Native Silver Research Articles

АКЦЕССОРНЫЕ САМОРОДНЫЕ МЕТАЛЛЫ И ИХ ОКСИДЫ ИЗ МАССИВНЫХ ХРОМИТИТОВ КЕМПИРСАЙСКОГО УЛЬТРАМАФИТОВОГО МАССИВА (ЮЖНЫЙ УРАЛ, КАЗАХСТАН)

Актуальность исследования обусловлена недостаточной всесторонней изученностью минералогических аспектов ультрамафитовых реститовых массивов, что не дает возможности их обобщения на минералогическом уровне и восстановления полной истории их формирования и преобразования, а также решения целого ряда спорных вопросов петрологии данных объектов. Минералогия самородных металлов и их оксидов из реститовых ультрамафитов является крайне слабо изученным направлением. Цель: изучение минерализации самородных металлов и их оксидов в густовкрапленных и сливных хромититах Кемпирсайского ультрамафитового массива, реконструкция механизма ее формирования. Методы: изучение рудной минерализации в аншлифах с использованием поляризационного микроскопа AxioScope Carl Zeiss; диагностика химического состава рудной минерализации методом рентгеноспектрального микроанализа с применением электронного сканирующего микроскопа Tescan Vega II LMU, оборудованного энергодисперсионным спектрометром (с полупроводниковым Si(Li) детектором INCA x-sight) INCA Energy 450 и волнодисперсионным спектрометром INCA Wave 700. Результаты. Впервые в хромититах Кемпирсайского массива выполнена детальная диагностика акцессорной минерализации самородных металлов и их оксидов, по результатам которой выявлены и охарактеризованы: самородный никель, самородное серебро, самородная медь, самородное железо, аваруит, касситерит, монтепонит, цинкит. Концентрирование рассмотренной минерализации, очевидно, было связано с ее мобилизацией в процессе серпентинизации и преобразования первичных силикатов, а также хромшпинелидов и сульфидов при восстановительных условиях. Образование металлов автор связывает с тенденцией Ni и подчиненного Fe высвобождаться из кремнекислородных связей первичного оливина, а Cu и Zn – из связей сульфидов и хромшпинелидов и переходить в форму свободных элементов. Очевидно, привнос части элементов (Cd, Sn) осуществлялся и самими серпентинизирующими растворами. Дальнейшая судьба данных металлов определялась их концентрированием и последующим отложением из высоконасыщенных надкритических флюидов.

Leaf inputs from invasive and native plants drive differential mosquito abundances

Ecological impacts of invasive alien species can be unpredictable and simultaneously span multiple habitat types and taxonomic groups. Invasive alien plants can have particularly severe impacts, and plant inputs into aquatic environments can profoundly alter community composition of invertebrates, such as mosquitoes. Here, we examine larval mosquito colonisation of aquatic containers treated with leaves from four different terrestrial plants: the invasive tickberry Lantana camara, invasive guava Psidium guajava, native sycamore fig Ficus sycomorus and native silver cluster-leaf Terminalia sericea. Larval mosquito abundances differed significantly accordingly to leaf treatment, whilst no mosquitoes colonised leaf-free controls. Leaf litter from the invasive L. camara, invasive P. guajava and native F. sycomorus drove significant increases in mosquito abundances relative to native T. sericea. We demonstrate the importance of plant identity for larval mosquito proliferations in aquatic habitats, with changes in plant community composition following terrestrial plant invasions potentially resulting in increased mosquito abundances. In turn, this may have implications for the vectoring of mosquito-borne disease.

