Jarosite versus Soluble Iron-Sulfate Formation and Their Role in Acid Mine Drainage Formation at the Pan de Azúcar Mine Tailings (Zn-Pb-Ag), NW Argentina

Secondary jarosite and water-soluble iron-sulfate minerals control the composition of acid mine waters formed by the oxidation of sulfide in tailings impoundments at the (Zn-Pb-Ag) Pan de Azúcar mine located in the Pozuelos Lagoon Basin (semi-arid climate) in Northwest (NW) Argentina. In the primary zone of the tailings (9.5 wt % pyrite-marcasite) precipitation of anglesite (PbSO4), wupatkite ((Co,Mg,Ni)Al2(SO4)4) and gypsum retain Pb, Co and Ca, while mainly Fe2+, Zn2+, Al3+, Mg2+, As3+/5+ and Cd2+ migrate downwards, forming a sulfate and metal-rich plume. In the oxidation zone, jarosite (MFe3(TO4)2(OH)6) is the main secondary Fe3+ phase; its most suitable composition is M = K+, Na+, and Pb2+and TO4 = SO42−; AsO42−. During the dry season, iron-sulfate salts precipitate by capillary transport on the tailings and at the foot of DC2 (tailings impoundment DC2) tailings dam where an acid, Fe2+ rich plume outcrops. The most abundant compounds in the acid mine drainage (AMD) are SO42−, Fe2+, Fe3+, Zn2+, Al3+, Mg2+, Cu2+, As3+/5+, Cd2+. These show peak concentrations at the beginning of the wet season, when the soluble salts and jarosite dissolve. The formation of soluble sulfate salts during the dry season and dilution during the wet season conform an annual cycle of rapid metals and acidity transference from the tailings to the downstream environment.Fil: Murray, Jesica María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Kirschbaum, Alicia Matilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Dold, Bernhard. Sustainable Mining Research & Consult EIRL; ChileFil: Mendes Guimaraes, Edi. Universidade do Brasilia; BrasilFil: Pannunzio Miner, Elisa Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin

Nanoscale mechanical control of surface electrical properties of manganite films with magnetic nanoparticles

Mechanical control of electrical properties in complex heterostructures, consisting of magnetic FeOx nanoparticles on top of manganite films, is achieved using atomic force microscope AFM based methods. Under applied pressure of the AFM tip, drop of the electrical conductivity is observed inducing an electrically insulating state upon a critical normal load. Current and surface potential maps suggest that the switching process is mainly governed by the flexoelectric field induced at the sample surface. The relaxation process of the electrical surface potential indicates that the diffusion of oxygen vacancies from the bulk of the manganite films towards the sample surface is the dominant relaxation mechanism. The magnetic FeOx nanoparticles, staying attached to the sample surface after the rubbing, protect the underlying manganite films and provide stability of the observed resistive switching effect. The employed mechanical control gives a new freedom in the design of resistive switching devices since it does not depend on the film thickness, and biasing is not neede

Nonstoichiometry driven ferromagnetism in double perovskite La2Ni1-xMn1+ xO6 insulating thin films

This is an open access article published under an ACS AuthorChoice License. See Standard ACS AuthorChoice/Editors' Choice Usage AgreementIn this work we report on the epitaxial growth of LaNiMnO double perovskite thin films on top of (001) oriented SrTiO substrates by RF magnetron sputtering. The influence of oxygen pressure (P O) and growth temperature on the microstructure, stoichiometry of the films, and magnetic and transport properties is thoroughly investigated. It is found that high oxygen pressure promotes the growth of stoichiometric films, with a Ni/Mn ratio almost equal to 1. However, these films exhibit poor ferromagnetic properties with respect to the expected optimum values corresponding to ferromagnetic ordering mediated by superexchange interaction between Mn and Ni according to the Goodenough-Kanamori rules. Most interestingly, films grown at low P O exhibit Ni/Mn ratios below 1, but ferromagnetic properties close to the optimal ones. The valence balance between Ni and Mn ions in nonstoichiometric sample has been elucidated by X-ray absorption spectroscopy. The results indicate that Ni deficiency plays a crucial role in the puzzling insulating ferromagnetic behavior observed in nonstoichiometric samples

Synthesis and crystal structure refinement by th Rietveld method of an antimony-bearing titanite Ca(Ti0.6Al0.2Sb0.2)OSiO4

