Ag Ore Research Articles

The Birkachan Epithermal Au–Ag Deposit in the Kedonsky Middle Paleozoic Volcanic Belt (Russian Northeast)

The Birkachan deposit in the Middle Paleozoic Kedonsky Volcanic Belt (KVB) is unique in Northeast Russia for its stockwork epithermal Au–Ag ores. The deposit is located in the northeastern part of the Gurnik volcanotectonic depression, in the Kedonsky segment of the KVB. The deposit is localized in the lying side of a large sublatitudinal thrust fault, due to which it was overlain in the Jurassic–Early Cretaceous by allochthon rocks and, therefore, was slightly eroded, as evidenced by the preserved fragments of the argillisite cap. The ore-bearing Gurnik sequence is composed of felsic tuffs and lavas with intercalations of ignimbrites. The main ore-bearing zone of the Birkachan deposit is 4.5 km long and 200–300 m wide consists of several echelon-like vein zones of northeast strike, falling to the southeast at angles of 55°–70°. Most of the ore bodies are linear stockworks. Single, lenticular rich ore bodies represented by mineralized breccias have been found at deep horizons. In the section, the system of ore bodies of the Birkachan deposit forms a fan-shaped structure. The main textures of ores are vein-disseminated, breccia, and rhythmically banded. The ores are enriched in comparison with the upper continental crust in a rather narrow range of elements (Au, Ag, Sb, As, Mo, W, and Li) and are poor in rare-earth elements, among which light lanthanides predominate. The sulfide grade of ores is 0.1–0.5%. The vein minerals in ores are dominated by quartz, sericite, and siderite. Among the ore minerals, pyrite dominates, with fahlore, native gold and chalcopyrite, and minerals of the series acanthite → Se–acantite → naumannite, pearceite, and Se–pearceite being less common. The average fineness value of native gold is 643‰. The parameters of mineral-forming solutions correspond to typical medium-temperature fluids of epithermal low-sulfidized deposits: homogenization temperature of 93–291°С, salt concentration of 0.2–7.0 wt % eq. NaCl, and fluid density of 0.71–0.99 g/cm3. The main indicators of fluid composition are CO2/CH4 = 15.8–23.6, Na/K = 2.3–4.3, and K/Rb = 2007. The prospects for increasing the reserves of Au and Ag are associated with further study and exploration of the flanks and deep horizons of the deposit.

Investigation of pyrolysis for the recovery of metallic values from ball grid arrays.

The massive generation of electronic waste has led to a significant interest in sustainable metal recovery and recycling. Ball grid arrays, mounted on printed circuit boards, are identified as a potentially valuable source of metals (Cu, Ni, Au, Ag, Pb, and Sn). In this study, pyrolysis is found as a promising treatment for the degradation of the epoxy resin of ball grid arrays. As a consequence, the liberation of metallic values and glass fibers is attained. The thermal analysis revealed that the major degradation occurs in the temperature range of 300-650°C, with overall activation energy estimated as ~ 243kJ/mol. The concentration of CO gas reaches a maximum value at a comparatively lower residence time with an increase in pyrolysis temperature. The metal enrichment was significantly influenced by the variation in pyrolysis temperatures with an optimal condition chosen as 600°C. The metallic fractions (Cu, Ni, Ag, and Au) were separated from the glass fibers by water-based density separation and enriched in the sink product by three-fold. The recovery of Cu, Ni, Ag, and Au is achieved at 97%, 88%, 95%, and 96%, respectively. The metal fraction can be either used as a feedstock for the Cu smelting process or can be subjected to selective hydrometallurgical treatment. The glass fiber fraction comprises of Si, Al, and Ca oxides with potential application in laminate fabrication. High-quality gaseous products can be reutilized as fuel for other metallurgical processes. It can be concluded that 100g of BGA yielded Cu ~ 23.7g, Ni ~ 0.57g, Ag ~ 23.4mg, and Au ~ 73mg after pyrolysis and density separation, which is equivalent to 1.35kg, of primary Cu ore, 0.042kg Ni ore, 4.68kg Ag ore, and 14.6kg Au ore.

