3. Producción

Browse

Search Results

Now showing 1 - 10 of 21

Some of the metrics are blocked by your
consent settings
Heavy metal contents in soils and native flora inventory at mining environmental liabilities in the Peruvian Andes
(Elsevier, 2020-12-16)
Inadequate waste management in Mining Environmental Liabilities (MEL) represents a risk for the environment and human health and generates social problems. The aim of this article is twofold: i) to evaluate the environmental quality of soils from a geo-ecological perspective; and ii) to inventory native flora around two MEL in the Hualgayoc district in the Peruvian Andes. Soil samples collected for topsoil (upper 30 cm; i.e., soil arable layer) and subsoil (30–60 cm) were classified as Gleyic Cambisols and showed extremely acid pH (3.50–4.19 in site #1 and 2.74–4.02 in site #2). The mineralogical composition of soils is dominated by illite, kaolinite, quartz, and jarosite. The concentrations of six potentially toxic elements (Pb, Zn, As, Cu, Ag, and Cd) were determined. High concentrations of Pb (4683 mg kg−1), Zn (724.2 mg kg−1), Cu (511.6 mg kg−1), Ag (33.4 mg kg−1), and As (3611 mg kg−1) exceeded the maximum permissible limits for agricultural soils according to Peruvian and Canadian regulations. Applied geochemical indexes classified some of the soils as extremely polluted and therefore the studied MEL represent a very high ecological risk. Twenty-two species of native flora belonging to 12 family species were inventoried in such contaminated sites thus having the potential to be used for phytoremediation purposes.
Some of the metrics are blocked by your
consent settings
Cryptic alkaline magmatism in the oceanic Caribbean arc (Camagüey area, Cuba)
(Elsevier, 2020-12-01)
Mid and Late Cretaceous arc-related basaltic rocks in the Camagüey area, East Central Cuba, record an intriguing seemingly random enrichment in alkalis that suggests alkaline affinity, representing an oddity in the Greater Antilles. In this study, the petrology and geochemistry of volcanic rocks from the Camujiro, Piragua and La Mulata Formations have been investigated. The rocks bear a diverse mineral assemblage including feldspars (plagioclase and potassium feldspar), clinopyroxene, phlogopite and amphibole with both equilibrium and disequilibrium textures. Clinopyroxene porphyritic crystals show conspicuous oscillatory and convolute zoning and reveal events of mafic recharge and crystallization in equilibrium with alkaline and calc-alkaline basaltic magmas and their mixtures. Composition of fluorophlogopite xenocrystals is consistent with crystallization from mafic alkaline liquids. Unlike whole-rock major element composition, immobile trace element abundances suggest a systematic calc-alkaline affinity. Chondrite-normalized rare-earth element (REE) patterns are similar to those of calc-alkaline and high-K (and [sbnd]Th) calc-alkaline rocks from the Caribbean Antilles. Geochemical modelling indicates that the parental basic magmas formed by a 5–10% hydrous partial melting of spinel-facies depleted mantle fluxed by fluids evolved from subducted oceanic crust and pelagic sediments, as well as fractional crystallization. Random enrichment in alkalis in studied samples is attributed to the entrainment during ascent of material derived from mafic alkaline melts injected in the upper mantle or the root of the island-arc. Our new data establish a mature stage in the evolution of the Caribbean island-arc by Cenomanian times capable of sourcing alkaline melts and the existence of a thickened island arc crust that favored fractional crystallization and magma chamber recharge processes unlike in previous stages of the island-arc construction.
Some of the metrics are blocked by your
consent settings
Speciation of metals in indigenous plants growing in post-mining areas: dihydroxynicotianamine identified as the most abundant Cu and Zn ligand in Hypericum laricifolium
(Elsevier, 2021-10-21)
