Zinc extraction from Iranian low-grade complex zinc–lead ore by two native microorganisms: Acidithiobacillus ferrooxidans and Sulfobacillus

A mesophilic iron oxidizing bacterium, Acidithiobacillus ferrooxidans, has been isolated (33 °C) from a typical, chalcopyrite concentrate of the Sarcheshmeh copper mine in the region of Kerman located in the south of Iran. In addition, a thermophilic iron oxidizing bacterium, Sulfobacillus, has been isolated (60 °C) from the sphalerite concentrate of Kooshk lead and zinc mine near the city of Yazd in the center point of Iran. Variation of pH, ferrous and ferric concentration on time and effects of some factors such as temperature, cell growth, initial ferrous concentration and pH on bioleaching of low-grade complex zinc–lead ore were investigated. The results obtained from bioleaching experiments indicate that the efficiency of zinc extraction is dependent on all of the mentioned variables; especially the temperature and initial Fe(II) concentration have more effect than other factors for these microorganisms. In addition, results show that the maximum zinc recovery was achieved using a thermophilic culture. Zinc dissolution reached 58% with Sulfobacillus while it was 51% with A. ferrooxidans at pH = 1.5, initial Fe(II) concentration = 7 and 9 g/L for A. ferrooxidans and Sulfobacillus, respectively, after 30 days.     

Bioleaching of high pyrite carbon-rich sphalerite preflotation tailings

In this work, zinc extraction was investigated using bioleaching process. The used samples were carbon-rich preflotation tailings prepared from a lead–zinc mineral processing plant, located in Yazd province, Iran. Two samples were obtained with high amount of pyrite, while the first sample contained high arsenic (As) substitution in the pyrite crystal lattice, and it was about 4–5 times more than that of the second sample. The organic matter in both samples has presented a signature of poorly crystalline carbon. Bioleaching experiments were designed and carried out by a mixed culture of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans in shake flasks. The results showed that in the optimum point of experiments (pH 1.94–2, pulp density 10 %, without initial Fe⁺²), about 95 % of Zn would be extracted within 14 days, while with no use of bacteria, merely 35 % of Zn content was dissolved (under the same condition). Because of the characteristics of the prepared samples, the bacterial medium (9K) was removed in the optimum condition of bioleaching tests. Results showed that even in the absence of 9K medium, bacteria had proper growth too, such that more than 93 % of Zn content was extracted. In fact, the same results were achieved in the absence and presence of 9K medium. Comparison of the obtained results in bioleaching tests under the optimum condition indicated that Zn extraction was the same for both high and low As samples, while Fe extraction from low As content sample was nearly 4 times higher than that of the other sample.     

氧化亚铁硫杆菌浸取黄铜矿石影响因素的试验研究

本文通过对氧化亚铁硫杆菌浸出青海某地区低品位黄铜矿石的试验,探讨了接种量、矿石粒度、矿浆含量对黄铜矿石摇瓶浸出过程的影响。结果表明：在无菌硫酸浸出过程中,黄铜矿可以自发氧化分解,最终浸出率为15.98%;在有菌浸出过程中,氧化亚铁硫杆菌接种量为5/100（mL/mL）时铜浸出率最高可达31.16%。氧化亚铁硫杆菌浸出黄铜矿在接种量为5/100（mL/mL）,矿石粒径为〈104μm,矿浆含量为5/100（mL/mL）时较为适宜。     

Efficient separation of zinc from zinc containing copper sulfide concentrate by chemical leaching

As the most abundant copper containing resource and zinc containing resource, chalcopyrite and sphalerite/marmatite commonly coexist as Cu-Zn mixed ores in deposits. However, it is difficult to completely separate sphalerite and chalcopyrite by flotation, thus resulting in the existence of zinc impurity in copper concentrate. Sphalerite/marmatite existed in copper sulfide concentrate as impurity may lead to severe damage of the smelting equipment, and cause the waste of copper and Zn resources, it will also decrease of the sale price of copper concentrates. Therefore, the deep separation of zinc from zinc bearing copper sulfide concentrate is of great significance. In this work, selective chemical leaching was developed to efficiently remove zinc from zinc containing copper sulfide concentrate. Under the optimal condition (i.e., sulfuric acid concentration exceed 100 g/L, temperature of 80 °C, pulp density of 10%, leaching time of 48 h), over 85% Zn was extracted into the leaching solution together with only about 10% Cu and Fe, according to the leaching experiment. Leaching slurry had good solid-liquid separation characteristics, and zinc can be further effectively recovered from the leaching solution. According to X-ray diffraction (XRD) and scanning electron microscope/energy dispersive spectrometer (SEM/EDS) analysis, chalcopyrite was the main mineralogical phase in the residues, which can be regarded as high quality copper concentrate for metallurgy. Accordingly, a new process for deep and efficient separation of Cu-Zn mixed ores has been proposed.     