Sulfidická mineralizace s Au-bohatým stříbrem z Utína v havlíčkobrodském rudním revíru (Česká republika)

Sulphide mineralization was found in relics of mine dumps from medieval mining near Utín, at SE part of the Havlíčkův Brod ore district (Bohemian-Moravian Highlands, Czech Republic). It is represented by pyrite, Fe-rich sphalerite, chalcopyrite, arsenopyrite, galena (with chemical compositions corresponding to other occurrences of this ore district) and more rare jamesonite and boulangerite. The main Ag ore was probably Ag-rich member of tetrahedrite group - kenoargentotetrahedrite-(Fe) with empirical formula (Ag5.45Cu4.48)Σ9.93(Fe1.75Zn0.32Mn0.01)Σ2.08Sb4.00S12.05. Another interesting mineral found in this association is Au-rich silver with Au contents in the range 53.35 - 56.40 wt. % and average empirical formula Ag0.60Au0.39. Schultenite, minerals of the pharmacosiderite group and inhomogeneous Fe-arsenates were detected from the rarely represented supergene mineralization.

Новые данные о петците Балейского рудного поля в Восточном Забайкалье

The relevance lies in the need to get data on the chemical composition, abundance and paragenesis of petzite, which is one of the mineral carriers of Te, Au and Ag in the gold and silver ores of the Baley ore field in Transbaikalia. During the development of deposits in the ore field, only Au and Ag were extracted, Te went to the dump. The deposits have not been fully developed. The remaining Au reserves of the Taseevskoye deposit are 105 tons, the Au resources of the Baley deposit are estimated at 35 tons. In connection with the extraction of the remaining reserves of Au–Ag ores of these deposits, where part of Te is in the form of petzite Ag3AuTe2, information about it will be important for the development of technology for its extraction along with other tellurides. The purpose of the study is to understand the chemical composition and paragenesis of petzite. The tasks are to study the composition of petzite and petzite-bearing mineral associations of the Baley ore field. The object of the study is Au–Ag ores of the Baley ore field, the subject of the study is the forms of isolation and the chemical composition of petzite. Methodology and methods – optical and electron microscopy with the identification of shapes and sizes of individuals and aggregates of petzite, determination of its chemical composition. Research results are the following: for the first time, the study of the chemical composition of petzite in the ores of the Baley ore field, its abundance and paragenesis has been carried out. It is found in association with hessite, native gold, miargyrite, tetrahedrite, tennantite, pyrite, chalcopyrite, sphalerite, altaite, coloradoite, schützite, andorite, robinsonite, quartz, adularia, carbonates, kaolinite and other minerals. The chemical composition varies within the limits (wt%): Ag 41.57–48.16; Au 18.55–26.01; Te 30.79–35.18. Petzite average chemical composition (wt%): Ag 43.91; Au 22.61; Te 33.16. This indicates the nonstoichiometric composition of its composition and an excess of Ag and Te and a deficit of Au. Petzite, as a carrier of these elements, can be one of the sources of Te in the technology of processing gold and silver ores.

Ni-Co Bearing Laterites from Halmahera Island (Indonesia)

Eastern Indonesia, including the island of Halmahera, is a region with a high mineral potential, particularly Ni-Co, Au-Cu, and Ag ores, which are a globally important and critical source of raw materials (CRMs). The research was conducted within the framework of scientific cooperation between the Faculty of Geology, University of Warsaw (Poland), and PT Halmahera Resources Percasa Ltd. (Jakarta, Indonesia) Between the years of 2009 and 2011, 42 boreholes were drilled using an impact system (up to 15 m below surface) and 3 test pits (up to 8 m below surface). The presence of a laterite deposit containing Ni-Co mineralization was identified on the license area. The resources estimated in accordance with JORC Code, with a cut-off grade Ni ≥ 0.5%, equaling 185,510 t Ni and 17,747 t Co, with the stock of raw material amounting to 14.8 million t and with an average content of 1.00% Ni and 0.13% Co. The ore in the deposit has mixed character. To date, studies have shown the dominance of oxide ore, but saprolite composed of magnesium silicates was also identified in significant amount. The Ni mineralization in oxide ore (limonite) is bound to goethite and manganese minerals, while in the case of silicate (saprolite) ore, it occurs locally in the form of veins as well as zonally in the weathered serpentinites. Cobalt mineralization is almost entirely related to the Mn minerals that occur in the lower oxide zone. It has been found that both serpentinites and harzburgites (and possibly locally lherzolite) are the parent rocks for laterite deposit.

