineralogical–geochemical, and isotope–geochemical features of the gold–sulfide–quartz and gold–sulfide occurrences in the area suggest their formation in a single hydrothermal system.

Metal Nanoparticles: Synthesis Approach, Types and Applications – A Mini Review

The study of nanoparticles has grown in significance during the last several years. Nanoparticles are a kind of material that is composed of very tiny particles. Nanoparticle characteristics vary greatly depending on their size and form. The surface of a nanoparticle significantly affects its optical, mechanical, magnetic, and other characteristics. Nanoparticles are categorised according to their size, origin and chemical composition. We created nanoparticles using both top-down and bottom-up techniques. In this article, we discuss various different methods for creating nanomaterials, such as sol-gel processes, gas condensation, vacuum deposition and vaporisation, chemical vapour deposition and condensate, mechanical attrition, chemical precipitation, electrodeposition, and chemical vapour condensation. When it comes to creating nanoparticles, green synthesis is one of the most effective approaches. In this article, we explore eco-friendly techniques for manufacturing alloy nanoparticles, silver, gold, silver oxide and silver sulphide. We also explore the process by which microorganisms in this setting produce nanoparticles. Size and form must be maintained under certain conditions. We consider ways in which to enhance the production of nanoparticles in the future. The risks posed by nanoparticles and the ways in which to mitigate them were also taken into account.

Ore-fluid source of multiphase gold mineralization at Tuanshanbei in the central Jiangnan Orogen (NE Hunan, South China): Insight from geology, quartz H-O and monazite in-situ Nd isotope compositions

The Jiangnan Orogen is China’s third largest gold province, and has undergone complex orogenic processes and tectonic overprinting, forming multistage magmatism, deformation, metamorphism, and gold mineralization. Our field studies indicate that the Tuanshanbei gold ores (central Jiangnan Orogen) have two generations of auriferous quartz-ankerite-pyrite-arsenopyrite veins (Q2 and Q3), with the latter containing abundant ankerite and base metal sulfides. Both Q2 and Q3 veins are younger than the emplacement of the Tuanshanbei granodiorite vein-ore host, and cut by post-ore diabase dikes. Q2 veins were likely associated with the Early Devonian near N-S-directed shortening, along sub-horizontal EW-/WNW-striking transpressive faults, whereas Q3 veins (hosting ∼ 70% of the total Au resource), were primarily hosted in the Early Triassic moderately-/steeply-dipping NW-striking tensional/transtensional faults and moderately-dipping NE-/NNE-striking transpressive faults, associated with NW-SE-directed shortening. Discrete structural styles and mineral assemblages from Q2 and Q3 suggest superimposing gold mineralization at Tuanshanbei. To determine the source(s) of the ore-forming aqueous-carbonic fluids, we conducted mineralogical and in-situ LA-(MC)-ICP-MS Nd-isotope analyses on two generations of hydrothermal monazite, and H-O isotope analyses on the quartz from Q2 and Q3 veins.The results suggest that the Tuanshanbei ore fluids have δD = −66.7 to −57.6‰ (Q2) and −66.8 to −66.2‰ (Q3), and calculated δ18OH2O = 4.5–9.7‰ (Q2) and 6.1–7.8‰ (Q3). The H-O isotopic data suggest a metamorphic and/or magmatic water source for the ore fluids. Hydrothermal monazite (coexists with native gold and auriferous sulfides) from Q2 and Q3 veins displays subtle heterogeneous BSE response along cracks and grain margin, suggesting alteration there. The 147Sm/144Nd and 143Nd/144Nd ratios of altered parts of Q2 and Q3 monazite grain are significantly perturbed via dissolution–recrystallization by the hydrothermal fluids, whereas their initial Nd isotope compositions seem to be less affected. The unaltered Q2 and Q3 monazite samples have similar initial εNd values (Q2: −8.07 to −7.36, Q3: −10.87 to −9.99) to the Neoproterozoic Cangxiyan Group greenschist–amphibolite-facies metamorphic rocks. Geological and structural evidence suggest both Q2 and Q3 ore-forming events were related to metamorphism, typical of orogenic gold deposits. We interpreted that various parts of the basement were metamorphosed (to near the greenschist-amphibolite-facies boundary) at different times, during which the gold-bearing metamorphic fluids produced migrated into the same structural conduits and deposited the ores there in two ore-forming episodes.