Cu-Zn Mine Research Articles

Mechanisms of nitrogen isotope fractionation at an ancient black smoker in the 2.7 Ga Abitibi greenstone belt, Canada

Abstract The biological nitrogen (N) cycle on early Earth is enigmatic because of limited data from Archean (meta-)sediments and the potential alteration of primary biotic signatures. Here we further investigate unusual 15N enrichments reported in 2.7 Ga meta-sediments from the Abitibi greenstone belt, Canada, purportedly related to a 15N-enriched Archean atmosphere. Given that sediments from this region are contemporaneous with large-scale volcanogenic massive sulfide deposits, we utilize Cu and Zn contents to trace the effects of hydrothermal circulation on N isotope fractionation. We show that high δ15Nbulk values as high as +23‰ are associated with Cu-Zn mineralization, whereas unmineralized organic-rich shales exhibit much lower δ15Nbulk and δ15Nkerogen values. Moreover, we find a large offset between δ15Nbulk and δ15Nkerogen of as much as 17‰ and relate this to the addition of organic-bound N during the late-stage emplacement of organic-rich veins. We conclude that the previously reported high δ15N values are most parsimoniously explained by biotic and abiotic mechanisms rather than a 15N-enriched atmosphere. Crucially, both mechanisms require the presence of NH4+ in hydrothermal fluids, supporting the hypothesis that hydrothermal discharge was an important nutrient source for Neoarchean marine life.

Mineralization of the Liwu large-scale stratiform copper deposits in Sichuan Province, China: Constraints from fluid inclusions

The Liwu stratiform copper deposit is located in the NW Jianglang dome, western China. Current studies mainly focus on the genetic type and mineralization of this deposit. Detailed fluid inclusion characteristics of metallogenic period quartz veins were studied to reveal the ore-forming fluid features. Laser Raman analysis indicates that the ore-forming fluids is a H₂O-NaCl-CH₄ (-CO₂) system. Fluid inclusions microthermometry shows a homogenization temperature of 181–375°C and a salinity of 5.26%–16.99% for the disseminated-banded Cu-Zn mineralization; but a homogenization temperature of 142–343°C and a salinity of 5.41%–21.19% for the massive-veined Cu-Zn mineralization. These features suggest a medium–high temperature and a medium salinity for the ore-forming fluids. H-O isotopic data indicates that the ore-forming fluids were mainly from the metamorphic and magmatic water, plus minor formation water. And sulfur isotopic data indicates that sulfur was mainly derived from the formation and magmatic rocks. Metallogenesis of the disseminated-banded mineralization was mainly correlated with fluid mixing and water-rock reaction; whereas that of the massive-veined mineralization was mainly correlated with fluid boiling. The genetic type of the deposit is a medium-high temperature hydrothermal deposit related to magmatism and controlled by shear zones. This study is beneficial to understand the stratiform copper deposit.

In-situ trace element and S isotope compositions of sulfides from the Tonggou Cu deposit, Eastern Tianshan Orogen: Implication for ore-forming process

