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Item type:Publication, Dissolution kinetics and solubilities of copper sulfides in cyanide and hydrogen peroxide leaching: applications to increase selective extractions(Elsevier, 2021-11-01)Accurate quantification of secondary and primary sulfide minerals is fundamental for resource evaluation, ore processing, and long-term sustainability of mining operations. In addition to visual mapping and automated mineral quantification, chemical analysis can also be harnessed to characterize the mineralogy of ore deposits. By evaluating the conditions in which certain minerals can be selectively dissolved from others, a chemical evaluation could provide geochemical speciation data of low-abundance minerals, such as copper/iron sulfides present in low-grade copper ores. The selective dissolution of copper sulfide minerals is, however, understudied. Here, we evaluate the use of potential selective dissolution conditions to differentiate supergene copper sulfides from hypogene copper sulfides. By characterizing the dissolution kinetics of chalcocite, covellite, bornite, enargite, chalcopyrite, and pyrite concentrates, we found that alkaline cyanidation (and not hydrogen peroxide or acid leaching in the presence of oxidizing agents) selectively dissolves supergene copper sulfides, which can be applied in a sequential extraction scheme to estimate the sulfide mineralogy of tailings samples. Cyanide completely dissolved chalcocite and covellite within 5–15 min, whereas dissolution in acid oxidative media only partially dissolved copper sulfides. Pyrite, chalcopyrite, enargite, and bornite under 0.5% KCN leaching (1 mg/mL) for 10 min showed approximately 1, 10, 30, and 40% of copper recovery, respectively. Cyanide leaching applied in sequential extractions of porphyry copper tailings samples from the Piuquenes impoundment, La Andina, Chile, improved the selective dissolution of secondary sulfides compared to a previously proposed hydrogen peroxide dissolution method, thus allowing their differentiation from primary sulfide minerals. The selective leaching of supergene sulfides by cyanidation provides a cheap and efficient method to estimate the copper sulfide mineralogy in copper ores, facilitating the sustainability and resource evaluation of mining operations. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Seasonal fluctuations and geochemical modeling of acid mine drainage in the semi-arid Puna region: the Pan de Azúcar Pb–Ag–Zn mine, Argentina(Elsevier, 2021-08-01)Pan de Azúcar is an inactive Pb–Ag–Zn mine in the semi-arid Puna region of NW Argentina at 3600 m above sea-level. The mine is situated in Los Pozuelos basin, which is a UNESCO Biosphere Reserve. Substantial pyrite and few carbonate minerals are present in the tailings. The generated acid mine drainage (AMD) has low pH (1.92–4.06) and is mainly Fe–Zn–SO4 type water with high concentrations of metals that in order of relative abundance vary as: Al ≫ Cd > As(T) > Ni > V > Cu > Co > Sb > Cr > Pb > Sn > Ag. The strong annual cycle of dry and wet seasons in the Puna generates a significant influence on AMD geochemistry. In the dry season, there is no runoff and AMD drains mainly in the form of seepages with low pH (1.92–2.21), high concentrations of metals, and the formation of metal-rich soluble efflorescent salts is favored by strong evaporation. At the beginning of the wet season, the efflorescent salts rapidly dissolve and metals concentrations in AMD increase significantly, creating the most hazardous period for the surrounding fluvial environment. At the end of the wet season the pH increases (3.44–4.06) and the concentration of metals decreases, especially arsenic associated with ferric iron precipitates. As a consequence of the DC3 dam restoration, a large volume of AMD is retained forming an acid pond, in which processes of AMD mixing, secondary minerals precipitation, and sulfide oxidation were quantified by inverse modeling with mixing. Jarosite and schwertmannite precipitates in the surface of the pond and favors the attenuation of As and Pb. However, subaqueous oxidation of sulfide minerals, hydrolysis of silicates, and mixing with upstream AMD seepage increases the concentrations of SO42-, Fe(II), and the other metals in the seepage of the pond that migrates downstream. The results of this study indicate the necessity to improve the remediation methods of Pan de Azúcar mine. It is expected that other sulfide mines in the Puna region will have a similar variability of the AMD geochemistry, which should be considered for mine closure, remediation, and monitoring of water quality in mining. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Release of trace elements during bioreductive dissolution of magnetite from metal mine tailings: potential impact on marine environments(Elsevier, 2021-09-20)Adverse impacts of mine tailings on water and sediments quality are major worldwide environmental problems. Due to the environmental issues associated with the deposition of mine tailings on land, a controversial discussed alternative is submarine tailings disposal (STD). However, Fe(III) bioreduction of iron oxides (e.g., magnetite) in the tailings disposed might cause toxic effects on coastal environments due to the release of different trace elements (TEs) contained in the oxides. To study the extent and kinetics of magnetite bioreduction under marine conditions and the potential release of TEs, a number of batch experiments with artificial seawater (pH 8.2) and a marine microbial strain ( Shewanella loihica ) were performed using several magnetite ore samples from different mines and a mine tailings sample. The elemental composition of the magnetite determined in the tailings showed relatively high amounts of TEs (e.g., Mn, Zn, Co) compared with those of the magnetite ore samples (LA-ICP-MS and EMPA analyses). The experiments were conducted at 10 °C in the dark for up to 113 days. Based on the consumption of lactate and production of acetate and aqueous Fe(II) over time, the magnitude of Fe(III) bioreduction was calculated using a geochemical model including Monod kinetics. Model simulations reproduced the release of iron and TEs observed throughout the experiments, e.g., Mn (up to 203 μg L −1 ), V (up to 79 μg L −1 ), As (up to 17 μg L −1 ) and Cu (up to 328 μg L −1 ), suggesting a potential contamination of pore water by STD. Therefore, the results of this study can help to better evaluate the potential impacts of STD.2 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Neoformation of exotic copper minerals from gel-like precursors at the Exótica deposit, Chuquicamata, Chile(Springer Science+Business Media, 2022-11-16)At the Exótica deposit, south of the giant porphyry copper deposit of Chuquicamata (Atacama Desert, Chile), Cu-rich groundwater seeped out at several locations in the Exótica open pit (Mina Sur) during sampling in 2009–2011. At their outflows, these solutions formed blueish and greenish copper-bearing gel-like precipitates. These gels contained atacamite and copper sulfate hydroxides such as devilline, spangolite, posnjakite, schulenbergite, and brochantite, which were identified by XRD, SEM, ESEM, and FTIR. The formation of the gel materials was studied under humid and dry conditions during and after maturation and water evaporation. Atacamite was found associated to outflowing saline solutions with pH 5.7, SO4/Cl weight ratios of 0.42–0.48, SO4/NO3 ratios of 0.48–0.50. These solutions are seen as an expression of the the lower aquifer of the Calama basin. Most copper sulfate hydroxides (spangolite, posnjakite, schulenbergite) were associated with slightly acidic freshwaters (pH 6.0 to 6.5, SO4/Cl ratios of 3.08–4.99, SO4/NO3 ratios of 2.52–3.13). In contrast, devilline formed in gels with near neutral to slightly alkaline water (pH 7.2 to 7.8, SO4/Cl ratio of 8.34, and SO4/NO3 ratio of 6.05). Non-copper-bearing precipitates formed by evaporation of the supernatant solutions from the gel. Gypsum precipitated first, then blödite (sodium-magnesium sulfate), and finally halite. Slightly negative sulfur isotope values suggest that the sulfur source in the neoformed gels is primarily the oxidation of sulfides rather than sulfate of sedimentary origin. The studied copper-gel seeps suggest that they might represent a modern precursor of the latest atacamite-brochantite-gypsum mineralization event at Exótica. These data support that the atacamite-brochantite-gypsum mineralization at Exótica is linked to the inflow of Cl-SO4-dominated groundwater from the lower saline aquifer of the Calama basin into the Chuquicamata-Exótica-Radomiro Tomic complex. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Genesis of the exotic chrysocolla — “copper pitch/wad” — atacamite/brochantite ore at the Exótica (Mina Sur) deposit, Chuquicamata, Chile(Springer Science+Business Media, 2022-11-09)Detailed mineralogical and textural studies, combined with sequential X-ray diffraction and geochemical modeling, helped to solve the “copper pitch/wad” enigma in the Exótica deposit located downstream of the Chuquicamata porphyry copper deposit. Copper pitch and copper wad are essentially chrysocolla with co-precipitated Mn oxides, mainly birnessite, as well as pseudo-amorphous Mn oxide/oxyhydroxides. Linking the mineralogical, geochemical, and textural evidences with the geological, tectonic, and climatic evolution of the Chuquicamata–Calama area, a four-step genetic model for the evolution of the Exótica deposit is presented: (A) formation of a mature supergene enrichment profile at Chuquicamata (~ 30–25 Ma to ~ 15 Ma) during an erosion-dominated regime (∼900 m of erosion) which was accompanied by acidic (pH ∼2–4) Cu-Mn-Si-dominated rock drainage (ARD) with fluid flow southwards through the Exótica valley towards the Calama Basin, resulting in a strongly kaolinized and chrysocolla/copper wad-impregnated bedrock of the Exótica deposit; (B) deposition of the Fortuna gravels in the Exótica valley (starting ∼19 Ma) intercepted the Cu-Mn-Si-dominated ARD, triggering the main chrysocolla, copper pitch/wad mineralization as syn-sedimentary mineralization by chiefly surficial flow in strongly altered gravels; (C) tectonic freezing and onset of hyper-aridity (∼15–11 Ma) exposed the enriched chalcocite blanket of Chuquicamata to oxidation, resulting in acidic (pH ~ 2–4) and Cu-Si-dominated solutions with less Mn. These solutions percolated in a slightly more reducing groundwater flow path and mineralized relatively unaltered gravels with pure chrysocolla; and (D) ingression of confined chloride-rich groundwater in the upper oxidation zone of Chuquicamata, most likely between 6 and 3 Ma, is responsible for the atacamite/brochantite mineralization (pH ~ 5.5–7) of mainly unaltered gravels in the northern and central part of the Exótica deposit.1 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Reconstructing a pre-mining geochemical baseline using a proximal natural analog and geochemical modeling: Los Bronces and Yerba Loca, Central Chile(Elsevier BV, 2025-10-01)• ARD of analog site helps to reconstruct pre-mining geochemical baseline. • Schwertmannite and hydrobasaluminite control pH along flow path below 5. • Coprecipitation and sorption processes control trace element concentrations. • ARD source freezing and snow- and glaciermelt control annual element cycling. • Pre-mining ARD had pH between 2.5 and 5 with important copper concentration. Due to the lack of pre-mining mineralogical and geochemical data at historic mine sites, evaluation of the pre-mining geochemical baseline condition is required. For this purpose, we reconstructed the pre-mining geochemical baseline for Los Bronces mine (Central Chile) using the Yerba Loca Nature Sanctuary, located 6 km south, as a proximal natural analog where in similar altitudes (4000–4200 m) than in Los Bronces (3600–4000 m), mineralized breccias are currently undergoing natural weathering, leading to acid rock drainage (ARD) with pH values as low as 2.57 with SO 4 at 2893 mg/L, Fe at 285 mg/L, Al at 64.4 mg/L, and Cu at 54.4 mg/L during summer. The stream's pH, initially controlled by jarosite and later by schwertmannite, remains below 3.94, sustaining elevated Cu concentrations. In winter, pH rises towards neutral due to frozen ARD sources at high elevation (>3600 m asl) combined with rainfall-driven dilution in the lower catchment, decreasing metal loads in the streams. Archival data indicates that pre-mining breccias at Los Bronces, with a Cu grade of 1.43 wt%, were composed of 1.43 wt% pyrite, 0.92 wt% chalcopyrite, and other sulfide minerals, leading to significant ARD when weathered. Based on similarities with Yerba Loca and geochemical modeling results, it is inferred that pre-mining drainage at Los Bronces had a pH range of 2.5 to 5 during summer, with likely higher Cu concentrations but similar trace element levels, suggesting a similar annual cycle as today observed at Yerba Loca with a potential increase towards neutral pH in winter.1 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Rare Earth Element and Yttrium (REY) Hyper-Enriched Karst Bauxites of the Mercedes-Aceitillar Mining District, Sierra de Bahoruco, SW Dominican Republic(Society of Economic Geologists, Inc, 2026-02-23)Rare earth elements, including yttrium (REYs), are the most sought-after among the so-called critical or strategic elements for the low-carbon energy industry. In the past decade, karst bauxite deposits have been targeted as potential nonconventional sources of these elements. The karst bauxite deposits from the Mercedes-Aceitillar mining district, classified as Fe-rich bauxites and bauxites sensu stricto, contain anomalously high REY contents oscillating between 514 and 28,787 ppm (median of 1,489 ppm), making them the most REY-enriched karst bauxites globally. Most of the samples studied are enriched in light rare earth elements (La-Nd; up to 7,449 ppm) and Y (up to 14,830 ppm). However, the most REY-enriched bauxites yield particularly high middle rare earth element (Sm-Gd; up to 4,579 ppm) and heavy rare earth element (Tb-Lu; up to 6,163 ppm) contents. In addition, the studied bauxites contain significant amounts of other critical metals, such as Sc and Ga (median of 62 and 39 ppm, respectively). The mineralogy consists predominantly of Al oxyhydroxides (mostly gibbsite), with variable amounts of Fe oxyhydroxides and kaolinite. The REY mineralogy in samples with high REY contents (>3,000 ppm) consists mainly of REY-bearing phosphates (e.g., monazite, xenotime, rhabdophane, churchite) and/or