A synthetic analogue, Ca(Ti0.6Al0.2Sb0.2)OSiO4, of antimony-bearing titanite of a composition similar to that found at St. Marcel-Praborna (Italy) was synthesized using ceramic methods and the crystal structure was refined using the Rietveld method. Unit-cell dimensions (in Å) are a=7.0184(1), b=8.7097(2), c=6.5586(1), and β=113.700(1)°. The substitution of 40% Ti by (Al+Sb) in octahedra causes a loss of long-range coherency of the off-centered Ti atoms. The space group of Sb-bearing titanite is A2/a, like other cases of M3+-M5+-doped titanites. This study confirms that titanite with up to 0.2 Sb atom per f.u. can exist and that the substitution scheme is 2Ti4+↔Al3++Sb5+.Fil: Colombo, Fernando. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pannunzio Miner, Elisa Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin

Mineralogical characterization of topaz from miarolitic pegmatites and W-bearing greisen in the A-type El Portezuelo granite, Papachacra (Catamarca Province), Argentina

The El Portezuelo Granite (Catamarca Province, NW Argentina), probably of Late Devonian or Early Carboniferous age, was emplaced at ≤ 2 kbar and displays the chemical characteristics of an A-type granite. It hosts small miarolitic pegmatites and dikes that belong to the NYF petrogenetic family, miarolitic class, miarolitic-REE subclass, with features more similar to those reported for the gadolinite-fergusonite type. Topaz is widespread both in pegmatites and in a W-bearing greisen genetically related to the granite. In pegmatites it occurs as crystals up to over 15 cm long, showing the forms {120} and {041} (dominant), and also {100}, {010}, {001}, {110}, {130}, {230}, {410}, {150}, {340}, {201}, {203}, {011}, {021}, {031}, {111}, {112}, {221}, {223}, and {445}. Crystals are colorless to pale yellow, more rarely brownish or bluish. Electron-microprobe analyses of gemmy crystals from pegmatites and greisen show that topaz is F-rich (between 19.01 and 20.12 wt. % F, most crystals being slightly zoned) and has very low MgO and TiO2 (≤ 0.02 wt.%), low FeO (≤; 0.03 wt.%), and up to 0.10 wt.% CaO. Refractive indices and unit-cell dimensions reflect the F-rich nature of the studied topaz. This occurrence produces the finest crystals yet known from western South America but probably has no economic potencial as gemstock producer.El Granito El Portezuelo (Provincia de Catamarca, Argentina noroccidental), de probable edad devónica superior a carbonífera inferior, se emplazó a ≤ 2 kbar y posee las características de un granito de tipo A. Aloja pegmatitas miarolíticas y diques de reducidas dimensiones que pertenecen a la familia petrogenética NYF, clase miarolítica, subclase miarolítica-elementos de tierras raras, con rasgos más similares a los del tipo gadolinita-fergusonita. El topacio está bastante difundido en las pegmatitas y en un greisen portador de W genéticamente relacionado al granito. En pegmatitas se encuentra en cristales que superan los 15 cm, mostrando las formas {120} and {041} (dominantes), y también {100}, {010}, {001}, {110}, {130}, {230}, {410}, {150}, {340}, {201}, {203}, {011}, {021}, {031}, {111}, {112}, {221}, {223} y {445}. Los cristales son incoloros a amarillo pálido, más raramente pardos o celestes. Análisis con microsonda de electrones hechos en cristales de calidad de gema muestran que el topacio es rico en F (entre 19,01 y 20,12% F), y con muy bajo MgO y TiO2 (≤ 0,02 %), bajo FeO (≤ 0,03%), y hasta 0,10% de CaO. Los índices de refracción y las dimensiones de la celda unidad reflejan la naturaleza rica en F del topacio estudiado. Esta localidad produce los mejores cristales hasta ahora conocidos del occidente de Sudamérica pero probablemente carece de potencial como depósito de material gemológico.Fil: Colombo, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Lira, Raul. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Pannunzio Miner, Elisa Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin

Study of Kβ X-ray emission spectroscopy applied to Mn(2−x)V(1+x)O4 (x=0 and 1/3) oxyspinel and comparison with XANES