The Tonggou deposit is located in the western Bogda Orogen, the northern margin of Eastern Tianshan. Porphyry Cu and vein-type Cu-Zn mineralization are both developed in the Tonggou orefield. This well-preserved porphyry-vein system, therefore offers an excellent opportunity to evaluate the genetic relationship and ore-forming process between porphyry Cu and vein-type Cu-Zn mineralization. Porphyry mineralization consists of magnetite-quartz (P1) and chalcopyrite-quartz (P2) stages, whilst vein-type mineralization includes pyrite-quartz (V1), polymetallic sulfide-quartz (V2), and pyrite-calcite (V3) stages. Four pyrite generations are identified, including porphyry Cu ore-related (Py1) and vein-type Cu-Zn ore-related (Py2, Py3, and Py4) ones. In most cases, Py1 (stage P2) occurs as anhedral grains, Py2 (stage V1) as fine anhedral grains, Py3 (stage V2) as euhedral-subhedral grains, and Py4 (stage V3) as anhedral aggregates. The Sb content first decreases from Py1 to Py2, then increases from Py2 to Py3, and finally decreases from Py3 to Py4. Cobalt and Ni contents show opposite trend to that of Sb. The relatively high Sb but low Co-Ni contents in Py1 and Py3 indicate that the main ore stage (P2 and V2) environment was high oxygen fugacity and low sulfur fugacity. Moreover, the contents of Cu (Py1: avg. 4108 ppm, Py2: avg. 735 ppm, Py3: avg. 284 ppm, Py4: avg. 149 ppm) and Ag (Py1: avg. 204 ppm, Py2: avg. 11.1 ppm, Py3: avg. 6.29 ppm, Py4: avg. 2.98 ppm) gradually decrease from Py1 to Py4, indicating that the initial ore fluid was Cu-Ag rich. The δ34S values obtained are 4.6–6.8 ‰ (avg. 5.9 ‰; Py2), 5.7–7.4 ‰ (avg. 6.6 ‰; Py3), and 7.3–8.8 ‰ (avg. 8.1 ‰; Py4), which indicate that the sulfur of vein-type mineralization was initially derived from felsic magma, and subsequently mixed with strata sulfur. Furthermore, the similar δ34S range of Ccp1 (4.7–5.3 ‰) from porphyry ore and Ccp2 (3.3–4.8 ‰) from vein-type ore indicates that they have a similar felsic-magma-derived sulfur source. Combining with principal component analysis (PCA) of pyrite trace elements and REE patterns, the different pyrite generations can be divided into porphyry pyrite and vein-type pyrite, albeit with similar fluid source.Consequently, we suggest that the Tonggou porphyry and vein-type ores have similar ore-fluid source, and may belong to the same porphyry mineralization system with different ore-forming processes. Redox change may have played an important role in the metal enrichment and precipitation at Tonggou.

The Magmatic-Hydrothermal Ore-Forming Processes of the Tonggou Cu-Zn Deposit, NW China: Constraints from Magnetite Chemistry and Fluid Inclusions

The Tonggou deposit is a porphyry Cu and vein-type Cu-Zn mineralization system located in the Bogda Orogenic Belt, north of Eastern Tianshan. Systematic fluid inclusion analyses were performed on granular quartz from the magnetite–quartz stage and pyrite–chalcopyrite–quartz stage from the porphyry Cu mineralization. During the early stage of porphyry Cu mineralization, the ore-forming fluids were at high temperatures (450–501 °C) and high salinity (51.2–55.2 wt.% NaCl equiv.) H2O-NaCl hydrothermal fluids with fluid boiling. These fluids evolved to high temperature (412–450 °C) and intermediate to low salinity (8.3–14.2 wt.% NaCl equiv.) H2O-NaCl hydrothermal fluids during the pyrite–chalcopyrite–quartz stage. In addition, magnetite from the Tonggou deposit was studied as a marker for the ore-forming process evolution of porphyry and vein-type mineralization. Sampled magnetite can be divided into MagI (allotriomorphic magnetite from altered granodiorite), MagII (magnetite from altered granodiorite found in veinlets or as granular aggregates), MagIII (from the magnetite–quartz stage of porphyry mineralization), and MagIV (from the polymetallic sulfide–epidote–quartz stage of vein-type mineralization). Magnetite LA-ICP-MS data indicate a hydrothermal origin. The contents of Ti, Si, Al, and Ta are controlled by temperature, and these elements gradually decrease from MagI to MagIV. Moreover, fO2 has considerable influence on the substitution of Sn, V, and Mn in magnetite, and the contents of these elements generally decrease from MagI to MagIII—increasing only in MagIV. Indeed, high fO2 in the polymetallic sulfide–epidote–quartz stage (MagIV) of vein-type mineralization is shown by the presence of a replacement texture in ilmenite grains within hydrothermal magnetite. On the other hand, magnetite samples from the Tonggou deposit have relatively low Ti + V contents compared to other porphyry Cu deposits—plotting in the skarn field of the (Ti + V) vs. (Ca + Al + Mn) diagram—and shows negative correlations in the (Ti + V) vs. Sn diagram. These data indicate that the porphyry Cu mineralization at Tonggou formed at relatively lower fO2 conditions than the Tonggou vein-type mineralization and other typical porphyry Cu deposits. Finally, porphyry and vein-type mineralization at Tonggou are both sourced from the porphyry system, as a result of ore-forming fluid transfer to a different location.