Ag, As, Cu, Pb and Zn were found to be the principal metallic contaminants of a post-mining area of Peru (Hualgayoc, Cajamarca). Study of metal distribution amongst roots, stems, and leaves of four indigenous hypertolerant plant species, Arenaria digyna, Puya sp., Hypericum laricifolium, Nicotiana thyrsiflora indicated significant translocation of Zn (0.6 < TF ≤ 10.0) and Cu (0.4 < TF ≤ 6.5) into aerial plant organs and substantial water-extractable fraction (20–60%) of these metals, except for A. digyna (root and stems). A study of the metal speciation by ultrahigh-performance size-exclusion (fast-SEC) and hydrophilic ion interaction (HILIC) liquid chromatography with dual ICP (inductively coupled plasma) and electrospray (ESI) Orbitrap MS detection revealed the presence of nicotianamine and deoxymugineic acid copper and zinc complexes in roots, stem and leaves of N. thyrsiflora and Puya sp., and nicotianamine alone in A. digyna. A previously unreported compound, dihydroxy-nicotianamine was identified as the most abundant Cu and Zn ligand in H. laricifolium. The presence of arsenobetaine and an arsenosugar was confirmed by ESI MS. Ag and Pb were hardly translocated to leaves and were found as high molecular species; one of the Pb-containing species co-eluted in fast-SEC-ICP MS with rhamnogalacturonan-II-Pb complex commonly found in in the walls of plants.
Some of the metrics are blocked by your
consent settings
Trace element geochemistry of sphalerite and chalcopyrite in arc-hosted VMS deposits
(Elsevier, 2021-08-26)
Trace element compositions of sphalerite and chalcopyrite have been investigated for four arc-hosted Cretaceous VMS deposits (María Teresa, Perubar, and Palma in Peru, and Cerro de Maimón in the Dominican Republic) using laser ablation inductively-coupled plasma mass spectrometry. In sphalerite, Fe, Mn, Cd, Hg, Ag, Sb, Se, In, Ge, and Ga are lattice-bound, whereas Sn, Tl, Bi, and Pb occur at least partly as mineral microinclusions. Significant variations in the contents of minor and trace elements are observed in sphalerite grains from individual deposits. A strong negative correlation between Fe (Inter-Quartile Range [IQR] 44,009–18,168 ppm) and Zn indicates a dominant Fe2+ ↔ Zn2+ simple isovalent substitution. Regarding potential high-tech by-products, the contents of In (IQR 42–1.6 ppm, up to 415 ppm) and Ga (IQR 31–5.9 ppm, up to 96 ppm) in the studied sphalerite are normally much higher than those of Ge (IQR 0.85–0.16 ppm, up to 9.3 ppm). Correlation trends suggest Cu+ + In3+ ↔ 2Zn2+, Cu+ + Ga3+ ↔ 2Zn2+, and more complex substitution mechanisms of Zn involving combinations of monovalent (Cu+, Ag+), divalent (Ge2+?), trivalent (In3+, Ga3+, [Sn3+?]), and quadrivalent (Ge4+, Sn4+) cations. As for chalcopyrite, Zn, Ag, Sn, Cd, Se, In, Ga, and Ge are interpreted to be lattice-bound, whereas Mo, Au, Tl, Sb, Pb, and Bi probably occur as microinclusions. Relative to sphalerite, chalcopyrite is depleted in In (IQR 28–8.4 ppm, up to 49 ppm) and Ga (IQR 8.3–2.9 ppm, up to 24 ppm) and enriched in Ge (IQR 5.9–0.70 ppm, up to 80 ppm). Of the other trace elements, Zn (IQR 426–190 ppm) is the most highly concentrated in the studied chalcopyrite, followed by Ag (IQR 136–23 ppm), Se (IQR 64–22 ppm), Sn (IQR 53–1.3 ppm), and Cd (IQR 12–6.0 ppm). General positive correlation trends between Zn, Cd, In, Ge, and Ga in chalcopyrite suggest varied coupled substitution mechanisms of Fe and Cu with fluctuating valences due to covalent bonding. Trace-element distribution patterns in sphalerite and chalcopyrite were studied for the zone-refined Sofía-D massive sulfide body in the María Teresa deposit, which comprises a lower lower portion of dominant pyrite sheathed upward by zones of chalcopyrite (Cu zone), sphalerite (Zn zone) and galena + sphalerite ± fahlore ± barite (Pb – Zn – Ag zone). Bottom to top of the sulfide body, sphalerite records progressive depletion in In, Cu, Mn, and Se, and enrichment in Ge. This distribution pattern agrees with increasing crystallization temperatures and/or volatile magmatic influx towards the lower portion of the massive mineralization. Distribution of trace elements in chalcopyrite is rather uneven except for a sustained enrichment in Se towards the basal portion of the sulfide body. The fact that such trends are preserved in spite of extensive recrystallization during thermal metamorphism in parts of the Sofía-D massive sulfide mineralization suggests i) a closed metamorphic system and ii) that element interdiffusion was prominently local. Accordingly, we propose that sphalerite lattice-bound trace elements distribution patterns described in this article can help determine the polarity of massive sulfide bodies in VMS districts in metamorphosed and tectonized terranes.
Some of the metrics are blocked by your
consent settings
