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1.
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.  相似文献   

2.
The 7.1 Ma Broken Hills adularia-sericite Au–Ag deposit is currently the only producing rhyolite-hosted epithermal deposit in the Hauraki Goldfield of New Zealand. The opaque minerals include pyrite, electrum, acanthite (Ag2S), sphalerite, and galena, which are common in other adularia-sericite epithermal deposits in the Hauraki Goldfield and elsewhere worldwide. Broken Hills ores also contain the less common minerals aguilarite (Ag4SeS), naumannite (Ag2Se), petrovskaite (AuAgS), uytenbogaardtite (Ag3AuS2), fischesserite (Ag3AuSe2), an unnamed silver chloride (Ag2Cl), and unnamed Ag?±?Au minerals. Uytenbogaardtite and petrovskaite occur with high-fineness electrum. Broken Hills is the only deposit in the Hauraki Goldfield where uytenbogaardtite and petrovskaite have been identified, and these phases appear to have formed predominantly from unmixing of a precursor high-temperature phase under hypogene conditions. Supergene minerals include covellite, chalcocite, Au-rich electrum, barite, and a variety of iron oxyhydroxide minerals. Uytenbogaardtite can form under supergene and hypogene conditions, and textural relationships between uytenbogaardtite and associated high-fineness electrum may be similar in both conditions. Distinguishing the likely environment of formation rests principally on identification of other supergene minerals and documenting their relationships with uytenbogaardtite. The presence of aguilarite, naumannite, petrovskaite, and fischesserite at Broken Hills reflects a Se-rich mineral assemblage. In the Hauraki Goldfield and the western Great Basin, USA, Se-rich minerals are more abundant in provinces that are characterized by bimodal rhyolite–andesite volcanism, but in other epithermal provinces worldwide, the controls on the occurrences of Se-bearing minerals remain poorly constrained, in spite of the unusually high grades associated with many Se-rich epithermal deposits.  相似文献   

3.
The standard thermodynamic properties (Δf G°, S°, Δf H°) of the following synthetic minerals and compounds in the Ag-Au-Se and Ag-Au-Te systems were determined by the EMF method: β-Ag2Se (low-temperature naumannite), α-Ag2Se (high-temperature naumannite), Ag3AuSe2 (fischesserite), AuSe, Ag5Te3 (stützite), Ag2 Te (hessite), and Ag3AuTe2 (petzite). All minerals and compounds were produced by solid-phase synthesis from elements or electrum of the given composition in evacuated ampoules made of quartz glass. The phases were verified by X-ray diffraction analysis, microscopically in reflected light, and with an electron microprobe. The absence of the ternary compound AgAuSe in the Ag-Au-Se system was confirmed by solid-phase annealing. On the basis of experimental data on the electromotive force E versus temperature, the equations E(T) were calculated, from which the temperature-dependent relationships of the Gibbs energy in the relevant reactions and the standard thermodynamic functions of compounds within the range 300–502 K were obtained.  相似文献   

4.
Gold–silver sulfoselenides of the series Ag3AuSexS2–x (x = 0.25; 0.5; 0.75; 1; 1.5) were synthesized from melts on heating stoichiometric mixtures of elementary substances in evacuated quartz ampoules. According to X-ray single-crystal analysis, compound Ag3Au1Se0.5S1.5 has the structure of gold–silver sulfide Ag3AuS2 (uytenbogaardtite) with space group R3c. The volume of this compound is 1.5% larger than that of the sulfide analog. According to powder X-ray diffraction, compounds Ag3AuSe0.25S1.75 and Ag3AuSe0.75S1.25 also show trigonal symmetry. Compounds Ag3AuSeS and Ag3AuSe1.5S0.5 are structurally similar to the low-temperature modification of gold–silver selenide Ag3AuSe2 (fischesserite) with space group I4132. These data suggest the existence of two solid solutions: petzite-type cubic Ag3AuSe2–Ag3AuSeS (space group I4132) and trigonal Ag3AuSe0.75S1.25–Ag3AuS2 (space group R3c).It was found that fischesserite from the Rodnikovoe deposit (southern Kamchatka) contains 3.5–4 wt.% S. At the Kupol deposit (Chukchi Peninsula), fischesserite contains up to 2.5 wt.% S and uytenbogaardtite contains up to 5.3 wt.% Se. At the Ol’cha and Svetloe (Okhotskoe) deposits (Magadan Region), uytenbogaardtite contains up to 0.5 and 1.8 wt.% Se, respectively. Literature data on the compositions of silver–gold selenides and sulfides from different deposits were summarized and analyzed. Analysis of available data on the S and Se contents of natural fischesserite and uytenbogaardtite confirms the miscibility gap near composition Ag3AuSeS.  相似文献   

