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1.
《Applied Geochemistry》2000,15(2):235-243
Sulfide mineral weathering is a major source of acid generation in mining environments. Oxidation and hydrolysis reactions in soil and geologic material under earth surface conditions causes weathering of reduced sulfide minerals resulting in liberation of weathering products including acid. Pyrite and marcasite are minerals common in mine environments that cause acid generation. Many other sulfide minerals are present in mining environments which may or may not form acid upon weathering. Characterization of complex mineral assemblages containing S compounds is therefore critically important to pre-mine planning and postmine waste characterization. Despite the importance of mineral weathering behavior, little is known about the acid generation characteristics of common sulfide and sulfate minerals. To assess the response of common sulfide and sulfate minerals to oxidizing conditions, 13 minerals were subjected to treatment with 10% H2O2. The resulting leachate was analyzed for pH, electrical conductivity, S and titratable acidity. The sulfide minerals arsenopyrite, pyrite, chalcopyrite, pyrrhotite, marcasite and sphalerite demonstrated significantly elevated levels of titratable acidity and are acid generating in contrast to galena, chalcocite and all the sulfates. The sulfate minerals barite, anhydrite, gypsum, anglesite and jarosite were included in experimentation and were found not to form acid under strongly oxidizing conditions. Remediation strategies for disturbed lands containing reduced S minerals must therefore consider not only the total quantity of sulfide minerals present, but the specific mineralogy of the S compounds.  相似文献   

2.
Karavansalija ore zone is situated in the Serbian part of the Serbo‐Macedonian magmatic and metallogenic belt. The Cu–Au mineralization is hosted mainly by garnet–pyroxene–epidote skarns and shifts to lesser presence towards the nearby quartz–epidotized rocks and the overlying volcanic tuffs. Within the epidosites the sulfide mineralogy is represented by disseminated cobalt‐nickel sulfides from the gersdorfite‐krutovite mineral series and cobaltite, and pyrite–marcasite–chalcopyrite–base metal aggregates. The skarn sulfide mineralization is characterized by chalcopyrite, pyrite, pyrrhotite, bismuth‐phases (bismuthinite and cosalite), arsenopyrite, gersdorffite, and sphalerite. The sulfides can be observed in several types of massive aggregates, depending on the predominant sulfide phases: pyrrhotite‐chalcopyrite aggregates with lesser amount of arsenopyrite and traces of sphalerite, arsenopyrite–bismuthinite–cosalite aggregates with subordinate sphalerite and sphalerite veins with bismuthinite, pyrite and arsenopyrite. In the overlying volcanoclastics, the studied sulfide mineralization is represented mainly by arsenopyrite aggregates with subordinate amounts of pyrite and chalcopyrite. Gold is present rarely as visible aggregate of native gold and also as invisible element included in arsenopyrite. The fluid inclusion microthermometry data suggest homogenization temperature in the range of roughly 150–400°C. Salinities vary in the ranges of 0.5–8.5 wt% NaCl eq for two‐phase low density fluid inclusions and 15–41 wt% NaCl eq for two‐phase high‐salinity and three‐phase high‐salinity fluid inclusions. The broad range of salinity values and the different types of fluid inclusions co‐existing in the same crystals suggest that at least two fluids with different salinities contributed to the formation of the Cu–Au mineralization. Geothermometry, based on EPMA data of arsenopyrite co‐existing with pyrite and pyrrhotite, suggests a temperature range of 240–360°C for the formation of the arsenopyrite, which overlaps well with the data for the formation temperature obtained through fluid inclusion microthermometry. The sulfur isotope data on arsenopyrite, chalcopyrite, pyrite and marcasite from the different sulfide assemblages (ranging from 0.4‰ to +3.9‰ δ34SCDT with average of 2.29 δ34SCDT and standard deviation of 1.34 δ34SCDT) indicates a magmatic source of sulfur for all of the investigated phases. The narrow range of the data points to a common source for all of the investigated sulfides, regardless of the host rock and the paragenesis. The sulfur isotope data shows good overlap with that from nearby base‐metal deposits; therefore the Cu–Au mineralization and the emblematic base‐metal sulfide mineralization from this metallogenic belt likely share same fluid source.  相似文献   

