Carbonate Gangue Minerals Research Articles

The selective flotation separation of apatite from dolomite and calcite utilizing a combination of 2-chloro-9-octadecenoic acid collector and sodium pyrophosphate depressant

In apatite flotation, oleic acid is a commonly used fatty acid collector but is limited by its selectivity and solubility. Acknowledging the reactivity of the α-C atom within oleic acid molecular structure, this study introduces a Cl atom at this site, leading to the synthesis of a novel collector, 2-chloro-9-octadecenoic acid (2-Cl-9-ODA). This collector is utilised in the flotation separation of apatite from its associated carbonate gangue minerals, dolomite and calcite. Flotation experiments reveal that the application of 2-Cl-9-ODA collector, in conjunction with sodium pyrophosphate (NaPP) inhibitor, facilitates the effective separation of these three minerals. Analysis on these mineral surface solubilities, augmented by NaPP, illustrates a solubility sequence: calcite surpasses dolomite, which marginally exceeds apatite. Interestingly, this sequence inversely matches the flotation recoveries, suggesting the superior recoveries of apatite over dolomite and significantly over calcite. The inhibition effect of NaPP on dolomite and calcite flotations is inferred to associate closely with the scarcities of the surface Ca2+ ions. Moreover, adsorption quantity and zeta potential experiments indicate that NaPP depressant significantly reduces the adsorption amounts of 2-Cl-9-ODA on dolomite and calcite surfaces, while barely affecting its adsorption on apatite. First-principles calculations show that the Cl atom introduction allows 2-Cl-9-ODA collector to adopt a parallel adsorption configuration on the mineral surfaces, decreasing its collecting abilities. This research offers theoretical underpinnings for the industrial use of 2-Cl-9-ODA collector in apatite flotation and delivers key understandings for the advancement of groundbreaking apatite flotation collectors.

The base metal sulfide and Ni–Co arsenide-bearing veins of Valsassina, Lombardy, Italy: a preliminary study

Abstract Valsassina (Lombardy, Northern Italy) is located in the Lombard Southern Alps and is characterised by the presence of a metamorphic basement, by a major late Variscan intrusive complex and by Carboniferous–Permian volcano-sedimentary cover units. These rocks host a pervasive system of inadequately studied mineralised veins. These veins are characterised by base metal (Pb, Zn, Cu and Fe) and complex polymetallic assemblages. In this study, we have investigated the ore textures, mineral compositions of sulfides and sulfosalts (by EMPA–WDS and LA–ICP–MS analyses), and stable isotopes (C and O) in carbonate gangue minerals of various mineralised veins to determine the conditions of deposition of these ore deposits. Two different vein families can be recognised in Valsassina: NNW–SSE veins characterised by a complex polymetallic sulfide–sulfosalt assemblage, also with Ni–Co–Fe arsenides and other Ag–Bi-bearing minerals; and NE–SW veins with a simpler, base metal sulfide assemblage. The Ni–Co-bearing NNW–SSE veins have some distinctive features of the ‘five-element vein’ type deposits, with the Ni–Co–Fe arsenide ore stage pre-dating a sulfide-tetrahedrite-dominated ore stage. LA–ICP–MS data for pyrite and sphalerite, and stable isotopic compositions (C and O) of the carbonate gangue minerals, show no clear differences between the two families of veins, which are probably linked genetically. The isotopic compositions of the Valsassina vein carbonates are closely comparable with the signature of several major five-element ore districts. Preliminary temperature estimates for the Valsassina vein systems were based on the sphalerite composition, applying the GGIMFis geothermometer. The estimated temperatures for the sulfide-dominated ore stage post-dating the Ni–Co minerals precipitation range between 100 and 250°C. The crosscutting relationships, observed for all the veins with the host rocks, suggest a possible late to post Variscan (late Permian) age, making these vein systems comparable with other late–post Variscan polyphase hydrothermal events affecting large sectors of the Southern Alpine domain.