关于辉钼矿中Re含量示踪来源的讨论

对近年来国内已发表的744个辉钼矿Re-Os同位素测年数据进行了汇总,发现所有样品辉钼矿中的Re含量具有混合分布的特征.按照岩性和共生矿物种类对所有数据进行了分类统计分析,结果显示辉钼矿中Re含量(质量分数,下同)与岩性和共生矿物种类存在密切的关系:长英质脉和花岗岩中辉钼矿的Re含量最低,几何平均值分别为7.41×10...     

Hydrothermal evolution of the Sar-Cheshmeh porphyry Cu–Mo deposit,Iran: Evidence from fluid inclusions

The Sar-Cheshmeh porphyry Cu–Mo deposit is located in Southwestern Iran (∼65 km southwest of Kerman City) and is associated with a composite Miocene stock, ranging in composition from diorite through granodiorite to quartz-monzonite. Field observations and petrographic studies demonstrate that the emplacement of the Sar-Cheshmeh stock took place in several pulses, each with associated hydrothermal activity. Molybdenum was concentrated at a very early stage in the evolution of the hydrothermal system and copper was concentrated later. Four main vein Groups have been identified: (I) quartz+molybdenite+anhydrite±K-feldspar with minor pyrite, chalcopyrite and bornite; (II) quartz+chalcopyrite+pyrite±molybdenite±calcite; (III) quartz+pyrite+calcite±chalcopyrite±anhydrite (gypsum)±molybdenite; (IV) quartz±calcite±gypsum±pyrite±dolomite. Early hydrothermal alteration produced a potassic assemblage (orthoclase-biotite) in the central part of the stock, propylitic alteration occurred in the peripheral parts of the stock, contemporaneously with potassic alteration, and phyllic alteration occurred later, overprinting earlier alteration. The early hydrothermal fluids are represented by high temperature (350–520 °C), high salinity (up to 61 wt% NaCl equivalent) liquid-rich fluid inclusions, and high temperature (340–570 °C), low-salinity, vapor-rich inclusions. These fluids are interpreted to represent an orthomagmatic fluid, which cooled episodically; the brines are interpreted to have caused potassic alteration and deposition of Group I and II quartz veins containing molybdenite and chalcopyrite. Propylitic alteration is attributed to a liquid-rich, lower temperature (220–310 °C), Ca-rich, evolved meteoric fluid. Influx of meteoric water into the central part of the system and mixing with magmatic fluid produced albitization at depth and shallow phyllic alteration. This influx also caused the dissolution of early-formed copper sulphides and the remobilization of Cu into the sericitic zone, the main zone of the copper deposition in Sar-Cheshmeh, where it was redeposited in response to a decrease in temperature.     

滇西北雪鸡坪铜矿床流体包裹体特征研究及矿床成因讨论

雪鸡坪铜矿床产于印支晚期石英二长闪长玢岩-石英闪长玢岩-石英二长斑岩复式侵入体内,为一斑岩型铜矿床。矿床形成经历了多阶段热液成矿作用,主要有微细脉浸染状黄铁矿±黄铜矿-石英、细脉状辉钼矿±黄铁矿±黄铜矿-石英及微细脉状贫硫化物-石英-方解石等。流体包裹体岩相学、显微测温、激光拉曼及碳、氢、氧同位素综合研究表明,微细脉浸染状黄铁矿±黄铜矿-石英阶段石英中主要发育含Na Cl子矿物三相及气液两相包裹体,与含矿的石英二长斑岩石英中发育的流体包裹体特征相似,表明成矿流体主要为中高温、高盐度Na Cl-H2O体系热液,可能主要来源于印支期石英二长斑岩侵入体;辉钼矿±黄铁矿±黄铜矿-石英中主要发育含CO2三相及气液两相包裹体,成矿流体为中温、低盐度Na Cl-CO2-H2O体系热液,与前者来源明显不同;贫硫化物-石英-方解石石英中主要发育气液两相包裹体,成矿流体为中低温、低盐度Na Cl-H2O体系热液,推测其可能较多来自于大气降水。因此,雪鸡坪铜矿床为不同来源、不同地球化学性质热液叠加成矿作用的结果。     