3.
《Applied Geochemistry》2006,21(2):269-288
Reliable quantification of mineral weathering rates is a key to assess many environmental problems. In this study, the authors address the applicability of pure mineral laboratory rate laws for dissolution of mill tailings samples. Mass-normalised sulfide and aluminosilicate mineral dissolution rates, determined in oxygenated batch experiments, were found to be different between two samples from the same ∼50-year-old, carbonate-depleted mill tailings deposit. Consideration of difference in particle surface area and mineralogy between the samples resolved most of this discrepancy in rates. While the mineral surface area normalised dissolution rates of pyrite in a freshly crushed pure pyrite specimen and a sulfide concentrate derived from the tailings were within the range of abiotic literature rates of oxidation by dissolved molecular O2, as were rates of sphalerite and chalcopyrite dissolution in the tailings, dissolution rates of pyrite and aluminosilicates in the tailings generally differed from literature values. This discrepancy, obtained using a consistent experimental method and scale, is suggested to be related to difficulties in quantifying individual mineral reactive surface area in a mixture of minerals of greatly varying particle size, possibly due to factors such as dependence of surface area-normalised mineral dissolution rates on particle size and time, or to non-proportionality between rates and BET surface area.  相似文献   

4.
Data on the mineral and chemical composition of samples of sulfide deposits from the Broken Spur and TAG (Mid-Atlantic Ridge) are presented. The main minerals in the Broken Spur field are marcasite, pyrrhotite, pyrite, chalcopyrite, and sphalerite; in sample from TAG: chalcopyrite, pyrite, and marcasite. It has been established that these sulfide minerals of Fe, Cu, and Zn are natural ion exchangers and belong to the class of adsorbents. Exchange capacity of sulfide minerals in terms of heavy metal cations (Ni2+, Co2+, Cd2+, and Pb2+) is 0.022–0.32 mg-equiv/g. In the exchange reaction products, the mineral composition of sulfide deposits is retained, and new phases do not appear. It is suggested that the adsorbed heavy metal cations populate either vacant cationic or interstitial defect sites in the structures of sulfide minerals. Bond strength of the adsorbed heavy metal cations with the main structural elements of minerals is low, which is confirmed by their high extraction in an acid medium. The results of adsorption-desorption experiments indicate two forms of heavy metal cations in sulfide minerals: adsorbed (basic) and chemically bound.  相似文献   

5.
《Applied Geochemistry》2001,16(7-8):803-819
Sulfide mineral oxidation, primarily pyrite and pyrrhotite, generates acid mine drainage during weathering. Successful management of acid generating wastes entails the suppression of the initiation of oxidation reactions. The reactivity of pyrite depends on ore mineralogy, including the effects of associated sulfide impurities. The electrochemical surface characterization study using cyclic voltammetry with carbon paste electrodes containing minerals particles (CPE-Mineral) is an effective tool for demonstrating how the various mineral characteristics work together to influence the overall reactivity of the mineral. This study was supported by chemical, mineralogical and leachate chemistry data. The results show that the presence of other sulfides in contact with pyrite at the beginning of the weathering process is the most important parameter affecting pyrite reactivity, which is likely to be oxidized and passivated. In more advanced stages of leaching, mineral coatings which passivate the pyrite surfaces tend to play the most important role in defining the reactivity of pyrite. The electrochemical response of pyritic samples in conjunction with the evolution of the chemical quality of the leach solution in the simple experimental device here used, could then provide valuable information on acid mine drainage generation.  相似文献   

6.
我国是世界上最大的铜精矿进口国,研究不同产地铜精矿的矿物学特征,能支撑铜精矿原产地分析及相关固体废物属性鉴定。本文研究对象为来自8个国家12个矿区的进口铜精矿样品,采用X射线荧光光谱(XRF)、X射线粉晶衍射(XRD)以及偏光显微镜进行综合分析,探寻这些矿区铜精矿的元素组成、矿物组合特征,探讨不同成因类型铜精矿的矿物学差异。X射线荧光光谱分析表明铜精矿样品主要元素为Cu、Fe、S、O,普遍含有Zn、Si、Al、Mg、Ca、Pb;X射线粉晶衍射物相分析表明铜精矿样品主要物相为黄铜矿,其次常含有黄铁矿和闪锌矿等物相;偏光显微镜光片鉴定表明铜精矿样品金属矿物中黄铜矿的含量在88%~98%之间,观察到黄铜矿与闪锌矿、黄铁矿、磁黄铁矿共生,闪锌矿与斑铜矿、砷黝铜矿共生,黄铜矿、砷黝铜矿和斑铜矿共生等连生体矿相。结合铜精矿不同成矿类型分析表明,斑岩型、矽卡岩型、火山成因块状硫化型铜矿床样品中常见黄铜矿、黄铁矿、闪锌矿,并分别含有黑云母、草酸钙石、硫酸铅特征矿物;铁氧化物铜金矿床样品主要矿物为黄铜矿,常见磁黄铁矿、滑石特征矿物。通过本文采用多种技术表征不同产地铜精矿样品元素含量、物相组成、矿相组成的差异,能够全面分析不同产地铜精矿样品的矿物学特征,对进口铜精矿的风险识别和管控具有重要意义。  相似文献   