Incorporation of sulphidic mining waste material in ceramic roof tiles and blocks

The demand for building and construction materials increases as the world population keeps growing, thus increasing the need of shelter, as a basic human need. This increasing demand for building and construction materials not only leads to higher demand for primary raw materials, such as clay or sand, but also to higher emissions of carbon dioxide that contribute to the greenhouse effect, leading us to the biggest and ongoing threat to life on earth: global warming. The potential use of secondary raw material sources, such as mining waste, in building and construction products not only minimises the ecological footprint of this sector but also minimises the pressure on the primary raw material sector, hence fostering the transition towards a more resource efficient and sustainable world. The goal of this study is to evaluate the potential use of uncleaned sulphidic mining tailing material from two inactive Pb-Zn (Plombières, Belgium) and Cu-Zn-Pb (Freiberg, Germany) mines, and uncleaned sulphidic mining waste rock material from an active Cu-Zn mine (Neves-Corvo, Portugal), in ceramic roof tiles and blocks taking into account production parameters (shaping, drying, and firing processes), product quality (technical, aesthetical, and chemical properties) and environmental compliance of secondary raw materials for use as building products. After a detailed physical, mineralogical, chemical, and thermal characterisation of the materials, blends for ceramic roof tiles and blocks were made by partly or totally replacing some primary raw materials (mainly clay and sand) by 4 different mining waste materials. Roof tile and block blends containing 5 wt% and 10 wt% mining waste materials, respectively, were produced on a lab scale. The required technical, aesthetical, and chemical properties for each ceramic product were evaluated. Freiberg tailing and Neves Corvo waste rock materials presented considerable amounts of sulphur and metal(loid)s. Moreover, technical, aesthetical, and chemical properties of the blends using these mining waste materials were not satisfying and the Neves Corvo waste rock materials have the disadvantage of needing a mechanical treatment (grinding and sieving) before integrating them into the ceramic blends. Therefore, the Freiberg tailing and both of the Neves Corvo waste rock materials are less suitable to replace primary raw materials in ceramic roof tile and block blends, even in smaller amounts (5 wt% and 10 wt%, respectively). In contrast, the Plombières fine tailing material was characterised by a low sulphur and metal(loid) content, as well as satisfying environmental performance. The roof tile and block blends, in which the Plombières tailing material was integrated, showed satisfying technical, aesthetical, and chemical properties. Consequently, the Plombières tailing material can be considered as the best fit to partly or totally replace primary raw materials in both ceramic roof tile and block blends.

The mineral deposits of Panama: Arc metallogenesis on the trailing edge of the Caribbean large igneous province

