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  • 1.
    Aiglsperger, Thomas
    et al.
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona.
    Proenza, Joaquín A.
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona.
    Font-Bardia, Mercé
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona .
    Baurier-Aymat, Sandra
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona .
    Galí, Salvador
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona .
    Lewis, John F.
    Department of Earth and Environmental Sciences, George Washington University, .
    Longo, Francisco
    Faculty of Engineering, Universidad Católica Tecnológica del Cibao (UCATECI), La Vega.
    Supergene neoformation of Pt-Ir-Fe-Ni alloys: multistage grains explain nugget formation in Ni-laterites2016In: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, p. 1-15Article in journal (Refereed)
    Abstract [en]

    Ni-laterites from the Dominican Republic host rare but extremely platinum-group element (PGE)-rich chromitites (up to 17.5 ppm) without economic significance. These chromitites occur either included in saprolite (beneath the Mg discontinuity) or as ‘floating chromitites’ within limonite (above the Mg discontinuity). Both chromitite types have similar iridium-group PGE (IPGE)-enriched chondrite normalized patterns; however, chromitites included in limonite show a pronounced positive Pt anomaly. Investigation of heavy mineral concentrates, obtained via hydroseparation techniques, led to the discovery of multistage PGE grains: (i) Os-Ru-Fe-(Ir) grains of porous appearance are overgrown by (ii) Ni-Fe-Ir and Ir-Fe-Ni-(Pt) phases which are overgrown by (iii) Pt-Ir-Fe-Ni mineral phases. Whereas Ir-dominated overgrowths prevail in chromitites from the saprolite, Pt-dominated overgrowths are observed within floating chromitites. The following formation model for multistage PGE grains is discussed: (i) hypogene platinum-group minerals (PGM) (e.g. laurite) are transformed to secondary PGM by desulphurization during serpentinization; (ii) at the stages of serpentinization and/or at the early stages of lateritization, Ir is mobilized and recrystallizes on porous surfaces of secondary PGM (serving as a natural catalyst) and (iii) at the late stages of lateritization, biogenic mediated neoformation (and accumulation) of Pt-Ir-Fe-Ni nanoparticles occurs. The evidence presented in this work demonstrates that in situ growth of Pt-Ir-Fe-Ni alloy nuggets of isometric symmetry is possible within Ni-laterites from the Dominican Republic.

  • 2.
    Aiglsperger, Thomas
    et al.
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona.
    Proenza, Joaquín A.
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona.
    Galí, Salvador
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona .
    Rius, Jordi
    Institut de Ciència de Materials de Barcelona, CSIC, Campus de la Universitat Autònoma de Barcelona.
    Longo, Francisco
    Falcondo Glencore, Santo Domingo .
    Domènech, Cristina
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB).
    The supergene origin of ruthenian hexaferrum in Ni-laterites2017In: Terra Nova, ISSN 0954-4879, E-ISSN 1365-3121, Vol. 29, no 2, p. 106-116Article in journal (Refereed)
    Abstract [en]

    For two decades, the nature of Fe‐rich, oxygen‐bearing, Ru–Os compounds found in the supergene environment has been debated. Ru–Os–Fe‐oxides and nano‐intergrowths of ruthenium with magnetite have been proposed. We applied FE‐SEM, EMPA, μ‐Raman spectroscopy and synchrotron tts‐μXRD to Ru–Os–Fe compounds recovered from Ni‐laterites from the Dominican Republic. The results demonstrate that a significant portion of Fe exists in a common structure with the Ru–Os alloy, that is, ruthenian hexaferrum. This mineral occurs both as nanoparticles and as micrometric patches within a matrix of Fe‐oxide(s). Our data suggest that supergene ruthenian hexaferrum with a (Ru0.4(Os,Ir)0.1Fe0.5)Ʃ1.0 stoichiometry represents the most advanced weathering product of primary laurite within Ni‐laterites from the Dominican Republic.

  • 3.
    Aiglsperger, Thomas
    et al.
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona .
    Proenza, Joaquín A.
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona .
    Lewis, John F.
    Department of Earth and Environmental Sciences, George Washington University, .
    Labrador, Manuel
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona.
    Svojtka, Martin
    Institute of Geology, Academy of Sciences.
    Rojas-Purón, Arturo
    Departamento de Geología, Instituto Superior Minero Metalúrgico de Moa.
    Longo, Francisco
    Falcondo Glencore Nickel.
    Ďurišová, Jana
    Institute of Geology, Academy of Sciences.
    Critical metals (REE, Sc, PGE) in Ni laterites from Cuba and the Dominican Republic2016In: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 73, p. 127-147Article in journal (Refereed)
    Abstract [en]

    Ni laterites are considered worthy targets for critical metals (CM) exploration as Rare Earth Elements (REE), Sc and platinum group elements (PGE) can be concentrated during weathering as a result of residual and secondary enrichment. In this contribution geochemical and mineralogical data of CM from two different nickel laterite types (i) from the Moa Bay mining area in Cuba (oxide type) and (ii) from the Falcondo mining area in the Dominican Republic (hydrous Mg silicate type) are presented. Emphasis is given on examining their potential to accumulate CM and on processes involved. Results show that CM are concentrated towards the surface in specific zones: (i) REE in clay minerals rich horizons and within zones composed of secondary Mn oxide(s), (ii) Sc within zones rich in secondary Fe and Mn bearing oxide(s) and (iii) PGE in zones with high concentrations of residual chromian spinel and secondary Fe and Mn bearing oxide(s) at upper levels of the Ni laterite profiles. Concentration factors involve (i) residual enrichment by intense weathering, (ii) mobilization of CM during changing Eh and pH conditions with subsequent reprecipitation at favourable geochemical barriers and (iii) interactions between biosphere and limonitic soils at highest levels of the profile (critical zone) with involved neoformation processes. Total contents of CM in both Ni laterite types are low when compared with conventional CM ore deposits but are of economic significance as CM have to be seen as cost inexpensive by-products during the Ni (+ Co) production. Innovative extraction methods currently under development are believed to boost the significance of Ni laterites as future unconventional CM ore deposits.

  • 4.
    Aiglsperger, Thomas
    et al.
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona.
    Proenza, Joaquín A.
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona.
    Longo, Francisco
    Falcondo Glencore, Santo Domingo .
    Font-Bardia, Mercé
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona .
    Galí, Salvador
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona .
    Roqué, Josep
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona.
    Baurier-Aymat, Sandra
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona .
    Fibrous Platinum-Group Minerals in “Floating Chromitites” from the Loma Larga Ni-Laterite Deposit, Dominican Republic2016In: Minerals, ISSN 2075-163X, E-ISSN 2075-163X, Vol. 6, no 4, article id 126Article in journal (Refereed)
    Abstract [en]

    This contribution reports on the observation of enigmatic fibrous platinum-group minerals (PGM) found within a chromitite body included in limonite (“floating chromitite”) from Ni-laterites in the Dominican Republic. Fibrous PGM have a Ru-Os-Ir-Fe dominated composition and are characterized by fibrous textures explained by grain-forming fibers which are significantly longer (1–5 _m) than they are wide (~100 nm). Back-scattered electron (BSE) images suggest that these nanofibers are platinum-group elements (PGE)-bearing and form <5 _m thick layers of bundles which are oriented orthogonal to grains’ surfaces. Trace amounts of Si are most likely associated with PGE-bearing nanofibers. One characteristic fibrous PGM was studied in detail: XRD analyses point to ruthenian hexaferrum. However, the unpolished fibrous PGM shows numerous complex textures on its surface which are suggestive for neoformation processes: (i) features suggesting growth of PGE-bearing nanofibers; (ii) occurrence of PGM nanoparticles within film material (biofilm?) associated with PGE-bearing nanofibers; (iii) a Si-rich and crater-like texture hosting PGM nanoparticles and an Ir-rich accumulation of irregular shape; (iv) complex PGM nanoparticles with ragged morphologies, resembling sponge spicules and (v) oval forms (<1 _m in diameter) with included PGM nanoparticles, similar to those observed in experiments with PGE-reducing bacteria. Fibrous PGM found in the limonite may have formed due to supergene (bio-)weathering of fibrous Mg-silicates which were incorporated into desulphurized laurite during stages of serpentinization.

  • 5.
    Aiglsperger, Thomas
    et al.
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona, .
    Proenza, Joaquín A.
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona.
    Zaccarini, Frederica
    Department of Applied Geological Sciences and Geophysics, University of Leoben.
    Lewis, John F.
    Department of Earth and Environmental Sciences, George Washington University, .
    Garuti, Giorgio
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Labrador, Manuel
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona, .
    Longo, Francisco
    Falcondo Glencore, Santo Domingo .
    Platinum group minerals (PGM) in the Falcondo Ni-laterite deposit, Loma Caribe peridotite (Dominican Republic)2015In: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 50, no 1, p. 105-123Article in journal (Refereed)
    Abstract [en]

    Two Ni-laterite profiles from the Loma Caribe peridotite (Dominican Republic) have been investigated for their platinum group element (PGE) geochemistry and mineralogy. One profile (Loma Peguera) is characterized by PGE-enriched (up to 3.5 ppm total PGE) chromitite bodies incorporated within the saprolite, whereas the second profile is chromitite-free (Loma Caribe). Total PGE contents of both profiles slightly increase from parent rocks (36 and 30 ppb, respectively) to saprolite (∼50 ppb) and reach highest levels within the limonite zone (640 and 264 ppb, respectively). Chondrite-normalized PGE patterns of saprolite and limonite reveal rather flat shapes with positive peaks of Ru and Pd. Three types of platinum group minerals (PGM) were found by using an innovative hydroseparation technique: (i) primary PGM inclusions in fresh Cr-spinel (laurite and bowieite), (ii) secondary PGM (e.g., Ru-Fe-Os-Ir compounds) from weathering of preexisting PGM (e.g., serpentinization and/or laterization), and (iii) PGM precipitated after PGE mobilization within the laterite (neoformation). Our results provide evidence that (i) PGM occurrence and PGE enrichment in the laterite profiles is independent of chromitite incorporation; (ii) PGE enrichment is residual on the profile scale; and (iii) PGE are mobile on a local scale leading to in situ growth of PGM within limonite, probably by bioreduction and/or electrochemical metal accretion.

  • 6.
    Ballivián Justiniano, Carlos A.
    et al.
    Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Instituto de Recursos Minerales (INREMI), Universidad Nacional de La Plata–Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, La Plata, Argentina.
    Lajoinie, María F.
    Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Instituto de Recursos Minerales (INREMI), Universidad Nacional de La Plata–Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, La Plata, Argentina.
    Recio, Clemente
    Departamento de Geología, Facultad de Ciencias, Universidad de Salamanca (USAL), Salamanca, Spain.
    Sato, Ana M.
    Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Centro de Investigaciones Geológicas (CIG), CONICET–Universidad Nacional de La Plata, La Plata, Argentina.
    Basei, Miguel A.S.
    Centro de Pesquisas Geocronológicas (CPGeo), Instituto de Geociências, Universidade de São Paulo, Cidade Universitária, São Paulo (SP), Brazil.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Barcelona, Spain.
    Aiglsperger, Thomas
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Barcelona, Spain.
    de Barrio, Raúl E.
    Instituto de Recursos Minerales (INREMI), Universidad Nacional de La Plata–Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, La Plata, Argentina.
    Curci, Marcela V.
    Instituto de Recursos Minerales (INREMI), Universidad Nacional de La Plata–Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, La Plata, Argentina.
    Lanfranchini, Mabel E.
    Comisión de Investigaciones Científicas de la Provincia de Buenos Aires (CIC). Instituto de Recursos Minerales (INREMI), Universidad Nacional de La Plata–CIC, La Plata, Argentina.
    Metamorphic evolution of the Loma Marcelo skarn within the geotectonic context of the crystalline basement of the Ventania System (Argentina)2019In: Journal of South American Earth Sciences, ISSN 0895-9811, E-ISSN 1873-0647, Vol. 92, p. 56-76Article in journal (Refereed)
    Abstract [en]

    This study describes the mineralogical and isotopic changes that carbonate xenoliths experienced under multiple metamorphic events and hydrothermal fluid circulation during the evolution of the Ventania System basement. The high reactivity of carbonate xenoliths allowed the preservation of mineral assemblages corresponding to at least three metamorphic events in the resulting Loma Marcelo skarn. The Ventania System basement is composed of Neoproterozoic granites and ignimbrites, Early Cambrian granites, and Middle Cambrian rhyolites. Carbonate xenoliths were incorporated during the intrusion of a calc-alkaline granite with an LA-ICP-MS U-Pb crystallization age of 621.6 Å} 2.2 Ma. The intrusion induced pyroxene–hornfels facies metamorphism in the carbonate xenoliths and the associated metasomatism generated calcic and magnesian skarns depending on the protolith composition. Garnet, clinopyroxene, wollastonite, bytownite, and meionite were formed in the calcic skarn (CaS), whereas forsterite and spinel were formed in the magnesian skarn (MgS). Crystallization of Early Cambrian alkaline granites was accompanied by intense hydrothermal activity that was responsible for low temperature (≤300 ÅãC) F-metasomatism in the skarn, as evidenced by the presence of F-rich vesuvianite (CaS) and chondrodite (MgS), among other minerals. Vesuvianite was formed from calc-silicate mineral assemblages of the previous metamorphic event, whereas chondrodite was formed by replacement of forsterite. The low temperature formation of these typical high-grade minerals could be an evidence of mineral formation under disequilibrium conditions favoured by the high reactivity of hydrothermal fluids. Neopalaeozoic basement mylonitization under greenschist facies metamorphism was accompanied by hydrothermal fluid circulation. This event promoted extreme mobility of chemical elements in the basement rocks and epidotization (CaS) and serpentinization (MgS) in the Loma Marcelo skarn. The elongated and boudinaged shape of the skarn bodies, parallel to the mylonitic foliation, is a consequence of dextral shearing that affected the basement rocks. Additionally, almost pure grossular crystallized post-tectonically in the CaS. Carbonates of the Loma Marcelo skarn are depleted in 13C and 18O (δ13CV PDB=−2.5/−10.1‰; δ18OV-SMOW = +7.3/+14.0‰) relative to carbonate sedimentary rocks. The δ13C and δ18O variations can be attributed to the interaction between large amounts of hydrothermal fluids (W/R=30–50) and Neoproterozoic carbonate sedimentary rocks.