7.
Petrographic, SEM, and EPMA analyses are used to study the micro-textures and mineralogical composition of samples collected by a TV-grab from the 26°S SMAR (southern Mid-Atlantic Ridge) hydrothermal field. The investigated samples include the outermost chimney walls and sulfide debris. Isocubanite-chalcopyrite intergrowths are the major Cu-Fe sulfide phase in the chimney wall samples. These intergrowths include normal chalcopyrite, anomalous chalcopyrite (Cu-poor, Zn- and Fe-rich), normal isocubanite with Cu/Fe < 0.50, and Cu-rich isocubanite with Cu/Fe > 0.50. Anomalous chalcopyrite and Cu-rich isocubanite represent the intermediate phases between stoichiometric chalcopyrite and isocubanite in the Cu-Fe-S system. Anomalous chalcopyrite occurs as cores or thin rims bordering isocubanite, which associated with sphalerite. While Cu-rich isocubanite commonly associates pyrite. Based on textural relationships and microanalytical data of both phases, we interpret the abundant anomalous chalcopyrite and Cu-rich isocubanite as metastable or as high-temperature (~300 °C) rapidly precipitated hydrothermal sulfides. This interpretation advocates the SMAR 26°S hydrothermal field as an immature and short-living system.  相似文献   

8.
《Ore Geology Reviews》2003,22(1-2):61-90
Quantitative laser ablation (LA)-ICP-MS analyses of fluid inclusions, trace element chemistry of sulfides, stable isotope (S), and Pb isotopes have been used to discriminate the formation of two contrasting mineralization styles and to evaluate the origin of the Cu and Au at Mt Morgan.The Mt Morgan Au–Cu deposit is hosted by Devonian felsic volcanic rocks that have been intruded by multiple phases of the Mt Morgan Tonalite, a low-K, low-Al2O3 tonalite–trondhjemite–dacite (TTD) complex. An early, barren massive sulfide mineralization with stringer veins is conforming to VHMS sub-seafloor replacement processes, whereas the high-grade Au–Cu ore is associated with a later quartz–chalcopyrite–pyrite stockwork mineralization that is related to intrusive phases of the Tonalite complex. LA-ICP-MS fluid inclusion analyses reveal high As (avg. 8850 ppm) and Sb (avg. 140 ppm) for the Au–Cu mineralization and 5 to 10 times higher Cu concentration than in the fluids associated with the massive pyrite mineralization. Overall, the hydrothermal system of Mt Morgan is characterized by low average fluid salinities in both mineralization styles (45–80% seawater salinity) and temperatures of 210 to 270 °C estimated from fluid inclusions. Laser Raman Spectroscopic analysis indicates a consistent and uniform array of CO2-bearing fluids. Comparison with active submarine hydrothermal vents shows an enrichment of the Mt Morgan fluids in base metals. Therefore, a seawater-dominated fluid is assumed for the barren massive sulfide mineralization, whereas magmatic volatile contributions are implied for the intrusive related mineralization. Condensation of magmatic vapor into a seawater-dominated environment explains the CO2 occurrence, the low salinities, and the enriched base and precious metal fluid composition that is associated with the Au–Cu mineralization. The sulfur isotope signature of pyrite and chalcopyrite is composed of fractionated Devonian seawater and oxidized magmatic fluids or remobilized sulfur from existing sulfides. Pb isotopes indicate that Au and Cu originated from the Mt Morgan intrusions and a particular volcanic strata that shows elevated Cu background.  相似文献   

9.
《Applied Geochemistry》2006,21(7):1216-1225
The aim of the study was to determine whether the application of bulk industrial chemicals (potassium permanganate and water-soluble phosphate fertilizer) to partly oxidized, polyminerallic mine wastes can inhibit sulfide oxidation, and metal and metalloid mobility. The acid producing waste rocks were metal (Pb, Zn, Cu) and metalloid (As, Sb) rich and consisted of major quartz, dickite, illite, and sulfide minerals (e.g., galena, chalcopyrite, tetrahedrite, sphalerite, pyrite, arsenopyrite), as well as minor to trace amounts of pre- and post-mining oxidation products (e.g., hydrated Fe, Cu, Pb, and alkali mineral salts). SEM-EDS observations of treated waste material showed that metal, metal–alkali, and alkali phosphate coatings developed on all sulfides. The abundance of phosphate phases was dependant on the fertilizer type and the availability of metal and alkali cations in solution. In turn, the release of cations was dependent on the amount of sulfide oxidation induced by KMnO4 during the experiment and the dissolution of soluble sulfates. Mn, Ca, Fe, and Pb phosphates remained stable during H2O2 leaching, preventing acid generation and metal release. In contrast, the lack of complete phosphate coating on arsenopyrite allowed oxidation and leaching of As to proceed. The mobilized As did not form phosphate phases and consequently, As displayed the greatest release from the coated waste. Thus, the application of KMnO4 and the water-soluble phosphate fertilizer Trifos (Ca(H2PO4)2) to partly oxidized, polyminerallic mine wastes suppresses sulfide oxidation and is most effective in inhibiting Cu, Pb, and Zn (Sb) release. However, the technique appears ineffective in suppressing oxidation of arsenopyrite and preventing As leaching.  相似文献   