The mineral deposits of the Panama microplate are hosted by a composite volcano-plutonic island arc of Late Cretaceous to Quaternary age developed on an oceanic plateau, the Caribbean Large Igneous Province (CLIP), on the western, trailing edge of the Caribbean Plate. Large igneous provinces are formed by gold and chalcophile element-enriched, mantle plume-related magmas, which may explain the strong metal endowment of Panama of about 32 Mt copper and >984 t gold. The progressive collision of the Panama arc with South America since the middle Eocene resulted in deformation and oroclinal bending of the arc and metallogenic belts. In western Panama, the copper-gold belts young from south to north away from the subduction zone, whereas in eastern Panama the belts young from north to south. An Early Arc of late Campanian to Eocene age (71-34 Ma) developed related to northerly subduction of the Farallon Plate. It has submarine Si-Mn-Fe exhalite deposits in the Nombre de Dios and Montijo belts with showings of Au-rich VMS Cu-Zn mineralization. The San Blas porphyry Cu-Au belt formed in eastern Panama (Rio Pito and other porphyry Cu-Au prospects), while the western continuation, offset by 200 km sinistrally to the Azuero Belt, hosts high sulphidation epithermal Au-Cu deposits (Cerro Quema and others) in porphyry lithocaps.The arc migrated to the northern Azuero-Soná belt in the middle to late Eocene with the formation of epithermal Au-Ag-Pb-Cu mineralization, and a porphyry Au prospect (Soná). A Middle Arc developed in the Oligocene to lower Miocene (31-18 Ma) related to the NE-dipping subduction of the Farallon Plate followed by the Nazca Plate. In eastern Panama, the arc formed intermediate sulphidation epithermal Au deposits in high grade breccias (Espiritu Santo de Cana mine) and carbonates (Rio Mogue prospect), and porphyry Cu mineralization (Ipeti). The eastern Panama arc shut down in the lower Miocene as a result of the change of the Nazca Plate convergence to strike slip. The Middle Arc in western Panama, on the northern side of the Central Cordillera, hosts the Petaquilla belt of porphyry Cu (the supergiant Cobre Panama porphyry Cu-Mo-Au-Ag deposit) and epithermal Au (Molejon) deposits, and probably the epithermal Au deposits of the Veraguas belt. The Later Arc of Miocene to Quaternary age (18-0 Ma) of the Central Cordillera of western Panama hosts low sulphidation epithermal Au vein and breccia-hosted deposits (Capira, Remance, Santa Rosa), high sulphidation epithermal Au deposits (Cerro Lloron, Rio Liri), and porphyry Cu deposits (the supergiant Cerro Colorado porphyry Cu-Mo-Au-Ag deposit and the Cerro Chorcha porphyry Cu-Au deposit). Uplift of the young porphyries in the western part of the belt is related to the subduction of the Cocos aseismic oceanic ridge. Deposits formed by Quaternary weathering include lateritic bauxite and iron ore in the Chiriqui-Veraguas belt; heavy mineral Fe-Ti sands in beach/marine placer deposits in the Gulf of Panama; and extensive placer Au deposits in Northern Darien, Darien, Chepo, Coclé, Veraguas, western Azuero-Soná, and many other small deposits.

Controls on cobalt and nickel distribution in hydrothermal sulphide deposits in Bergslagen, Sweden - constraints from solubility modelling

ABSTRACT We address controls on Co and Ni distribution, based on their solubility in hydrothermal fluids as functions of pH, ƒO2 and T, in two end-member types of sulphide deposits in Bergslagen, Sweden. Oxidized hydrothermal fluids, as have been suggested for the formation of the Zinkgruvan deposit, would efficiently transport Co and Ni in solution, even at 150 °C. Formation of Co and Ni sulphides and sulphosalts supersedes or overlaps the precipitation of other sulphides along a reduction or H2S-mixing path. This is consistent with the presence of Co and Ni sulphides and sulphosalts in vent-proximal Cu-Zn mineralization at Zinkgruvan. Reduced, acidic and hot (≥250 °C) hydrothermal fluids that have been invoked for the formation of deposits like Falun and Stollberg could also transport Co and Ni in solution. However, their solubility is strongly dependent on high T and low pH. Cooling and neutralization are here proposed as likely key triggers for the deposition of Co and Ni, yet, unlike in the Zinkgruvan scenario, saturation will occur within the pyrite stability field, whereby these metals may be sequestered as stoichiometric lattice substitutions in pyrite and other sulphides rather than forming minerals of their own. We conclude that at any T or realistic pH, hydrothermal systems involving oxidized brines have a greater ability to traverse and leach large rock volumes of Co and Ni. Consequently, areas hosting deposits that formed from such brines have a significant exploration potential for these metals, even in areas where Co-enriched source rocks are lacking or subordinate.