Distinct Au and Ag precipitation mechanism in the Xiayingfang Au–Ag deposit, North China Craton

The Yan-Liao Au polymetallic ore belt, located in the northern margin of the North China Craton, hosts a number of sizeable hydrothermal Au–Ag deposits with abundant Pb-, Sb-, Bi-minerals. These minerals are closely linked to the Au and Ag precipitation, but are rarely studied. The Xiayingfang deposit (22.5 Mt @ 1.9 g/t Au and 9.9 g/t Ag) is a typical Au–Ag deposit in this ore belt, and has characteristic Pb–Sb–Bi–Au–Ag-mineral assemblages. We conducted an integrated study on the mineral assemblages and geochemical components and sulfur isotopes to constrain the Au–Ag precipitation mechanism at Xiayingfang.The Xiayingfang mineralization can be divided into three stages: (I) quartz-pyrite, (II) quartz-polymetallic sulfide, and (III) quartz-sphalerite-galena-electrum (main Au–Ag ore stage), which comprises the sphalerite-galena-native bismuth-pyrite-electrum (IIIA) and galena-freibergite-bournonite-pyrrhotite-electrum (IIIB) substages. The δ34SV-CDT of the paragenetic pyrite and galena pairs reveals a general temperature drop from 300 to 330 °C (Stage I), through 250–290 °C (Stage II), to 170–250 °C (Stage III). The Stage I and II fluid temperature is higher than the melting point of Bi-melt (271 °C) and Au–Bi eutectic (241 °C), which probably caused the “liquid bismuth collector model”. Bi-minerals are widely distributed in later Stage II, and are represented by the coexisting native bismuth and maldonite with dissolution pits on the surface (occurring as droplet-shape or eutectic texture in Stage II galena), which indicates the temperature evolved to lower than 241 °C. Such inference is also supported by fluid inclusion data (216–286 °C for Stage II). The pH generally shifts from the felspar-illite buffer (∼7.0) in Stages I and II to the illite-calcite buffer (ca. 5.2–5.6) in Stage IIIA, which could lead to Au solubility decrease (but minor impact on Ag solubility) in the fluid, favoring electrum precipitation (19.0–31.2 wt% Ag). Moreover, oxygen fugacity drop is revealed by pyrite stable from the Stage IIIA (–41 to –46) to pyrrhotite stable in Stage IIIB (≤–46), which may have markedly decreased both Au and Ag solubility in the fluid. Meanwhile, freibergite coexisting with bournonite and galena in Stage IIIB is highly heterogeneous under EPMA element map, suggesting that it was mainly derived from retrograde and solid-state reactions. These reactions could effectively remobilize Ag from galena and Pb–Sb–Ag-sulfosalts via decomposition and exsolution during fluid cooling. These processes may have contributed to the second-phase precipitation of electrum with a steep rise of Ag (57.5–77.8 wt%) in Stage IIIB. The different mechanisms of Au and Ag precipitation at Xiayingfang are also consistent with the different Au-/Ag- mineral assemblages, i.e., electrum-pyrite-chalcopyrite-enargite assemblages in Stages I and II, and electrum-maldonite-freibergite in Stage III.

Новые данные о гессите Балейского рудного поля в Восточном Забайкалье (Россия)

The relevance lies in the need to have information about the prevalence and paragenesis of hessite, which is one of the main mineral carriers of Te in the gold and silver ores of the unique Baley ore field in Transbaikalia. Te refers to the rarest chemical elements, the use of which has been steadily increasing lately. During the development of the Baleysky and Taseyevsky gold and silver deposits in 1929–1993, only Au and Ag were extracted from the ores, all Te went into the dump. Both deposits are not fully developed. The resources of the Au category P1 of the Baleyskoye field are estimated at 35 tons. The remaining Au reserves of the Taseyevskoye field, approved by the GKZ, amount to 105 tons. In the coming years, it is planned to extract the remaining reserves of Au-Ag ores from these deposits, containing Te mainly in the form of hessite, so knowledge about it will be important for the development of technology for its associated extraction. The purpose of the research is to study the mineral associations of the Baley ore field containing hessite. The object of research is Au–Ag ores of the Baley ore field, the subject of research is the forms of isolation and variations of the chemical composition of hessite. Method and methodology – optical and electron microscopy with the identification of shapes and sizes of individuals and aggregates of hessite, as well as the determination of its chemical composition. Research results: for the first time, the study of the ores of the Baley ore field with a high Te content was carried out and the relatively wide development of hessite was established. It is in association with petzite, altaite, silvanite, empresite, stutzite, pilsenite, as well as tellurium-containing uytenbogaardite, gold, many sulfosols and sulfides, quartz, dolomite, siderite, kaolinite, adular and other minerals. The peculiarity of the hessite Baley ore field is the variability of its composition. Two groups of hessite individuals have been identified. The first one includes hessite, which does not contain impurities. Of these, stoichiometric composition has only 22 %. They correspond to the composition of Ag2Te, in 32.2 % of cases there is an excess of Ag compared to Te (up to Ag2,1Te0,9), and in 45,8 % of samples there is a lack of Ag (up to Ag1,86 Te1,14). In part of the hessite individuals, it is compensated by the Au replacing it. For the first time, hessite containing an admixture of Pb, probably replacing Ag, was identified