10.
New investigations are carried out on the mineralogy and mineral chemistry of sulfide assemblages obtained in samples from one core in the hydrothermally active, southwest basin of the Atlantis II deep, Red Sea. The most abundant sulfide phases are the exsolved intermediate solid solution (ISS) and chalcopyrite. Sphalerite, pyrrhotite, marcasite, mackinawite, and presumably wurtzite are also observed. Two distinct groups of paragenesis were encountered: (a) Intermediate solid solution with sphalerite incrustations and intergrowths, and (b) intermediate solid solution barren of sphalerite intergrowths. The first group is confined to the upper part of the Co zone and the SOAN zone (Bäcker and Richter 1973), and the second is present in the entire core 100-3-7. An optically isotropic chalcopyrite is found for the first time as a natural mineral in Atlantis II, Red Sea. Yet its existence as a novel phase needs x-ray confirmation. It exhibits a lower reflectivity than normal chalcopyrite and is isotropic. Chalcopyrite occurs either as a single phase or in association with tetragonal chalcopyrite. Our investigations indicate that the formation of Atlantis II deposits is a result of complex processes. These processes are characterized by compositional changes in the ore-bearing fluids and the change in sulfur fugacity (especially with depth). The presence of exsolved chalcopyrite lamellae in ISS indicates slow cooling below 450°C. However, it is difficult to understand why the cubic chalcopyrite is not converted to the tetragonal form even though the temperature of transformation lies above 450°C (470° – 500°C, Cabri 1973). The Cu/Fe ratio changes in the exsolved chalcopyrite lamellae from core to rim of the composite grains. The ratio is higher in the rims. This suggests that primary inhomogenous ISS grains formed from solutions with a continuous increase in the Cu/Fe ratio. Slow cooling is also required to account for the exsolution of chalcopyrite lamellae in ISS. The low sulfur content in isotropic chalcopyrite is also suggestive of low fs2. The low S content in the chalcopyrite may be the controlling factor for the sluggish conversion from cubic to tetragonal chalcopyrite. Mackinawite lamellae show the same orientation in ISS and exsolved isotropic chalcopyrite indicating that mackinawite exsolved before the breakdown of ISS. This strongly suggests that mackinawite is stable above 300°C (contrary to experimental results by Zoka et al. 1973). Pyrrhotite was probably formed by the sulfurization of ilvaite. The pyrrhotite grains with several complex successive zones show the sequence of the sulfurization episodes.Metalliferous sediments related to hot brines were discovered in the Red Sea in 1964 (Miller et al. 1966). Since then, several papers have been published on this subject (Degens and Ross 1969, Bäcker and Schoell 1972, Bäcker and Richter 1973, Bignell et al. 1976, Shanks and Bishoff 1977, Weber-Diefenbach 1977, Nöltner 1979, Pottorf 1980, Pottorf and Barnes 1983, Oudin et al. 1984).Complex sulfide phases including intermediate solid solution (ISS), chalcopyrite, and a chalcopyritelike mineral (which exhibits a lower reflectivity than normal chalcopyrite and appears to be isotropic occur in the metalliferous sediments. These phases were found in association with several minerals in different parageneses. In an attempt to understand the origin of the formation of the sulfide-bearing sediments in the Atlantis II deep of the Red Sea, a detailed study of the phase relations of the Cu-Fe sulfide ores of this locality was carried out.  相似文献   