Fluid Origin and Evolution of the Roc Blanc Silver Deposit (Jebilet Massif, Variscan Belt, Morocco): Constraints from Geology and Fluid Inclusions

The Roc Blanc Pb-Zn-Ag-Au vein deposit is located in the NW of Marrakech, in the Central Jebilet massif. It is spatially related to Bramram-Tabouchennt-Bamega (BTB) granodioritic pluton (ca. 330 Ma) metamorphism aureole. The main veins hosted in black shales are oriented N-S to NNW-SSE. Pb-Zn-Ag-Au ore is associated with quartz, chlorite, sericite, and carbonate gangue minerals. Two major stages of ore deposition were distinguished. The preore stage (stage I) comprises two quartz-mineralised vein generations with Fe, As, Zn, and Cu ores (vg1 and vg2). The main ore stage (stage II) consists mainly on Ag, Au, Pb, Zn, Cu, and Sb ores, which is hosted by carbonaceous vein (vg3) and by two late quartz generations veins (vg4 and vg5 with a geodic quartz). Three types of fluid inclusions have been recognized in silver mineralisation bearing quartz veins according to petrographic investigations, microthermometry, and Raman spectroscopy studies: (i) liquid-rich H2O-N2-CH4±CO2-(salt) fluid inclusions (type 1), (ii) vapour-rich H2O-CO2-CH4-N2-(salt) fluid inclusions (type 2), and (iii) aqueous H2O-(salt) fluid inclusions (type 3). The interpretation of fluid inclusion data shows a mixing of two fluids that are metamorphic and surface to subsurface origin, trapped at boiling state. The first mineralised stage was deposited at 350 ± 20 ° C (this temperature of ore deposition was supported also by chlorite geothermometry) with salinity of 13.7 wt% NaCl equiv., while the deposition of the argentiferous stage, which consists of the main economic mineralisation of the Roc Blanc deposit, occurs during decreasing temperature at 150°C with a salinity of 12.1 wt% NaCl equiv. The all-mineralised ore was deposited at relatively low pressure, below ~1-1.1 kbar. So, fluid dilution and cooling are probably the main factor for silver deposition in the Roc Blanc polymetallic vein deposit. In addition, fluid inclusion studies reveal that the mineralising fluid corresponds to a mixture of metamorphic fluid (H2O-CH4-N2-CO2) with surface to subsurface aqueous gas-free fluids (H2O-salt, meteoric, or brine).

Study of the effect of pH, conditioning and flotation time on the flotation efficiency of phosphate ores by a soybean oil collector

The mid-low grade of phosphate ore, rich by the silicate and carbonate gangue minerals needs a special treatment using the flotation process. Where the collectors play a pivotal role. This study was conducted to enrich an untreated phosphate ore (without washing, desliming, hydrocycling, etc.), with an eco-friendly and economic collector based on soybean oil. Different analytical techniques such as UV-Visible, ATR-FTIR spectrometric and XRD were used in order to analyse and characterize the flotation products. The effects of the parameters, pulp pH, conditioning time and flotation time on gangue removal efficiency by flotation, were investigated. Flotation tests were applied for granulometric class (90 mm to 125 µm). Consequently, a good quality phosphate concentrate was obtained in an acidic medium (pH = 4.05) with 1 g of soybean oil soap collector, 20 min flotation time, 10 min conditioning time, 0.17 L×min-1 air superficial velocity, 800 rpm at 25℃ and 6% solid content. The concentrate contained 29.0% phosphorus pentoxide (P2O5), with a recovery of 94.5% from a feed sample containing about 24.5% P2O5.

Copper Extraction from Oxide Ore of Almalyk Mine by H2SO4 in Simulated Heap Leaching: Effect of Particle Size and Acid Concentration

In this investigation, a laboratory-scale study to extract copper (Cu) from its oxide ore (0.425–11.2 mm particle size) was conducted using varied sulfuric acid (H2SO4) concentrations (0.05–0.5 M) as a lixiviant. Through a physicochemical and mineralogical analysis of real field ore samples from the Almalyk mine heap site (Tashkent, Uzbekistan), malachite was identified as a Cu-bearing mineral. Extraction rates were analyzed according to the ore particle size and acid concentration. The Cu extraction with the smallest particle size (in 24 h) varied between 76.7% and 94.26% at varied H2SO4 concentrations (0.05–0.5 M). Almost half (50%) of Cu was extracted from the ore within 4 and 72 h of contact time for 0.425–2 mm and 5.6–11.2 mm particle sizes, respectively, using 0.15 M H2SO4. Weeklong leaching experiments with 0.5 M H2SO4 revealed a higher copper extraction rate (≥73%) from coarse ore particles (5.6–11.2 mm). Along with the copper extraction, iron (29.6 wt%), aluminum (70.2 wt%), magnesium (85.4 wt%), and calcium (44.4 wt%) were also leached out considerably through the dissolution of silicate and carbonate gangue minerals. In this study, an 80.0–94.26% copper extraction rate with reduced acid consumption (20%) proved to be a cost-effective approach.