New 40Ar/39Ar ages from the Kalatag district in the Eastern Tianshan, NW China: Constraints on the timing of Cu mineralization and stratigraphy

The Kalatag region in the Eastern Tianshan of NW China contains a number of economically important Cu deposits. Among these, the South Meiling VMS deposit is hosted in the Late Ordovician to Early Silurian dacitic tuff belonging to the Daliugou Formation. The deposit is composed of two domains: a concordant massive sulfide ore domain and a discordant vein-type ore domain located in the footwall phyllic alteration zone. Here we report new 40Ar/39Ar ages on sericite from the phyllic alteration zone to better constrain the timing and genesis of mineralization. The sericite displays markedly flat 40Ar/39Ar age spectra, yielding a 40Ar/39Ar plateau age of 438.8±3.0Ma, and an isochron age of 443.0±11.0Ma. The 40Ar/39Ar age is in good agreement with the ReOs age reported earlier, placing the timing of CuZn mineralization at 434.2±3.9Ma. The age is also consistent with the field relationships that concordant massive sulfide orebody formed later than discordant vein-type orebody. Another deposit at Hongshi is hosted in basaltic andesites of the Daliugou Formation. The orebodies cut the phyllic alteration zone indicating that the Cu mineralization formed later than the phyllic alteration. Hydrothermal sericite from the phyllic alteration zone from this deposit yielded flat 40Ar/39Ar age spectra, with 40Ar/39Ar plateau ages of 441.5±3.2Ma and 446.4±4.6Ma, and isochron ages of 445.8±5.6Ma and 448.8±7.3Ma, respectively. This age is obviously older than the ReOs age, which is also in conformity with the field relations that quartz-sulfide veins cut the sericitization zone.Our 40Ar/39Ar ages offer precise constraints on Early Paleozoic Cu mineralization in the Eastern Tianshan Orogen. These results indicate that the Lower Unit basaltic andesites of the Daliugou Formation formed earlier than 446Ma. We thus consider that the Daliugou Formation formed during Middle Ordovician to Early Silurian. We also propose several metallogenic events in the Kalatag area including: (1) an Early VMS CuZn and hydrothermal vein Cu mineralization at 440–430Ma; (2) porphyry Cu and skarn Fe mineralization at 390–380Ma; and (3) a Late CuAu mineralization at ca. 300Ma. These three metallogenic events were coeval with the distinct magmatic pulses in the Kalatag area.

On-line Analyser optimizing mill feed at FQM Kevitsa Nickel-Copper-PGE mine

The new on-line analyser version has been tested first in FQM Pyhasalmi Cu-Zn mine and then in FQM Kevitsa Ni-Cu mine in analyzing primary crushed ROM -ore. This paper reports results of these tests. The new on-line analyser is part of ore grade control system in loading. This new analyser and new information enables new optional methods to control and optimize ore grade in loading. Short economic calculation shows obvious benefits of the new methods. There is ongoing research and development in FQM Kevitsa mine to optimize use of the new system.

Comparing the Effects of a Biosurfactant and a Humic Acid on Arsenic Mobilization from Mine Tailings

AbstractBatch experiments were carried out to investigate the effects of a rhamnolipid biosurfactant (JBR425) and a humic acid (Fluka HA) on arsenic mobilization from a Cu-Zn mine tailings sample collected from Val d’Or, QC, Canada. When pH was below 7, the addition of HA at a low mass ratio (below 2.0 mg HA/g mine tailings) inhibited the mobilization of arsenic significantly. Arsenic mobilization increased with the mass ratio of added HA to the mine tailings. Especially under basic conditions, the introduction of HA significantly enhanced arsenic mobilization. Rhamnolipids were more efficient than HA at enhancing arsenic mobilization when pH was above 7. At a mass ratio of 10 mg/g and pH 11, arsenic mobilization reached 10 mg/kg by HA and 14 mg/kg by rhamnolipids, respectively. Capillary electrophoresis analyses indicated that arsenic oxidation-reduction and methylation reactions might not be a significant mechanism that was involved in arsenic mobilization by the HA and rhamnolipids. It was found tha...