11.
The Sargaz Cu–Zn massive sulfide deposit is situated in the southeastern part of Kerman Province, in the southern Sanandaj–Sirjan Zone of Iran. The stratigraphic footwall of the Sargaz deposit is Upper Triassic to Lower Jurassic (?) pillowed basalt, whereas the stratigraphic hanging wall is andesite. Mafic volcanic rocks are overlain by andesitic volcaniclastics and volcanic breccias and locally by heterogeneous debris flows. Rhyodacitic flows and volcaniclastics overlie the sequence of basaltic and andesitic rocks. Based on the bimodal nature of volcanism, the regional geologic setting and petrochemistry of the volcanic rocks, we suggest massive sulfide mineralization in the Sargaz formed in a nascent ensialic back-arc basin. The current reserves (after ancient mining) of the Sargaz deposit are 3 Mt at 1.34% Cu, 0.38% Zn, 0.08%Pb, 0.24 g/t Au, and 7 g/t Ag. The structurally dismembered massive sulfide lens is zoned from a pyrite-rich base, to a pyrite?±?chalcopyrite-rich central part, and a sphalerite–chalcopyrite-rich upper part, with a sphalerite-rich zone lateral to the upper part. The main sulfide mineral is pyrite, with lesser chalcopyrite and sphalerite. The feeder zone, comprised of a vein stockwork consists of quartz–sulfide–sericite pesudobreccia and, in the deepest part, chlorite–quartz–pyrite pesudobreccia. Footwall hydrothermal alteration extends at least 70–80 m below the massive sulfide lens and more than a hundred meters along strike from the massive sulfide lens. Jasper and Fe–Mn bearing chert horizons lateral to the sulfide deposit represent low-temperature hydrothermal precipitates of the evolving hydrothermal system. Based on mineral textures and paragenetic relationships, the growth history of the Sargaz deposit is complex and includes: (1) early precipitation of sulfides (protore) on the seafloor as precipitation of fine-grained anhedral pyrite, sphalerite, quartz, and barite; (2) anhydrite precipitation in open spaces and mineral interstices within the sulfide mound followed by its subsequent dissolution, formation of breccia textures, and mound clasts and precipitation of coarse-grained pyrite, sphalerite, tetrahedrite–tennantite, galena and barite; (3) replacement of pre-existing sulfides by chalcopyrite precipitated at higher temperatures (zone refining); (4) continued “refining” led to the dissolution of stage 3 chalcopyrite and formation of a base-metal-depleted pyrite body in the lowermost part of the massive sulfide lens; (5) carbonate veins were emplaced into the sulfide lens, replacing stage 2 barite. The δ34S composition of the sulfides ranges from +2.8‰ to +8.5‰ (average, +5.6‰) with a general increase of δ34S ratios with depth within the massive sulfide lens and underlying stockwork zone. The heavier values indicate that some of the sulfur was derived from seawater sulfate that was ultimately thermochemically reduced in deep hydrothermal reaction zones.  相似文献   

12.
δ34S values of pyrite, molybdenite and chalcopyrite were determined from the Malanjkhand copper deposit. These minerals constitute the primary sulfide phases that were deposited after the initial magnetite deposition in the main orebody and host granitoid. Pyrite exhibits a depleted range of values (?2.63 to ?0.56‰), chalcopyrite, a very narrow range of values around zero (?0.039 to 0.201‰) and molybdenite furnishes a range of enriched values (0.68 to 1.98‰). On back calculation of the δ34S values of H2S in the fluid from which the minerals were likely to have precipitated, using standard expressions for equilibrium fractionation at the temperature range obtained from fluid inclusion and mineral fluid equilibria, it is observed that H2S in the fluid at pyrite deposition was depleted and gradually became enriched towards molybdenite and chalcopyrite deposition. This trend is best explained as being due to inorganic reduction of SO42? in the fluid and is very much in agreement with the paragenetic sequence indicating increasing activity of H2S in the fluid. The very restricted range in the δ34S values of sulfide minerals in the fluid does indicate a single, possibly magmatic, source of sulfur that also agrees well with the earlier deduced model of genesis of the deposit as an ancient geothermal system associated with granitic magmatism.  相似文献   

13.
The southwestern Sabzevar basin is the north of Central Iranian Microcontinent hosts abundant mineral deposits, including exhalative Mn mineralization and Cu-Zn volcanogenic massive sulfide (VMS) deposits. Amongst them, the Nudeh Besshi-type Cu–Zn volcanogenic massive sulfide (VMS) deposit is hosted within the lower part of a Late Cretaceous volcano-sedimentary sequence composed of alkali olivine basalt flows and tuffaceous silty sandstone. Based on investigations into the ore geometry, mineralogy, and texture, we recognized three different ore facies: (1) a stockwork of sulfide-bearing quartz veins cutting across the footwall volcano-sedimentary rocks and representing the stringer zone; (2) a massive ore type, displaying replacement texture with pyrite, chalcopyrite, sphalerite, friedrichite, and minor magnetite; and (3) a bedded ore type, with laminated to disseminated pyrite and chalcopyrite. EPMA studies indicate a distinctive minor element distribution between the different ore types of the Nudeh deposit. The Fe content in the sphalerite ranges from 0.65–1.80?wt.%, indicating the Fe-poor nature of the sphalerite. However, the Cd content in sphalerite ranged between 0.164–0.278?wt.%. According to the mineral compositions, Zn, Se, and Ag are found in bornite as minor elements. In the bedded ore facies, the pyrite contains higher levels of Se (up to 0.35?wt.%). The Zn content in the friedrichite in all of the ore samples is low. The Co/Ni ratios in pyrite from the Nudeh ore are lower than those of most magmatic deposits, but are similar to those from volcanogenic deposits, and hence support the proposed hydrothermal origin of the deposit. Two generations of quartz, Q1 and Q2 in the stockwork veins, contain primary fluid inclusions and these contain two phases (liquid and vapor). The lack of vapor-rich inclusions or variable liquid/vapor ratios indicate that the fluids did not boil at the site of trapping. Salinity for both Q1 and Q2 fluid inclusions ranges between 2.2–6.8?wt.% eq. NaCl. Homogenization temperatures for inclusions in the Q1 and Q2 veins average at about 296?°C and are similar to the temperatures of hydrothermal fluids discharged through vents in many modern seafloor VMS deposit. The Nudeh Besshi-type VMS deposit appears to have formed on the seafloor and based on the salinity and temperature constraints from the underlying stockwork, a buoyancy plume model is proposed as a mechanism for precipitation.  相似文献   

14.
Modes of occurrence of Au‐ and Ag‐bearing phases and their relation with associated hypogene ore minerals were examined with the objective to elucidate Au‐Ag distribution at the Esperanza porphyry deposit in the Eocene Centinela copper belt, using ore‐microscope modal analysis, semi‐quantitative analyses by automated mineralogy, electron probe microanalysis, and secondary ion mass spectrometer. The Esperanza hypogene mineralization is characterized by early‐stage chalcopyrite‐rich veinlets in the potassic alteration zone and later polymetallic stage with tennantite and galena in the chlorite‐sericitic alteration zone. Only the early‐stage chalcopyrite contains fine‐grained electrum (Au68Ag32 ‐ Au81Ag19) and hessite (Ag2Te), and thus yields positive correlations in Cu vs. Au and Cu vs. Ag grades that are clearly recognized in the hypogene sulfide zone. The early‐stage chalcopyrite grains frequently exhibit polysynthetic twinning suggestive of inversion from intermediate solid solution. These features suggest that the fine‐grained electrum and hessite are products exsolved in the cooling process with the intermediate solid solution to chalcopyrite inversion. In contrast, tennantite and galena of the later‐stage mineralization contain no detectable Ag, and it is thus proposed that the early‐stage inverted chalcopyrite is the principal storage of economically important precious metals.  相似文献   

15.
The mineralogy of the Istala deposit, Gümüşhane, northeastern Turkey, was studied in detail, and a geochemical investigation was carried out using electron probe micro-analysis (EPMA). Sphalerite, galena, chalcopyrite and pyrite are the major sulfide minerals found in the Istala deposit, with minor amounts of bornite, idaite, tetrahedrite–tennantite, anilite, yarrowite, mckinstryite, covellite and chalcocite. In addition to these, barite and a small quantity of quartz occur as gangue minerals. Based on the textural relations and mineral assemblages, five different stages of crystallization have been recognized. Mineral paragenesis of the first four stages has been found to be similar, whereas clear enrichment has been observed in the modal abundance of the copper sulfide mineral assemblage at the fifth-stage ore formation. Whole-rock geochemical analyses of the Istala ore show an enrichment of Ag content up to 3328 ppm. Optical observations and EPMA study indicated that abundant silver mineralization was found in the Istala ore, especially during the later-stage ore deposition. Repetition to the presence of native silver in the samples, a significant amount of silver was incorporated in bornite, idaite, tetrahedrite–tennantite, anilite, yarrowite, mckinstryite, covellite and chalcocite, whereas a trace amount of silver has been detected in sphalerite, galena, chalcopyrite and pyrite. The homogenization temperatures (Th) of the primary fluid inclusions were measured between 98 and 284 °C, with frequency peaks around 140 °C, 190 °C and 240 °C. All data obtained support the theory that later stage copper-rich sulfides, formed under the low temperature conditions, are responsible for the large amounts of silver content in the Istala mine.  相似文献   