Mineral bioflotation optimization: Comparison between artificial neural networks and response surface methodology

The present work studied the fundamental of polynomial modeling and artificial neural network (ANN) techniques applied to the bioflotation of apatite, calcite and dolomite using the Rhodococcus opacus biosurfactant. Both techniques were used to model the bioflotation process and optimize some bioflotation parameters (pH and biosurfactant concentration). A full quadratic model optimized with genetic algorithm (GA) and a three-layer feedforward neural network were used to describe the mineral recovery. Different training algorithms and activation functions were tested to gather to an ANN with the best generalization capacity. Although the variation of the sigmoid activation function did not lead to a considerable change in the robustness of the ANN, the use of standard numerical training algorithms produced ANN models with better accuracy. ANN models demonstrated higher adequacy to describe and predict the mineral recovery than polynomial models. For all mineral studied, mineral recovery increased for a more acidic medium and for a higher biosurfactant concentration (BC). BC exhibited a higher effect on mineral recovery than pH, showing pH an increasing effect on mineral recovery as the optimal BC values were approached. Rhodococcus opacus biosurfactant demonstrated to be a promising solution for the separation of carbonate gangue minerals from phosphate ores.

Novel approach for processing complex carbonate-rich copper-cobalt mixed ores via reverse flotation

The vast majority of current global production of cobalt from primary sources originates from extraction of Cu-Co sediment-hosed deposits in the Democratic Republic of Congo. With the progressive depletion of oxidic supergene mineralisation, many operations are progressively starting to extract sulphide ore at depth. Ore in the transition zone between oxides and sulphides usually hosts both oxide and sulphide mineralisation which is extremely difficult to process by conventional flotation. These mixed ores are complex to process by flotation alone because carbonate minerals, such as dolomite and magnesite, may represent a significant proportion of the gangue. Hence, mixed ores are usually processed through flotation of sulphides followed by oxide flotation using controlled potential sulphidisation (CPS) and further processing via acid leaching. The main challenges associated with carbonate-rich mixed ores are the low recovery of cobalt, mostly due to cobalt present in oxide minerals, the floatability of the carbonate gangue minerals, which can make up to 50% of the concentrate, and technical difficulties with regards to industrial application of CPS. This study investigates alternative options to the classic two-step CPS flotation route, including direct reverse flotation of the carbonate gangue at neutral or acid pH, as well as a two-step combined sulphide-reverse flotation route. The latter, including a sulphide flotation stage at neutral pH, followed by an acidic reverse flotation stage at pH 4.5–5, increased the overall copper and cobalt recoveries. The best performance is achieved with reverse flotation, using Na-Oleate and a mixture of phosphoric and sulphuric acid (ratio of 4:1). Overall Cu-Co recoveries of 93.5% and 85.1% respectively were achieved. It is postulated that phosphoric acid acts as a depressant of the Cu-Co oxide minerals through surface passivation while enabling selective flotation of magnesite and dolomite. Further investigation into the effect of phosphoric acid on flotation of these minerals is required. Overall, the results suggest that, following flotation of sulphides, an acidic reverse flotation stage increases the global Cu-Co recovery while producing a concentrate which is suitable for further processing by flotation or acid leaching. Hence, the suggested combined approach could be a viable alternative to aforementioned CPS stage in Cu-Co oxide-sulphide mixed ores flotation plants, especially in operations where the mixed ore contains significant proportions of carbonate gangue minerals.

Study on the effect of collector and inhibitor acid on the floatability of collophane and dolomite in acidic media by TOF‐SIMS and XPS

Most of the phosphate ore in southern China is contained within siliceous dolomite phosphate rock, and more than 90% of it is medium and low‐grade collophane. Reverse flotation of carbonate gangue minerals (dolomite) from phosphate in acidic media is still the most economical method for the reduction of carbonate in collophane concentrates. It has been recognized that the collophane and dolomite in acidic media affect the surface properties of minerals, thereby affecting their flotation properties. In this paper, HCl and H3PO4 were used as regulators or inhibitors to study the flotation behaviour of collophane and dolomite. The inhibition mechanism of collophane and dolomite in two acid media was studied by time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) and X‐ray photoelectron spectroscopy (XPS) analyses. It was found that the addition of an inhibiting acid can partially depress the collophane and improve the flotation of dolomite, thus achieving their flotation separation, and the inhibition effect of H3PO4 on collophane is better than that of HCl. And it was found by TOF‐SIMS analysis that the increase in acid concentration did not reduce the adsorption concentration of the collector, and the main reason for the inhibition was not the decrease in the adsorption concentration of the collector. The adsorption capacity of collector on dolomite surface with H3PO4 is greater than that with HCl. The XPS test indicated that metaphosphate (PO3−1) is the pivotal ion for depressing collophane under acid conditions.