Oxidation state and coordination of transition metal cations seems to be hard to assess when considering multiple cations, each one with different possible oxidation states. In fact, this is the case of the spinel-type double oxides family. High resolution Kβ X-ray fluorescence spectra were measured in Mn(2−x)V(1+x)O4 (x=0 and 13) spinels-type double oxides in order to determine the oxidation state and coordination of V and Mn cations. The relative intensity of radiative Auger effect KM2,3M4,5 to the total intensity and the integral absolute difference value were used as reference parameters for the characterization of Mn oxidation states. The coordination of Mn ions was inferred by the intensity of the Kβ5 line. In the case of V compounds, it was used as the intensity of the line Kβ′ relative to the total area of Kβ region. The obtained results were further compared with X-ray absorption spectra analysis, showing good agreements regarding the oxidation state characterization. However, there were found some discrepancies in coordination, due to customary oversimplifications in the Kβ5 line origin. The obtained results might represent valuable and useful data for chemical scopes of characterizing spinel-type oxides family.Fil: Ceppi, Sergio Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Mesquita, A.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Pomiro, Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Pannunzio Miner, Elisa Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Tirao, German Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentin

Barbosalita y lipscombita en Cerro Blanco, Córdoba (Argentina): descripción y génesis de fosfatos secundarios en pegmatitas con triplita y apatita

Los dimorfos barbosalita y lipscombita, idealmente Fe2+Fe3+ 2(PO4)2(OH)2, se presentan en la pegmatita El Criollo (64º39¿9¿¿W, 31º21¿28¿¿S), Cerro Blanco, Córdoba, Argentina. En una de las zonas intermedias de esta pegmatita se encuentra un nódulo de triplita bordeado discontinuamente por la asociación portadora de barbosalita y lipscombita. La paragénesis primaria consiste en cuarzo con cristales euhedrales de flúor-apatita, zircón y sulfuros intersticiales (pirita>>calcopirita). La apatita está corroída y los sulfuros están reemplazados por una masa negra verdosa compuesta por granos anhedrales de barbosalita y lispcombita con numerosas inclusiones de fluorita, hematita y escasa fosfosiderita. Los parámetros de celda, obtenidos mediante refinamiento Rietveld, son (en Å): barbosalita (grupo espacial P21/n): a=7.326(2), b=7.446(2), c=7.401(2), ß=118.79(2)º; lipscombita (grupo espacial P43212): a=b=7.388(2), c=12.924(6). Análisis químicos de la barbosalita y lipscombita (microsonda de electrones, n=4) dieron (% en peso) P2O5: 35.72, SiO2: 0.07, FeO: 17.98, Fe2O3: 39.96, MnO: 0.40, Al2O3: 0.22, Na2O: 0.18, CaO: 0.12, MgO: 0.01, F: 0.27, H2O (calculado como 2-F): 4.45, Cl no detectado, total corregido por F=O (99.27). La cantidad de FeO y Fe2O3 se calculó para dar una relación Fe2+: Fe3+ de 1:2 en la fórmula estructural. En general, los fosfatos secundarios en estas pegmatitas indican ambiente oxidante y ácido y un fuerte control de la mineralogía primaria, subrayando la importancia del ambiente a escala muy local en las asociaciones de especies secundarias. Los minerales que cristalizan están muy influenciados por los aspectos cinéticos de las reacciones de disolución y precipitación, y no sólo por las configuraciones estructurales termodinámicamente estables. Las fases secundarias con H2O indican que la alteración continuó hasta temperaturas por debajo de los 250ºCThe dimorphs lipscombite and barbosalite, ideally Fe2+Fe3+ 2(PO4)2(OH)2, occur in El Criollo pegmatite (64º39¿9¿¿W, 31º21¿28¿¿S), Cerro Blanco, Córdoba, Argentina. In one of the intermediate zones of this pegmatite there is a nodule of triplite discontinuously rimmed by the lipscombite-barbosalite-bearing assemblage. The primary paragenesis consists of quartz with euhedral fluorapatite crystals, zircon, and interstitial sulfides (pyrite>>chalcopyrite). Apatite is corroded and sulfides have been replaced by a greenish black mass of anhedral grains of lipscombite and barbosalite, with myriads of inclusions of fluorite, hematite, and scarce phosphosiderite. Cell parameters, obtained by Rietveld refinement, are (in Å): barbosalite (space group P21/n): a=7.326(2), b=7.446(2), c=7.401(2), ß=118.79(2)º; lipscombite (space group P43212): a=b=7.388(2), c=12.924(6). Chemical analyses of barbosalite and lipscombite (electron microprobe, n=4) gave (wt. %) P2O5: 35.72, SiO2: 0.07, FeO: 17.98, Fe2O3: 39.96, MnO: 0.40, Al2O3: 0.22, Na2O: 0.18, CaO: 0.12, MgO: 0.01, F: 0.27, H2O (calculated as 2-F): 4.45, Cl not detected, total corrected for F=O (99.27). The amounts of FeO and Fe2O3 were calculated to give a Fe2+:Fe3+ ratio of 1:2 in the structural formula. In general, secondary phosphates in these pegmatites indicate an oxidizing and acidic environment and a strong control of the primary mineralogy, stressing the importance of the environment at a very local scale in determining the secondary species assemblage. Crystallizing minerals are very influenced by kynetic aspects of the dissolution and precipitation reactions, and not only by the thermodynamically stable structural configurations. Secondary phases containing H2O indicate that alteration continued to temperatures below 250º