5.
New data on the mineral composition and the first data on the geochemical composition of ores of the Rogovik gold-silver deposit (Omsukchan ore district, northeastern Russia) have been obtained. Study of the regularities of the spatial distribution of ore mineralization shows that the deposit ores formed in two stages. Epithermal Au-Ag ores of typical poor mineral and elemental compositions were generated at the early volcanic stage. The major minerals are low-fineness native gold, electrum, acanthite, silver sulfosalts, kustelite, and pyrite. The typomorphic elemental composition of ores is as follows: Au, Ag, Sb, As, Se, and Hg. The content of S is low, mostly < 1%. Silver ores of more complex mineral and elemental compositions were produced under the impact of granitoid intrusion at the late volcanoplutonic stage. The major minerals are high-Hg kustelite and native silver, silver sulfosalts and selenides, fahlore, pyrite, chalcopyrite, galena, and sphalerite. The typomorphic elemental composition of ores is as follows: Ag, As, Sb, Se, Hg, Pb, Zn, Cu, and B. The content of S is much higher than 1%. The ores also have elevated contents of Mo, Ge, F, and LREE (La, Ce, and Nd). At the volcanoplutonic stage, polychronous Au-Ag ores formed at the sites of the coexistence of silver and epithermal gold-silver mineralization. Their specific feature is a multicomponent composition and a strong variability in chemical composition (both qualitative and quantitative). Along with the above minerals, the ores contain high-Hg gold, hessite, argyrodite, canfieldite, orthite, fluorapatite, and arsenopyrite. At the sites with strongly rejuvenated rocks, the ores are strongly enriched in Au, Ag, Hg, Cu, Pb, Zn, Ge, Se, La, Ce, Nd, S, and F and also contain Te and Bi. The hypothesis is put forward that the late silver ores belong to the Ag-complex-metal association widespread in the Omsukchan ore district. A close relationship between the ores of different types and their zonal spatial distribution have been established. In the central part of the Rogovik deposit, epithermal Au-Ag ores are widespread in the upper horizons, Ag ores are localized in the middle horizons, and rejuvenated polyassociation Au-Ag ores occur at the sites (mostly deep-seated) with ore-bearing structures of different ages.  相似文献   

6.
We consider mineral assemblages and mineralogical and geochemical peculiarities of hypogene gold from the Khaak-Sair multistage low-sulfide gold-quartz ore occurrence in listwanites. Three productive substages of Au-and Ag-mineral formation have been recognized on the basis of mineralogical studies: gold-sulfosalt-sulfide-quartz, gold-mercury-quartz, and gold-selenide-telluride-sulfide-quartz. These substages were characterized by the following sequences of mineral formation: (1) ultrahigh-fineness gold → high-fineness gold → argental gold (medium- and low-fineness gold) → electrum + Ag-bearing and argental fahlores (up to 50 wt.% Ag) ± acanthite ± hessite; (2) high-fineness gold → Hg-bearing and mercurian gold → mercurian electrum → mercurian kustelite → Au-bearing mercurian silver; and (3) high-fineness gold → mercurian gold → mercurian electrum + naumannite + Te-bearing naumannite + fischesserite + tiemannite + hessite + coloradoite + Ag-bearing minerals of the galena-clausthalite series (up to 6 wt.% Ag) ± Se-cinnabar ± Se-imiterite. Productive mineral assemblages of the ore occurrence formed in the hypabyssal facies (depth ~ 1.5 km, P ~ 0.5 kbar) on the background of a temperature decrease from 290 to 160 °C and variations in f(O2), f(S2), f(Se2), and f(Te2).  相似文献   

7.
Geology and mineralogy of the Ulakhan Au-Ag epithermal deposit (northeastern Russia, Magadan Region) are considered. A four-stage scheme of mineral formation sequence is proposed. Concentrations of Au and Ag in minerals of early and late parageneses were determined. It has been established that uytenbogaardtite is associated with native gold and hypergenesis stage minerals — goethite, hydrogoethite, or limonite replacing pyrite. The compositions of uytenbogaardtite (Ag3AuS2), acanthite (Ag2S), and native gold were studied. The composition of the Ulakhan uytenbogaardtite is compared with those of Au and Ag sulfides from other deposits. Thermodynamic calculations in the system H2O–Fe–Au–Ag–S–C–Na–Cl were carried out, which simulate the interaction of native gold and silver with O2- and CO2-saturated surface waters (carbonaceous, sulfide-carbonaceous, and chloride-sodium-carbonaceous) in the presence and absence of acanthite and pyrite at 25 °C and 1 bar. In closed pyrite-including systems, native silver and kustelite are replaced by acanthite; electrum, by uytenbogaardtite, acanthite, and pure gold; and native gold with a fineness of 700–900‰, by pure gold and uytenbogaardtite. Under the interaction with surface waters in the presence of Ag2S and pyrite, Au-Ag alloys form equilibrium assemblages with petrovskaite or uytenbogaardtite and pure gold. The calculation results confirmed that Au and Ag sulfides can form after native gold in systems involving sulfide-carbon dioxide solutions (H2Saq > 10–4 m). The modeling results support the possible formation of uytenbogaardtite and petrovskaite with the participation of native gold in the hypergenesis zone of epithermal Au-Ag deposits during the oxidation of Au(Ag)-containing pyrite, acanthite, or other sulfides.  相似文献   

8.