The effect of carbon dioxide and nitrogen on pyrite surface properties and flotation response

In 1997 Newmont USA Ltd. introduced the N2TEC process for the flotation recovery of auriferous pyrite and other sulfide minerals in Carlin type ores, using nitrogen as the flotation gas, and low pH to prevent oxidation and hydrolysis of the pyrite surface. However, increased amounts of carbonate gangue minerals in certain Carlin type ores adversely affect the flotation recovery due to difficulties with pH control in the presence of carbonate minerals, i.e. calcite, dolomite, etc. Subsequently, it was discovered that by using CO2 for flotation, the pH of the system can be more effectively controlled, and consequently the recovery and rate of pyrite flotation can be improved significantly.In our current laboratory research on pyrite flotation chemistry these results were confirmed, as both fresh and oxidized pyrite particles exhibited an increased flotation response in CO2 saturated solution. It was found that the water contact angle at the pyrite surface increased in CO2 and N2 saturated solutions, while surface oxidation and bubble attachment time decreased. In addition to decreased surface oxidation and the influence of pH on surface hydrolysis, the significance of bubble attachment phenomena in these CO2 flotation systems helps to explain the improved flotation response.

Effect of Depressants and Temperature on Bastnaesite and Monazite Flotation Separation from a Canadian Rare Earth Element (REE) Ore

A full factorial experimental design was conducted to investigate the effect of temperature and depressants on the flotation of monazite and bastnaesite from carbonate gangue minerals. Temperature, sodium silicate, and guar gum dosage were examined. Mineral reconstruction from energy-dispersive x-ray fluorescence (EDXRF) data was performed to quantify bastnaesite, monazite, and gangue mineral recoveries. Bastnaesite and monazite both follow first-order rates of recovery, with bastnaesite recovering faster and to a larger extent than monazite. The main gangue minerals were depressed together. Optimal separation efficiency was achieved using a larger Na2SiO3 dosage (2400 g/t), no guar gum addition, and a high temperature (75 °C). The rate of bastnaesite recovery increased with the temperature, while sodium silicate improved the ultimate recovery. An economic analysis was performed to evaluate the impact of increasing Rare Earth Element (REE) recovery by allowing a lower grade concentrate to be generated. Despite the high value of REEs, increasing recovery by producing a concentrate bearing more than 68 wt % carbonaceous gangue was uneconomical.

Carbonate-related metallic and non-metallic mineralization within and proximal to granites (Fichtelgebirge Pluton, Germany): “Mantle-crust marker mineralization”

Metacarbonate rocks (marble, calcsilicate rock, skarn) hosting strata- and structurebound Fe-, As-Sb, Bi-, Ni-Co, Cu-Pb-Zn, U-, W- ore minerals as well as talc, clay minerals, barite and fluorite are widespread in the country rocks south of the collisional calc-alkaline felsic to intermediate intrusive rocks of the Fichtelgebirge Pluton, Germany. At its western rim, thrustbound and vein-type mineral assemblages with Au-As-Sb and F-Ba minerals associated with carbonate gangue minerals developed. Only recently, a calcite-hosted Sb mineralization was encountered in a deep-seated lineamentary fault zone cutting through metaultrabasic rocks along the northern edge of the granites. The same structure zone forms the loci of calcite-bearing U episyenite situated within this pluton. A composite geological, mineralogical and chemical (major and trace elements, REE, C- and O isotopes) study has been conducted to distinguish the heat and element source in subcrustal or deep-seated crustal areas and in the largely exposed granite complex. Only Sn-W skarn deposits are genetically related to the highly fractionated granitic members of the Variscan pluton. Pegmatite skarn has a strong subcrustal component as to the heat source and the provenance of rare elements and a moderate crustal one as far as the silicates are concerned. Deep-seated fault zones were active over a rather long period of time and acted as conduits venting magmas and hydrothermal fluids from the waning stages of the Variscan deformation through the Neogene. Calcsilicate and carbonate mineral assemblages are an efficacious tool to constrain the physico-chemical regime in this mineral province, covering the temperature range from 745 °C down to 53 °C in a medium to low pressure regime at strongly varying redox conditions. The major and trace elements, the REE variation, the Ce and Eu anomalies as well as carbon and oxygen isotopes of the various mineral assemblages enable us to identify the fluid sources and depict the element concentration processes, e.g., mixing of fluids, connate fluid and meteoric fluid interaction. From the economic point of view, the mineralizing system is most prospective for rare element deposits, talc, kaolinite-group minerals, iron, and uranium. Accumulations of fluorite and barite are subeconomic in mineral assemblages inside as well as outside the granites, while base metals and precious metals are only of mineralogical interest.