Spatial and Temporal Evolution of the Freiberg Epithermal Ag-Pb-Zn District, Germany

Abstract The Freiberg district hosts one of the largest series of epithermal polymetallic vein deposits in Europe. The availability of a systematic collection of historical samples provides an excellent opportunity to study the anatomy of these epithermal systems. Detailed petrographic investigations, geochemical analyses, and fluid inclusion studies were conducted on several vertical profiles within the Freiberg district to decipher mineralogical and geochemical zoning patterns. Six distinctive mineral associations have been recognized within the Freiberg epithermal veins; sphalerite-pyrite-quartz and galena-quartz±carbonate associations are most abundant in the central sector, as well as in the deepest sections of veins on the periphery of the district. A high-grade sphalerite-Ag-sulfides-carbonate association occurs laterally between the central and peripheral sectors and at intermediate depth in veins on the periphery. Shallow and peripheral zones are dominated by an exceptionally Ag-rich Ag-sulfides-quartz association, whereas the shallowest veins locally comprise Ag-poor stibnite-quartz and quartz-carbonate associations. Fluid inclusion assemblages returned low salinities (<6.0 wt % NaCl equiv), and homogenization temperatures successively decrease from ~320°C associated with the proximal and deep sphalerite-pyrite-quartz association, to ~170°C related to the distal and shallow Ag-sulfides-quartz association. The architecture of the Freiberg district is related to the temporal and spatial evolution of magmatic-hydrothermal fluid systems, including boiling and concomitant cooling, as well as CO2 loss. Constraints on the paleodepth indicate that the veins formed between 200 and 1,800 m below the paleowater table. High-grade Ag ore occurs over a vertical interval of at least 500 m and is bracketed by shallower stibnite-quartz and barren quartz, and deeper base metal-sulfide-quartz zones.

Textural Characteristics of Barren and Mineralized Colloform Quartz Bands at the Low-Sulfidation Epithermal Deposits of the Omu Camp in Hokkaido, Japan: Implications for Processes Resulting in Bonanza-Grade Precious Metal Enrichment

Abstract The Miocene low-sulfidation epithermal deposits of the Omu camp in northeastern Hokkaido, Japan, are small past-producers of precious metals and represent significant exploration targets for high-grade Au and Ag ores. The quartz textures of ore samples and the distribution of ore minerals within quartz veins were studied to identify the processes that resulted in the bonanza-grade precious metal enrichment in these deposits. In the high-grade vein samples, which are crustiform or brecciated in hand specimen, ore minerals exclusively occur within colloform quartz bands. High-magnification microscopy reveals that ore-bearing colloform bands consist of fine-grained quartz exhibiting relic microsphere textures and quartz having a mosaic texture that formed through recrystallization of the microspheres. The presence of relic microspheres is evidence that the microcrystalline quartz hosting the ore minerals formed through recrystallization of a noncrystalline silica precursor phase. The ore-hosting colloform bands composed of agglomerated microspheres alternate with barren colloform quartz bands that are composed of fibrous chalcedonic quartz and mosaic quartz formed through recrystallization of the chalcedony. The findings of this study are consistent with previous models linking bonanza-grade precious metal enrichment and the formation of bands of noncrystalline silica in low-sulfidation epithermal veins to episodic vigorous boiling or flashing of the hydrothermal system in the near-surface environment.

From commodity to money: The rise of silver coinage around the Ancient Mediterranean (sixth-first centuries bce).