16.
The Myra mine, now inactive, produced Zn and Cu concentrates from a Zn-rich, Kuroko-type, volcanogenic massive sulfide deposit located in the mountainous interior of Vancouver Island. The climate at the site is classified as “Marine West Coast”, with annual precipitation exceeding 2200 mm. Water from a losing stream on the mountainside above the mine follows preferential, fracture-controlled pathways to the upper workings before draining through the 10-Level portal. With a view toward mine decommissioning, portal discharge rate was monitored continuously over a 17-month period during which 46 water samples were collected. Effluent chemistry, dominated by Ca, HCO3 and SO4, shows moderate to high total base metal concentrations and near-neutral pH. Carbonatization, mainly of mafic rocks in the hangingwall, provides significant acid neutralizing potential. Metal concentrations vary seasonally, with smaller spikes associated with summer storm events, and a main peak associated with flushing of the workings during the first heavy autumn rains. Aqueous speciation modeling suggests that Fe and Al concentrations are controlled by the solubilities of hydrous ferric oxides and microcrystalline gibbsite, respectively. Concentrations of Zn, Cu and Cd appear controlled by sorption rather than by the solubilities of mineral phases. A comparison of precipitate concentrations observed in portal effluent with predictions from mass balance (inverse) modeling results suggests that less than 5% of the precipitated Fe and Al hydroxides are transported from the mine. However, amounts of sorbed Cu, Zn and Cd measured in the effluent are only slightly lower than modeled values. This suggests that the small fraction of (probably finer) Fe precipitates in portal effluent sorbs most of the Zn, Cu and Cd predicted by modeling. Based on mass balance calculations, metal loadings are explained by the oxidation of 3830 kg of pyrite, 600 kg of sphalerite and 190 kg of chalcopyrite, annually. Circum-neutral drainage conditions are maintained by the reaction of almost 19,800 kg of calcite, annually.  相似文献   

17.
通过化学分析、扫描电镜以及工艺矿物学自动定量分析系统(MLA)等测试方法对河南嵩县下蒿坪金矿进行了系统的工艺矿物学研究,包括原矿化学组成、矿物组成、金的赋存状态、主要载金矿物嵌布特征以及矿物解离特性等。结果表明,该金矿中主要可回收的有价金属为金,其品位为3.75×10-6。该金矿的原矿矿物主要由石英、钾长石、钠长石、黄铁矿和铁白云石组成,此外还有少量的赤铁矿、萤石、白云石以及方解石。原矿中的金主要赋存在黄铁矿中,而黄铁矿大部分以细粒、微细粒形式嵌布在石英和长石颗粒中。原矿中自然金的含量非常少,多以单独的自然金颗粒形式存在。原矿磨至P80=0.074 mm(-0.074 mm粒级含量占80%)时载金矿物黄铁矿、方铅矿、闪锌矿的单体解离度相对较高,有利于通过浮选回收。  相似文献   

18.
Massive Zn‐Pb‐Ag sulfide mineralization appears conformable with felsic volcanism, developed in an Upper Jurassic volcanic arc to the Southwest (SW) of the Serbo‐Macedonian continent in Northern Greece. The host volcanic sequence of the mineralization comprises mylonitized rhyolitic to rhyodacitic lavas, pyroclastics, quartz‐feldspar porphyries, and cherty tuffs. A “white mica—quartz—pyrite” mineral assemblage characterizes the volcanic rocks in the footwall and hanging‐wall of massive sulfide ore layers, formed as a result of greenschist‐grade regional metamorphism on “clay‐quartz‐pyrite” hydrothermal alteration haloes. Massive ore lenses are usually underlain by deformed Cu‐pyrite and quartz‐pyrite stockworks. Most of the sulfide ore bodies have proximal‐type features. Ductile deformation and regional metamorphism have transformed many of the stockwork structures. The mineralization is characterized by high Zn, Pb, and Ag contents, while Cu and critical metals are low. Primary depositional textures, for example, layering, clastic pyrite, colloform, and atoll textures were identified. The overall textural features of the mineralization indicate it has undergone mechanical deformation. The most prominent features of the effects of metamorphism, folding and shearing, are modification of the ore body morphology toward flattened and boudinage structures and transformation of the ore textures toward the dominance of planar fabrics. Sulfur isotope analyses of sulfides along with textural observations are consistent with a dual source of sulfide sulfur. Sulfur isotope values for sphalerite, non‐colloform pyrite, galena, and chalcopyrite fall in a limited range from ?1.6 to +4.8‰ (mean δ34S + 2‰), indicating a hydrothermal source derived from the reduction of coeval seawater sulfate in the convective system. Pyrites with colloform and atoll textures are characterized by a 34S depletion, indicating a bacterial reduction of coeval seawater sulfate. The morphology of ore beds, the mineralogy, sulfide textures, and ore chemistry along with the petrology and tectonic setting of the host rocks can be attributed to typical of a bimodal‐felsic metallogenesis. Although similar in many respects to classic Kuroko‐type volcanogenic massive sulfide mineralization, it has some atypical features, like the absence of barite ore, which is possibly a result of significant temporal depletion in sulfate due to bacterial reduction, a conclusion supported by the widespread occurrence of colloidal and atoll textures of pyrite.  相似文献   