Ambient Temperature Flotation of Sedimentary Phosphate Ore Using Cottonseed Oil as a Collector

The mid-low grade sedimentary phosphate ore, abundant in silicate and carbonate gangue minerals, exhibits a poor processability. It is conventionally enriched using high temperature flotation to remove silicate gangues with fatty acid as a collector. Cottonseed oil has been proved to be an efficient collector for achieving ambient temperature flotation of the sedimentary phosphate ore used in this study. Flotation kinetics was investigated to ascertain the excellent collecting performance of cottonseed oil, as compared with oleic acid, and the phosphate flotation fitted well with the first-order flotation model. Based on the analysis of flotation reagent effect on the direct flotation process using the response surface methodology (RSM), a closed circuit of direct-reverse flotation for stepwise removing silicate and carbonate gangues from the sedimentary phosphate ore was established. Consequently, a required high quality of phosphate concentrate containing 30.16% P2O5 was obtained, with a recovery of 90.90%. Scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD) of the flotation products confirmed that the majority of silicate and carbonate gangues were effectively removed from the concentrate products.

A salt diapir-related Mississippi Valley-type deposit: the Bou Jaber Pb-Zn-Ba-F deposit, Tunisia: fluid inclusion and isotope study

The Bou Jaber Ba-F-Pb-Zn deposit is located at the edge of the Bou Jaber Triassic salt diapir in the Tunisia Salt Diapir Province. The ores are unconformity and fault-controlled and occur as subvertical column-shaped bodies developed in dissolution-collapse breccias and in cavities within the Late Aptian platform carbonate rocks, which are covered unconformably by impermeable shales and marls of the Fahdene Formation (Late Albian–Cenomanian age). The host rock is hydrothermally altered to ankerite proximal to and within the ore bodies. Quartz, as fine-grained bipyramidal crystals, formed during hydrothermal alteration of the host rocks. The ore mineral assemblage is composed of barite, fluorite, sphalerite, and galena in decreasing abundance. The ore zones outline distinct depositional events: sphalerite-galena, barite-ankerite, and fluorite. Fluid inclusions, commonly oil-rich, have distinct fluid salinities and homogenization temperatures for each of these events: sphalerite-galena (17 to 24 wt% NaCl eq., and Th from 112 to 136 °C); ankerite-barite (11 to 17 wt% NaCl eq., and Th from 100 to 130 °C); fluorite (19 to 21 wt% NaCl eq., Th from 140 to 165 °C). The mean temperature of the ore fluids decreased from sphalerite (125 °C) to barite (115 °C) and increased during fluorite deposition (152 °C); then decreased to ∼110 °C during late calcite precipitation. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of fluid inclusions in fluorite are metal rich (hundreds to thousands ppm Pb, Zn, Cu, Fe) but the inclusions in barite are deficient in Pb, Zn, Cu, Fe. Inclusions in fluorite have Cl/Br and Na/Br ratios of several thousand, consistent with dissolution of halite while the inclusions analysed in barite have values lower than seawater which are indicative of a Br-enriched brine derived from evaporation plus a component of halite dissolution. The salinity of the barite-hosted fluid inclusions is less than obtained simply by the evaporation of seawater to halite saturation and requires a dilution of more than two times by meteoric water. The higher K/Na values in fluid inclusions from barite suggest that the brines interacted with K-rich rocks in the basement or siliciclastic sediments in the basin. Carbonate gangue minerals (ankerite and calcite) have δ13C and δ18O values that are close to the carbonate host rock and indicate fluid equilibrium between carbonate host rocks and hydrothermal brines. The δ34S values for sphalerite and galena fall within a narrow range (1 to 10 ‰) with a bulk value of 7.5 ‰, indicating a homogeneous source of sulfur. The δ34S values of barite are also relatively homogeneous (22 ‰), with 6 ‰ higher than the δ34S of local and regional Triassic evaporites (15 ‰). The latter are believed to be the source of sulfate. Temperature of deposition together with sulfur isotope data indicate that the reduced sulfur in sulfides was derived through thermochemical sulfate reduction of Triassic sulfate via hydrocarbons produced probably from Late Cretaceous source rocks. The 87Sr/86Sr ratio in the Bou Jaber barite (0.709821 to 0.711408) together with the lead isotope values of Bou Jaber galena (206Pb/204Pb = 18.699 to 18.737; 207Pb/204Pb = 15.635 to 15.708 and 208Pb/204Pb = 38.321 to 38.947) show that metals were extracted from homogeneous crustal source(s). The tectonic setting of the Bou Jaber ore deposit, the carbonate nature of the host rocks, the epigenetic style of the mineralization and the mineral associations, together with sulfur and oxygen isotope data and fluid inclusion data show that the Bou Jaber lead-zinc mineralization has the major characteristics of a salt diapir-related Mississippi Valley-type (MVT) deposit with superimposed events of fluorite and of barite deposition. Field relations are consistent with mineral deposition during the Eocene–Miocene Alpine orogeny from multiple hydrothermal events: (1) Zn-Pb sulfides formed by mixing of two fluids: one fluid metal-rich but reduced sulfur-poor and a second fluid reduced sulfur-rich; (2) barite precipitation involved the influx of a meteoric water component that mixed with a barium-rich fluid; and (3) fluorite precipitated from a highly saline fluid with higher temperatures.

Fluid mixing as the mechanism of formation of the Dajing Cu-Sn-Ag-Pb-Zn ore deposit, Inner Mongolia

Dajing Cu-Sn-Ag-Pb-Zn ore deposit, in the Inner Mongolia Autonomous Region of China, is a fissure-filling hydrothermal ore deposit. The δ D values of quartz-hosted inclusion water are centered at −100‰ — −130‰. The δ 34 S values of sulfide ore minerals and δ 13 C values of carbonate gangue minerals vary from −0.3‰ to 2.6‰ and from −2.9‰ to −7.0‰, respectively. Integrated isotopic data point to two major contributions to the mineralizing fluid that include a dominant meteoric-derived groundwater, and sulfur and carbon species from hypogene magma. Linear trends are exhibited on the gaseous H 2 O versus CO 2 plot, and plots of CO, N 2 , CH 4 , and C 2 H 6 . It is shown by quantitative simulation that magma degassing cannot explain the linear trends. Hence, these linear trends are interpreted in terms of mixing of CO 2 -rich magmatic fluid with meteoric-derived groundwater. The groundwater circulated in Paleozoic sedimentary rocks and absorbed CO, N 2 , CH 4 , C 2 H 6 and radiogenic Ar from organic matter. Cooling effects resulting from mixing have caused the precipitation of ore minerals.

Raman microprobe mineral identification

Raman spectroscopy and associated imaging techniques are generally non-destructive, and can be used to identify a wide range of minerals and gemstones. Raman is a sensitive technique which requires minimal sample preparation and can be used on massive specimens from lump ore to fine powders and liquids. Since glass and water are weak Raman scatterers, spectra from minerals can be obtained from samples in air, through glass, and/or immersed in water. Examples of the application of Raman spectroscopy to minerals of importance in mineral processing are discussed. These include: detection of minerals of light elements such as carbon and fluorine; distinguishing between polymorphs such as those of iron sulfides; characterizing sulfides containing minor elements such as iron in sphalerite; and the identification of silicate, oxide, and carbonate gangue minerals. The Raman microprobe also permits Raman imaging and mapping of surfaces and inclusions. Imaging of diamond is presented as an example of this technique.

Petrogenetic and Metallogenetic Background of the Dajing Cu–Sn–Ag–Pb–Zn Ore Deposit, Inner Mongolia, and Characteristics of the Mineralizing Fluid

Abstract: The Dajing Cu–Sn–Ag–Pb–Zn ore deposit, Inner Mongolia of China, is a fissure‐filling hydrothermal ore deposit that occurs within the Upper Permian Linxi group. No magmatic pluton and volcanic rocks outcrop on the surface of the deposit. Most of ore veins show clear‐cut boundary with country rocks. Wallrock alterations that include silicification, carbonation, chlori–tization, and sericitization are generally weak and occur in the close vicinity of ore veins.Mineralization is divided into three stages: (1) cassiterite–arsenopyrite–quartz stage, (2) sulfide stage, and (3) Pb–Zn–Ag–carbonate stage. These mineralization stages have distinct ranges of homogenization temperatures, 290–350C for Stage 1, 260–320C for Stage 2, and 150–250C for Stage 3. However, salinities for Stages 1, 2, and 3 overlap and range between 2.2 and 10.4 wt % NaCl equivalent. The dD values relative to V‐SMOW of inclusion water from quartz are lower than –88% and centered at –100 to –130%. The δ34S values relative to CDT of sulfide ore minerals and δ13C values relative to PDB of carbonate gangue minerals, vary from –0.3 to +2.6%, and from –7.0 to –2.9%, respectively. Integrated isotopic data point to two major contributions to the mineralizing fluid that include a dominant meteoric‐derived water and the other from hypogene magma for sulfur and carbon species.Analyses of inclusion gas and liquid compositions are performed. The H2O and CO2 are the two most abundant gaseous components, whereas SO42‐ and Cl‐, and Na+, Ca2+, and K+ are the major anions and cations, respectively. A linear trend is shown on the gaseous H2O versus CO2 plot. Phase separation is excluded as cause for the trend on the basis of isotope data and fluid inclusion microthermometry. In addition, a weak wallrock alteration does not support fluid‐rock interaction as an efficient mechanism. Hence, the linear H2O–CO2 trend is interpreted in terms of absorption or dilution of CO2–dominant magmatic vapor by meteoric‐derived water. Cooling effects resulting from dilution may have caused precipitation of ore minerals.Major and trace element compositions of regional granites show a high‐K calc–alkaline characteristics and an arc–affinity. Lead isotopic compositions of galena samples from the Dajing deposit exhibit elevated U/Pb and Th/Pb ratios. These characteristics indicate a common source of supra subduction zone mantle wedge for regional granites and metals from the Dajing deposit.

Age and Origin of Base and Precious Metal Veins of the Coeur D'Alene Mining District, Idaho

Ore-bearing quartz-carbonate veins of the Coeur d’Alene mining district yield 87Sr/86Sr ratios of 0.74 to >1.60 for low Rb/Sr, carbonate gangue minerals, similar to current ranges measured in Middle Proterozoic, high Rb/Sr rocks of the Belt Supergroup. Stable isotope and fluid inclusion studies establish a genetic relationship between vein formation and metamorphic-hydrothermal systems of the region. These extraordinary 87Sr/86Sr ratios require accumulation of radiogenic 87Sr in a high Rb/Sr system over an extended period prior to incorporation of Sr into the hydrothermal veins. Evaluation of the age and composition of potential sources of highly radiogenic Sr indicates that the ore-bearing veins of the Coeur d’Alene district formed during the Cretaceous from components scavenged from rocks of the Belt Supergroup, the primary host rocks of the district. Proterozoic Pb isotope ratios observed in galena from many Coeur d’Alene veins were established when Pb separated from uranium during deposition or diagenesis of the Belt Supergroup at 1400 to 1500 Ma, possibly as disseminated syngenetic deposits. K-Ar and Rb-Sr apparent ages and δ 18O values of Belt Supergroup rocks decrease from the Coeur d’Alene district toward the Idaho and Kaniksu batholiths, approximately normal to the trends of metamorphic isograds, fold axes, foliation, and the major reverse faults of the district. Isoclinal folding, thrust faulting, high-temperature metamorphism, granitic plutonism, and regional-scale metamorphic-hydrothermal activity is documented in the region between 140 and 45 Ma, representing the only such combination of events in the Coeur d’Alene region subsequent to about 1300 Ma. The Sr and oxygen results and geologic evidence favor formation of the ore-bearing carbonate veins by fluids related to a complex metamorphic-hydrothermal system during the Cretaceous. Pb with Proterozoic isotopic compositions was probably mobilized and incorporated like other metals into the hydrothermal veins during this event. The ore-bearing veins were sheared and displaced during early Tertiary northwest-trending dextral strike-slip faulting along the Osburn fault and related structures of the Lewis and Clark line.

Geology and geochemistry of the Kokomo mining district, Colorado

The ores of the Kokomo mining district, Colorado, are Ag-Pb-Zn massive sulfide replacement deposits (mantos) controlled by northeast-striking, high-angle faults and hosted by limestone beds in the Pennsylvanian Minturn Formation. The Minturn Formation is as much as 1,830 m thick and consists of interbedded nonmarine, coarse clastic sedimentary rocks and thin marine limestones. The sedimentary section is greatly expanded by Cretaceous-Tertiary porphyritic granodiorite and quartz monzonite sills, dikes, and stocks.Hydrothermal alteration is dominated by skarns in calcareous sedimentary rocks centered on the Tucker Mountain area. Manto orebodies occur to the south in an updip direction distal to the skarns. Intrusive rocks throughout the Kokomo district have been affected by propylitic alteration. Argillic and sericitic alteration of sedimentary and intrusive rocks is restricted to areas immediately around the mantos and along faults that served as conduits for hydrothermal solutions. Mantos are surrounded by halos of siderite-manganosiderite, hydrothermal dolomite, and/or jasperoid in the limestone.Massive sulfide replacement ore exhibits banded and tabular textures very similar to ores at Leadville and Gilman, Colorado. Ore deposition occurred in the general sequence: jasperoid,; iron sulfides (pyrrhotite, marcasite, and pyrite) + siderite, quartz, high iron sphalerite, ferroan dolomite, galena, chalcopyrite and sulfosalts, barite, ferroan calcite, and calcite. Fluid inclusion analyses of quartz and carbonate gangue minerals indicate that temperatures averaged 350 degrees C during the early stages of ore deposition and decreased to about 160 degrees C during the late stages. Ore fluid salinities also decreased through the ore deposition event from 4.6 to 18 O and delta 18 C values compared to diagenetic dolomite due to isotopic exchange between limestones and hydrothermal fluids. Carbonate gangue minerals within the ore zone exhibit lower delta 18 O and delta 13 C values, and these values yield a calculated fluid delta 18 O (sub H 2 O) = 5.0 to 6.9 per mil, within the range for magmatic water. Sulfur isotope values of sulfide minerals range from -0.6 to + 0.8 per mil. The narrow range of delta 34 S values around 0 per mil suggests a magmatic sulfur source.The fission track age of the Kokomo ore system is about 40 Ma. Fission track dates are younger to the north and indicate a thermal center around Tucker Mountain. A porphyritic rhyolite plug on Tucker Mountain, described as a Pennsylvanian volcanic feature in previous literature, yields a fission track age of 39.5 Ma.The Kokomo stable isotope values, fluid inclusion homogenization temperatures, and salinities are comparable to data from other Leadville-type (magmatic hydrothermal) carbonate-hosted sulfide replacement deposits in the Colorado mineral belt, including Leadville and Gilman.

Metal concentrations and concomitant metal mobility in unsaturated mine and mill wastes

The shallow sediments in the Smelterville Flats portion of the Coeur d'Alene River Valley in north Idaho consist of a heterogeneous mixture of mine wastes and alluvium reworked during flood events. The wastes cover an area of approximately eight square kilometres. Atomic Absorption Spectroscopy and Inductively-Coupled Plasma analyses on mine waste-sediment samples collected to the depth of the water table show maximum metal concentrations of about 20% Fe, 12% Pb, 10% Zn, 3% Mn, 2.8% Al, 0.13% Cu, 0.1% Cd, 370 ppm As, 170 ppm Ag, 150 ppm Sb, and 70 ppm Ni. The positive correlation between Fe, Ca, and Mg concentrations and sample pH suggests that the carbonate gangue minerals (siderite, ferrodolomite, and ankerite) control the pH. Other metals that exhibit a positive correlation with sample pH also may be present in the carbonate minerals. Identification of factors that govern metal mobility suggests that: (a) the pH of the water in the uppermost aquifer plays a minor role in controlling the solubility of most metals in the solid waste samples; b) the carbonate gangue minerals buffer the ground water pH and hence the solubility of metal sulfides; c) solubility of the carbonate gangue minerals decreases under anaerobic conditions, thereby allowing the ground water pH to decrease; d) solubility of Pb, Zn, and Cd correlates directly to anaerobic conditions as opposed to aerobic conditions.

Stable isotopic composition of the hydrothermal fluids responsible for the Nanisivik Zn [sbnd]Pb deposits, Northwest Territories, Canada

Direct measurements of ° 18O and δD of water in inclusion fluids in sulfide and carbonate gangue minerals from the Nanisivik deposit are used to place constraints on the origin of the fluids responsible for hydrothermal mineralization. Values of δD of inclusion fluids in sphalerite and dolomite are near −50%, whereas those of inclusion fluids in two galena samples are much lower at −72 ± 3‰; δ 18O of inclusion fluids in sphalerite are −2.5 ± 3‰; dolomite inclusions are 2‰ lighter, perhaps due to post-trapping exchange with host dolomite. Dolomite-water fractionations calculated from the inclusion data are consistent with other estimates of temperature of deposition (70°C to 250°C). Previous isotopic studies by the same authors have shown that S in the ore was derived from coeval sea water SO 4. However, water in the hydrothermal fluid cannot have been trapped, unaltered sea water (either fresh or evaporated), nor coeval meteoric water (which would have resembled sea water), ultrafiltered sea water, or meteoric water. Values of δ 18O and δD of inclusions can best be explained by a scenario which includes: 1. infiltration or entrapment of either sea water, or meteoric water that has redissolved evaporitic SO 4; 2. exchange of the water with shales of the Arctic Bay Formation to lower δD, with subsequent leaching of the metals; and 3. further H isotope exchange with fluid or solid organic matter prior to entrapment.