Cooperative extraction of metals from chalcopyrite by bio-oxidation and chemical oxidation

Chalcopyrite bio-dissolution plays an important role in the processing of copper sulfide ores. However, due to the slow dissolution rates of CuFeS₂, bio-dissolution processes have not yet found widespread application. In order to enhance the dissolution of chalcopyrite, a novel method for enhancing the dissolution using ozone was proposed and verified. The generated products in chalcopyrite dissolution process in the presence of Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans was studied. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results indicate that a surface layer mainly consisting of jarosite and polysulfide (S_nⁿ⁻/S⁰) might be formed during biotic stage, which can be eliminated with the introduction of ozone. Electrochemical results show that ozone significantly increased the electrochemical reactivity of bioleached chalcopyrite, further proving that ozone enhanced the dissolution through destroying the surface layer. Hence, a bi-stage method for dissolution of chalcopyrite can be proposed.     

Re–Os and Pb–Pb geochronology of the Archean Salobo iron oxide copper–gold deposit, Carajás mineral province, northern Brazil

Rhenium–osmium ages were determined for two molybdenite samples and a Pb–Pb age was derived from bornite–chalcopyrite–magnetite at the Salobo iron oxide copper–gold deposit to determine the timing of mineralization and its relation to the nearby Old Salobo Granite. Rhenium–osmium dating of molybdenite spatially associated with copper sulfide minerals yields ages with weighted means of 2576±8 and 2562±8 Ma. Removing the error multiplier introduced by the decay constant uncertainty, appropriate for comparing ages from the same isotopic system, these data convincingly argue for two temporally separated pulses of molybdenite deposition at 2576.1±1.4 Ma (n=2) and 2561.7±3.1 Ma (n=3). The 2576±8 Ma age coincides with a previously published U–Pb age of 2573±2 Ma for the Old Salobo Granite, suggesting that main stage ore formation may have been contemporaneous with granite magmatism. The slightly younger 2562 Ma age most likely represents new molybdenite precipitation associated with the development or reactivation of local shear zones. Lead–lead stepwise leaching of copper sulfide minerals yields a less precise isochron age of 2579±71 Ma, and supports an Archean age for the Salobo ores. This is the first documentation of an Archean iron oxide copper–gold deposit, and the Re–Os and Pb–Pb geochronology herein support 2580–2550 Ma estimates for basement reactivation and regional granite magmatism associated with the development of brittle–ductile shear zones.     

Hydrothermal evolution of the Sar-Cheshmeh porphyry Cu–Mo deposit, Iran: Evidence from fluid inclusions

The Sar-Cheshmeh porphyry Cu–Mo deposit is located in Southwestern Iran (65 km southwest of Kerman City) and is associated with a composite Miocene stock, ranging in composition from diorite through granodiorite to quartz-monzonite. Field observations and petrographic studies demonstrate that the emplacement of the Sar-Cheshmeh stock took place in several pulses, each with associated hydrothermal activity. Molybdenum was concentrated at a very early stage in the evolution of the hydrothermal system and copper was concentrated later. Four main vein Groups have been identified: (I) quartz+molybdenite+anhydrite±K-feldspar with minor pyrite, chalcopyrite and bornite; (II) quartz+chalcopyrite+pyrite±molybdenite±calcite; (III) quartz+pyrite+calcite±chalcopyrite±anhydrite (gypsum)±molybdenite; (IV) quartz±calcite±gypsum±pyrite±dolomite. Early hydrothermal alteration produced a potassic assemblage (orthoclase-biotite) in the central part of the stock, propylitic alteration occurred in the peripheral parts of the stock, contemporaneously with potassic alteration, and phyllic alteration occurred later, overprinting earlier alteration. The early hydrothermal fluids are represented by high temperature (350–520 °C), high salinity (up to 61 wt% NaCl equivalent) liquid-rich fluid inclusions, and high temperature (340–570 °C), low-salinity, vapor-rich inclusions. These fluids are interpreted to represent an orthomagmatic fluid, which cooled episodically; the brines are interpreted to have caused potassic alteration and deposition of Group I and II quartz veins containing molybdenite and chalcopyrite. Propylitic alteration is attributed to a liquid-rich, lower temperature (220–310 °C), Ca-rich, evolved meteoric fluid. Influx of meteoric water into the central part of the system and mixing with magmatic fluid produced albitization at depth and shallow phyllic alteration. This influx also caused the dissolution of early-formed copper sulphides and the remobilization of Cu into the sericitic zone, the main zone of the copper deposition in Sar-Cheshmeh, where it was redeposited in response to a decrease in temperature.     

Pyrite oxidation by Acidithiobacillus ferrooxidans at various concentrations of dissolved oxygen

Pyrite oxidation rates were examined at various concentrations of dissolved oxygen (DO) in the presence of the sulfur and iron oxidizer Acidithiobacillus ferrooxidans. Five different batch experiments were performed at room temperature for 75 days under various DO levels (273, 129, 64.8, 13.2, and ≤ 0.006 μM), containing pyrite grains (particle size 63–250 μm) and a modified 9K nutrient medium at pH 3. The reactors were inoculated with A. ferrooxidans. In all experiments, pH decreased with time and sulfur and iron were released to the solution, indicating pyrite oxidation at all DO levels. Pyrite oxidation rates (ca. 5 × 10^− 10 mol m^− 2 s^− 1 at 273 μM DO) from all experiments showed positive correlation with DO, Fe(III), and bacterial concentration. These rates were significantly slower than rates presented in other published studies, but this is probably due to the significantly greater Fe(III) concentration at lower pH in these previous studies. The results obtained in this study suggest that ferric iron reduction at the pyrite surface is the primarily mechanism for microbial pyrite oxidation in the presence of DO. The results from our study support the indirect mechanism of sulfide oxidation, where A. ferrooxidans oxidizes ferrous iron in the presence of DO, which then oxidizes pyrite.     

安庆月山铜钼矿床金的赋存状态与分布规律研究

应用光学显微镜、化学分析、电子探针和质子探针等多咎分析研究方法,系统地研究了安庆月山铜矿区铜牛井矿床不同类型的铜矿石中金的赋存状态。研究结果表明,金主要以独立矿物含银自然金、银金矿和自然金等赋存于石英脉型铜矿石、铜方矿化岩石型及闪长岩型铜矿石中,与之共生的矿物为同放、斑放、辉铜矿、辉钼矿和石英等;矿石中金的平均含量为0.3g/t,具有综合利用价值。金－银系列矿物中以含银自然金为主,粒度一般为0．15～0．30mm,大者0．5mm以上。金的矿化随着深度的增加而有明显的减弱趋势,同一水平面则有西低东高的趋向,但水平上的变化幅度比垂直方向小得多。这不仅为矿床伴生金的选冶工作提供了依据,而且对提高矿山经济效益及增加生产附加值．有着重要意义。     

Microbial mutualism in leaching of Cu−Ni sulfide concentrate

With tightening legislations on air pollution and decreasing grades of Cu and Ni ores, the mineral processing industry will have to find an alternative to smelting. One such hydrometallurgical alternative is bacterial leaching; it utilizes the action of Thiobacillus ferrooxidans on sulfide minerals converting them to metal sulfates which can be leached by acid produced by the bacteria. The metal is recovered by cementation, solvent extraction or electrowinning. In the present paper, the authors report their test work with a Cu-Ni sulfide concentrate and show that the mutualistic association of T. ferrooxidans with nitrogen-fixing bacteria Beijerinckia lacticogenes helps leach more metal faster in a leaching medium devoid of any added carbon or nitrogen source. Use of intentionally mixed bacterial culture in ore leaching has not been previously reported.     

Selective separation of pyrite from chalcopyrite and arsenopyrite by biomodulation using Acidithiobacillus ferrooxidans

This paper discusses the selective depression of pyrite from chalcopyrite and arsenopyrite by biomodulation using Acidithiobacillus ferrooxidans under natural conditions of pH. The effect of bacteria–mineral interaction on the surface charge of mineral and bacterial cell was studied by microelectrophoresis. Adhesion experiments were conducted to establish the relationship between cell adhesion to specific minerals and the electrokinetic behaviour of the minerals subsequent to interaction with cells. Effect of bacterial interaction on the xanthate-induced flotation of all the minerals was assessed. Adhesion of A. ferrooxidans on pyrite was rapid and tenacious and subsequent to interaction with cells, pyrite remained hydrophilic even in presence of xanthate collector. The collector, on the other hand, was able to render good flotability to chalcopyrite even after interaction with bacterial cells. Copper activated arsenopyrite was able to retain its hydrophobicity in presence of cells due to poor attachment kinetics of cells to the mineral surface. Thus, by suitably conditioning with the cells and collector, it was possible to effectively depress pyrite from chalcopyrite and arsenopyrite.     

Cu isotopic fractionation in the supergene environment with and without bacteria

The isotopic composition of dissolved Cu and solid Cu-rich minerals [δ⁶⁵Cu (‰) = (⁶⁵Cu/⁶³Cu_sample/⁶⁵Cu/⁶³Cu_std) - 1)*1000] were monitored in batch oxidative dissolution experiments with and without Thiobacillus ferrooxidans. Aqueous copper in leach fluids released during abiotic oxidation of both chalcocite and chalcopyrite was isotopically heavier (δ⁶⁵Cu = 5.34‰ and δ⁶⁵Cu = 1.90‰, respectively, [±0.16 at 2σ]) than the initial starting material (δ⁶⁵Cu = 2.60 ± 0.16‰ and δ⁶⁵Cu = 0.58 ± 0.16‰, respectively). Isotopic mass balance between the starting material, aqueous copper, and secondary minerals precipitated in these experiments explains the heavier isotopic values of aqueous copper. In contrast, aqueous copper from leached chalcocite and chalcopyrite inoculated with Thiobacillus ferrooxidans was isotopically similar to the starting material. The lack of fractionation of the aqueous copper in the biotic experiments can best be explained by assuming a sink for isotopically heavy copper present in the bacteria cells with δ⁶⁵Cu = 5.59 ± 0.16‰. Consistent with this inference, amorphous Cu-Fe oxide minerals are observed surrounding cell membranes of Thiobacillus grown in the presence of dissolved Cu and Fe.Extrapolating these experiments to natural supergene environments implies that release of isotopically heavy aqueous Cu from oxidative leach caps, especially under abiotic conditions, should result in precipitates in underlying enrichment blankets that are isotopically heavy. Where iron-oxidizing cells are involved, isotopically heavy oxidized Cu entrained in cellular material may become associated with leach caps, causing the released aqueous Cu to be less isotopically enriched in the heavy isotope than predicted for the abiotic system. Rayleigh fractionation trends with fractionation factors calculated from our experiments for both biotic and abiotic conditions are consistent with large numbers of individual abiotic or biotic leaching events, explaining the supergene chalcocites in the Morenci and Silver Bell porphyry copper deposits.     

X射线荧光光谱-X射线粉晶衍射-偏光显微镜分析12种产地铜精矿矿物学特征

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...     

Bioleaching potential of bacterial communities in historic mine waste areas

Microbial activity has the potential to alter all cultural heritage in mining and metallurgy, due to metal mobilization by leaching. This communication shows the consequences of the bioleaching ability of two natural enrichments on copper slag samples from a historic ore smelting site in Sangerhausen (Mansfeld, Südharz, Saxony-Anhalt, Germany). Enrichment cultures gained from mine drainage were dominated by either the iron and sulfur-oxidizing Acidithiobacillus ferrivorans, or by the iron-oxidizing Leptospirillum. During 35 days of bioleaching in media containing copper slag pulp, inoculated with these enrichments, the change in pH and solubilized metal concentrations of the systems were monitored. Both bacterial strains were completely different from each other in their pattern of pH variation and rates of metal solubilization. The maximum removal of Cu (1725 mg/l) and Zn (715 mg/l) from copper slag substrate was achieved with enrichment culture of A. ferrivorans SCUT-1. However, maximum Mn (207 mg/l), Pb (86 mg/l), and Ni (75 mg/l) removal was observed with enrichment culture of Leptospirillum strain YQP-1. Implications for metal mobilization along with alteration of artifacts from not only historic mining areas but also aspects of decontamination and remediation are discussed.     

Geology and Re-Os Geochronology of Mineralization of the Miduk Porphyry Copper Deposit, Iran

The Miduk porphyry copper deposit is located in Kerman province, 85 km northwest of the Sar Cheshmeh porphyry copper deposit, Iran. The deposit is hosted by Eocene volcanic rocks of andesitic–basaltic composition. The porphyry‐type mineralization is associated with two Miocene calc‐alkaline intrusive phases (P1 and P2, respectively). Five hypogene alteration zones are distinguished at the Miduk deposit, including magnetite‐rich potassic, potassic, potassic–phyllic, phyllic and propylitic. Mineralization occurs as stockwork, dissemination and nine generations (magnetite, quartz–magnetite, barren quartz, quartz‐magnetite‐chalcopyrite‐anhydrite, chalcopyrite–anhydrite, quartz‐chalcopyrite‐anhydrite‐pyrite, quartz‐molybdenite‐anhydrite ± chalcopyrite ± magnetite, pyrite, and quartz‐pyrite‐anhydrite ± sericite) of veinlets and veins. Early stages of mineralization consist of magnetite rich veins in the deepest part of the deposit and the main stage of mineralization contains chalcopyrite, magnetite and anhydrite in the potassic zone. The high intensity of mineralization is associated with P2 porphyry (Miduk porphyry). Based on petrography, mineralogy, alteration halos and geochemistry, the Miduk porphyry copper deposit is similar to those of continental arc setting porphyry copper deposits. The Re‐Os molybdenite dates provide the timing of sulfide mineralization at 12.23 ± 0.07 Ma, coincident with U/Pb zircon ages of the P2 porphyry. This evidence indicates a direct genetic relationship between the Miduk porphyry stock and molybdenite mineralization. The Re‐Os age of the Miduk deposit marks the main stage of magmatism and porphyry copper formation in the Central Iranian volcano‐plutonic belt.     

Weathering of phlogopite in simulated bioleaching solutions

The purpose of this study was to examine structural alterations of finely ground phlogopite, a trioctahedral mica, when exposed to acid, iron- and sulfate-rich solutions typical of bioleaching systems. Phlogopite suspensions were supplemented with ferrous sulfate and incubated with iron- and sulfur-oxidizing bacteria (Acidithiobacillus ferrooxidans) at 22 °C. As bacteria oxidized ferrous iron, ferric iron thus formed partially precipitated as K-jarosite. K-jarosite precipitation was contingent on the preceding ferrous iron oxidation by bacteria and the release of interlayer-K from phlogopite. This chemically and microbially induced weathering involved alteration of phlogopite to a mixed layer structure that included expansible vermiculite. The extent of phlogopite weathering and structure expansion varied with duration of the contact, concentration of ferrous iron and phlogopite, and the presence of monovalent cations (NH₄⁺, K⁺, or Na⁺) in the culture solution. NH₄⁺ and K⁺ ions (100 mM) added to culture suspensions precipitated as jarosite and thereby effectively prevented the loss of interlayer-K and structural alteration of phlogopite. Additional Na⁺ (100 mM) was insufficient to precipitate ferric iron as natrojarosite and therefore the precipitation was coupled with interlayer-K released from phlogopite. When ferrous iron was replaced with elemental sulfur as the substrate for A. ferrooxidans, the weathering of phlogopite was based on chemical dissolution without structural interstratification. The results demonstrate that iron oxidation and the concentration and composition of monovalent ions can have an effect on mineral weathering in leaching systems that involve contact of phlogopite and other mica minerals with acid leach solutions.     

德兴铜厂斑岩铜矿脉体类型、分布规律及其对成矿的指示意义

德兴铜矿是中国东部重要的大型斑岩铜矿,由朱砂红、铜厂和富家坞等3个矿床组成。在详细的野外脉体填图基础上,文章把德兴铜厂斑岩铜矿的成矿脉体划分为A脉、B脉、D脉和H脉等4种类型。研究发现,A脉的形成与钾化蚀变有关,脉体不规则且不连续,以粒状石英±钾长石±黑云母±磁铁矿±少量黄铁矿±少量黄铜矿的矿物组合为特征;B脉的形成与钾质硅酸盐水解有关,脉体较规则且连续,以石英±辉钼矿±黄铜矿±黄铁矿的矿物组合为特征,石英颗粒呈典型的梳状或长柱状对称于脉壁生长;D脉的形成与石英-绢云母化蚀变有关,以黄铁矿±石英±黄铜矿的矿物组合为特征,脉壁发育绢云母晕;H脉的形成与碳酸盐化有关,以方解石±赤铁矿±黄铁矿±黄铜矿的矿物组合为特征。这4种脉体分别记录了成矿流体演化至不同阶段,热液蚀变作用的特点及其与Cu-Mo硫化物沉淀的关系。脉体的宽度-间距定量统计分析表明,脉体宽度(T)服从于幂次分布定律;脉体间距(S)服从于负指数分布或介于对数正态分布与负指数分布之间。脉体宽度分维值D值(0.91~1.35)普遍>1,反映脉体系统的连通性较差,矿化程度较弱。脉体间距变差系数Cν值(0.49~0.92)均<1,说明脉体簇生聚集程度较低,矿化程度较弱;处于脉体聚集中心的脉体,代表着热液流体运移的通道,制约着其他脉体的展布。