Fluid inclusions, isotopic characteristics and geochronology of the Sinongduo epithermal Ag-Pb-Zn deposit, Tibet, China

The Sinongduo Ag-Pb-Zn deposit is the first documented low-sulfidation epithermal deposit in Tibet and located on the southern side of the Longge’er-Gongbujiangda arc fault belt of the Lhasa terrane. The Ag-rich base metal veins and relatively low-grade breccias and stockworks in the Sinongduo deposit occur in the Paleocene high-potassium calc-alkaline to shoshonitic series volcanic rocks, including rhyolitic welded tuff breccia and volcanic breccia, rhyolitic ignimbrite, rhyolitic crystal fragment tufflava, rhyolite, and rhyolitic tuff. A nearly N-S-trending fault is the most important ore-controlling structure in the deposit. Galena and sphalerite are the dominant ore minerals in quartz-sericite-illite ± adularia veins, with subordinate argentite, pyrargyrite, native silver, chalcopyrite, pyrite and tennantite. The most widespread silver minerals are argentite, pyrargyrite, pearceite and native silver, which occur in fissures in Fe-Mn carbonates, jasper and early sulfides. The mineralization process can be divided into a pre-ore stage, main ore stage, and post-ore stage, and the main metallogenic stage is divided into the galena substage, sphalerite substage and silver minerals substage.Microthermometric analyses of the primary liquid-rich and vapour-rich fluid inclusions (FIs) in the sphalerite (SpII), main ore stage quartz (QzII) and post-ore stage quartz (QzIII) of the Sinongduo deposit indicate that the FIs in SpII, QzII and QzIII are mainly homogenized at temperatures of 197.2–280.8 °C, 185.6–290.4 °C and 148.2–218.7 °C with salinities of 1.40–5.71 wt% NaCl equiv., 1.59–5.71 wt% NaCl equiv. and 2.07–8.94 wt% NaCl equiv., respectively. These data indicate that the deposit was formed in a low-temperature and low-salinity environment, corroborating an epithermal system of mineralization. The O and H isotope compositions of the ore-forming fluids (δ18O = −0.6 to −6.3‰; δD = −177 to −151‰) indicate there was a major contribution from a meteoric water component to metallogenesis. All of the Pb isotope data from the metal sulfides and country rocks in the Sinongduo deposit in this study are similar and imply a close genetic relationship. The δ34S values of galena and sphalerite exhibit narrow distributions, ranging from +4.1‰ to +5.6‰ and from +7.6‰ to +8.4‰ respectively, with average values of +5.0‰ and +8.1‰, respectively, suggesting a uniform source. The Ar-Ar ages determined from sericite in the quartz-sericite-illite-sulfide veins range from 60.9 ± 0.7 to 63.1 ± 0.7 Ma, showing that the timing of epithermal Ag-Pb-Zn mineralization in the study area is consistent with the eruption of the Dianzhong Formation volcanic rocks (DVR) (U-Pb dating, 65–62 Ma), which indicates a genetic relationship. The characteristics of FIs, the H-O-S-Pb isotope data and the mineralization ages suggest that the ore-forming fluids were primarily sourced from circulating meteoric water, while S and Pb were derived from the DVR. Our results, combined with previous data on the regional geology, ore geology, FIs, and tectonic setting, indicate that the Sinongduo Ag-Pb-Zn deposit was produced in an epithermal system that formed on the southern side of the Longge’er-Gongbujiangda fault-block uplift belt, following the northward subduction of the Neo-Tethyan oceanic plate beneath the Asian continent.

From Iberia to the Southern Levant: The Movement of Silver Across the Mediterranean in the Early Iron Age

The origins of the silver trade across the Mediterranean, and the role of the Phoenicians in this phenomenon, remain contentious. This is partly because of difficulties encountered when trying to assign archaeological silver to its geological sources. Here we present a reanalysis of Iron Age silver hoards in the southern Levant, which demonstrates not only that recycling of silver was widespread in the Early and Late Iron Age, but that the components of this mixed silver originated from the Aegean, Anatolia and the western Mediterranean. An assessment of lead isotope analyses combined with compositional data allows the identification of mixing lines based on gold levels in the silver and the Pb crustal age (or, more loosely, geological age) of the ore from which the silver originated. It is shown that, from as early as the 11th century BC, these mixed silver signatures derive from the Taurus mountains in Anatolia, from Iberia and an unknown source—with Sardinia as an additional possibility—and Laurion in Greece in the Late Iron Age. In contrast to copper, which was deliberately alloyed with silver, gold appears to have been mixed unintentionally, through the melting down of silver objects with gold parts. It is suggested that vertical mixing lines (with constant Pb crustal age but variable Au), may indicate the melting down and mixing of silver in times of unrest, both here and in other contexts. Gold and lead concentrations in the silver indicate that native silver from Iberia was most likely used in the Early Iron Age, suggesting that the first people to convey silver to the southern Levant were not miners but traders who had acquired silver directly from the indigenous Bronze Age inhabitants of Iberia. However, evidence of the exploitation of jarosite also supports that silver ore mining and cupellation was ongoing in Iberia at a similar time, and continued in the Late Iron Age—potentially a result of technological transfer from the East. In essence, the western Mediterranean origin of the silver in these Early Iron Age southern Levantine hoards supports an emerging picture of Mediterranean interactions and trade relations in the increasingly bright Dark Ages (c. 1200–800 BC).