Distribution of indium, germanium, gallium and other minor and trace elements in polymetallic ores from a porphyry system: the Morococha district, Peru
(Elsevier, 2021-09-01)
We report indium, germanium, gallium, and other minor and trace elements contents in sphalerite, chalcopyrite, galena, and tetrahedrite-tennantite occurring in skarn and skarn-free (“Cordilleran”) polymetallic mantos and vein ore bodies in the Miocene porphyry-related Morococha District, Central Peru. Among the investigated minerals, LA-ICP-MS measurements indicate that In and Ga concentrate mostly in sphalerite (Inter-Quartile Range [IQR] 217–2.7 ppm and up to 4608 ppm In; IQR 61–2.0 ppm and up to 2137 ppm Ga) and chalcopyrite (IQR 109–32 ppm and up to 1070 ppm In; IQR 62–1.5 ppm and up to 630 ppm Ga). In coeval generations of sphalerite and chalcopyrite, the contents of In and Ga in sphalerite are at least two times higher than in chalcopyrite. Germanium content is generally low in the four analyzed minerals (IQR 1.2–0.19 ppm), although late Fe-poor sphalerite may yield much higher values (IQR 129–74 ppm). Certain trace element contents appear to correlate with (i) the evolving characteristics of the hydrothermal fluids during individual mineralization events, and (ii) the location of the studied ore bodies relative to the hydrothermal feeders. The highest In values in sphalerite are found in high-sulfidation assemblages in Cordilleran polymetallic veins and, with lower amounts, in low-sulfidation assemblages in skarn bodies. In intermediate-sulfidation assemblages in Cordilleran mineralization, In content decreases from early to late generations of sphalerite, while that of Ge increases. Spatial trace-element trends in Cordilleran veins and replacement bodies formed during the so-called “Morococha district-scale polymetallic event” include, from porphyry-distal to porphyry-proximal locations: i) In and Cu, and to a lesser extent Ga, enrichment in sphalerite; ii) Se and Hg enrichment and Sn and Ag depletion in chalcopyrite; iii) In enrichment in galena; and iv) Ag depletion in tetrahedrite-tennantite. Our dataset suggests that In is incorporated in the sphalerite crystal lattice via coupled substitutions involving Cu and subordinately also Sn and Ag. Availability of Cu in the mineralizing fluids is therefore key to In enrichment in sphalerite. Progressive dilution of metal-rich magmatic-hydrothermal fluids and Cu precipitation probably account for the progressive In depletion in distal-to-porphyry Zn-Pb-Ag and Ag-Pb Cordilleran polymetallic mineralization and in late sphalerite generations in intermediate-sulfidation assemblages.
Some of the metrics are blocked by your
consent settings
Accumulation of As, Ag, Cd, Cu, Pb, and Zn by native plants growing in soils contaminated by mining environmental liabilities in the Peruvian Andes
(MDPI AG, 2021-02-01)
The capability of native plant species grown in polluted post-mining soils to accumulate metals was evaluated in view of their possible suitability for phytoremediation. The study areas included two environmental liabilities in the Cajamarca region in the Peruvian Andes. The content of As, Ag, Cd, Cu, Pb, and Zn was determined in individual plant organs and correlated with soil characteristics. The degree of the pollution depended on the metal with results ranging from uncontaminated (Cd) to moderately (Zn), strongly (As, Cu), and extremely contaminated (Pb, Ag) soils. The metals were mainly present in the fractions with limited metal mobility. The bioaccu-mulation of the metals in plants as well the translocation into overground organs was determined. Out of the 21 plants evaluated, Pernettya prostrata and Gaultheria glomerate were suitable for Zn, and Gaultheria glomerata and Festuca sp. for Cd, phytostabilization. The native species applicable for Cd phytoremediation were Ageratina glechonophylla, Bejaria sp., whereas Pernettya prostrata Achyrocline alata, Ageratina fastigiate, Baccharis alnifolia, Calceolaria tetragona, Arenaria digyna, Hypericum laricifolium, Brachyotum radula, and Nicotiana thyrsiflora were suitable for both Cd and Zn. None of the studied plants appeared to be suitable for phytoremediation of Pb, Cu, As and Ag.
Some of the metrics are blocked by your
consent settings
Trace element composition and U-Pb ages of cassiterite from the Bolivian tin belt
(Springer Science and Business Media Deutschland GmbH, 2021-11-01)
The Bolivian tin belt is a metallogenic province in the Eastern Cordillera of the Andes known for its Sn, W, Ag, and base metal deposits. Cassiterite, which is a major constituent in many magmatic-hydrothermal ore deposits from the Bolivian tin belt, can incorporate dozens of elements within its crystal lattice, making it a useful geological tracer mineral and also a potential host of critical elements. New U-Pb dating of cassiterite yields Late Triassic (Kellhuani deposit) and Late Oligocene to earliest Miocene (Viloco, Huanuni, and Llallagua deposits) ages. These ages confirm that Sn mineralization in the Bolivian tin belt occurred at least in two separate events during two major magmatic episodes apparently triggered by mantle upwelling, decompression melting, and basalt production promoting high heat flow into the overlying crust. The composition of studied hydrothermal cassiterite yields some geochemical trends that are attributed to its distance to the causative intrusion and/or level of emplacement. For example, cassiterite is generally enriched in Nb and Ta and yields higher Ti/Zr and Ti/Sc ratios in samples from xenothermal ore deposits located adjacent to intrusive complexes relative to shallow xenothermal and epithermal ore deposits. Therefore, these geochemical trends in cassiterite are useful tracers pointing to magmatic-hydrothermal centers. REE distribution in cassiterite was likely influenced by boiling processes, which resulted in tetrad-type irregularities. Cassiterite from the Bolivian tin belt is unattractive as a source for Nb (interquartile range [IQR] 4.84–0.037 ppm), Ta (IQR 0.0924–0.0126 ppm), and Ge (IQR 3.92–0.776 ppm). Some deposits, however, contain cassiterite relatively enriched in In (IQR 96.9–9.78 ppm, up to 1414 ppm) and Ga (IQR 92.1–3.03, up to 7437 ppm), that could constitute an attractive supplementary source for these elements in addition to sulfide minerals in the same deposits.
Some of the metrics are blocked by your
consent settings
Geology, mineralogy, and cassiterite geochronology of the Ayawilca Zn-Pb-Ag-In-Sn-Cu deposit, Pasco, Peru
(Springer Science+Business Media, 2021-09-13)
The Ayawilca deposit in Pasco, Peru, represents the most significant recent base-metal discovery in the central Andes and one of the largest undeveloped In resources globally. As of 2018, it hosts an 11.7 Mt indicated resource grading 6.9% Zn, 0.16% Pb, 15 g/t Ag, and 84 g/t In, an additional 45.0 Mt inferred resource grading 5.6% Zn, 0.23% Pb, 17 g/t Ag, and 67 g/t In, and a separate Sn-Cu-Ag inferred resource of 14.5 Mt grading 0.63% Sn, 0.21% Cu, and 18 g/t Ag. Newly obtained U–Pb dates for cassiterite by LA-ICP-MS (22.77 ± 0.41 and 23.05 ± 2.06 Ma) assign the Ayawilca deposit to the Miocene polymetallic belt of central Peru. The polymetallic mineralization occurs as up to 70-m-thick mantos hosted by carbonate rocks of the Late Triassic to Early Jurassic Pucará Group, and subordinately, as steeply dipping veins hosted by rocks of the Pucará Group and overlying Cretaceous sandstones-siltstones of the Goyllarisquizga Group. Relicts of a distal retrograde magnesian skarn and cassiterite (stage pre-A) were identified in the deepest mantos. The volumetrically most important mineralization at Ayawilca comprises a low-sulfidation assemblage (stage A) with quartz, pyrrhotite, arsenopyrite, chalcopyrite, Fe-rich sphalerite, and traces of stannite and herzenbergite. Stage A sphalerite records progressive Fe depletion, from 33 to 10 mol% FeS, which is compatible with the observed transition from low- to a subsequent intermediate-sulfidation stage (B) marked by the crystallization of abundant pyrite and marcasite. Finally, during a later intermediate-sulfidation stage (C) sphalerite (up to 11 mol% FeS), galena, native bismuth, Cu-Pb-Ag sulfosalts, siderite, Mn-Fe carbonates, kaolinite, dickite, and sericite were deposited. This paragenetic evolution shows striking similarities with that at the Cerro de Pasco Cordilleran-type polymetallic deposit, even if at Ayawilca stage C did not reach high-sulfidation conditions. The occurrence of an early retrograde skarn assemblage suggests that the manto bodies at Ayawilca formed at the transition between distal skarn and skarn-free (Cordilleran-type) carbonate-replacement mineralization. Mineral assemblages define a T-fS2 evolutionary path close to the pyrrhotite-pyrite boundary. Buffering of hydrothermal fluids by underlying Devonian carbonaceous phyllites of the Excelsior Group imposed highly reduced conditions during stage A mineralization (logfO2 < − 30 atm). The low fO2 favored efficient Sn mobility during stages pre-A and A, in contrast to other known ore deposits in the polymetallic belt of central Peru, in which the occurrence of Sn minerals is minor. Subsequent cooling, progressive sealing of vein walls, and decreasing buffering potential of the host rocks promoted the shift from low- (stage A) to intermediate-sulfidation (stages B and C) states. LA-ICP-MS analyses reveal significant In contents in Fe-rich sphalerite (up to 1.7 wt%), stannite (up to 1908 ppm), and chalcopyrite (up to 1185 ppm). The highest In content was found in stage A sphalerite that precipitated along with chalcopyrite and stannite, thus pointing to the early, low-sulfidation assemblage as prospective for this high-tech metal in similar mineral systems. Indium was likely incorporated into the sphalerite crystal lattice via Cu+ + In3+ ↔ 2 Zn2+ and (Sn, Ge)4+ + (Ga, In)3+ + (Cu + Ag)+ ↔ 4 Zn2+ coupled substitutions. Indium incorporation mechanisms into the stannite and chalcopyrite crystal lattices remain unclear.
Some of the metrics are blocked by your
consent settings
Low-temperature hydrothermal Pt mineralization in uvarovite-bearing ophiolitic chromitites from the Dominican Republic
(Springer Science+Business Media, 2021-10-15)
Platinum-group elements (PGEs) occur in ophiolitic chromitite in the Dominican Republic as platinum-group minerals (PGMs) in spatial association with hydrothermal uvarovite and chromian clinochlore. Bulk-rock total PGE content in a single analyzed chromitite sample is of 6.54 g/t. Three main PGM types are distinguished: euhedral magmatic laurite completely encased in chromite, subhedral to euhedral Ru-Os-Fe-(Ir) compounds partially encased in chromite, and anhedral Pt-Fe–Ni-rich grains exclusively embedded in uvarovite or chromian clinochlore. The Ru-Os-Fe-(Ir) compounds are interpreted as magmatic Ru-Os sulfides that experienced desulfurization during hydrothermal alteration of the chromitites, whereas the Pt-Fe–Ni-rich grains are hydrothermal in origin. We propose a model in which the Pt-Fe–Ni-rich PGMs formed via the accumulation of nanoparticles directly precipitated from the hydrothermal fluids. An estimation of the temperature of crystallization of uvarovite and chromian clinochlore suggests hydrothermal alteration of the chromitite within the thermal range of 150–350 °C. Thermodynamic modeling shows that, within this range of temperature, Pt could be mobilized as aqueous bisulfide complexes (HS−) by S-poor, highly reducing hydrothermal fluids originated during serpentinization of the host chromitite rock. The crystallization of Ni sulfides in the chromitite would drop the S concentration of the fluid, causing the precipitation of Pt as native element. Ultimately, this process contributes to constrain the conditions for the genesis of hydrothermal PGE mineralizations in ophiolitic chromitites.
Some of the metrics are blocked by your
consent settings
Petrology, metallogeny and U-Pb geochronology of the Paleoproterozoic mafic-ultramafic Hamutenha intrusion, Angolan Shield
(Elsevier BV, 2022-10-12)
The Hamutenha intrusion (Huíla province, SW Angola) is a 3-km-long elongated magmatic body defined by a set of two intrusive units. The northern unit is formed by alternating bands of dunites and olivine gabbros, while the southern unit is composed of amphibole diorites. The Hamutenha body is hosted by the Paleoproterozoic Epupa Complex in the Angolan Shield, SW margin of the Congo Craton. A mineralogical, petrological and geochemical study of the Hamutenha intrusion has been performed. The constrained compositional features of the parental melt suggest interaction of tholeiitic magmas with a significant enrichment in Fe and Ti. Although disseminated Fe–Ni–Cu-(Co) secondary sulphides are observed, both the crustal contamination parameters and generally low bulk-rock metals contents indicate that these elements were most likely previously extracted from the parental melt. U–Pb zircon dating of amphibole diorite samples from the southern unit yields a date of 1844 ± 14 Ma. These data suggest that the emplacement of these rocks was previous to the KC emplacement and it was probably related to the Paleoproterozoic Epupa Complex magmatism.

3. Producción

Browse

Filters

Settings

Sort By

Results per page

Search Results