Oxidation state characterization in Cr oxides by means of Cr Kb emission spectroscopy

High resolution Kb spectra of Cr oxide were measured using a non-conventional spectrometer. Theoretical spectra were obtained using the DV-Xa method in order to interpret the Kb spectrum structures. Kb spectrum structures were analyzed and spectral parameters show a great sensitivity to the oxidation state and to the Cr-O distance. Purity samples of CrO2 were obtained by means of thermal treatment at 513 ºC under oxygen pressure of 200 bar. X-ray diffraction patterns show a typical rutile structure, without spurious phases. The CrO2 data allowed to confirm the linear dependency of the Kb1,3 and Kb5 energy positions with the oxidation state. The energy of the Kb2,5 line relative to the Kb1,3 line seems to be a suitable parameter for characterization of the oxidation state. The relative Kb´´ transition probability per Cr-O falls exponentially with Cr-O increasing distance. This behaviour was not found in the literature for Cr oxides.Fil: Tirao, German Alfredo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ceppi, Sergio Andres. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Cappelletti, Ariel Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones En Fisico- Química de Córdoba. Universidad Nacional de Córdoba. Facultad de Cs.químicas. Instituto de Investigaciones En Fisico- Química de Córdoba; ArgentinaFil: Pannunzio Miner, Elisa Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones En Fisico- Química de Córdoba. Universidad Nacional de Córdoba. Facultad de Cs.químicas. Instituto de Investigaciones En Fisico- Química de Córdoba; Argentin

Crystal and magnetic structure and cation distribution of Mn2-xV1+xO4 spinels (x = 0, 1/3 and 1)

We synthesized the spinel-type compounds belonging to the Mn2-xV1+xO4 series with x = 0, 1/3 and 1 as polycrystalline powders. Crystal and magnetic structures were refined using synchrotron X-ray and neutron powder diffraction. At 300 K all members crystallize in the cubic system, space group F d over(3, ̄) m, and show a structural transition at low temperature, changing to a tetragonal symmetry (space group I41/amd). Cations distributions between octahedral and tetrahedral sites were refined from neutrons diffraction (ND) data and explained based on crystal field stabilization energies (CFSE) and ionic radii. The magnetic unit cell is the same as the crystallographic one, having identical symmetry relations. The magnetic structure was refined as an arrangement of collinear spins, antiferromagnetically ordered, parallel to the c-axis of the unit cell. The refined site magnetic moments are smaller than those obtained from hysteresis cycles of the M vs. H measurements, indicating that some non-collinear disordered component coexists with the ordered component along the c-axis.Fil: Pannunzio Miner, Elisa Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: de Paoli, Juan Martin. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Resonancias Magnéticas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Sanchez, Rodolfo Daniel. Comision Nacional de Energía Atómica. Gerencia de Área Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Bariloche). División Resonancias Magnéticas; ArgentinaFil: Carbonio, Raul Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin

Nonadiabatic small polarons, positive magnetoresistance, and ferrimagnetism behavior in the partially inverse Mn2-xV1+xO4 spinels

We present experimental results of electrical resistivity (ρ), magnetoresistance (MR), Seebeck coefficient (S), and magnetic susceptibility () experiments at high temperature on the spinel Mn2-xV 1+xO4 series with x=0, 1/ 3, and 1, prepared by solid state reaction. The Rietveld analysis of neutron powder diffraction (NPD) patterns confirm the expected cubic symmetry (SG: Fd-3m) with cell parameters around 8.5 Å. We also precisely calculate the distribution of Mn/V cations, in the tetrahedral and octahedral sites, for the whole series showing an important degree of inversion. The magnetic susceptibility and electrical transport properties show ferrimagnetic and semiconductor behaviors, respectively. A large difference detected between the activation energies for S and ρ indicates the presence of small polarons and the temperature dependence of ρ is well fitted with the nonadiabatic polarons model. All the samples present positive MR at room temperature, in particular, the highest value (around 1%) was observed in the MnV2O4 sample.Fil: Pannunzio Miner, Elisa Victoria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: de Paoli, Juan Martin. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Carbonio, Raul Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Sanchez, Rodolfo Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin