Sulfide Mine Research Articles

Acidithiobacillus ferrianus sp. nov.: an ancestral extremely acidophilic and facultatively anaerobic chemolithoautotroph

Strain MG, isolated from an acidic pond sediment on the island of Milos (Greece), is proposed as a novel species of ferrous iron- and sulfur-oxidizing Acidithiobacillus. Currently, four of the eight validated species of this genus oxidize ferrous iron, and strain MG shares many key characteristics with these four, including the capacities for catalyzing the oxidative dissolution of pyrite and for anaerobic growth via ferric iron respiration. Strain MG also grows aerobically on hydrogen and anaerobically on hydrogen coupled to ferric iron reduction. While the 16S rRNA genes of the iron-oxidizing Acidi-thiobacillus species (and strain MG) are located in a distinct phylogenetic clade and are closely related (98–99% 16S rRNA gene identity), genomic relatedness indexes (ANI/dDDH) revealed strong genomic divergence between strain MG and all sequenced type strains of the taxon, and placed MG as the first cultured representative of an ancestral phylotype of iron oxidizing acidithiobacilli. Strain MG is proposed as a novel species, Acidithiobacillus ferrianus sp. nov. The type strain is MGT (= DSM 107098T = JCM 33084T). Similar strains have been found as isolates or indicated by cloned 16S rRNA genes from several mineral sulfide mine sites.

Chapter 6 Paleoproterozoic (1.9–1.8 Ga) syn-orogenic magmatism, sedimentation and mineralization in the Bergslagen lithotectonic unit, Svecokarelian orogen

Abstract Felsic volcanic rocks ( c. 1.91–1.89 Ga) and interlayered limestone, hosting Zn–Pb–Ag ± Cu ± Au ± Fe sulphide and Fe oxide deposits, characterize the Bergslagen lithotectonic unit, Svecokarelian orogen, south-central Sweden. Three sulphide mines are currently in operation. Siliciclastic sedimentary rocks stratigraphically envelop this volcanic succession and all the rocks are intruded by a dominant calc-alkaline, c. 1.91–1.87 Ga plutonic suite. Fabric development associated with folding and localized shear deformation followed at c. 1.87–1.86 Ga (D 1 ) and was succeeded by strongly partitioned strain (D 2 ). Dextral transpression along steeply dipping, WNW–ESE or NW–SE shear zones prevailed in the northern and southern domains, whereas major folding with east to northeasterly axial surface traces and shearing along limbs occurred in the central domain. Open folding (D 3 ) subsequently affected the western areas. Polyphase metamorphism under low-pressure and variable temperature conditions included anatexis at c. 1.86 Ga (M 1 ) and 1.84–1.80 Ga (M 2 ). More alkali–calcic magmatic activity, combined with the emplacement of anatectic granite and pegmatite, overlapped and succeeded the M 1 and M 2 migmatization events at c. 1.87–1.83 Ga and c. 1.82–1.75 Ga, respectively. The younger granites are genetically linked in part to W skarn deposits and host Mo sulphide mineralization. Switching between retreating and advancing subduction systems during three separate tectonic cycles along a convergent, active continental plate margin is inferred.

Metal dissolution behavior from deep-sea hydrothermal sulfide samples; Impact assessment for seafloor massive sulfide mining

Metal dissolution behavior from deep-sea hydrothermal sulfide samples; Impact assessment for seafloor massive sulfide mining

Temporal Changes of Pyrite Oxidation Rate in Bolivian Sulphidic Mining Wastes

Since the 70's, when huge sulphidic open pits were developed, the acidic rock drainage (ARD) become the leader problem of the sulphidic mining industry. Although the recycling is an essential technology, it cannot cover the demand alone, thus mining activity needs to continue. Acidity in mine drainage commonly requires most of the attention, but the main problem is the caused elevated level of metal mobility and leaching, which are generated by the increased rates of sulphide weathering under acidic conditions. The Itos mine is a polymetallic vein deposit in Bolivia, had been mined for silver and tin until 1990, leaving behind much and huge tailings and mine waste heaps, where quite often the pyrite content exceeds 10 %. Serious ARD effects take place in the mine waste heaps. These processes can be well characterized with the pH 1 or 2 of the seepage water, which forms serious alteration in the waste itself and the neighbouring rocks. In three consecutive years, the pyrite oxidation rate was investigated on the same 7 samples by humidity cell test. 5-6 months pauses were left between the humidity cell test periods, which mimics the alternation of wet and dry periods, typical for the place. The results give much more information, than the oxidation rate in the individual test periods, showing the changes by time. This applied method gave good result to characterize the behaviour of the waste in long-term. The column test was complemented with mineralogical analyses, such as electron probe micro analysis. The mineralogical and column test analyses show, that the changes of the pyrite oxidation rate split the samples into three different groups, one where the oxidation rate decreases, second where it increases with time and the third where oxidation rate is maximal and stays stable for several years.

Temporal Changes of Pyrite Oxidation Rate in Bolivian Sulphidic Mining Wastes

Temporal Changes of Pyrite Oxidation Rate in Bolivian Sulphidic Mining Wastes

Determination of pore structures and adsorption properties of activated iron sulfide ores

To better reveal the pore structures and adsorption characteristics of iron sulfide ores after the mechanical activation, the raw sulfur-rich ore obtained from a sulfide mine was activated into several samples under different billing conditions. Both the scanning electron microscopy (SEM) and low-temperature N2 gas adsorption/desorption (LT-N2GA) methods were used to understand the features of the pore structures, such as the pore volume, specific surface area (SSA), and pore size distribution (PSD). Moreover, the Frenkel-Halsey-Hill (FHH) model was applied to determine corresponding fractal dimensions. The research results indicate that the N2 adsorption of the activated samples mostly takes place in the mesopores ranging from 2 to 30 nm. The change order of the SSA and pore volume for the activated samples with different sample-ball ratios is as follows: a (1:2)< b (1:4)< c (1:6); and that with diverse milling rates is as follows: d (200 r/min)< e (400 r/min)< f (600 r/min). The transformations in the fractal dimensions agree with those in SSA and pore volume development, while the alterations are on the contrary in average pore diameter. The mechanical activation can increase the fractal dimensions of iron sulfide samples and alters their oxygen adsorption properties, so it promotes the tendency of iron sulfide ores to oxidation and spontaneous combustion.

Redistribution and speciation of elements in gold-bearing sulfide mine tailings interbedded with natural organic matter: case study of Novo-Ursk deposit, Kemerovo Region, Siberia

The paper presents data on two cores from the dispersion train of gold-bearing sulfide tailings in the Novo-Ursk deposit (Kemerovo region, Russia), where organic-bearing mud and natural organic matter are interbedded with cyanide tailings and acid mine drainage (AMD). The study focuses on speciation of Au, Ag and potentially toxic elements (PTE), including Fe, Cu, Zn, As, Se and Pb according to selective sequential extractions. Since large contents of elements are found in water solution and bound to Fe(III) compounds, sulfides and/or organic matter in both cores, the organic material behaves as a natural biogeochemical barrier for potentially toxic elements and precious metals released from AMD. The interaction with organic matter results in biogeochemical sorption and immobilization of elements and is favourable for secondary enrichment in gold and silver. It leads to immobilization of elements that further form new mineral phases or become partitioned between existing phases. On the other hand, very high concentrations of water-soluble and oxidizable species of PTE and Au, which are unstable in surface conditions and may become remobilized when the environment changes, make the organic material less workable and even potentially hazardous. Thus, both positive (secondary enrichment) and negative (pollution) effects should be taken into account in the planning and design of systems for purification, disposal of cyanide tailings and recovery of useful components from tailings using natural organic matter as a geochemical barrier.

Release of technology critical metals during sulfide oxidation processes: the case of the Poderosa sulfide mine (south-west Spain)

Environmental contextNatural weathering of rocks may release technology critical elements (TCEs) to the environment, and anthropogenic activities can noticeably increase TCE release rates. We investigated acid mine drainage outflows from an underground sulfide mine in south-west Spain, reporting TCE concentrations orders of magnitude higher than those observed in natural waters. The findings improve our knowledge on mobility of TCEs in different geological settings. AbstractExtensive extraction of technology critical elements (TCEs) from the lithosphere and their use results in a growing dispersion and remobilisation of these elements within the environmental compartments. We investigated the concentration and mobility of different TCEs (rare earth elements (REEs), Sc, Y, Ga and Tl) in acid mine drainage (AMD) outflows from a massive sulfide underground mine in south-west Spain for around 2 years. High levels of TCEs were observed; average concentrations of 8.2mgL−1 of REEs, 1.5mgL−1 of Y, 80µgL−1 of Ga, 53µgL−1 of Sc and 42µgL−1 of Tl were reported, several orders of magnitude higher than those observed in natural waters. The TCEs source in the study site is primarily accessory minerals in the host rocks, although the contribution of Ga and Tl by sulfides cannot be discarded. A seasonal variability in TCEs is observed in AMD waters, although their maximum concentrations do not coincide with those of sulfide-related elements. TCEs seem not to be controlled by the precipitation of secondary minerals, but by the intensity of chemical weathering inside the mined zone. A positive correlation between REEs and the Si/Na+K ratio seems to indicate that these elements are linked to resistant minerals to weathering.

PSO-SVM Model for Classifying Spontaneous Combustion Tendency Grade of Sulfide Ores

Three main factor indexes that most reflect spontaneous combustion tendency of sulfide ores were selected such as oxidation increment of ore sample under low temperature, self-heating point temperature and self-burning point temperature as the basic discriminate factors of the classification model. Based on the theory of cross validation and particle swarm optimization(PSO) to optimize the parameters of support vector machine (SVM),the PSO-SVM model for classifying spontaneous combustion tendency grade of sulfide ores was built by using training samples from measured data, and was verified by engineering data. It shows that the model has high predication accuracy, which also is scientific and feasible, it provides a new approach to evaluate the spontaneous combustion tendency grade of ores in any sulfide mines.

Terrestrial Ecosystem Impacts of Sulfide Mining: Scope of Issues for the Boundary Waters Canoe Area Wilderness, Minnesota, USA

Large-scale metal mining operations are planned or underway in many locations across the boreal forest biome in North America, Europe, and Asia. Although many published analyses of mining impacts on water quality in boreal landscapes are available, there is little guidance regarding terrestrial impacts. Scoping of potential impacts of Cu-Ni exploration and mining in sulfide ores are presented for the Boundary Waters Canoe Area Wilderness (BWCAW), Minnesota USA, an area of mostly boreal forest on thin soils and granitic bedrock. Although the primary footprint of the proposed mines would be outside the BWCAW, displacement and fragmentation of forest ecosystems would cause spatial propagation of effects into a secondary footprint within the wilderness. Potential negative impacts include disruption of population dynamics for wildlife species with migration routes, or metapopulations of plant species that span the wilderness boundary, and establishment of invasive species outside the wilderness that could invade the wilderness. Due to linkages between aquatic and terrestrial ecosystems, acid mine drainage can impact lowland forests, which are highly dependent on chemistry of water flowing through them. The expected extremes in precipitation and temperature due to warming climate can also interact with mining impacts to reduce the resilience of forests to disturbance caused by mining.

Megabenthic assemblages at the southern Central Indian Ridge – Spatial segregation of inactive hydrothermal vents from active-, periphery- and non-vent sites

Active hydrothermal vents are small-scale habitats hosting endemic fauna in a well-defined zonation around fluid effluents. The fauna of inactive hydrothermal vents and its relation to active vents and non-vent area is poorly known. Characterizing inactive areas is prerequisite to establish protected areas, especially in the context of potential seafloor massive sulfide mining, which targets inactive sites. Hierarchical clustering and Distance-based Redundancy Analysis revealed five assemblages, with significantly associated substrate types: I) active hydrothermal vent, II) periphery, III) inactive hydrothermal vent and IV) soft- and V) hard-substrate within the non-vent area. For the first time, a unique inactive faunal assemblage could be identified within the hydrothermally extinct inactive Gauss field and on adjacent hard substrates. The spatial separation from the active Edmond field and periphery and the non-vent area indicates the existence of an inactive assemblage.

Zinc and lead encapsulated in amorphous ferric cements within hardpans in situ formed from sulfidic Cu-Pb-Zn tailings

Hardpans are massively indurated layers formed at the top layer of sulfidic tailings dams, which develop cementation structures and result in heavy metal immobilization. However, the micro-structural and complex forms of the cementing materials are not fully understood, as well as the mechanisms by which Zn and Pb are stabilized in the hardpans. The present study deployed synchrotron-based X-ray fluorescence microscopy (XFM) to have characterized the cementing structures, examined the distribution of Fe, Zn and Pb, and obtained laterally-resolved speciation of Zn within the hardpans using fluorescence X-ray absorption near-edge structure (XANES) imaging. The XFM analyses revealed that the Fe-rich cement layers consisted of Fe (oxyhydr)oxides coupled with amorphous Si materials, immobilizing Zn and Pb. Through laterally-resolved XANES imaging analyses, Zn-ferrihydrite-like precipitates were predicted to account for >76% of the total Zn within the Fe-rich cement layers. In contrast, outside of the cement layers, 9–63% of the Zn was estimated as labile ZnSO4.7H2O, with the remainder in the form of Zn-sulfide. These findings demonstrated that the Fe-rich cement layers were critical in immobilizing Zn and Pb within hardpans via mineral passivation and encapsulation, as the basis for long-term geochemical stability in the hardpan layer of sulfidic mine tailings.

Mineral reactivity in sulphide mine wastes: influence of mineralogy and grain size on metal release

The authors thank two anonymous reviewers for helpful comments that clearly improved the quality of the manuscript, and Associate Editor Encarnacion Ruiz-Agudo and Chief Editor Carlos Rodriguez-Navarro for their handling. This work was supported by the Spanish Ministry of Economic and Competitiveness through the projects CGL2016-78783-C2-1-R (SCYRE) and ERAMIN PCIN2015-242. C.R. Canovas was funded by the Talent Consolidation Program of the University of Huelva. MD Basallote also thanks the Spanish Ministry of Economy and Competitiveness for the Postdoctoral Fellowship granted under application reference FJCI-2015-24765.

Improvement of chemical quality of percolated leachates by in situ application of aqueous organic wastes on sulfide mine tailings

One of the major environmental concerns in the mining industry is the generation of acid leachates from tailings deposits, which are highly concentrated in potentially hazardous elements. The continuous processing of these leachates in treatment plant is unsustainable, so the in situ chemical improvement of the mine wastes and their leachates, mainly with another waste produced in the mining area, can reduce treatment and operational costs. This study aimed to evaluate the effect of two types of domestic wastewaters (DWW) on the improvement of the chemical characteristics of the leachates generated from mine wastes containing sulfides.A mesocosm assay was performed under greenhouse and controlled conditions with mine wastes collected in La Zanja mining area (Peru). Three irrigation treatments were tested: untreated DWW, treated DWW and water as control. Percolated leachates of each treatment were collected once per week, for a period of 10 weeks. Electrical conductivity, pH and multi-elemental concentration were analysed.During the assay, the mine wastes generated acid leachates (≈4) with significant concentrations of elements (mg/L; Al: 1.4–30.0; Cd: 0.05–0.19; Cu: 5.7–22.1; Fe: 1.6–19.4; Mn: 2.6–26.0; Zn: 1.2–9.2) and sulfates (204.3–997.8 mg/L), which exceed the thresholds established by Peruvian legislations. After DWW application, pH in the leachates increased to ≈7 and concentrations of several studied elements (e.g. Al, As, Fe, Cu, Zn, Cd, Pb, Ni, Mn) and sulfates decreased (>70% depending on DWW type, element and sampling) compared to the control. This fact allowed that the Environmental Quality standards from Peru (except for Cu and Mn) were reached. However, an enrichment of Na and K was obtained at the same leachates. At short term, the DWW application (especially untreated) on the mine wastes containing sulfides was effective in the improvement of the general chemical quality of their leachates. Moreover, the combined management of these two studied wastes (domestic wastewater and mine wastes) represents a promising cost-effective strategy during mining operation.

Pollution evaluation on the salt-marshes under the phosphogypsum stacks of Huelva due to deep leachates

In the salth-marshes of the Tinto River (Huelva estuary, SW Spain), are stored in stacks around 100 Mt of PG, covering a surface of 1000 ha without any type of isolation, which produce an important impact in the surrounding environment. On the other hand, this ecosystem it is affected by acid mine drainage (AMD) from sulphide mines located upstream the Tinto River.The aim of this study is to evaluate the deep pollution of the underlain salt-marsh sediments due to leachates from the PG stacks. For that purpose, 7 cores were collected from zones 2 and 3 of the stacks, and PG and salt-marsh sediments samples from different depths were analyzed. The physicochemical parameters, mineralogy, granulometry and the concentration of the main elements of interest were determined in the samples.Most analysed salt-marsh sediments are not affected by PG stacks pollution, because sediments act as a “barrier” for the leachates from the PG, concentrating the contaminants in the first decimetres (0.5 m) under PG-sediments contact, and the deep infiltration is very limited. The obtained results suggest that the perimeter channel which is projected to build in the restauration project, should has a depth of 1 m below the level of the PG stacks for assuring the complete collection of leachates from the stacks, and avoid their liberation into the Tinto River estuary.

Cost-Effective Seismic Exploration: 2D Reflection Imaging at the Kylylahti Massive Sulfide Deposit, Finland

We show that by using an advanced pre-stack depth imaging algorithm it is possible to retrieve meaningful and robust seismic images with sparse shot points, using only 3–4 source points per kilometer along a seismic profile. Our results encourage the use of 2D seismic reflection profiling as a reconnaissance tool for mineral exploration in areas with limited access for active seismic surveys. We used the seismic data acquired within the COGITO-MIN project comprising two approximately 6 km long seismic reflection profiles at the polymetallic Kylylahti massive sulfide mine site in eastern Finland. The 2D seismic data acquisition utilized both Vibroseis and dynamite sources with 20 m spacing and wireless receivers spaced every 10 m. For both source types, the recorded data show clear first breaks over all offsets and reflectors in the raw shot gathers. The Kylylahti area is characterized by folded and faulted, steeply dipping geological contacts and structures. We discuss post-stack and pre-stack data processing and compare time and depth imaging techniques in this geologically complex Precambrian hardrock area. The seismic reflection profiles show prominent reflectors at 4.5–8 km depth utilizing different migration routines. In the shallow subsurface, steep reflectors are imaged, and within and underneath the known Kylylahti ultramafic body reflectivity is prominent but discontinuous.

Efficiency of MgO activated GGBFS and OPC in the stabilization of highly sulfidic mine tailings

Abstract MgO activated ground granulated blast furnace slag (GGBFS) is a form of alkali-activated composite, which is successfully used as a binder in the stabilization of highly sulfidic mine tailings. The aim of this study was to compare alkali activated composite (AAC) and ordinary Portland cement (PC) as stabilization agents, as well as their efficiency to stabilize sulfidic tailings and the results of three different diffusion and leaching methods. The Life Cycle Assessment (LCA) method was used to compare the environmental impacts of the binders. The lab-scale program covered hydraulic conductivity, compression strength, and freeze-thaw resistance tests of the stabilized tailings. The results indicate that the hydraulic conductivity (6.08 · 10−9 m/s) and compressive strength (11.5 MPa at 28 days) of AAC were better in comparison, if the corresponding amount of PC (2.04 · 10−8 m/s and 10.3 MPa at 28 days) was used. LCA shows clear ecological benefits when using AAC instead of PC in terms of lower global warming potential. Diffusion and leaching tests indicated better immobilization efficiency of AAC than PC concerning As, Cr, Cu, Ni, Se, Zn, and especially Mo. In comparison with plain tailings, AAC stabilization reduced leaching of As, Cr, Cu, Mo, Ni, Pb, Se, Zn, Cl, and SO4 better than PC.

Indium distribution in metalliferous mine wastes of the Iberian Pyrite Belt, Spain–Portugal

Indium is a rare, post-transition metal that is widely used in modern technological applications. However, despite its known toxicity the environmental processes of this element are poorly understood. This study reports on the abundance, mineralogical siting and mobility of indium in waste rock at six selected historic mine sites (Angostura, La Zarza, Rio Tinto, San Telmo, Sao Domingos, Tharsis) of the Iberian Pyrite Belt (IPB), Spain–Portugal. Sulfidic waste rock samples are invariably enriched in indium (mean 6 mg/kg In), with concentrations well above average crustal abundances (50 µg/kg In). Indium is largely present as cation substitutions in the crystal lattices of sulfide minerals, in particular kesterite (max. 0.5 wt% In), sphalerite (max. 0.27 wt% In) and chalcopyrite (max. 0.05 wt% In). The sulfidic wastes have undergone extensive oxidation prior to and after mining, with partially oxidized sulfidic waste rocks invariably enriched in indium (mean 1.5 mg/kg In). At the toe of waste dumps, oxygenation of acid rock drainage (ARD) waters leads to the development of abundant secondary metal and/or alkali (hydrous) sulfates and the formation of Fe-rich precipitates and evaporative salts (mean 1.5 mg/kg In). Consequently, indium is significantly enriched in sulfidic mine wastes of the IPB and displays mobility in ARD environments, with its mobility somewhat constrained by oxygenation of ARD waters and subsequent iron precipitation.

Interactions among microfungi and pyrite-chalcopyrite mineralizations: tolerance, mineral bioleaching, and metal bioaccumulation

Abandoned sulfide mines represent one of the most important causes of pollution in the world. These environments are characterized by the absence of a real soil and plant life and are colonized only by pioneer microorganisms such as bacteria and fungi. Mycelial fungi interact with mineral compounds through many direct or indirect strategies develop a significant biomass in soil and sequester significant amounts of metals. In this study, three fungal species (Penicillium brevicompactum, P. glandicola, and a strain of Trichoderma harzianum species complex), isolated from the Libiola sulfide mine (Liguria, Italy), were tested on mineral tolerance to pyrite-chalcopyrite mineralizations, mineral bioleaching, and metal accumulation. All the species were able to grow on extremely acid media enriched with sulfide mineralizations. In particular, T. harzianum revealed the great capacity to bioconcentrate Ag, Cu, Cd, and Zn, which were released during pyrite alteration. These results showed the microfungi active role played in the pedogenetic processes and their potential use in metal mining and bioremediation.

Regularities in the Evolution of Groundwater Quality at Abandoned Copper Sulfide Mines at the Levikha Ore Field, Central Urals, Russia

Over the past decades, dozens of copper sulfide mines in the Urals were decommissioned, abandoned, and flooded. At many of them, acidic mine waters are still generated and poured out on the surface. Concentrations of most components in these waters are several orders of magnitude higher than the maximum permissible concentrations. The chemical composition of the acidic groundwaters is generated in a highly dynamic regime: the concentrations of all components in the water first drastically increase after flooding and then decrease during many years. At the Levikha copper sulfide deposit, Sverdlovsk oblast, the filling of the depression cone in 2007 was followed by the origin of focused groundwater discharge: an anthropogenically produced water body (pond) in a caving within the collapse and subsidence zone. The concentrations of many indicator components were higher ten years after the flooding was terminated than when the mining operations were in progress. The dominant source of the acidic waters with elevated mineralization (total dissolved solids, TDS) is the collapse zone, in which an anthropogenically generated sulfuric-acid weathering crust enriched in secondary minerals developed for tens of years in the process of mine drainage. According to results of numerical geofiltration simulations, the lateral flow makes up 60% of the hydrodynamic balance and dilutes the solution generated in the collapse zone. The movement time of this flow through the collapse zone is six–eight years, and this period of time is marked by extremely high values of practically all indicators in the anthropogenic pond. The composition of rocks whose dissolution–precipitation controls the composition of groundwater in the area of the flooded mine was determined by numerical simulations with the Visual MINTEQ ver.3.0/3.1 software. The duration of the process that forms the composition of the acidic groundwaters is estimated at tens of years.