carbonates (bastnäsite group). In samples with moderate REY contents (<3,000 ppm), the main REY-bearing minerals are Al oxyhydroxides, onto which the REYs are most likely adsorbed. These findings indicate that the potential extraction of REYs and other critical metals, such as Sc and Ga, in the studied bauxites from the Mercedes-Aceitillar mining district could add, on average, an ~20% surplus to the revenue obtained from Al2O3 exploitation. The unprecedented REY contents discovered in these karst bauxites from the Dominican Republic present a unique opportunity to unravel critical metal concentration mechanisms in supergene environments and to develop new geochemical models for nonconventional REY deposits.8 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Comparative study of iron and trace element mobilization during Fe-oxide bioreduction in mine tailings: a case study of Ensenada Chapaco (Chile) and Portman Bay (Spain): Bioreduction and metal release in mine-tailings(Universitat de Barcelona, 2025-01-01)elements (e.g. Ti, Ni, Cd, Pb), leading to contamination of the marine environment. Sea-Tailings Disposal (STD) along the northern coast of Chile (Ensenada Chapaco) and along the eastern coast of Spain (Portman Bay) results in an adverse impact on the environment. This paper focuses on bioreduction under marine conditions. To this end, two column experiments were carried out with samples from Portman Bay and Ensenada Chapaco. Lactate (i.e. organic matter source) was supplied during the experiments. The results obtained are compared with those from batch experiments performed under similar conditions.In the column filled with Portman Bay tailings, the high content of magnetite (15wt%) in contact with water gives rise to a large magnetite surface area and abundant Fe(III), which results in a high release of Fe(II) and Trace Elements (TE). Since Fe(II) adsorbs onto the magnetite surface reducing the availability of Fe(III), the magnetite bioreduction and the consequent TE release decrease after 2000h. By contrast, the magnetite bioreduction lasts longer (3000h) in the column with Ensenada Chapaco tailings. This is because a lower magnetite content in the tailings (1wt%) provides a smaller reactive surface area yielding less Fe(III). Consequently, the concentrations of Fe(II) and TE in the output solutions are lower, which slows down the Fe(II) adsorption onto magnetite. This results in a longer magnetite bioreduction. Bioreduction is regulated by the availability of Fe(III) in both columns.It is inferred that the bioreduction rate diminishes as a function of time and increases as a function of soluble Fe(II) concentration. Moreover, the concentrations of TE released from the two bioreduced tailings exceed the elemental concentrations under marine conditions.1 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Comparative Study of Iron and Trace Element Mobilization during Fe-Oxide Bioreduction in Mine Tailings: a case study of Ensenada Chapaco (Chile) and Portman Bay (Spain)(Cartographic and Geological Institute of Catalonia, 2025-02-01)elements (e.g. Ti, Ni, Cd, Pb), leading to contamination of the marine environment. Sea-Tailings Disposal (STD) along the northern coast of Chile (Ensenada Chapaco) and along the eastern coast of Spain (Portman Bay) results in an adverse impact on the environment. This paper focuses on bioreduction under marine conditions. To this end, two column experiments were carried out with samples from Portman Bay and Ensenada Chapaco. Lactate (i.e. organic matter source) was supplied during the experiments. The results obtained are compared with those from batch experiments performed under similar conditions.In the column filled with Portman Bay tailings, the high content of magnetite (15wt%) in contact with water gives rise to a large magnetite surface area and abundant Fe(III), which results in a high release of Fe(II) and Trace Elements (TE). Since Fe(II) adsorbs onto the magnetite surface reducing the availability of Fe(III), the magnetite bioreduction and the consequent TE release decrease after 2000h. By contrast, the magnetite bioreduction lasts longer (3000h) in the column with Ensenada Chapaco tailings. This is because a lower magnetite content in the tailings (1wt%) provides a smaller reactive surface area yielding less Fe(III). Consequently, the concentrations of Fe(II) and TE in the output solutions are lower, which slows down the Fe(II) adsorption onto magnetite. This results in a longer magnetite bioreduction. Bioreduction is regulated by the availability of Fe(III) in both columns.It is inferred that the bioreduction rate diminishes as a function of time and increases as a function of soluble Fe(II) concentration. Moreover, the concentrations of TE released from the two bioreduced tailings exceed the elemental concentrations under marine conditions.1