Geochemical and mineralogical characteristic of the VHMS alteration pipe, major elements variations and peraluminous ratio, in high grade metamorphosed rocks

The massive sulphide deposit at Kantienpan Cu-Zn mine is hosted by volcano sedimentary succession known as the Areachap Group, in the eastern part of Namaqua Metamorphic Province, South Africa. The deposits were affected by a complex deformation and metamorphic history and represent examples of upper amphibolite to granulite grade metamorphosed volcanic-hosted massive sulphide (VHMS) deposits. The principal purpose of this research is to characterise the primary geochemical halo’s related to VHMS deposits in this mine. Lithogeochemical characterization of the primary haloes is based on borehole samples of the footwall, ore zone and hanging wall successions. Geochemically, the ore zone and alteration zones at Kantienpan VHMS ore deposit display a high peraluminous ratio confirming the peraluminous nature of these zones as indicated mineralogically and lithologically. The intervals identified in sampled borehole core with low CaO and Na2O and with high MgO and K2O contents represent the alteration zone in the original footwall rocks of the deposit.

A NORMALIZATION SOLUTION TO MASS TRANSFER ILLUSTRATION OF MULTIPLE PROGRESSIVELY ALTERED SAMPLES USING THE ISOCON DIAGRAM

This study complements the isocon method of Grant (1986) for describing mass transfer during metasomatic alteration by introducing a normalization solution to illustrate sequential mass transfers among multiple progressively altered geologic samples. The principle of the normalization solution involves adjusting all the isocons (defined by unaltered and altered sample pairs) to a single unified isocon without modifying the relative concentration changes of the corresponding components. When the normalization solution is applied to a sequence of progressively altered samples, an immobile component is defined or assumed, and the measured concentrations of all components in all altered samples are normalized by multiplying the corresponding normalizing factors; these factors are calculated using the concentration data for the immobile component. The normalized compositions of the altered samples are then plotted against the original measured composition of the unaltered sample in a single normalized isocon diagram that illustrates all the mass changes for a series of progressively altered samples. This study applies the above approach to a set of progressively altered hydrothermal quartz-feldspar-porphyries at the Millenbach Cu-Zn mine (Riverin and Hodgson, 1980). The graphically displayed result indicates that the normalized isocon diagram can illustrate not only the mass changes of any component between any two altered zones, but also mass transfer trends of all components in the entire alteration zone. The normalization solution can be applied to any group of progressively altered geologic samples.

The Empire Cu-Zn Mine, Idaho: Exploration Implications of Unusual Skarn Features Related to High Fluorine Activity

The Empire Cu-Zn skarn deposit is unusual because of the proximal position of Zn mineralization, abundance of endoskarn, and the extremely vermicular texture of quartz phenocrysts in the related intrusive rocks. Cu-Zn skarn occurs at the contact between Upper Mississippian White Knob limestone and the granite porphyry phase of the Mackay Stock which consists, from early to late, of quartz monzodiorite, granophyre, granite porphyry, porphyritic granite, and many dikes. The late phases have high F and also extremely vermicular quartz phenocrysts. Endoskarn is more abundant than exoskarn. The earliest alteration of the intrusive rocks consists of disseminated diopsidic pyroxene (Di64Hd36 to Di88Hd12), actinolite, and titanite. This assemblage was cut by early scapolite (Me18 to Me35, mostly Me18-26) and/or green pyroxene (Di14Hd80 to Di20Hd77) veinlets, with or without wollastonite halos. These early veins were then cut by main-stage endoskarn veins that typically have a garnet + minor pyroxene inner zone, a wollastonite and/or pyroxene ± Ca-rich plagioclase (An56 to An89) envelope, and a halo containing disseminated, fine-grained alteration minerals of the same assemblage as the envelope. Some veins contain only the envelope assemblage and are interpreted to represent the alteration front. The inner zone locally contains vesuvianite. Where many veins intersect, endoskarn is massive. Pyroxene is zoned around fluid conduits; the distal pyroxene is Fe rich (hedenbergitic) whereas the proximal pyroxene is Fe poor (diopsidic). The garnet changes in the opposite way, being Fe poor-Al rich (grossularitic) in locations distal to the fluid conduits, and Fe rich (andraditic) in proximal locations. In contrast, in the exoskarn, all pyroxene is diopsidic and garnet is andraditic. Weak, retrograde alteration composed of quartz + calcite + chlorite with minor fluorite, talc, and epidote overprinted both endoskarn and exoskarn. Magnetite precipitated after garnet-pyroxene in both endoskarn and exoskarn. Sphalerite precipitated together with chalcopyrite in proximal locations and is associated with retrograde alteration. Other ore minerals include minor molybdenite, bornite, pyrite, galena, arsenopyrite, native Au, as well as supergene minerals such as chrysocolla, malachite, azurite, native Cu, and limonite. Fluid xenoliths from pyroxene in early endoskarn veinlets homogenize at >600°C. Massive endoskarn and exoskarn replacing limestone inclusions in granite porphyry formed at 500° to >700°C, whereas the highest temperature inclusions, >700°C, occur in narrow garnet + minor pyroxene veins. Fluid inclusions in exoskarn replacing wall rock have homogenization temperatures of 500° to 650°C. Retrograde alteration and Cu-Zn mineralization occurred at 250° to 300°C. Fluid inclusions in prograde minerals contain daughter minerals, whereas fluid inclusions in retrograde minerals do not, indicating a decrease in salinity with time. Late-stage fluids have low eutectic temperatures, indicating the possible presence of KCl, NaCl, FeCl2, CaCl2, MgCl2, K2CO3, and/or Na2CO3. Formation of the unusually abundant endoskarn, the proximal position of Zn mineralization, and the extremely vermicular texture of quartz phenocrysts are all believed to have been promoted by the high F content of the magmatic fluid. These features may serve as exploration indicators of associated high F mineralization such as buried porphyry Mo deposits.

Microbial sulfate reduction and metal attenuation in pH 4 acid mine water

Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4.0 to 7.5). The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing bacteria (SRB) were active in moderately acidic conditions present in the underground mine workings. Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation are occurring in the pH-4 mine environment. Water-chemistry analyses of the mine water reveal: (1) preferential complexation and precipitation by H2S of Cu and Cd, relative to Zn; (2) stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2–3 ‰ heavier in the mine water, relative to those in surface waters; (3) reduction/oxidation conditions and dissolved gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur. DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures.

Role of Microbial Activity in Fe and S Cycling in Sub-Oxic to Anoxic Sulfide-Rich Mine Tailings

Acid-mine drainage is an important environmental problem associated with base-metal mining and numerous studies have looked at the chemical and microbial processes involved in the oxidation of metal sulfides under oxic conditions. However, little is known about the activity of bacteria living in the same sulfide-rich tailings, but under sub-oxic to anoxic conditions. Recent work on Cu-Zn mine tailings have shown that sulfate-reducing bacteria (SRB) are present and active in these tailings (under a wide range of pH conditions) and that their activity is season dependent. In fact, acidic conditions and low organic carbon availability in the spring tend to greatly limit the activity of SRB in the tailings. On the other hand, IRB populations tend to increase in number in the spring, maybe as a result of the lack of activity of SRB. These findings are in agreement with studies on acidic coal mining lakes in Germany, which showed that IRB were mainly active in acidic and oxic sediments whereas SRB dominated in the more anoxic and pH neutral sediments. The presence and activity of SRB and IRB also represents a potential bioremediation tool, because both microbial pathways generate alkalinity. Recent work on acidic mining lakes indicates that IRB and SRB activity could be enhanced in a control manner and be used as an acidity neutralizing process to treat environments impacted by AMD.