19.
Mineralogical, geochemical and microbial characterization of tailings solids from the Greens Creek Mine, Juneau, Alaska, was performed to evaluate mechanisms controlling aqueous geochemistry of near-neutral pH pore water and drainage. Core samples of the tailings were collected from five boreholes ranging from 7 to 26 m in depth. The majority of the 51 samples (77%) were collected from the vadose zone, which can extend >18 m below the tailings surface. Mineralogical investigation indicates that the occurrence of sulfide minerals follows the general order: pyrite [FeS2] >> sphalerite [(Zn,Fe)S] > galena [PbS], tetrahedrite [(Fe,Zn,Cu,Ag)12Sb4S13] > arsenopyrite [FeAsS] and chalcopyrite [CuFeS2]. Pyrite constitutes <20 to >35 wt.% of the tailings mineral assemblage, whereas dolomite [CaMg(CO3)2] and calcite [CaCO3] are present at ?30 and 3 wt.%, respectively. The solid-phase geochemistry generally reflects the mineral assemblage. The presence of additional trace elements, including Cd, Cr, Co, Mo, Ni, Se and Tl, is attributed to substitution into sulfide phases. Results of acid–base accounting (ABA) underestimated both acid-generating potential (AP) and neutralization potential (NP). Recalculation of AP and NP based on solid-phase geochemistry and quantitative mineralogy yielded more representative results. Neutrophilic S-oxidizing bacteria (nSOB) and SO4-reducing bacteria (SRB) are present with populations up to 107 and 105 cells g−1, respectively. Acidophilic S-oxidizing bacteria (aSOB) and iron-reducing bacteria (IRB) were generally less abundant. Primary influences on aqueous geochemistry are sulfide oxidation and carbonate dissolution at the tailings surface, gypsum precipitation–dissolution reactions, as well as Fe reduction below the zone of sulfide oxidation. Pore-water pH values generally ranged from 6.5 to 7.5 near the tailings surface, and from approximately 7–8 below the oxidation zone. Elevated concentrations of dissolved SO4, S2O3, Fe, Zn, As, Sb and Tl persisted under these conditions.  相似文献   

20.
Metal L2,3, sulfur K and oxygen K near-edge X-ray absorption fine structure (NEXAFS) spectra for chalcopyrite, bornite, chalcocite, covellite, pyrrhotite and pyrite have been determined from single-piece natural mineral specimens in order to assess claims that chalcopyrite should be regarded as CuIIFeIIS2 rather than CuIFeIIIS2, and that copper oxide species are the principal initial oxidation products on chalcopyrite and bornite exposed to air. Spectra were obtained using both fluorescence and electron yields to obtain information representative of the bulk as well as the surface. Where appropriate, NEXAFS spectra have been interpreted by comparison with the densities of unfilled states and simulated spectra derived from ab initio calculations using primarily the FEFF8 code and to a lesser extent WIEN2k. Metal 2p and S 2p photoelectron spectra excited by monochromatised Al Kα X-rays were determined for each of the surfaces characterised by NEXAFS spectroscopy. The X-ray excited Cu LMM Auger spectrum was also determined for each copper-containing sulfide. FEFF8 calculations were able to simulate the experimental NEXAFS spectra quite well in most cases. For covellite and chalcocite, it was found that FEFF8 did not provide a good simulation of the Cu L3-edge spectra, but WIEN2k simulations were in close agreement with the experimental spectra. Largely on the basis of these simulations, it was concluded that there was no convincing evidence for chalcopyrite to be represented as CuIIFeIIS2, and no strong argument for some of the Cu in either bornite or covellite to be regarded as Cu(II). The ab initio calculations for chalcopyrite and bornite indicated that the density of Cu d-states immediately above the Fermi level was sufficient to account for the Cu L3-edge absorption spectrum, however these incompletely filled Cu d-states should not be interpreted as indicating some Cu(II) in the sulfide structure. It was also concluded that the X-ray absorption spectra were quite consistent with the initial oxidation products on chalcopyrite and bornite surfaces being iron oxide species, and inconsistent with the concomitant formation of copper-oxygen species.  相似文献   

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