  • 7.
    Cabri, Louis J.
    et al.
    Cabri Consulting Inc, Ottawa, Canada.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    A review of hexaferrum based on new mineralogical data2018In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 82, no 3, p. 531-538Article in journal (Refereed)
    Abstract [en]

    Hexaferrum, defined as an hcp Fe mineral containing varying amounts of Ru, Os, or Ir(Mochalov et al. 1998) was re-examined in the light of new analyses of similar alloys from the Loma Peguera and Loma Larga chromitites, in the central part of Loma Caribe peridotite, Cordillera Central of the Dominican Republic, together with a review of the phase chemistry inthe Fe-Ni-Ir and Fe-Ru-Ir systems. We conclude that the hcp (Fe,Ir) mineral corresponds to theε-phase of Raub et al. (1964) and should be differentiated from hexaferrum [(Fe,Os) and(Fe,Ru)] because it is separated by one to two miscibility gaps and therefore is not a continuous solid solution with Fe.

  • 8.
    Kaasalainen, Hanna
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. Sweco Environment, Luleå, Sweden.
    Lundberg, Paula
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Alakangas, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Impact of declining oxygen conditions on metal(loid) release from partially oxidized waste rock2019In: Environmental science and pollution research international, ISSN 0944-1344, E-ISSN 1614-7499, Vol. 26, no 20, p. 20712-20730Article in journal (Refereed)
    Abstract [en]

    The best available technology for preventing the formation of acid drainage water from the sulfidic waste rock at mine closure aims to limit the oxygen access to the waste. There is, however, a concern that contaminants associated with secondary minerals become remobilized due to changing environmental conditions. Metal(loid) mobility from partially oxidized sulfidic waste rock under declining and limited oxygen conditions was studied in unsaturated column experiments. The concentrations of sulfate and metal(loid)s peaked coincidently with declining oxygen conditions from 100 to < 5 sat-% and to a lesser extent following a further decrease in the oxygen level during the experiment. However, the peak concentrations only lasted for a short time and were lower or in the similar concentration range as in the leachate from a reference column leached under atmospheric conditions. Despite the acid pH (~ 3), the overall quality of the leachate formed under limited oxygen conditions clearly improved compared with atmospheric conditions. In particular, the release of As was two orders of magnitude lower, while cationic metals such as Fe, Cu, Mn, and Zn also decreased, although to a lesser extent. Decreased sulfide oxidation is considered the primary reason for the improved water quality under limited oxygen conditions. Another reason may be the immobility of Fe with the incorporation of metal(loid)s in Fe(III) minerals, in contrast to the expected mobilization of Fe. The peaking metal(loid) concentrations are probably due to remobilization from solid Fe(III)-sulfate phases, while the relatively high concentrations of Al, Mn, and Zn under limited oxygen conditions were due to release from the adsorbed/exchangeable fraction. Despite the peaking metal(loid) concentrations during declining oxygen conditions, it is clear that the primary remediation goal is to prevent further sulfide oxidation.

  • 9.
    Navidad, Marina
    et al.
    Área de Petrología y Geoquímica, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid.
    Castiñeiras, Pedro
    Área de Petrología y Geoquímica, Facultad de Ciencias Geológicas, Universidad Complutense de Madrid.
    Casas, Josep M.
    Department de Dinàmica de la Terra i de l'Oceà-Institut de Recerca Geomodels, Universitat de Barcelona.
    Liesa, Montserrat
    Department de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona.
    Belousova, Elena
    Department of Earth and Planetary Sciences, ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), GEMOC Macquarie University, Sydney.
    Proenza, Joaquín A.
    Department de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ordovician magmatism in the Eastern Pyrenees: Implications for the geodynamic evolution of northern Gondwana2018In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 314-315, p. 479-496Article in journal (Refereed)
    Abstract [en]

    New data on the geochemistry and geochronology of different felsic gneisses and metabasites from the Variscan massifs of Eastern Pyrenees have allowed us to shed some light on the Ordovician magmatic evolution in northern Gondwana during the opening of the Rheic Ocean. According to these data, the Ordovician magmatism represents a continuous event of anatectic melting, with limited mantle influence, that lasted 20 m.y., from Early to Late Ordovician. In the Canigó massif, peraluminous monzogranitic and granodioritic metaigneous rocks intruded a late Ediacaran-early Cambrian sequence at 464.3 ± 1.6 Ma and 461.6 ± 1.5 Ma, respectively, and leucogranitic gneisses intruded at 457.4 ± 1.6 Ma. Whole-rock geochemistry of the felsic rocks (plutonic and subvolcanic) points to a volcanic arc setting. However, the geological context and the geochemistry of the coeval metabasites are incompatible with this tectonic setting and point out to the inception of an extensional margin. Sm-Nd isotopic data suggest that the felsic rocks are derived from the anatexis of juvenile igneous rocks (probably Cadomian), mixed with older crustal components present in a late Neoproterozoic crust. We interpret that the Ordovician magmas inherited the geochemical signature of the rocks formed at the former Cadomian convergent margin. The variation of the εNd values from −2 to −4 in the Lower Ordovician rocks, to −5 in the Upper Ordovician rocks suggests a greater implication of the older component in a within-plate geodynamic context, coeval with the evolution of an extensional marginal basin linked to the opening of the Rheic Ocean. A similar isotopic evolution, more depleted first and with a greater implication of the crust in the younger sample, is shown by the studied metabasites.

  • 10.
    Pašava, Jan
    et al.
    Czech Geological Survey.
    Ackerman, Lukáš
    Institute of Geology of the Czech Academy of Sciences .
    Halodová, Patricie
    Czech Geological Survey.
    Pour, Ondrej
    Czech Geological Survey.
    Durišová, Jana
    Institute of Geology of the Czech Academy of Sciences.
    Zaccarini, Frederica
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Aiglsperger, Thomas
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona.
    Vymazalová, Anna
    Czech Geological Survey.
    Concentrations of platinum-group elements (PGE), Re and Au in arsenian pyrite and millerite from Mo-Ni-PGE-Au black shales (Zunyi region, Guizhou Province, China): results from LA-ICPMS study2017In: European journal of mineralogy, ISSN 0935-1221, E-ISSN 1617-4011, Vol. 29, no 4, p. 623-633Article in journal (Refereed)
    Abstract [en]

    Lower Cambrian Mo-Ni sulphidic black shales from the Huangjiawan mine (Guizhou Province, south China) have anomalous platinum-group element (PGE) concentrations (up to ~1 ppm in total). We used LA-ICPMS to study the distribution of PGE in pyrite and Ni-sulphide (millerite) and FE-SEM/EDS for determination of As in pyrite. A sulphide concentrate was produced by innovative hydroseparation techniques from one representative sample, which contained 162 ppb Pt, 309 ppb Pd, 12.2 ppb Ru, 11.3 ppb Rh, 1.5 ppb Ir, 11 212 ppb Re and 343 ppb Au. Mineralogical analysis revealed that pyrite forms ~12 vol%, which corresponds to a calculated ~18.4 wt% of all mineral phases in mineralized black shale. We found that pyrite contains on average (144 analyses) 0.10 ppm Pt, 0.11 ppm Re and 1.40 ppm Au (Ru, Rh, Pd, Os and Ir were below detection limit). It also contains from ~0.5 to ~1.8 wt% As and can be therefore classified as arsenian pyrite. Millerite (77 analyses) showed PGE, Re and Au values below detection limit. We suggest that pyrite represents a dominant Au carrier, containing between 64 and 83% Au of the total Au mineralised rock budget. Conversely, pyrite does not bear any significant amount of Re and Pt, contributing up to ~0.2% and ~12.5% to their whole rock budgets, respectively. Time resolved LA-ICPMS spectra in pyrite indicate that Pt, Re and Au behave as typical lattice-bound elements, with only Re locally forming micro-inclusions. Arsenic is heterogeneously distributed in pyrite and the Au/As ratio (much lower than 0.02) is in support of Au to be structurally bound in solid solution. © 2017 E. Schweizerbart’sche Verlagsbuchhandlung.

  • 11.
    Pašava, Jan
    et al.
    Czech Geological Survey.
    Zaccarini, Frederica
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Aiglsperger, Thomas
    University of Barcelona.
    Vymazalová, Anna
    Czech Geological Survey.
    Platinum-group elements (PGE) and their principal carriers in metal-rich black shales: An overview with a new data from Mo-Ni-PGE black shales (Zunyi region, Guizhou Province, south China)2013In: Journal of Geosciences, ISSN 1802-6222, E-ISSN 1803-1943, Vol. 58, no 3, p. 213-220Article in journal (Refereed)
    Abstract [en]

    Lower Cambrian Mo–Ni sulfidic black shales from the Huangjiawan mine (Guizhou Province, south China) have anomalousplatinum-group elements (PGE) concentrations (up to ~1 ppm in total). In order to identify principal PGE carriers,we used heavy mineral separates which were produced by innovative hydroseparation techniques. Subsequent detailedmineralogical study using electron microprobe did not result in the identification of discrete platinum-group minerals.Pyrite (grainy, not framboidal), millerite and gersdorffite that were found in our heavy concentrate were analyzed forPGE and Re. We found that they contain the following concentrations of PGE and Re: pyrite (up to 490 ppm Pt, 390ppm Pd and 220 ppm Rh), millerite (up to 530 ppm Pt, 430 ppm Pd and 190 ppm Rh) and gersdorffite (up to 410 ppmPt and 320 ppm Pd; no Rh detected). Rhenium was detected only in grainy pyrite (up to 1060 ppm). It was found thatdespite anomalous PGE concentrations, the Mo–Ni black shales do not contain any platinum-group minerals and thatthe PGE are bound to pyrite and Ni-sulfides (millerite and gersdorffite).

  • 12.
    Proenza, J. A.
    et al.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, C/Martí i Franquès s/n, 08028, Barcelona, Spain.
    González-Jiménez, J. M.
    Departamento de Mineralogía y Petrología, Universidad de Granada, Facultad de Ciencias, Fuentenueva s/n 18002, Granada, Spain.
    Garcia-Casco, A.
    Departamento de Mineralogía y Petrología, Universidad de Granada, Facultad de Ciencias, Fuentenueva s/n 18002, Granada, Spain; Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Avda. de las Palmeras 4, E-18100, Armilla, Granada, Spain.
    Belousova, E.
    ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), GEMOC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney.
    Griffin, W. L.
    ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), GEMOC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney.
    Talavera, C.
    John de Laeter Centre, Curtin University, Perth, WA 6102, Australia.
    Rojas-Agramonte, Y.
    Geocycles-Earth System Research Center, Institut für Geowissenschaften, Johannes Gutenberg-Universität, Becherweg 21, D-55099 Mainz, Germany; Departamento de Geociencias, Universidad de los Andes, Bogotá, Colombia.
    Aiglsperger, Thomas
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, C/Martí i Franquès s/n, 08028, Barcelona, Spain.
    Navarro-Ciurana, D.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, C/Martí i Franquès s/n, 08028, Barcelona, Spain.
    Pujol-Solá , N.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, C/Martí i Franquès s/n, 08028, Barcelona, Spain.
    Gervilla, F.
    Departamento de Mineralogía y Petrología, Universidad de Granada, Facultad de Ciencias, Fuentenueva s/n 18002, Granada, Spain; Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Avda. de las Palmeras 4, E-18100, Armilla, Granada, Spain .
    O’Reilly, S. Y.
    ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), GEMOC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney.
    Jacob, D. E.
    ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), GEMOC National Key Centre, Department of Earth and Planetary Sciences, Macquarie University, Sydney.
    Cold plumes trigger contamination of oceanic mantle wedges with continental crust-derived sediments: Evidence from chromitite zircon grains of eastern Cuban ophiolites2018In: Geoscience Frontiers, ISSN 1674-9871, Vol. 9, no 6, p. 1921-1936Article in journal (Refereed)
    Abstract [en]

    The origin of zircon grains, and other exotic minerals of typical crustal origin, in mantle-hosted ophiolitic chromitites are hotly debated. We report a population of zircon grains with ages ranging from Cretaceous (99 Ma) to Neoarchean (2750 Ma), separated from massive chromitite bodies hosted in the mantle section of the supra-subduction (SSZ)-type Mayarí-Baracoa Ophiolitic Belt in eastern Cuba. Most analyzed zircon grains (n = 20, 287 ± 3 Ma to 2750 ± 60 Ma) are older than the early Cretaceous age of the ophiolite body, show negative εHf(t) (−26 to −0.6) and occasional inclusions of quartz, K-feldspar, biotite, and apatite that indicate derivation from a granitic continental crust. In contrast, 5 mainly rounded zircon grains (297 ± 5 Ma to 2126 ± 27 Ma) show positive εHf(t) (+0.7 to +13.5) and occasional apatite inclusions, suggesting their possible crystallization from melts derived from juvenile (mantle) sources. Interestingly, younger zircon grains are mainly euhedral to subhedral crystals, whereas older zircon grains are predominantly rounded grains. A comparison of the ages and Hf isotopic compositions of the zircon grains with those of nearby exposed crustal terranes suggest that chromitite zircon grains are similar to those reported from terranes of Mexico and northern South America. Hence, chromitite zircon grains are interpreted as sedimentary-derived xenocrystic grains that were delivered into the mantle wedge beneath the Greater Antilles intra-oceanic volcanic arc by metasomatic fluids/melts during subduction processes. Thus, continental crust recycling by subduction could explain all populations of old xenocrystic zircon in Cretaceous mantle-hosted chromitites from eastern Cuba ophiolite. We integrate the results of this study with petrological-thermomechanical modeling and existing geodynamic models to propose that ancient zircon xenocrysts, with a wide spectrum of ages and Hf isotopic compositions, can be transferred to the mantle wedge above subducting slabs by cold plumes.

  • 13.
    Reinhardt, Nils
    et al.
    Institute of Mineralogy, Technische Universität Bergakademie Freiberg, Germany;Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Spain; Institute of Applied Mineralogy and Economic Geology (IML), RWTH Aachen University, Germany.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Spain.
    Villanova-de-Benavent, Cristina
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Spain;School of Environment and Technology (SET), University of Brighton, UK.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Spain.
    Bover-Arnal, Telm
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Spain.
    Torró, Lisard
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Spain;Especialidad Ingeniería Geológica, Sección Ingeniería de Minas, Pontificia Universidad Católica del Perú, Peru.
    Salas, Ramon
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Spain.
    Dziggel, Annika
    Institute of Applied Mineralogy and Economic Geology (IML), RWTH Aachen University, Germany.
    Geochemistry and Mineralogy of Rare Earth Elements (REE) in Bauxitic Ores of the Catalan Coastal Range, NE Spain2018In: Minerals, ISSN 2075-163X, E-ISSN 2075-163X, Vol. 8, no 12, article id 562Article in journal (Refereed)
    Abstract [en]

    Karst bauxite deposits are currently investigated as a new resource for rare earth elements (REE) in order to avoid present and future supply shortfalls of these critical metals. The present work focuses on the geochemistry and mineralogy of the REE in karst bauxite deposits of the Catalan Coastal Range (CCR), NE-Spain. It is revealed that the studied bauxitic ores have a dominant breccia and local ooido-pisoidic and pelitomorphic texture. The bauxitic ores are mostly composed of kaolinite and hematite, as well as of lesser amounts of boehmite, diaspore, rutile and calcite. The mineralogy and major element composition indicate incomplete bauxitization of an argillaceous precursor material possibly derived from the erosion of the Mesozoic Ebro massif paleo-high. The studied bauxites are characterized by ∑REE (including Sc, Y) between 286 and 820 ppm (av. 483 ppm) and light REE to heavy REE (LREE/HREE) ratios up to 10.6. REE are mainly concentrated in phosphate minerals, identified as monazite-(Ce) and xenotime-(Y) of detrital origin and unidentified REE-phosphates of a possible authigenic origin. REE remobilization presumably took place under acidic conditions, whereas REE entrapment in the form of precipitation of authigenic rare earth minerals from percolating solutions was related to neutral to slightly alkaline conditions. During the bauxitization process no significant REE fractionation took place and the REE distribution pattern of the bauxitic ores was governed by the REE budget of the precursor material. Finally, adsorption as a main REE scavenging mechanism in the studied CCR bauxite deposits should not be considered, since the presented data did not reveal significant REE contents in Fe-and Mn-oxyhydroxides and clay minerals.

  • 14.
    Rivera, Javier
    et al.
    Department of Geology and Andean Geothermal Center of Excellence (CEGA), FCFM, Universidad de Chile, Santiago, Chile.
    Reich, Martin
    Department of Geology and Andean Geothermal Center of Excellence (CEGA), FCFM, Universidad de Chile, Santiago, Chile.
    Schoenberg, Ronny
    Department of Geosciences, University of Tübingen, Tübingen, Germany.
    González Jiménez, José María
    Departmento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Spain.
    Barra, Fernando
    Department of Geology and Andean Geothermal Center of Excellence (CEGA), FCFM, Universidad de Chile, Santiago, Chile.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Proenza, Joaquín
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Barcelona, Spain.
    Carretier, Sebastien
    GET, Université de Toulouse, CNRS, IRD, Toulouse, France.
    Platinum-group element and gold enrichment in soils monitored by chromium stable isotopes during weathering of ultramafic rocks2018In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 499, p. 84-99Article in journal (Refereed)
    Abstract [en]

    Weathering of ultramafic rocks can lead to the formation of soil profiles with high contents of Fe, Ni, Co, platinum-group elements (PGE) and gold. Traditionally, these metal-rich soils are known as “laterites” and are formed under tropical climates and stable tectonic conditions. However, little is known about their possible development in cold/humid regions, and the factors governing PGE and gold mobility and enrichment under these weathering conditions are poorly constrained. In this study, five soil profiles developed on serpentinized, chromite-bearing ultramafic rocks at La Cabaña, located in the Coastal Range of south-central Chile (38° S) were studied by combining major and trace element geochemistry with chromium stable isotope data. The results show that the soils developed at La Cabaña have higher PGE and Au contents than the parent serpentinite rock, with ∑PGE and Au reaching up to 160 ppb and 29 ppb in a limonitic soil horizon and clay saprolite, respectively. Most soil samples have slightly negative δ53/52CrSRM979 values, within a range of −0.089 ± 0.012‰ to −0.320 ± 0.013‰ (average of −0.178‰), and are in agreement with previous data reported for modern soils. A noteworthy relation between δ53/52Cr data and PGE + Au contents is observed in the studied soil horizons, where isotopically lighter values of δ53/52Cr match the higher contents of PGE and gold. These results show that pedogenetic processes operating at the cold and humid La Cabaña area are capable of increasing the total PGE and Au contents of certain soil horizons. Such processes are complex and multivariate but are primarily modulated by chromite dissolution and the formation of secondary phases such as clay minerals and oxy-hydroxide phases in the soil. These findings provide evidence that important weathering and PGE + Au supergene accumulation are not only restricted to tropical latitudes, and that the chromium isotope system is a useful proxy to track surface redox process and noble metal enrichment during pedogenesis.

  • 15.
    Roqué Rosell, Josep
    et al.
    Department of Mineralogy, Petrology and Applied Geology, University of Barcelona, Barcelona, Catalunya, Spain.Institut de Nanociència i Nanotecnologia, IN2UB, Facultat de Química, Universitat de Barcelona, Barcelona, Catalunya, Spain..
    Portillo Serra, Joaquim
    Centres Científics i Tecnològics, Universitat de Barcelona, Barcelona, Catalunya, Spain.NanoMEGAS, Brussels, Belgium.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Plana Ruiz, Sergi
    Institut de Nanociència i Nanotecnologia, IN2UB, Facultat de Química, Universitat de Barcelona, Barcelona, Catalunya, Spain.Institut für Angewandte Geowissenschaften, Technische Universität Darmstadt, Darmstadt, Germany.
    Pratim Das, Partha
    NanoMEGAS, Brussels, Belgium.
    Mendoza Gonzalvez, Joan
    Centres Científics i Tecnològics, Universitat de Barcelona, Barcelona, Catalunya, Spain.
    Trifonov, Trifon
    Centre de Recerca en Ciència i Enginyeria Multiescala de Barcelona, Universitat Politècnica de Catalunya (UPC), Catalunya , Sant Adrià de Besòs, Spain.
    Proenza, Joaquin Antonio
    Department of Mineralogy, Petrology and Applied Geology, University of Barcelona, Barcelona, Catalunya, Spain.Institut de Nanociència i Nanotecnologia, IN2UB, Facultat de Química, Universitat de Barcelona, Barcelona, Catalunya, Spain .
    Crystallographic information data of natural occurring zaccariniite (RhNiAs) obtained by means of precession electron diffraction2019In: Data in Brief, E-ISSN 2352-3409, Vol. 25, article id 104346Article in journal (Refereed)
    Abstract [en]

    The crystal structure of naturally occurring zaccariniite (RhNiAs) has been studied in Transmission Electron Microscopy (TEM) with variable angle Precession Electron Diffraction (PED) techniques. The analysis of the data has yielded tetragonal cell parameters of 3.86, 3.86, 6.77 Å and space group of P4/nmm for the basic structure, and its constituent atom positions for Ni, As and Rh were determined as well by ab-initio structure resolution method. The data is related to “Structural characterization and ab-initio resolution of natural occurring zaccariniite (RhNiAs) by means of Precession Electron Diffraction” (Roqué Rosell et al., 2019).

  • 16.
    Roqué Rosell, Josep
    et al.
    Department of Mineralogy, Petrology and Applied Geology, University of Barcelona, Barcelona, Catalunya, Spain.Institut de Nanociència i Nanotecnologia, IN2UB, Facultat de Química, Universitat de Barcelona, Barcelona, Catalunya, Spain..
    Portillo Serra, Joaquim
    Centres Científics i Tecnològics, Universitat de Barcelona, Barcelona, Catalunya, Spain.NanoMEGAS, Brussels, Belgium.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Plana Ruiz, Sergi
    Institut de Nanociència i Nanotecnologia, IN2UB, Facultat de Química, Universitat de Barcelona, Barcelona, Catalunya, Spain.Institut für Angewandte Geowissenschaften, Technische Universität Darmstadt, Darmstadt, Germany.
    Pratim Das, Partha
    NanoMEGAS, Brussels, Belgium.
    Mendoza Gonzalvez, Joan
    Centres Científics i Tecnològics, Universitat de Barcelona, Barcelona, Catalunya, Spain.
    Trifonov, Trifon
    Centre de Recerca en Ciència i Enginyeria Multiescala de Barcelona, Universitat Politècnica de Catalunya (UPC), Catalunya , Sant Adrià de Besòs, Spain.
    Proenza, Joaquin Antonio
    Department of Mineralogy, Petrology and Applied Geology, University of Barcelona, Barcelona, Catalunya, Spain.Institut de Nanociència i Nanotecnologia, IN2UB, Facultat de Química, Universitat de Barcelona, Barcelona, Catalunya, Spain .
    Structural characterization and ab-initio resolution of natural occurring zaccariniite (RhNiAs) by means of Precession Electron Diffraction2019In: Microchemical journal (Print), ISSN 0026-265X, E-ISSN 1095-9149, Vol. 148, p. 130-140Article in journal (Refereed)
    Abstract [en]

    The crystal structure of naturally occurring zaccariniite from Loma Peguera (Republica Dominicana) has been studied in Transmission Electron Microscopy(TEM) with variable angle Precession Electron Diffraction (PED) techniques: 0.7° Precession Electron Diffraction Tomography (Precession EDT) for unit cell and Laue class sorting, 0.5° Scanning Precession Diffraction (SPED) for crystal orientation mapping and grain alignment, and high symmetry zone axis 1.2° to 2.2° Zone Axis High Angle Precession Electron Diffraction (ZA high angle PED) for Space Group assessment and supercell information gathering. The natural sample has been prepared into an electron thin lamella by means of Focused Ion Beam(FIB). The analysis of the data has yielded tetragonal cell parameters of 3.86, 3.86, 6.77 Å and space group of P4/nmm for the basic structure, and its constituent atom positions for Ni, As and Rh were determined as well by ab-initio structure resolution method in accordance to the elemental composition of the natural zaccariniite obtained with Energy Dispersive X-ray (EDX) and High Magnification Electron Microscopy (HMEM) analysis. A modulation of the crystal basic structure of 3 by 1 in the basal plane has been reported for the first time on natural occurring zaccariniite.

  • 17.
    Roqué Rosell, Josep
    et al.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Marti i Franquès s/n, Barcelona, Catalunya 08028, Spain.
    Portillo Serra, Joaquim
    Centres Científics i Tecnològics, Universitat de Barcelona, Lluís Solé i Sabaris, 1-3, Barcelona; NanoMEGAS, Boulevard Edmond Machtens 79, Brussels B-1080, Belgium .
    Aiglsperger, Thomas
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Marti i Franquès s/n, Barcelona, Catalunya 08028, Spain.
    Plana-Ruiz, Sergi
    Centres Científics i Tecnològics, Universitat de Barcelona, Lluís Solé i Sabaris, 1-3, Barcelona, Catalunya 08028, Spain.
    Trifonov, Trifon
    Centre de Recerca de Nanoenginyeria, Universitat Politècnica de Catalunya, Pascual i Vila, 15 Edifici C Planta-1, Barcelona, Catalunya 08028, Spain.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, Marti i Franquès s/n, Barcelona, Catalunya 08028, Spain.
    Au crystal growth on natural occurring Au-Ag aggregate elucidated by means of precession electron diffraction (PED)2018In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 483, p. 228-235Article in journal (Refereed)
    Abstract [en]

    In the present work, a lamella from an Au—Ag aggregate found in Ni-laterites has been examined using Transmission Electron Microscope to produce a series of Precision Electron Diffraction (PED) patterns. The analysis of the structural data obtained, coupled with Energy Dispersive X-ray microanalysis, made it possible to determine the orientation of twinned native gold growing on the Au—Ag aggregate. The native Au crystal domains are found to have grown at the outermost part of the aggregate whereas the inner core of the aggregate is an Au—Ag alloy (∼4 wt% Ag). The submicron structural study of the natural occurring Au aggregate points to the mobilization and precipitation of gold in laterites and provides insights on Au aggregates development at supergene conditions. This manuscript demonstrates the great potential of electron crystallographic analysis, and in particular, PED to study submicron structural features of micron sized mineral aggregates by using the example of a gold grain found in a Ni-laterite deposits.

  • 18.
    Salifu, Musah
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Hällström, Lina
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Martinsson, Olof
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Billström, Kjell
    Department of Geological Sciences, Swedish Museum of Natural History, Frescativagen 40, Box 50007, 104 05, Stockholm, Sweden.
    Ingri, Johan
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Dold, Bernhard
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Alakangas, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Strontium (87Sr/86Sr) isotopes: A tracer for geochemical processes in mineralogically-complex mine wastes2018In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 99, p. 42-54Article in journal (Refereed)
    Abstract [en]

    Interpretation of geochemical data based primarily on elemental concentrations often lead to ambiguous results due to multiple potential sources including mineral weathering, atmospheric input, biological cycling, mineral precipitation and exchange processes. The 87Sr/86Sr ratio is however not fractionated by these processes. In this study, Sr isotope (87Sr/86Sr) ratios have been coupled with chemical data of Sr and Rb-bearing minerals, tailings and leachates (water-soluble) to gain insight into the geochemical processes occurring within the Yxsjöberg Cu-W mine tailings, Sweden. The tailings have been exposed to oxidizing conditions resulting in three geochemical zones namely (i) oxidized, (ii) transition and (iii) unoxidized zones. Leachates from the oxidized zone are acidic (pH = 3.6–4.5) and contain elevated concentrations of metals (e.g. Fe, Cu and Zn) and SO4. The low pH has also led to subsequent weathering of most silicates, releasing Al, Ca, Mg and Na into solution. The 87Sr/86Sr ratio in the tailings ranges from 0.84787 to 1.26640 in the oxidized zone, 0.92660–1.06788 in the transition zone, whilst the unoxidized zone has values between 0.76452 and 1.05169. For the leachates, the 87Sr/86Sr ratio ranges from 2.44479 to 5.87552 in the oxidized zone, 1.37404–1.68844 in the transition zone and 1.03697–2.16340 in the unoxidized zone. Mixing (between mineral weathering and atmospheric sources) was identified as the major process regulating the Sr composition of the tailings and leachates. The highly radiogenic signatures of the leachates in the oxidized zone suggests weathering of biotite, K-feldspar and muscovite. Despite the very radiogenic signatures in the oxidized zone, increments in Ca/K ratios, Be, Ce, Tl, Al, Fe and SO4 concentrations in the water-soluble phase were recorded in its lower parts which suggests the dissolution of amphibole, pyroxene, plagioclase, fluorite, gypsum, Al and Fe –(oxy) hydroxides as well as cation exchange by clay minerals. Presence of clay minerals has led to the partial retainment of radiogenic 87Sr/86Sr resulting in increased 87Sr/86Sr in the solid tailings material at these depths. The 87Sr/86Sr ratios of the water-soluble phase in the transition zone is similar to that of helvine and could indicate its dissolution. In the upper part of the oxidized zone, the 87Sr/86Sr ratios and trends of Be, Ca, SO4, Tl and Zn in the water-soluble phase suggest the dissolution of gypsum which precipitated from a leachate with the isotopic signature of helvine. In the lower part of the unoxidized zone, elevated concentrations of W were recorded suggesting scheelite weathering. But the 87Sr/86Sr ratios are higher than that expected from dissolution of scheelite and indicates additional processes. Possible sources include biotite weathering and groundwater. This study reveals that when interpreting geochemical processes in mine waste environments, 87Sr/86Sr should be considered in addition to chemical constituents, as this isotopic tracer offers better insights into discriminating between different solute sources.

  • 19.
    Tauler, Esperança
    et al.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB) Barcelona, Spain.
    Lewis, John F.
    Department of Earth and Environmental Sciences, The George Washington University, Washington, USA.
    Villanova-de-Benavent, Cristina
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB) Barcelona, Spain.
    Aiglsperger, Thomas
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB) Barcelona, Spain.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB) Barcelona, Spain.
    Domènech, Cristina
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB) Barcelona, Spain.
    Gallardo, Tamara
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB) Barcelona, Spain.
    Longo, Francisco
    Faculty of Engineering, Universidad Católica Tecnológica del Cibao (UCATECI), La Vega, Dominican Republic.
    Galí, Salvador
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB) Barcelona, Spain.
    Discovery of Ni-smectite-rich saprolite at Loma Ortega, Falcondo mining district (Dominican Republic): geochemistry and mineralogy of an unusual case of “hybrid hydrous Mg silicate – clay silicate” type Ni-laterite2017In: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 52, no 7, p. 1011-1030Article in journal (Refereed)
    Abstract [en]

    Hydrous Mg silicate-type Ni-laterite deposits, like those in the Falcondo district, Dominican Republic, are dominated by Ni-enriched serpentine and garnierite. Recently, abundant Ni-smectite in the saprolite zone have been discovered in Loma Ortega, one of the nine Ni-laterite deposits in Falcondo. A first detailed study on these Ni-smectites has been performed (μXRD, SEM, EPMA), in addition to a geochemical and mineralogical characterisation of the Loma Ortega profile (XRF, ICP-MS, XRD). Unlike other smectite occurrences in laterite profiles worldwide, the Loma Ortega smectites are trioctahedral and exhibit high Ni contents never reported before. These Ni-smectites may be formed from weathering of pyroxene and olivine, and their composition can be explained by the mineralogy and the composition of the Al-depleted, olivine-rich parent ultramafic rock. Our study shows that Ni-laterites are mineralogically complex, and that a hydrous Mg silicate ore and a clay silicate ore can be confined to the same horizon in the weathering profile, which has significant implications from a recovery perspective. In accordance, the classification of “hybrid hydrous Mg silicate – clay silicate” type Ni-laterite deposit for Loma Ortega would be more appropriate.

  • 20.
    Torró, L.
    et al.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain; Universidad Tecnológica del Cibao Oriental (UTECO), Cotuí, Dominican Republic.
    Proenza, J. A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Aiglsperger, Thomas
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Bover-Arnal, T.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Villanova-de-Benavent, C.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Rodrí­guez-García, D.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Ramí­rez, A.
    Servicio Geológico Nacional, Av. Winston Churchill 75, Edificio “J. F. Martínez”, Santo Domingo, Dominican Republic.
    Rodríguez, J.
    Servicio Geológico Nacional, Av. Winston Churchill 75, Edificio “J. F. Martínez”, Santo Domingo, Dominican Republic.
    Mosquea, L. A.
    Universidad Tecnológica del Cibao Oriental (UTECO), Cotuí, Dominican Republic.
    Salas, R.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Geological, geochemical and mineralogical characteristics of REE-bearing Las Mercedes bauxite deposit, Dominican Republic2017In: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 89, p. 114-131Article in journal (Refereed)
    Abstract [en]

    Bauxite deposits, traditionally the main source of aluminum, have been recently targeted for their remarkable contents in rare earth elements (REE). With ∑REE (lanthanoids + Sc + Y) concentrations systematically higher than ∼1400 ppm (av. = 1530 ppm), the Las Mercedes karstic bauxites in the Dominican Republic rank as one of the REE-richest deposits of its style.