Manganese Mineralization in the Mesozoic Siliceous Deposits of the Central Sikhote-Alin and Nadanhada-Alin

The stratiform ferromanganese bodies in the Mesozoic chert formations of central Sikhote-Alin (Katen R., J3) and Nadanhada-Alin (Khuntseling settlement, J2–3), and the vein manganese deposit (Ktab) at the Glubinny settlement area (central Sikhote-Alin) are characterized for the first time. Jurassic primary ores occur as interlayers in clayey–siliceous units. They consist of grains and globules of Mn and Fe oxides of the psilomelane–pyrolusite group and goethite. The interlayers also contain the allogenic products of eroded sialic rocks (quartz, potassium feldspar, albite, kaolinite, muscovite, paragonite, illite, and zircon) and accessory ore minerals (monazite, sphalerite, galena, apatite, cassiterite, barite, pyrite, titanite, rutile, native silver, auricupride, cerianite, tetrahedrite, and intermetallic Cu5Zn3 and Ni7Cu4). In the vein ores, spessartine and rhodonite fill veinlets and form a matrix of tectonic breccia. Manganese oxides form crusts (up to 4 cm) on the Triassic chert lumps and blocks. They likely represent the products of oxidation and breakdown of former hydrothermal–metasomatic manganese carbonates and silicates in a supergene environment. In contrast to the manganese minerals from the stratiform ores, those of the vein ores do not contain Co, Ni, Zn, and Pb, which are involved in the sulfides and sulfoarsenides (Co-gersdorffite and Ni-cobaltite, smaltite, pentlandite, and other minerals). Magnetite; titanomagnetite; barite; chalcopyrite; pyrrhotite; galena; argentite; zircon; titanite; wollastonite; anhydrite; REE phosphates, silicates, and oxides; bismuthine; native Ag, W, Cu, Zn, and Ni; and intermetallic compounds (Cu5Zn3, (Pd, Pt)5Cu and Pd4Cu) are also recognized in the vein manganese ores.

An Archaeometallurgical Explanation for the Disappearance of Egyptian and Near Eastern Cobalt-Blue Glass at the end of the Late Bronze Age

A recent compositional study of Egyptian cobalt-blue glass from museum collections in Japan (18th Dynasty) and from the site of Dahshur (18th and 19th-20th Dynasties) concluded that a new source of cobalt was exploited for the later Dahshur glass, thereby suggesting that glass production continued into the Ramesside period (Abe et al. 2012). It is shown in the current article that some of this 18th Dynasty glass and the majority of the 19th-20th Dynasty glass had been recycled, not only supporting the general consensus that glass production virtually disappeared by 1250 BC, but that the cobalt source did not necessarily change. It is further proposed, however, that the generally accepted cobalt source for Egyptian glass was not the alum deposits of Egypt's Western Desert, but derived from cobaltiferous siliceous ores, possibly from central Iran. Re-analysis of the compositions of cobalt-blue glass frit found at Amarna, as well as Egyptian and Mesopotamian glass, suggests that the cobalt colourant was a by-product of silver extraction from these ores and can therefore be considered as a concentrated cobalt glass slag, which travelled in the form of a frit to glass producers who added it to locally derived base glasses and/or their precursors. Experiments conducted on ore containing cobalt-nickel arsenides with native silver demonstrate that not only can silver be extracted and that concentrated cobalt glass can be produced simply by adding a flux, but that some components of the ore partition preferentially into the silver or the glass slag, thereby weakening their associations with the other components in archaeological glass. Treating the cobalt-blue colourant as a slag composed of the gangue of a smelting system provides an explanation for the unique elevated levels of alumina and lower levels of potash found in cobalt-blue glasses, as well as providing an explanation for the cessation of cobalt exploitation at the end of the Late Bronze Age. It is suggested that the exhaustion of native silver and siliceous silver ore deposits during the Bronze Age, with argentiferous lead ores becoming the main source of silver, depleted the amount of cobalt available, thereby reducing the amount of glass produced which, in turn, led to increases in recycling during the New Kingdom period.