Determination of Acid Volatile Sulfides and Chromium Reducible Sulfides in Cu-Zn and Au Mine Tailings

The present study investigated the use of chemical extractions for the determination of acid volatile sulfides (AVS) and chromium reducible sulfides (CRS) in sulfidic mine tailings from Au and Cu-Zn mines. The main objectives of the study were to understand the factors affecting AVS and CRS extraction in mine tailings and to use the AVS and CRS data as indicator of biotic reactions, including microbial sulfate-reduction. Tailings from one Cu-Zn mine and two Au mines located in the Timmins area, Ontario, Canada, were extracted for AVS and CRS, along with pure metal sulfides. Tailings were also characterized by XRD and the relative abundance of pyrite and pyrrhotite in the samples was determined. Our results showed that AVS in mine tailings were generally not extractable at cold temperature, but they could be extracted from most tailings samples at ∼ 80 °C. AVS extraction of pure metal sulfides showed that pure pyrrhotite was partially soluble during cold and hot extractions and that it significantly contributed to the overall AVS fraction of the tailings. Such findings complicate the use of AVS as bio-indicators of microbial activity because a large fraction of the pyrrhotite present in the tailings originated from the ore deposit. The CRS fractions were found to be unaffected by the presence of pyrrhotite and truly represented the pyrite content of the tailings. The use of AVS and CRS data from mine tailings can be helpful in assessing the distribution of metal sulfides but attention must be paid to their true significance.

Occurrence of sulfate-reducing bacteria under a wide range of physico-chemical conditions in Au and Cu–Zn mine tailings

Sulfate-reducing bacteria (SRB) have been observed in mining environments, but their presence has not been linked to specific physico-chemical and mineralogical factors. The present study was undertaken to assess the presence of SRB in several Au and Cu-Zn mine tailings located near Timmins, Ont., Canada, and determine the factors responsible for their presence. Vegetated and non-vegetated mine tailings were sampled for SRB enumeration, pH, Eh, water content, total carbon content and sequential chemical extraction. Results first showed that SRB populations were present at all sites and that their distribution varied with depth. Populations were recovered from neutral pH and slightly anoxic tailings and from highly acidic (pH 2) and oxic tailings. The total carbon content of the tailings was generally low and not related to the presence of vegetation. In addition, the carbon content did not affect SRB population distribution and appeared to be more related to the type of tailings, i.e., oxidized and acidic Cu-Zn tailings contained on average more carbon than Au tailings. Results also indicated that the water content of the tailings varied greatly with depth and was not related to the presence of SRB populations. The sequential chemical extraction showed that the pyrite content of the tailings was lower in Au tailings than in Cu-Zn tailings, and that some oxidized Cu-Zn sites were depleted in pyrite due to microbial and chemical oxidation. Our results indicate that SRB could be cultured from a variety of sites and sample types, and that factors such as pH, Eh, water content and carbon content at the collection sites did not exert control on their presence.

Flotation in acid mine drainage control: Beneficiation of concentrate

This paper is focused on recovering residual sulfide minerals by flotation from the tailing of the Pyhäsalmi Cu-Zn mine in Finland. The tailing contains 4–8% sulfide sulfur and according to the static test it is strongly acid producing, having a low ratio of neutralization potential to acid production potential (NP/AP < 1). The NP/AP ratio could be markedly improved (> 1) by flotation treatment of the tailing. Fine pyrite caused sulfide losses in the flotation while incomplete liberation had only a minor effect on the acid production potential. The cleaner concentrate obtained during the flotation of the tailing contained 33% sulfur, 1% zinc, 0.7% copper, 2.8 g/t gold, and 40 g/t silver. Potential process options are available today for partial beneficiation of the concentrate but further development work is needed for recovering all the valuable elements and eliminating the waste pile. © 1997 Canadian Institute of Mining and Metallurgy.

The Pore-Water Geochemistry of the Cu-Zn Mine Tailings at Kidd Creek, Near Timmins, Ontario, Canada

The Pore-Water Geochemistry of the Cu-Zn Mine Tailings at Kidd Creek, Near Timmins, Ontario, Canada

Noble metal abundances and characteristics of six granitic magma series, Archean Abitibi Belt, Pontiac Subprovince; relationships to metallogeny and overprinting of mesothermal gold deposits

Noble metal abundances and characteristics of six granitic magma series, Archean Abitibi Belt, Pontiac Subprovince; relationships to metallogeny and overprinting of mesothermal gold deposits