Selenium is one of the most important minor elements in massive sulfide ores. This study focuses on selenium minerals present in the oxidation zone of the Yubeleinoe massive sulfide deposit, the South Urals, Russia: clausthalite (PbSe), tiemannite (HgSe), and naumannite (Ag2Se). These minerals are associated with goethite and siderite. Thermodynamic modeling was used to estimate the physicochemical parameters of selenide stability and the possible formation of Pb, Hg, and Ag selenites as a result of sulfide ore oxidation. The Eh–pH diagrams for the Fe–S–CO2–H2O and Fe–Se–CO2–H2O systems were calculated to estimate the physicochemical formation conditions of the Yubileinoe oxidation zone, as well as for the M–Se–Н2О and M–S–H2O (M = Hg, Pb, Ag) systems. The physicochemical parameters of clausthalite, naumannite, and tiemannite stability are consistent with these conditions. Only the formation of PbSeO3 is theoretically possible among Pb, Ag, and Hg selenites.

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9.
Abstract: Se-bearing benjaminite and matildite are described from the polymetallic zone of the Ikuno deposits, Japan. The former is the first occurrence in Japan, and is from two separate veins, the Nanten and Daimaru, while the locality of the latter could not be specified. The empirical formulae of two benjaminites based on 22 atoms are (Ag2. 74Cu0. 24)Σ2. 98(Bi7. 00Sb0. 01)Σ7. 01(S10. 89Se1. 12)Σ12. 01 (Nanten) and (Ag2. 90Cu0. 10)Σ3. 00(Bi6. 74Pb0. 18Sb0. 07)Σ6. 99(S11. 68Se0.33)Σ12. 01 (Daimaru), leading to the validation of the formula Ag3Bi7S12 as the ideal one for benjaminite, and that of matildite based on 4 atoms is Ag1. 00Bi1. 00(S1. 78Se0. 22)Σ2. 00. These designate the substitution of Se for S in all of them, where Se is preferentially incorporated into these Ag-Bi sulphosalts. The unit-cell parameters of them and matildite are: a 13. 272, b 4. 037, c 20. 185 Å, and β 103. 16° (Daimaru), a 13. 270, b 4. 040, c 20. 273 Å, and β103. 17° (Nanten); and a 4. 0670, c 18. 996 Å, respectively. The products of Au-Ag mineralization in the Ikuno polymetallic vein-type deposits also occur as such Ag-Bi sulfosalts as benjaminite and matildite, in addition to pavonite, “treasurite derivative” and “electrum” with cassiterite in the polymetallic zone, and also do as “electrum”, acanthite, and pyrargyrite-proustite in the Au-Ag zone. The significant quantity of the Ag-Bi sulfosalts does not violate the zoning occupying the outermost part of the zonal distribution of ores in the deposits.  相似文献   

10.
Gold- and silver-containing pyrites of the Tikhii area at the Julietta deposit (Engteri ore cluster, Magadan Region) were studied by optical and scanning electron microscopy and electron probe microanalysis. One- or two-phase rounded microinclusions consisting of electrum (450-680%c) and/or galena or of petrovskaite and/or uytenbogaardtite, galena, and sphalerite have been found in early pyrites. Later As-pyrites (up to 2.6 wt.% As) contain multiphase xenomorphic microinclusions of acanthite, uytenbogaardtite, freibergite, argentotetrahedrite-tennantite, naumannite, petzite, selenopolybasite-selenostephanite, tellurocanfieldite, and other ore minerals localized in pores, cracks, and interstices. Pyrites that underwent hypergene alterations have rims and veinlets formed by acanthite, goethite, anglesite, plattnerite, and native silver. The presence of rounded ore mineral microinclusions and large pores in the early pyrites suggests the participation of volatiles in the mineral formation and the uptake of large amounts of impurities by pyrite under high-gradient crystallization conditions. The thermobarogeochemical studies of fluid inclusions in quartz have shown that the ore zone formed under boiling-up of hydrothermal medium-concentration NaCl solutions at 230-105 °C. The results of thermodynamic calculations evidence that Ag-Au-S-Se minerals formed under decrease in temperature and fugacity of sulfur (log1Q/S2 = -22 to -9) and selenium (log1Q/Se2 = -27 to -14) and change of reducing conditions by oxidizing ones in weakly acidic to near-neutral solutions.  相似文献   

11.
Gold–silver sulfoselenides of Ag3Au(Se,S)2 series—Ag3AuSe1.5S0.5, Ag3AuSeS, and Ag3AuSe0.5S1.5—have been synthesized by fusing the elements in the required stoichiometric amounts in evacuated quartz ampoules. The single crystal X-ray diffraction data indicate the existence of two solid-solution series: petzite-type cubic Ag3AuSe2—Ag3AuSeS (space group I4132) and trigonal Ag3AuSe0.5S1.5—Ag3AuS2 (space group $ R\overline{3} c $ ). Both crystal structures differ in the distribution of Ag+/Au+ cations in the same distorted body-centered cubic sublattice of chalcogen anions. The morphotropic transformation results from the shrinkage of anion packing accompanied by the shortening of Ag–Ag distances. The structure of uytenbogaardtite mineral, earlier incorrectly interpreted as a tetragonal or cubic cell, is similar to that of the trigonal Ag3AuS2 end-member.  相似文献   