A New Type of Noble Metal Mineralization in Fluidolites of the Poperechny Deposit, Lesser Khingan, Russia

The fluid-explosive breccias of the Poperechny iron–manganese deposit, Lesser Khingan, Russia, contain high concentrations of platinum group elements (PGE), gold, and silver. Noble metals are represented by isoferroplatinum crystals, Os–Ir alloys, PGE sulfoarsenides, and gold grains with a size of tenths of a millimeter and micron-sized segregations of native silver. The mineral composition of the PGE of the Poperechny deposit is consistent with that of the ore and placer objects of the Ural–Alaskan type and corresponds to the isoferroplatinum–osmium magmatic assemblage. The euhedral morphology of the isoferroplatinum and PGE sulfoarsenides indicates that they were formed in a stable environment at the crust–mantle boundary owing to partial melting of slab rocks. The appearance of PGE minerals in the magmatic–hydrothermal system under subsurface conditions is related to a highly mobile gas-saturated fluid flux capable of transferring deep mineral phases. The high content of PGE (up to 11.3 g/t), gold (up to 2.58 g/t), and silver (up to 256 g/t) in the fluidolites of the Poperechny deposit makes it possible to revise the criteria for searching for the bedrocks and placer sources of noble metals in the Lesser Khingan.

Spiny Softshell (<i>Apalone spinifera</i>) turtles exhibit scarring consistent with attempted lamprey bites

We captured 46 Spiny Softshells (Apalone spinifera) during a mark–recapture study on Lake Erie (2012–2015). Six (13%) exhibited circular scars consistent with the bites of small parasitic lampreys. Two species of parasitic lampreys occur in Lake Erie: the invasive Sea Lamprey (Petromyzon marinus) and the native Silver Lamprey (Ichthyostomyzon unicuspis). The scars showed only the marks of the putative teeth surrounding the suctorial mouth, preventing identification based on the position of the supraoral teeth and suggesting that lampreys are rapidly dislodged from the turtles. To our knowledge, this is the first evidence of lampreys biting freshwater turtles.

Recent Mn-Ag deposits in coastal hydrothermal springs in the Baja California Peninsula, Mexico

Hot springs with associated Mn-Ag mineralization were identified in the intertidal zone of the Bahia Concepcion Bay of the central-eastern Baja California Peninsula. Hot spring activity is related to a system of NW-SE faults that are associated with the opening of the Gulf of California. The hot springs are hosted by Miocene volcanic and volcaniclastic units of the Comondu Group. The maximum discharge temperature recorded is 72 °C, with the pH ranging from 6.2 to 6.5 and salinity values reaching up to 27 g/kg. Veins, stockworks, breccias, crusts, and organosedimentary stromatolites of silica-carbonate and Mn oxides are associated with the hot springs. The Mn oxide and silica deposits show an association with Ag, As, Ba, Ca, Cu, Mg, Pb, Sb, Sr, Tl, V, W, and Zn. Acanthite and native silver occur along with pyrite in a mineral assemblage rich in opal-A, todorokite, romanechite, aragonite, high-Mg calcite, and barite. Three distinct mineral associations characterized by sulfides, sulfates, and oxides are recognized. The silver minerals formed late in the paragenesis. Textural evidence suggests a microbial mediation for the Mn mineral deposition. Pourbaix diagrams for Mn and Ag species were constructed for the physicochemical conditions of the coastal hot springs. These diagrams show that both Mn and Ag minerals are stable at low temperature (65 °C), and near neutral pH, under slightly reducing or oxidizing conditions. The characteristics of the subaerial to shallow submarine hot springs and the results of the geochemical modeling suggest that the hydrothermal system in the Bahia Conception Bay is formed through convection of meteoric waters, intermixed with some saline fluids or seawater.

Solid solutions in the system acanthite (Ag2S)–naumannite (Ag2Se) and the relationships between Ag-sulfoselenides and Se-bearing polybasite from the Kongsberg silver district, Norway, with implications for sulfur–selenium fractionation

Sulfoselenides [Ag2(S,Se)] and Se-bearing polybasite have been discovered at the Kongsberg silver district. The selenium-bearing minerals occur in two samples from the northern part of the district, forming either single or polyphase inclusions together with chalcopyrite within native silver. The Ag-sulfoselenides show large chemical variations, covering nearly the complete compositional range between acanthite (Ag2S) and naumannite (Ag2Se). For the data presented here, there is no local maximum at the composition Ag4SSe attributed to the distinct phase called aguilarite, suggesting that this composition can be considered as one of many possible along the monoclinic Ag2S–Ag2S0.4Se0.6 solid solution series rather than a specific mineral phase. We present a model explaining the variations in the Se-content of Ag2(S,Se) as a result of gradual de-sulfidization of the rock under oxidizing conditions. During this process, sulfur from the Ag2S-component of Ag2(S,Se) oxidized and dissolved in the fluid phase as SO42−, resulting in the formation of native silver. The activity ratio $${a_{{{\text{S}}^{2 - }}}}/{a_{{\text{S}}{{\text{e}}^{2 - }}}}$$ of the system gradually decreased due to the removal of SO42−, which resulted in the stabilization of a sulfoselenide with higher selenium content. As a result of reaction progress, grains of Ag2(S,Se) became gradually enclosed in newly formed native silver, and therefore isolated from further reactions with the grain-boundary fluid. Grains isolated early during the process show low content of Se reflecting high $${a_{{{\text{S}}^{2 - }}}}/{a_{{\text{S}}{{\text{e}}^{2 - }}}}$$ of the equilibrium fluid, while grains showing high Se reflect the composition of late low $${a_{{{\text{S}}^{2 - }}}}/{a_{{\text{S}}{{\text{e}}^{2 - }}}}$$ fluids. Analyses of Se-bearing polybasite show that selenium is preferentially partitioned into Ag2(S,Se) compared to polybasite. The model presented here demonstrates how oxidation of sulfoselenides leads to fractionation of sulfur and selenium.

Can the minerals calcium and sodium, chelated to propionic acid, influence the health and zootechnical parameters of native silver catfish Rhamdia quelen?

Intensive aquaculture production requires new strategies to improve the performance and health parameters of farmed fish to avoid developing resistance in bacterial genes and to avoid environmental pollution. The aim of this study was to evaluate the effects of calcium and sodium as chelants to propionic acid on the growth performance and hemato-immunological parameters of native silver catfish Rhamdia quelen fed for 60 days with a supplemented diet, in addition to evaluating survival and immunological parameters after exposure to the pathogenic bacterium Aeromonas hydrophila. A total of 225 fish were divided into 15 tanks, with 15 fish per tank in five groups: control (not supplemented), Ca-propionate 0.25% (Ca0.25%), Ca-propionate 1% (Ca1%), Na-propionate 0.25% (Na0.25%), and Na-propionate 1% (Na1%), with three replicates for each group. Fish fed Ca0.25% showed the best results in terms of weight gain (43.61 ± 4.89), biomass (779.06 ± 79.40), specific growth rate (3.00 ± 0.13) and survival after pathogen exposure. This group showed 54% more survival than the Na 1% group after 96 h of exposure. Fish fed Na 1% presented high leukocytosis (12.0 ± 4.20) and lymphocytosis (9.24 ± 2.57) in relation to those fed Na0.25% and Ca1% (before exposure). Total protein showed a significant decrease while lysozyme and agglutinating titer increased after exposure. These results suggest the Ca-propionate 0.25% as the best additive to be used in fish farming of native silver catfish.

Recovery of Residual Silver-Bearing Minerals from Low-Grade Tailings by Froth Flotation: The Case of Zgounder Mine, Morocco

The need to explore more complex and low-grade silver ores and to develop novel and cost-effective processes to recover silver from waste is becoming an important challenge. This paper aims to characterize old, low-grade, silver tailings generated by the former Zgounder silver mine, located in Morocco. Understanding the mineralogical composition, particularly the silver deportment, was critical to allow the recovery of silver from these tailings. More than 88 samples of low grade tailings were sampled and characterized using chemical and mineralogical techniques. Froth flotation was used to recover silver bearing minerals using a combination of different collectors (dithiophosphate, dialkyl dithiophosphinates, Aero 7518, Aero 7640, alkyl dithiophosphates and potassium butyl-xanthate). The main goal was to optimize the flotation process at a laboratory scale through the testing of different parameters, such as collectors and frother types and dosage, activators and sulphidizing agents, and pH conditions. The characterization results showed that silver content varied between 30 and 440 ppm with an overall average content of 148 ppm. Silver occurs mainly in the form of native silver as well as in association with sulphides, such as acanthite and pyrite. Minor amounts of sphalerite, chalcopyrite, arsenopyrite, and hematite were identified. The flotation results showed the following optimum conditions: particle size of 63 µm, conditioning pH of 8.5, a combination of butyl-xanthate and dithiophosphate as collectors at a dosage of 80 g/t each, a concentration of 200 g/t of the activating agent (CuSO4), 30 g/t of methyl isobutyl carbonyl (MIBC) frother and a duration time of 8 min with slow kinetics. With these optimal conditions, it was possible to achieve a maximum silver recovery yield of 84% with 1745 ppm Ag grade to be cyanided. Moreover, the environmental behavior of the final clean tailings was demonstrated to be inert using Toxicity characteristic leaching procedure (TCLP) leaching tests.

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Cupropearceite is a sulphosalt belonging to the pearceite-polybasite group, formed due to Cu-for-Ag substitution. It is a rare mineral of the Earth’s crust, described only in four locations so far. This work reports the occurrence of cupropearceite in the upper part of the Weissliegend sandstone from the Cu-Ag deposit in the Fore-Sudetic Monocline. The mineral is associated with stromeyerite, bornite, chalcocite, native silver, silver amalgams and, rarely, pyrite. Formation of cupropearceite is related to fluid activity during low-temperature hydrothermal events responsible for the formation of the Cu-Ag ore mineralization. The identification of cupropearceite is important in terms of constraining minerals bearing associated metals, particularly Ag and As. This work also presents occurrence of this rare mineral in the previously unnoted mineral assemblage mentioned above. The presence of cupropearceite confirms a low-temperature, hydrothermal origin of the Cu-Ag deposit in the Fore-Sudetic Monocline.

Collector's Note: Discovery of an Exceptional Silver Vein in Michigan's Keweenaw Peninsula

Twenty-sixth in a series of articles on the mines and minerals of Michigan's Copper CountryON 16 AUGUST 2017 an important discovery of a native silver vein located in Keweenaw County, Michigan, was...

Polyphase enrichment and redistribution processes in silver-rich mineral associations of the hydrothermal fluorite-barite-(Ag-Cu) Clara deposit, SW Germany

The silver-copper sulfide mineralization associated with the fluorite-barite vein system at the Clara deposit in SW Germany shows large scale vertical zoning. Low to moderate silver contents prevail in the upper 350 m, whereas high silver contents occur in the subsequent 450 m of the currently known vein system. This change in Ag tenor is related to conspicuous mineralogical changes with depth. A detailed petrographic and fluid inclusion study identifies evidence for five subsequent hydrothermal and one alteration stage—all contributing to mineralogical diversity. The vertical Ag zoning, however, is attributed only to the first of these stages. During this first stage, increasing oxidation of ascending hydrothermal fluids (90–160 °C, 24.2–26.7 wt% NaCl+CaCl2) led to the formation of high-Ag tetrahedrite-tennantite in the lower parts and basically Ag-free enargite in the upper parts of the vein system. The subsequent hydrothermal stage led to significant mineralogical changes, but inherited the pre-existing Ag zonation. In this second hydrothermal stage, which was related to fluids similar in composition to those of the first stage (70–125 °C, 23.1–26.5 wt% NaCl+CaCl2), dissolution of high Ag-tetrahedrite-tennantite resulted in the formation of complex Ag-sulfosalts together with moderately Ag-bearing tetrahedrite-tennantite and chalcopyrite. The first two stages were formed by fluid mixing of a sedimentary and a hot basement fluid. The influx of fluids with high Ag, Bi and Pb activity during stage 3 and 5 resulted in the local replacement of earlier Ag-sulfosalts by galena and Ag-(Bi)-sulfosalts. The fourth stage is marked by partial dissolution of sulfides and sulfosalts by a late, hot, undiluted basement fluid (250 °C, 18.7–20.9 wt% NaCl+CaCl2) precipitating fluorite, barite and quartz. Finally, supergene alteration lead to the dissolution of silver-bearing phases and the precipitation of acanthite and native silver. The study illustrates, how metal tenor and mineralogy are decoupled in vertically extensive, polyphase hydrothermal vein systems. This may be pertinent to similarly zoned polymetallic vein systems.

Fractionation of silver isotopes in native silver explained by redox reactions

Scant data exist on the silver isotope composition of native silver specimens because of the relative newness of the technique. This study increases the published dataset by an order of magnitude and presents 80 silver new isotope analyses from native silver originating from a diverse set of worldwide deposits (8 deposit types, 33 mining districts in five continents). The measured isotopic range (defined as δ109Ag/107Ag in per mil units compared to NIST 978 Ag isotope standard) is +2.1 to −0.86‰ (2σ errors less than 0.015); with no apparent systematic correlations to date with deposit type or even within districts. Importantly, the data centering on 0‰ all come from high temperature hypogene/primary deposits whereas flanking and overlapping data represent secondary supergene deposits. To investigate the causes for the more fractionated values, several laboratory experiments involving oxidation of silver from natural specimens of Ag-rich sulfides and precipitation and adsorption of silver onto reagent grade MnO2 and FeOOH were conducted. Simple leach experiments demonstrate little Ag isotope fractionation occurred through oxidation of Ag from native Ag (Δsolution-native109Ag = 0.12‰). In contrast, significant fractionation occurred through precipitation of native Ag onto MnO2 (up to Δsolution-MnO2109Ag = 0.68‰, or 0.3amu). Adsorption of silver onto the MnO2 and FeOOH did not produce as large fractionation as precipitation (mean value of Δsolution-MnO2109Ag = 0.10‰). The most likely cause for the isotopic variations seen relates to redox effects such as the reduction of silver from Ag (I) to Ag° that occurs during precipitation onto the mineral surface. Since many Ag deposits have halos dominated by MnO2 and FeOOH phases, potential may exist for the silver isotope composition of ores and surrounding geochemical haloes to be used to better understand ore genesis and potential exploration applications. Aside from the Mn oxides, surface fluid silver isotope compositions might provide information about geochemical reactions relevant to both environmental and hydrometallurgical applications.

Improving processes and natural production minerals recycling

The article is devoted to improving the processes of extraction of natural carbon minerals through increased selectivity and reduce dilution, as well as processing of ash-slag wastes to reduce environmental burdens and increasing complexity of extracting minerals. Data are elemental and mineral composition, energy dispersive microanalysis by scanning electron microscope JEOL JCM-6000. As a result of natural objects analysis carbon minerals, with their typing on structural and mineralogical composition, marked by the characteristic difficult structural signs plastoobraznyh and lenticular deposits. A method of treatment of structured development of carbonaceous deposits of minerals based on the improved design of the working body of the harvester, that will increase the efficiency of minerals through mining selectivity. As a result, microanalysis samples ash wastes found the presence of native gold, рlatinum and silver. The application of ways of dressing of secondary raw materials using innovative technologies developed, based on the processes of gravitational and ultrasonic cavitation effects, provide comprehensiveness of allocating valuable components micron level and reduce the pollution of Wednesday.

Platinum mineralization comparative characteristics of the some Far East deposits

In this article shown platinum mineralization comparative characteristics for three deposits: Kondoer-traditional unique deposit and other two probably alternative source of platinum: the Poperechnoe ironmanganese deposit and the Malmyzh copper-porphyry deposit. Platinoids of the Kondoer deposit are the chain Pt>>Ir>Os>Ru=Rh>Pd. The presences of platinum crystals are characteristic, there are over 50 rare and new platinoids minerals in different combinations. There are gold and silver. Platinoids from the iron-manganese ore of Poperechnoe are as Pt>>Rh≈Ir>Ru≈Os>Pd. A scattered dissemination of arsenide sulfate and sulfides of Rh, Ir, Ru, Os are noted in the platinum. Palladium is present as impurities in gold and platinum. The gold content is different-with admixtures Ag, Pb, Cd, Fe. At this stage the platinoids content in oxidized ores of the Malmyzh gold-copper porphyry deposit is Pt ≈ Pd. The gold is present as electrum. There is native silver cadmium.

Genetic Aspects of the Noble-Metal Mineralization at the Poperechnoe Deposit, Lesser Khingan, Russia

Bodies of cryptovolcanic rocks (fluidolites) play a significant role in the structure of the Poperechnoe ferromanganese deposit, Lesser Khingan, Russia. Fe-Mn ores in association with fluidolites are localized in ancient carbonate rocks. PGM, gold, and silver minerals up to tenths of a millimeter in size are established in the rocks and ores of the deposit. Characteristic admixtures in the platinum are iron (9-11%), with less common copper, iridium, and osmium. An intergrowth of isoferroplatinum polycrystal with forsterite is observed. There are also individual grains of Os-Ir-Ru-Rh intermetallides. The gold grains (up to 93% Au) are characterized by dendritic and clumpy morphology, frequently showing faceting elements. The grains are frequently rounded and sometimes have an almost perfect spherical shape. Native silver is distributed among the dolomites, as well as in the dolomitic fragments from the fluidolites. Ubiquitous admixtures in the silver are copper, iron, and more rarely zinc; single grains contain admixtures of molybdenum, nickel, gold, and palladium. PGM and high-fineness gold are related to the fluidolites, which are the only magmatic rocks in the studied range of the deposit. Silver, its minerals, low-fineness gold, and sulfides are confined to the rocks and ores subjected to the regional dolomitization, low-temperature hydrothermal reworking, and silicification. Samples contain up to 11.3 g/t platinum, 2.35 g/t gold, 296.2 g/t silver, which allows us to consider the studied object as economically promising for noble metals.

Contrasting effects of environmental change on the radial growth of co-occurring beech and fir trees across Europe

Under predicted climate change, native silver fir (Abies alba) and European beech (Fagus sylvatica) are the most likely replacement species for the Norway spruce (Picea abies) monocultures planted across large parts of continental Europe. Our current understanding of the adaptation potential of fir-beech mixed forests to climate change is limited because long-term responses of the two species to environmental changes have not yet been comprehensively quantified. We compiled and analysed tree-ring width (TRW) series from 2855 dominant, co-dominant, sub-dominant and suppressed fir and beech trees sampled in 17 managed and unmanaged mixed beech-fir forest sites across Continental Europe, including Bosnia and Herzegovina, Germany, Italy, Romania and Slovakia. Dendroecological techniques that combine various detrending methods were used to investigate variation in radial growth of co-occurring fir and beech trees. Coincidental with peak SO2 emissions, the growth of silver fir declined between 1950 and 1980 at most sites, whereas beech growth increased during this period. Correspondent to a significant warming trend from 1990–2010, average beech growth declined, but silver fir growth increased. Long-term growth patterns and growth-climate sensitivity of fir and beech trees did not significantly differ between managed and unmanaged forests. Multi-decadal changes in the growth rate of all vertical tree classes were similar. In contrast to previous indications of limited drought susceptibility of beech mixed stands, this study suggests that the mixture of tree species in forest stands does not necessarily prevent growth depressions induced by long-term environmental change. Our results further imply that forest management does not necessarily alter their sensitivity to environmental changes.