The reasons why the Western Mediterranean, especially Carthage and Rome, resisted monetization relative to the Eastern Mediterranean are still unclear. We address this question by combining lead (Pb) and silver (Ag) isotope abundances in silver coinage from the Aegean, Magna Graecia, Carthage and Roman Republic. The clear relationships observed between 109Ag/107Ag and 208Pb/206Pb reflect the mixing of silver ores or silver objects with Pb metal used for cupellation. The combined analysis of Ag and Pb isotopes reveals important information about the technology of smelting. The Greek world extracted Ag and Pb from associated ores, whereas, on the Iberian Peninsula, Carthaginians and Republican‐era Romans applied Phoenician cupellation techniques and added exotic Pb to Pb‐poor Ag ores. Massive Ag recupellation is observed in Rome during the Second Punic War. After defeating the Carthaginians and the Macedonians in the late second century bce, the Romans brought together the efficient, millennium‐old techniques of silver extraction of the Phoenicians, who considered this metal a simple commodity, with the monetization of the economy introduced by the Greeks.

Argillizite “Hats” of Kompleksnoe Ore Occurrence in Kayenmyvaam Volcanic Uplift (Central Chukotka)

The article is devoted to the results of mineralogical and geochemical studies of argillizites at Compleksnoe Au–Ag ore occurrence, localized on the southern flank of the Kajenmyvaam volcanic uplift in the inner zone of the Late Cretaceous marginal–continental Okhotsk-Chukchi volcanic belt (OChVB). At the ore occurrence, a series of isometric (oval) in plan view argillizite “hats” with diameters of 200 to 900 m are described. They are composed of red and light gray clay formations and accompanied by complex (Au–Ag–Mo–Cu–Pb–Zn–Bi–Sn) anomalies. In the recent relief, argillizite “hats” are characterized by gently sloping domes and crown subvolcanic bodies of granitoids and explosive breccias. A series of argillizite “hats” is surrounded by elongated lenticular bodies of secondary quartzites, which form the outer boundary of a large annular volcanostructure. The argillizites are composed of the following minerals: illite-smectite (mixed-layered formation), kaolinite, muscovite, jarosite, quartz, and rutile. The average content of Au and Ag in bulk samples are 0.06 and 0.075 g/t, respectively. Au is found in invisible form. According to the geological and geochemical data, argillizite “hats” record a near-surface (up to 300 m), slightly eroded, level of a large porphyry-epithermal mineral-forming system.

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.

Factors Controlling Deposition of Metallic Minerals in the Meng’entaolegai Ag-Pb-Zn Deposit, Inner Mongolia, China: Evidence from Fluid Inclusions, Isotope Systematics, and Thermodynamic Model

The Meng’entaolegai Ag-Pb-Zn vein-type deposit in Inner Mongolia, NE China is hosted in biotite/muscovite granite. This deposit includes the western (Zn-rich, deepest), middle (Zn-Pb rich) and eastern (Pb-Ag-rich, shallowest) ore-blocks. To better understand the metallogenic processes in ore district, we have undertaken a series of studies including fluid inclusion microthermometry, H-O-S-Pb isotope compositions and thermodynamic modeling. Based on fluid inclusion petrography, microthermometry results and HO isotope compositions, the ore-forming H2O-NaCl fluid inclusions are characterized by medium temperature and medium salinity. And two kinds of fluid processes (boiling in western and middle ore-block and fluid mixing in the eastern ore-block) were identified to explain the ore fluid evolution. More importantly, log ƒO2- pH diagrams of δ34S contours with the stability fields of Fe- and Cu-, Zn-, Pb-, and Ag-bearing minerals were constructed to restore the physicochemical conditions of ore-forming fluid in the western (270 °C and 80 bars), middle (250 °C and 70 bars), and eastern (230 °C and 50 bars) ore-blocks. As a result, the ore-forming conditions in the western and middle ore-block were similar. In the eastern ore-block, the fluids may have changed from acidic, S-poor and δ34S(ΣS)≈2.8 to neutral, S-richer and δ34S(ΣS)≈0.5, which imply that neutral S-rich meteoric water was mixed with the magmatic fluid. Meanwhile, the activity of Ag+ was estimated to be about 10 ppm–9 ppm in the middle ore-block, but in the eastern ore-block it was about ~10 ppm–12 ppm. We proposed that the key for Ag ore deposition was likely to be neutralization led by fluid mixing.

Formation of hydrothermal fluorite-hematite veins by mixing of continental basement brine and redbed-derived fluid: Schwarzwald mining district, SW-Germany

Hydrothermal fluorite-hematite veins represent a relatively rare vein type, which is sometimes associated with more common, fluorite-barite-quartz‑carbonate veins containing base metal mineralization. The origin and significance of the fluorite-hematite veins, and how they relate to the more common expression of mineralization, is essentially unknown. Here, we present new data illuminating the formation conditions of these “sulfide-barren” fluorite-hematite veins in a mining district known for hydrothermal Pb + Zn + Ag ores for which formation conditions are well understood: the Schwarzwald district in SW Germany. The exemplary Ödsbach-Hesselbach vein was chosen to study the fluids involved in fluorite-hematite precipitation through the first, direct investigation of fluid inclusions hosted in hydrothermal hematite using combined infra-red light microscopy, microthermometry and LA-ICPMS. The results indicate that the hematite-precipitating fluids are nearly identical to those observed in the associated fluorite, showing consistent salinities of 24.6–25.0 wt% (NaCl+CaCl2) and homogenization temperatures of 150 to 155 °C. Moreover, the trace element abundances determined by the LA-ICPMS analyses show a composition similar to other inclusions observed in the common mineralization in the mining district, including elevated Pb (>5000 μg/g) and Zn (>2000 μg/g) concentrations at low Cl/Br mass ratios, and sulfur contents mostly below the limits of detection. The results suggest fluid mixing between a continental basement brine and a redbed-derived fluid from the Triassic Buntsandstein. Therefore, the formation of the rare fluorite-hematite veins was probably triggered by a change of the sedimentary fluid endmember representing a shift from the Middle Triassic Muschelkalk fluid, which drove the more common Pb + Zn + Ag mineralization, towards fluids derived from the Buntsandstein. Furthermore, the absence of sulfur is interpreted to have precluded base metal sulfide precipitation, and the formation of hematite points to unusually oxidized conditions and hence towards a lack of a reducing agent, which would also have been required to generate a mineralization of base metal sulfides.

Ore geology, fluid inclusions, and C–H–O–S–Pb isotopes of Nagengkangqieergou Ag‐polymetallic deposit, East Kunlun Orogen, NW China

Several large Ag‐polymetallic deposits have been newly discovered in the eastern segment of the East Kunlun Orogen, with the largest one being the high‐grade Nagengkangqieergou deposit (3,017 tons Ag at 310.04 g/t). The Ag ore veins are hosted in the Palaeoproterozoic Jinshuikou Group and Upper Triassic Elashan Formation, principally along NW‐trending faults and volcanogenic ring fractures. Alteration and mineralization processes occurred in two periods (J and E), which are hosted in two different ore‐bearing sequences (Jinshuikou Group and Elashan Formation respectively). These two periods can be subdivided into Stages J‐I, J‐II, J‐III, and J‐IV and Stages E‐I, E‐II, and E‐III. Fluid inclusions in the ore‐bearing quartz and calcite comprise predominantly of vapour‐rich two‐phase (vapour + liquid) type and minor pure‐liquid type. Fluid inclusions in Stage J quartz and calcite homogenized mainly at 270–330°C, 250–310°C, 250–290°C, and 170–250°C, with salinities of 5–6 wt.%, 4–6 wt.%, 4–5 wt.%, and 3–5 wt.% NaCl equiv., respectively. Fluid inclusions in Stage E quartz homogenized mainly at 210–250°C, 170–230°C, and 150–170°C, with salinities of 6–7 wt.%, 4–5 wt.%, and 1–2 wt.% NaCl equiv., respectively. δ13C and δ18OSMOW values of the calcite samples are of −6.0‰ to −2.8‰ and 5.2‰ to 20.5‰, respectively. The results indicate a mantle‐derived magmatic source and low temperature alteration. and δDV–SMOW values of the quartz and calcite from the Jinshuikou Group vary from −1.9‰ to 9.0‰ and −116.5‰ to −69.3‰, respectively, whilst those of quartz from the Elashan Formation vary from −11.6‰ to 7.8‰ and −99.7‰ to −86.7‰. The results indicate that the ore‐forming fluids are of medium‐low temperatures and low salinities and were originated from magmatic water to meteoric water. Sulfide δ34SV–CDT values of the Jinshuikou Group and the Elashan Formation are of −6.1‰ to 0.8‰ and −3.4‰ to 0.9‰, respectively, suggesting a mantle‐derived magmatic source. Sulfide 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb ratios of the J‐period ores (18.190–18.622, 15.598–15.725, and 38.383–39.103, respectively) and E‐period ores (18.408–18.420, 15.746–15.758, and 38.879–38.895, respectively) are similar to those of granodiorite porphyry and Elashan Formation (sub)‐volcanic rocks, respectively, indicative of genetic connections between them. Integrating new evidence from fluid inclusions and C–H–O–S–Pb isotopes, we suggest that (a) mantle‐derived materials and their mixture with crust‐derived ones were critical to the ore formation, (b) the Nagengkangqieergou deposit was formed in a magmatic system and a (sub)‐volcanic system under the syn‐ and post‐collisional tectonics of the East Kunlun Orogen, respectively.

Epithermal Mineralization in the Okhotsk–Chukchi Volcano-Plutonic Belt

This paper considers the geochemistry and conditions of generation for the Mesozoic Au–Ag epithermal deposits in the Okhotsk–Chukchi volcanic–plutonic belt (OChVB) in Northeast Russia. We provide new data on the composition and concentrations of trace elements, including REEs, in the ores of epithermal Au–Ag deposits. The ores were found to be enriched in a wide range of trace elements. The REE distributions of these ores are dominated by light “hydrophile” lanthanoids of the “cerium” group. The Eu anomalies were found to vary between high negative to low and high positive levels. Comparative analysis over the classes of gold concentration showed a synchronous enrichment of the ores in similar sets of trace elements. A study of fluid inclusions revealed that the ore-forming solutions had hydrocarbonate potassium or hydrocarbonate sodium compositions. The fluids had high concentrations of sulfate ions for most deposits. The salinity of the fluids was frequently found to increase toward later low-temperature mineralization phases. We identified the tendency of increasing K+ percentage in the fluid from the earlier oreless quartz to productive quartz with increasing depth, as well as some decrease in the percentages of Na+, Ca++, and Cl–. The results indicate magma chambers of andesite magmas and meteoric waters as the most likely sources of the fluids that generated the epithermal Au–Ag ores in the OChVB deposits.

Mass balance and origin of fluids associated to smectite and chlorite/smectite alteration in Seival Mine Cu–Mineralization – Camaquã Basin – Brazil (Part II)

The Seival Mine, located in the Camaquã Basin, hosts several small Cu and Ag ore deposits in volcano–sedimentary sequence surrounding the Lavras do Sul Intrusive Complex. Alteration minerals consist of calcite, sulfate, smectite and chlorite/smectite associated with Cu–rich sulfides. The mass balance calculations from less altered to altered volcanic rocks show large chemical changes with the mobility of mettallic elements in major or trace amounts. Mass balance calculations for similar volcanic protoliths, with different degrees of alteration or textural variations, indicate that increasing proportions of clay minerals reflects higher degrees of alteration. This alteration did not mobilize Si, Al, Fe, and Mg and had a small effect on other metallic elements such as Cu, Zn, Ni, and Au. Consequently, fluids associated with propylitic to argillic alteration with chlorite–smectite precipitation did not participate in the transport of base metals and ore deposition. Interpretations of oxygen stable–isotopes for magmatic, late magmatic and hydrothermal minerals show decreasing proportion magmatic fluid (δ18Ofluid of andesine labradorite ca. 5 to 7‰), toward a predominance of meteoric fluid (δ18Ofluid of quartz and calcite) between −12 and 0‰ for the low–temperature alteration (250 to 80 °C). Carbon stable isotopes result suggest a mixture of inorganic carbon ca. −7 to −5‰ from volcanic CO2 with late carbonate precipitation with atmospheric signatures ca. −4 to −1‰. These mass balance and stable isotopes interpretations suggest that high–temperature late–magmatic fluid/rock interaction (650 to 350 °C) has promoted the base metal enrichment.

Updated Global and Oceanic Mercury Budgets for the United Nations Global Mercury Assessment 2018.

In support of international efforts to reduce mercury (Hg) exposure in humans and wildlife, this paper reviews the literature concerning global Hg emissions, cycling and fate, and presents revised global and oceanic Hg budgets for the 2018 United Nations Global Mercury Assessment. We assessed two competing scenarios about the impacts of 16th - late 19th century New World silver (Ag) mining, which may be the largest human source of atmospheric Hg in history. Consideration of Ag ore geochemistry, historical documents on Hg use, and comparison of the scenarios against atmospheric Hg patterns in environmental archives, strongly support a "low mining emission" scenario. Building upon this scenario and other published work, the revised global budget estimates human activities including recycled legacy emissions have increased current atmospheric Hg concentrations by about 450% above natural levels (prevailing before 1450 AD). Current anthropogenic emissions to air are 2.5 ± 0.5 kt/y. The increase in atmospheric Hg concentrations has driven a ∼ 300% average increase in deposition, and a 230% increase in surface marine waters. Deeper marine waters show increases of only 12-25%. The overall increase in Hg in surface organic soils (∼15%) is small due to the large mass of natural Hg already present from rock weathering, but this figure varies regionally. Specific research recommendations are made to reduce uncertainties, particularly through improved understanding of fundamental processes of the Hg cycle, and continued improvements in emissions inventories from large natural and anthropogenic sources.

The relationship between stratabound Pb–Zn–Ag and porphyry–skarn Mo mineralization in the Laochang deposit, southwestern China: Constraints from pyrite Re-Os isotope, sulfur isotope, and trace element data

The Laochang polymetallic deposit is located in the Sanjiang Tethyan metallogenic province of southwestern China. This deposit contains stratabound (and locally vein-type) Pb–Zn–Ag mineralization and underlying porphyry–skarn Mo mineralization. The stratabound Pb–Zn–Ag mineralization is characterized by massive sulfide ores composed mainly of pyrite, sphalerite, galena, and minor chalcopyrite, whereas the underlying porphyry–skarn Mo mineralization is characterized by quartz–sulfide veins comprising mainly pyrite, chalcopyrite, molybdenite, and minor sphalerite and galena. The age and origin of the stratabound Pb–Zn–Ag mineralization has long been debated, and its relationship to the porphyry–skarn Mo mineralization remains unknown. Integrated pyrite Re-Os isotope, sulfur isotope, and in situ trace element data are used here to constrain the age and origin of both types of mineralization and their genetic relationships.Pyrite related to porphyry–skarn Mo mineralization yields a Re-Os isochron age of 47.3 ± 4.8 Ma, which is consistent with a previous molybdenite Re-Os age of the quartz–sulfide ores and zircon U-Pb ages of the granite porphyry (~44–50 Ma). Pyrite from the stratabound Pb–Zn–Ag mineralization failed to yield a geologically meaningful age, but associated sphalerite and galena have a Re-Os isochron age of 308 ± 25 Ma (Liu et al., 2015), which is consistent with the Carboniferous age of the host basalts. Pyrite, sphalerite, galena, and chalcopyrite from the stratabound Pb–Zn–Ag mineralization have δ34S values (−2.1 to 0.5‰; average 0.48‰) indistinguishable from those of sulfides from the porphyry–skarn Mo mineralization (−4 to 1.9‰; average 0.52‰). Initial Os isotope ratios indicate a mainly crustal origin for both types of mineralization. The calculated (Se/S)fluid and Co/Ni values of pyrite from the stratabound Pb–Zn–Ag mineralization indicate a mixed sedimentary and hydrothermal origin, with a significant magmatic contribution. The identification of a magmatic component, Eocene sulfide mineralization, and phyllic and propylitization alteration in stratabound Pb–Zn–Ag ores indicates that the magmatic–hydrothermal component reflects the overprinting of Carboniferous volcanogenic massive sulfide mineralization by magmatic–hydrothermal fluids derived from an Eocene granite porphyry.

Surface Typochemistry of Native Gold

Using the methods of electron spectroscopy of the surface and SEM–EDS, it is shown that native gold of the deposit related to the epithermal Au–Ag ore formation contains oxidized gold with an oxidation degree of Au (I) or higher on the surface. A thin layer (~15 nm) with high concentrations of Ag and S and an underlying SiO2-bearing layer with a thickness of ~30–60 nm play a protective role providing preservation of Ag and Au sulfides in the surface parts of the Au–Ag grains under the oxidizing conditions. S-rich marginal parts of native gold particles may be represented by solid solutions Ag2–xAu x S or (with a lack of S) by agglomerates of Ag n Au m S clusters. The formation of surface zoning in the nanoscale on the surface of native Au is abundant in nature and may be applied in prospecting.