12.
Three types of oxidized ores are identified in the Ik-Davlyat gold-base-metal deposit in the southern Urals: (1) carbonate-sericite-chlorite mineralized rock, (2) vein-shaped quartz-goethite-illite clay, and (3) limonitized rock related to veins. Heavy concentrate of the first type of ore is composed of goethite, rutile, native gold Au0.91Ag0.08Cu0.01, and chalcophanite Zn1.02Mn2.98O4 · 3H2O. The second type of ore contains goethite, rutile, Pb-bearing jarosite, native gold Au0.90?0.93Ag0.06?0.08Cu0?0.01Fe0?0.01, silver amalgamide (schachnerite) Ag0.75Hg0.97Au0.98-Ag0.75Hg0.97Au0.28, coronadite (Pb1.72Mn7.51Fe0.41Cu0.36)8O16, a chalcophanite-hydrohetaerolite mixture, and cerussite. Gold of the highest fineness (Au0.98Ag0.01Cu0.01) is associated with silver amalgamide. The third type of ore is quite similar to the first variety but contains a jarosite impurity. The composition of oxidized ores indicates a difference in composition of primary ores, in particular, the presence of lead minerals in primary veins. The first finding of chalcophanite in Russia is confirmed by chemical, optical, and X-ray data.  相似文献   

13.

New data on mercurial mineralization are presented, and a detailed characteristic is given for the first discovery of mercurous silver in ores of the Rogovik gold–silver deposit (the Omsukchan trough, Northeastern Russia). It was found that native silver in the examined ores occurs as finely-dispersed inclusions in quartz filling microcracks and interstitions. It also occurs in associations with kustelite, Ag sulfosalts and selenides, selenitic acanthite, and argyrodite. The mercury admixture varies from “not detected” in the central parts of grains to 0.22–1.70 wt % along the edges, or, in independent grains, to the appearance of Ag amalgams containing 10.20–24.61 wt % of Hg. The xenomorph form of grains of 50 μm or less in size prevails. It is assumed that the appearance of mercurial mineralization is caused by the superposition of products of the young Hg-bearing Dogda–Erikit belt upon the more ancient Ag-bearing Omsukchan trough.

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14.
The solubility of silver sulphide (acanthite/argentite) has been measured in aqueous sulphide solutions between 25 and 400°C at saturated water vapour pressure and 500 bar to determine the stability and stoichiometry of sulphide complexes of silver(I) in hydrothermal solutions. The experiments were carried out in a flow-through autoclave, connected to a high-performance liquid chromatographic pump, titanium sampling loop, and a back-pressure regulator on line. Samples for silver determination were collected via the titanium sampling loop at experimental temperatures and pressures. The solubilities, measured as total dissolved silver, were in the range 1.0 × 10−7 to 1.30 × 10−4 mol kg−1 (0.01 to 14.0 ppm), in solutions of total reduced sulphur between 0.007 and 0.176 mol kg−1 and pHT,p of 3.7 to 12.7. A nonlinear least squares treatment of the data demonstrates that the solubility of silver sulphide in aqueous sulphide solutions of acidic to alkaline pH is accurately described by the reactions0.5Ag2S(s) + 0.5H2S(aq) = AgHS(aq) Ks,1110.5Ag2S(s) + 0.5H2S(aq) + HS− = Ag(HS)2− Ks,122Ag2S(s) + 2HS− = Ag2S(HS)22− Ks,232where AgHS(aq) is the dominant species in acidic solutions, Ag(HS)2− under neutral pH conditions and Ag2S(HS)22− in alkaline solutions. With increasing temperature the stability field of Ag(HS)2− increases and shifts to more alkaline pH in accordance with the change in the first ionisation constant of H2S(aq). Consequently, Ag2S(HS)22− is not an important species above 200°C. The solubility constant for the first reaction is independent of temperature to 300°C, with values in the range logKs,111 = −5.79 (±0.07) to −5.59 (±0.09), and decreases to −5.92 (±0.16) at 400°C. The solubility constant for the second reaction increases almost linearly with inverse temperature from logKs,122 = −3.97 (±0.04) at 25°C to −1.89 (±0.03) at 400°C. The solubility constant for the third reaction increases with temperature from logKs,232 = −4.78 (±0.04) at 25°C to −4.57 (±0.18) at 200°C. All solubility constants were found to be independent of pressure within experimental uncertainties. The interaction between Ag+ and HS− at 25°C and 1 bar to form AgHS(aq) has appreciable covalent character, as reflected in the exothermic enthalpy and small entropy of formation. With increasing temperature, the stepwise formation reactions become progressively more endothermic and are accompanied by large positive entropies, indicating greater electrostatic interaction. The aqueous speciation of silver is very sensitive to fluid composition and temperature. Below 100°C silver(I) sulphide complexes predominate in reduced sulphide solutions, whereas Ag+ and AgClOH− are the dominant species in oxidised waters. In high-temperature hydrothermal solutions of seawater salinity, chloride complexes of silver(I) are most important, whereas in dilute hydrothermal fluids of meteoric origin typically found in active geothermal systems, sulphide complexes predominate. Adiabatic boiling of dilute and saline geothermal waters leads to precipitation of silver sulphide and removal of silver from solution. Conductive cooling has insignificant effects on silver mobility in dilute fluids, whereas it leads to quantitative loss of silver for geothermal fluids of seawater salinity.  相似文献   

15.
Yongliang Xiong   《Ore Geology Reviews》2003,23(3-4):259-276
In this study, an attempt has been made to assess aqueous speciation of selenium and solubility product constants of common selenides at elevated temperatures (up to 300 °C) by using various extrapolation methods. This study predicts that reduced selenium species are dominant species in many geological processes even under relatively oxidized conditions such as those dictated by the magnetite–hematite buffer. On the basis of extrapolated equilibrium constants and solubility product constants for common Se-bearing mineral phases, critical ∑Se/∑S ratios (molal ratios) in mineralizing fluids are proposed for independent selenium mineralization. The minimum ∑Se/∑S ratios in mineralizing fluids for independent selenium mineralization should be at least 10−6, 10−5 and 10−4 at 100, 200 and 300 °C, respectively. For giant independent selenium deposits such as the La'erma and Qiongmo Au–Se deposits in the western Qingling mountains, and Yutangba Se deposits in Hubei Province, China, the mineralizing fluids have reached much higher ∑Se/∑S ratios ranging from 10−1 to 10−3 at 200 °C. This study also suggests that the equilibrium assemblage of pyrite–ferroselite among the common ore minerals requires the highest ∑Se/∑S ratios in mineralizing fluids, followed in decreasing order by the assemblages of stibnite–antimonselite, galena–clausthalite, cinnabar–tiemannite, and acanthite/argentite–naumannite. The assemblage of pyrite–ferroselite can also be formed under relatively oxidizing conditions where [∑H2Se]/[∑H2S] ratios can be high enough for the formation of independent ferroselite.  相似文献   

16.
Summary The gold-copper deposit at Waschgang (Southern Goldberg mountains, Upper Carinthia) belongs to a type of stratiform, dominantly pyritic deposit, which is hosted by greenschists (Alpine Kieslager;Friedrich, 1936). The ores occur as impregnations (ore type 1) and as massive ores (ore type 2) in prasinitic rocks of the Obere Schieferhülle of the Penninic unit. A N–S trending fault zone cuts the ore deposit to the W (Lettenkluft); the position of the displaced part is unknown.The mineralogical composition of type 1 ores is rather monotonous. Pyrite is the most important ore, minor components are chalcopyrite, bornite, sphalerite and magnetite. No visible native gold has been observed in this type of ore. Type 2 ores are dominated by chalcopyrite and are characterized by large amounts of visible native gold. The majority of these ores occur in the vicinity of the Lettenkluft.Type 2 ores carry a great variety of cogenetic mineral inclusions, of which several have been studied with the electron microprobe and investigated by X-ray methods. These include: tetradymite, Bi2Te1.81Se0.13S; hessite, Ag2Te; matildite, AgBiS2; gladite, Cu1.09Pb1.14Bi5.28S9; krupkaite, CuPbBiS6; pekoite, Cu1.09Pb0.97Bi12.56S18; (?) benjaminite, (Ag2.72Cu0.42)3.14 (Bi6.88Pb0.12)7(S11.08Se0.92)12; pavonite, (Ag0.74Cu0.45)1.19(Bi2.86Pb0.27)3.13 (S4.96Se0.04)5; (?) cupropavonite, (Cu0.73Ag0.4)1.13(Bi2.59Pb0.83)3.42S5; and siegenite, (Ni1.07Co1.76Cu0.19)3.02S4. Other components have been determined by qualitative and quantitative microscopy and include: bornite, idaite, mawsonite, sphalerite, millerite, magnetite, hematite, ilmenite, rutile and a variety of silicates.While the layered ore impregnations (type 1 ores) can be considered as being syngenetic with the associated volcanics of Jurassic age, a syn- to postkinematic (Alpidic) crystallization can be postulated for the type 2 ores. These ores are considered as remobilized and reconcentrated parts of the type 1 ores formed in tectonic stress zones. The crystallization of chalcopyrite and included ore minerals occurred during the cooling history of Alpidic metamorphism, for which in this region a maximum temperature of 500°C and pressures between 4–6 kb have been deduced from the mineral assemblage of the surrounding prasinites, consisting of albite with rims of oligoclase, epidote, chlorite, sphene and amphibole (Höck, 1980). Based onSpringer's limit of 300°C as approximately representing the maximum temperature at which natural members of the bismuthinite-aikinite mineral series have been formed, krupkaite and gladite with the intergrown pavonite type phases might have been deposited directly from solutions at or below 300°C. Unmixing of pekoite from gladite probably occurred at or below the same temperature.
Zur Erzmineralogie der Gold-Kupfer-Lagerstätte Waschgang, Oberkärnten, Österreich
Zusammenfassung Die Gold-Kupfer-Lagerstätte Waschgang (südliche Goldberggruppe, Oberkärnten) ist dem Typus der stratiformen Kiesvererzungen in Grüngesteinen (Alpine Kieslager;Friedrich, 1936) zuzurechnen. Die Erzmineralisationen treten als stoffkonkordante Imprägnationen (Vererzungstypus 1) und als Derberze (Vererzungstypus 2) in Prasiniten der Oberen Schieferhülle des Penninikums auf. Das Erzlager wird im W an einer N–S streichenden Störung abgeschnitten; die Position des verworfenen W-Flügels ist nicht bekannt.Die Imprägnationserze sind in ihrer mineralogischen Zusammensetzung monoton; Pyrit als Haupterz überwiegt bei weitem die sporadischen Begleiter Kupferkies, Bornit, Sphalerit und Magnetit. Dieser Typus führt kein Freigold.Die von Kupferkies dominierten und an Freigold reichen Derberze treten vor allem im Bereich der Lettenkluft auf. Sie sind durch eine Vielfalt zum Teil komplex zusammengesetzter Einschlußminerale gekennzeichnet, von denen einige mittels Mikrosonde und röntgenographischer Methoden untersucht wurden: Tetradymit, Bi2Te1,81Se0,13S; Hessit, Ag2Te; Matildit, AgBiS2; Gladit, Cu1,09Pb1,14Bi5,28S9; Krupkait, CuPbBiS6; Pekoit, Cu1,09Pb0,97Bi12,56S18; (?) Benjaminit (Ag2,72Cu0,42)3,14(Bi6,88Pb0,12)7(S11,08Se0,92)12; Pavonit, (Ag0,74Cu0,45)1,19(Bi2,86Pb0,27)3,13 (S4,96Se0,04)5; (?) Cupropavonit, (Cu0,73Ag0,4)1,13(Bi2,59Pb0,83)3,42S5; Siegenit, (Ni1,07Co1,76 Cu0,19)3,02S4. Andere Mineralphasen wurden mittels qualitativer und quantitativer Mikroskopie bestimmt: Bornit, Idait, Mawsonit, Sphalerit, Millerit, Magnetit, Hämatit, Ilmenit, Rutil und Silikate.Während die stoffkonkordaten Imprägnationserze syngenetisch mit den assoziierten jurassischen Vulkaniten anzusehen sind, wird für die Derberze eine syn- bis postkinematische Kristallisation angenommen. Sie sind als remobilisierte und rekonzentrierte Teile der Imprägnationserze in tektonisch besonders beanspruchten Lagerstättenteilen anzusehen. Die Kristallisation des Kupferkieses und seiner Einschlußminerale erfolgte während der Abkühlungsphase der alpidischen Metamorphose, für die im betrachteten Gebiet eine Maximaltemperatur von ca. 500°C und Drucke zwischen 4–6 kb aufgrund der Petrologie der erzführenden Prasinite angenommen werden können. Die dafür maßgebende Paragenese besteht aus Albit mit Oligoklasrändern, Epidot, Chlorit, Sphen und Amphibol (Höck, 1980). Zieht man die vonSpringer (1971) ermittelte Stabilitätsgrenze von ±300°C für natürliche Mischkristalle der Bismuthinit-Aikinit-Reihe in Betracht, können für Krupkait und Gladit und den damit verwachsenen Pavonit-Phasen Bildungstemperaturen um oder unterhalb 300°C angenommen werden. Die Kristallisation dieser Minerale dürfte dabei direkt aus Lösungen erfolgt sein. Die als Entmischungsstrukturen interpretierten Gladit-Pekoit-Verwachsungen legen den Schluß einer primären Bildung beider Minerale als feste Lösung nahe, deren Zerfall vermutlich unterhalb von 300°C erfolgte.

With 13 Figures

Herrn em. Univ.-Prof. Dr.-Ing. O. M. Friedrich zum 80. Geburtstag in Dankbarkeit gewidmet

This investigation forms part 2 of a major study on Genetic Types of Gold Deposits of the Alps.  相似文献   

17.
Zusammenfassung Für die Reaktionen im festen Zustand bei 200° zwischen Cu-Se, Ag-Se und Cu-Ag-Se wird eine Zusammenstellung der Bildung der bei Zimmertemperatur stabilen Phasen und ihrer Gemenge in Abhangigkeit von den Reaktionsgemischen gegeben.Cu and Se reagieren unter Bildung von-Cu2Se,-Cu2- Se ( = 0, 15–0,2), Cu3Se2, CuSe and CuSe2.Cu3Se2 konnte bei stochiometrischer Ausgangszusammensetzung als alleinige Phase nicht synthetisiert werden. Es bildet sich gleichzeitig Cu1,8Se and CuSe. Als Ursache hierfür wird die orientierte Verwachsung von Cu1,8Se and Cu3Se2 angesehen.Die synthetisierte Verbindung CuSe2 wurde bisher nicht beobachtet.In den Systemen Ag-Se and Ag-Cu-Se wurden unter den angegebenen Bedingungen weiterhin-Ag2Se and AgCuSe gefunden.  相似文献   

18.
We carried out experiments on crystallization of Fe-containing melts FeS2Ag0.1–0.1xAu0.1x (x = 0.05, 0.2, 0.4, and 0.8) with Ag/Au weight ratios from 10 to 0.1. Mixtures prepared from elements in corresponding proportions were heated in evacuated quartz ampoules to 1050 ºC and kept at this temperature for 12 h; then they were cooled to 150 ºC, annealed for 30 days, and cooled to room temperature. The solid-phase products were studied by optical and electron microscopy and X-ray spectroscopy. The crystallization products were mainly from iron sulfides: monoclinic pyrrhotite (Fe0.47S0.53 or Fe7S8) and pyrite (Fe0.99S2.01). Gold–silver sulfides (low-temperature modifications) are present in all synthesized samples. Depending on Ag/Au, the following sulfides are produced: acanthite (Ag/Au = 10), solid solutions Ag2–xAuxS (Ag/Au = 10, 2), uytenbogaardtite (Ag/Au = 2, 0.75), and petrovskaite (Ag/Au = 0.75, 0.12). They contain iron impurities (up to 3.3 wt.%). Xenomorphic micro- (<1–5 μm) and macrograins (5–50 μm) of Au–Ag sulfides are localized in pyrite or between the grains of pyrite and pyrrhotite. High-fineness gold was detected in the samples with initial ratio Ag/Au ≤ 2. It is present as fine and large rounded microinclusions or as intergrowths with Au–Ag sulfides in pyrite or, more seldom, at the boundary of pyrite and pyrrhotite grains. This gold contains up to 5.7 wt.% Fe. Based on the sample textures and phase relations, a sequence of their crystallization was determined. At ~1050 ºC, there are probably iron sulfide melt L1 (Fe,S ? Ag,Au), gold–silver sulfide melt L2 (Au,Ag,S ? Fe), and liquid sulfur LS. On cooling, melt L1 produces pyrrhotite; further cooling leads to the crystallization of high-fineness gold (macrograins from L1 and micrograins from L2) and Au–Ag sulfides (micrograins from L1 and macrograins from L2). Pyrite crystallizes after gold–silver sulfides by the peritectic reaction FeS + LS = FeS2 at ~743 ºC. Elemental sulfur is the last to crystallize. Gold–silver sulfides are stable and dominate over native gold and silver, especially in pyrite-containing ores with high Ag/Au ratios.  相似文献   

19.
The first data on native silver from the Rogovik Au–Ag deposit in northeastern Russia are presented. The deposit is situated in central part of the Okhotsk–Chukchi Volcanic Belt (OCVB) in the territory of the Omsukchan Trough, unique in its silver resources. Native silver in the studied ore makes up finely dispersed inclusions no larger than 50 μm in size, which are hosted in quartz; fills microfractures and interstices in association with küstelite, electrum, acanthite, silver sulfosalts and selenides, argyrodite, and pyrite. It has been shown that the chemical composition of native silver, along with its typomorphic features, is a stable indication of the various stages of deposit formation and types of mineralization: gold–silver (Au–Ag), silver–base metal (Ag–Pb), and gold–silver–base metal (Au–Ag–Pb). The specificity of native silver is expressed in the amount of trace elements and their concentrations. In Au–Ag ore, the following trace elements have been established in native silver (wt %): up to 2.72 S, up to 1.86 Au, up to 1.70 Hg, up to 1.75 Sb, and up to 1.01 Se. Native silver in Ag–Pb ore is characterized by the absence of Au, high Hg concentrations (up to 12.62 wt %), and an increase in Sb, Se, and S contents; the appearance of Te, Cu, Zn, and Fe is notable. All previously established trace elements—Hg, Au, Sb, Se, Te, Cu, Zn, Fe, and S—are contained in native silver of Au–Ag–Pb ore. In addition, Pb appears, and silver and gold amalgams are widespread, as well as up to 24.61 wt % Hg and 11.02 wt % Au. Comparison of trace element concentrations in native silver at the Rogovik deposit with the literature data, based on their solubility in solid silver, shows that the content of chalcogenides (S, Se, Te) exceeds saturated concentrations. Possible mechanisms by which elevated concentrations of these elements are achieved in native silver are discussed. It is suggested that the appearance of silver amalgams, which is unusual for Au–Ag mineralization not only in the Omsukchan Trough, but also in OCVB as a whole, is caused by superposition of the younger Dogda–Erikit Hg-bearing belt on the older Ag-bearing Omsukchan Trough. In practice, the results can be used to determine the general line of prospecting and geological exploration at objects of this type.  相似文献   

20.
Summary A second confirmed occurrence of wittite, one of the four known Pb-Bi-Se-sulfosalts, has been found in the Nevskoe tin deposit (Eastern Siberia). Microprobe analyses of wittite show pronounced variation of Se content (from 9.5 to 16.5 wt. %), due to S --> Se substitution; Pb and Bi contents vary from 29 and 43%, up to 34 and 46%, respectively. Minor elements are also present: Sb up to 1.5%, Ag up to 1.3 %, and Cu (0 to 0.2%). Comparison of microprobe data of wittite from Nevskoe and Falun, on the one hand, and cannizzarite from different deposits on the other hand, indicate that Ag is incorporated in the wittite/cannizzarite structure through the substitution 2 Pb -> Bi + Ag. Conversely, Ag substraction gives a constant Bi/(Bi + Pb) atomic ratio, independent of the Se/(Se+"S) ratio, and close to 55.1%. Se-rich wittite is compositionally very close to proudite and weibullite. X-ray powder and electron microdiffraction patterns are given; the incommensurate structure agrees with the 7H/12Q match along , like in wittite from Falun. Nevskoe wittite is close to Pb8Bi10(S, Se)23, but the 7H/12Q match requires the formula Pb11.61Bi14.26S33, with about 3% of the Pb atoms in the Q layer replaced by Bi atoms and vacancies (p). Taking into account all microprobe data, the general formula developed is: Pb11.61–2x0.13Agx(Bi14.26+x-ySby)(S1–zSez)33 with x and y 0.86 at., and z 0.45. At Nevskoe, associated bismuthinite contains from 5 to 12% Se, with minor Sb, Pb and Cu. Se-rich cosalite contains from 4 to 8% Se, with Sb from 2.7 to 5.3%, and minor Ag and Cu. Wittite in contact with cosalite clearly shows a relative Se-enrichment, that could be due to the pseudo-hexagonal sub-lattice of this incommensurate structure, very similar to the Bi2(Se, Te, S)3 sheet in the tetradymite series. According to microprobe data, there is a continuous change from Se-free cannizzarite to Se-rich wittite. Therefore, the validity of wittite as a specific mineral species appears questionable, and more accurate crystallographic studies on this incommensurate series are necessary.
Wittite avec Cosalite et Bismuthinite Séléniferes du Gisement d'Etain de Hevskoe (District de Magadan, Russie)
Resume Une seconde occurrence de wittite, l'un des quatre sulfosels de Pb-Bi-Se cormus, a été trouvée daps le gisement d'étain de Nevskoe (Sibérie Orientale). Son analyse á la microsonde électronique montre une forte variation de la teneur en sélénium (de 9,5 á 16,5%), qui se substitue au soufre; les teneurs en Pb et Bi varient de 29 à 43 et 34 á 46%, respectivement. On note la présence de Sb (, 1,5%), Ag ( 1,3%) et Cu (< 0,2%). La comparaison des analyses de wittite de Nevskoe et Falun, et de cannizzarite de différents gisements, montre que Bans cette série l'argent est incorporé suivant la substitution 2 Pb Bi + Ag. Après soustraction de Ag, le rapport atornique Bi/(Bi + Pb) corrigé apparaït constant, proche de 55,1%, et indépendant du rapport Se/(S + Se). La wittite la plus riche en Se est chimiquement très proche de la proudite et de la weibullite. Son diagramme de poudre aux rayons X ainsi que son étude en microdiffraction électronique sont présentés; la structure, de type incommensurable, s'accorde aver un ajustement selon le rapport 7H/12Q suivant , comme dans la wittite de Falun. La formule de la wittite de Nevskoe est proche de Pb8Bi10(S, Se)23, mais l'ajustement 7H/12Q demande la formule Pb11.61Bi14.26S33, avec environ 3% des sites à Pb du feuillet Q remplacés par des atomes de Bi et des sites vacants (). La prise en compte de l'ensemble des analyses conduit á la formule développée générale: Pb11.61-2x0.13Agx(Bi14,26+x–ySby)-(S1 –zSez)33 avec x et y 0,86 at., et z 0,45. A Nevskoe, la bismuthinite associée contient de 5 à 12% Se, avec Sb, Pb et Cu mineurs. La cosalite contient de 4 a 8% Se, 2,7 á 5,3% Sb, avec Ag et Cu mineurs. Lá où wittite et cosalite sont en contact étroit, la wittite montre clairement un enrichissement relatif en Se, qui pourrait etre du au sousréseau pseudo-hexagonal de cette structure incommensurable, très proche du feuillet Bi2(Se, Te, S)3 présent dans la série de la tétradymite. Les analyses à la microsonde indiquant une continuité chimique de la cannizzarite sans Se à la wittite 1a plus riche en Se, la validité de la wittite en tant qu'espéce spécifique apparaït discutable. Mais le caractère incommensurable de cette série demande une etude cristallographique plus détaillée.
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