    The bauxitic ore in the Las Mercedes deposit is mostly unlithified and has a homogeneous-massive lithostructure, with only local cross-stratification and graded bedding. The dominant arenaceous and round-grained texture is composed of bauxite particles and subordinate ooids, pisoids and carbonate clasts. Mineralogically, the bauxite ore is composed mostly of gibbsite and lesser amounts of kaolinite, hematite, boehmite, anatase, goethite, chromian spinel and zircon. Identified REE-minerals include cerianite and monazite-Ce, whose composition accounts for the steady enrichment in light- relative to medium- and heavy-REE of the studied bauxites.

    Considering the paleo-geomorphology of the study area, we propose that bauxites in the Las Mercedes deposit are the product of the erosion and deposition of lithified bauxites located at higher elevations in the Bahoruco ranges. Based on the available data, we suggest a mixed lithological source for the bauxite deposits at the district scale: bedrock carbonates and an igneous source of likely mafic composition.

  • 21.
    Yesares, Lola
    et al.
    Department of Geology, University of Huelva, Avenida de las Fuerzas Armadas.
    Aiglsperger, Thomas
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona.
    Sáez, Reinaldo
    Department of Geology, University of Huelva, Avenida de las Fuerzas Armadas.
    Almodóvar, Gabriel R.
    Department of Geology, University of Huelva, Avenida de las Fuerzas Armadas.
    Nieto, José Miguel
    Department of Geology, University of Huelva, Avenida de las Fuerzas Armadas.
    Proenza, Joaquín A.
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona.
    Gómez, Carmelo
    Geological Area, Mining Department of Cobre Las Cruces S.A., Gerena, Seville.
    Escobar, Juan Manuel
    Geological Area, Mining Department of Cobre Las Cruces S.A., Gerena, Seville.
    Gold behavior in supergene profiles under changing redox conditions: The example of the Las Cruces Deposit, Iberian Pyrite Belt2015In: Economic geology and the bulletin of the Society of Economic Geologists, ISSN 0361-0128, E-ISSN 1554-0774, Vol. 110, no 8, p. 2109-2126Article in journal (Refereed)
    Abstract [en]

    The Las Cruces deposit is in the eastern end of the Iberian Pyrite Belt (SW Spain). It is currently being mined by Cobre Las Cruces S.A. The main operation is focused on the supergene Cu-enriched zone (initial reserves of 17.6 Mt @ 6.2% Cu). An Au-Ag-Pb–rich gossan resource (3.6 Mt @ 3.3% Pb, 2.5 g/t Au, and 56.3 g/t Ag) occurs in the upper part of the deposit. The Au grade ranges from 0.01 ppm to >100 ppm, and occurs as three different Au ore types: (1) Au mineralization in the upper part of the gossan linked to Fe-oxides lithofacies, (2) Au concentration in the lower part of the gossan associated with leached black shales, and (3) Au ore in the cementation zone related to subvertical fractures.

    A hydroseparation device has been used to obtain heavy mineral concentrates from selected samples of different ore types. Reflected-light microscopy, scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and electron probe microanalysis (EPMA) were used to study the separated Au particles. Significant differences between the defined ore types include the Au-bearing lithologies, mineral associations, textural features, particle sizes, morphologies, and fineness. Au-rich minerals include native Au, Au-Ag electrum, and Au-Ag-Hg amalgams. Gold-bearing mineral associations include Pb-oxihalides, Fe-oxides, galena, pyrite, cinnabar, and Ag-sulfosalts.

    The Au enrichment mechanism in the supergene profile involves (1) dissolution of Au from the primary sulfides as chloride-rich ionic complexes during the weathering of the deposit under subaerial exposure; dissolved Au is transported downward through the supergene profile under acidic and oxidized conditions; (2) destabilization of the Au complexes by Fe-controlled redox reactions; as a consequence, coarse-grained, high-fineness Au particles precipitated in association with Fe-oxyhydroxides. This resulted in secondary concentration in the upper gossan; and (3) after deposition of cover sediments took place a progressive change in the system conditions resulting in a later Au remobilization as hydroxidehalide, hydroxide, thiosulfate, and bisulfide complexes in the lowermost gossan and cementation zone. The main pathways for migration of enriched fluids to the cementation zone are secondary permeability zones linked to Alpine reactivated faults. Deposition of Au seems to be related to fluid interaction with reductant lithologies, including black shales and the primary sulfides.

  • 22. Zaccarini, Federica
    et al.
    Bakker, Ronald J.
    Garuti, Giorgio
    Aiglsperger, Thomas
    Thalhammer, Oskar A. R.
    Campos, Lolita
    Proenza, Joaquin A.
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona.
    Lewis, John F.
    Department of Earth and Environmental Sciences, George Washington University, .
    Platinum group minerals in chromitite bodies of the Santa Elena Nappe, Costa Rica: mineralogical characterization by electron microprobe and Raman-spectroscopy2010In: Boletín de la Sociedad Geológica Mexicana, ISSN 1405-3322, Vol. 62, no 1, p. 161-171Article in journal (Refereed)
    Abstract [en]

    AbstractForty-seven grains of platinum group minerals (PGM) associated with small chromitite bodies of the Santa Elena ultramafic Nappe (Costa Rica) were mineralogically investigated with electron microscope, electron microprobe and Raman spectroscopy. The mineralogical assemblage includes sulfides of the laurite-erlichmanite series (RuS₂-OsS₂), irarsite (IrAsS), osmium, Ir-Rh sulfides containing relevant amounts of Ni, Fe and Cu, and a Ru-As-S compound, possibly ruarsite (RuAsS). Most platinum group element (PGE) sulfides and sulfarsenides represent primary magmatic phases entrapped in chromite at high temperatures, whereas native osmium is probably formed by subsolidus exsolution. The lack of primary PGE alloys suggests relatively high S-fugacity in the chromite forming system. This investigation emphasizes the efficiency of Raman spectroscopy in the identification of PGM of extremely small size, and shows how this technique can be used in revealing distinctive compositional differences among PGM of the laurite-erlichmanite series and irarsite.

  • 23.
    Zaccarini, Frederica
    et al.
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Garuti, Giorgio
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Proenza, Joaquín A.
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Universitat de Barcelona.
    Campos, L.
    Escuela Centroamericana de Geología, University of Costa Rica.
    Thalhammer, O. A. R.
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Aiglsperger, Thomas
    Departament de Cristal·lografia, Mineralogia i Dipòsits Minerals, Facultat de Geologia, Universitat de Barcelona.
    Lewis, John F.
    Department of Earth and Environmental Sciences, George Washington University, .
    Chromite and platinum group elements mineralization in the Santa Elena Ultramafic Nappe (Costa Rica): Geodynamic implications2011In: Geologica Acta, ISSN 1695-6133, E-ISSN 1696-5728, Vol. 9, no 3-4, p. 407-423Article in journal (Refereed)
    Abstract [en]

    Chromitites associated with strongly altered peridotite from six distinct localities in the Santa Elena ultramaficnappe (Costa Rica) have been investigated for the first time. Santa Elena chromitites commonly display acompositional variation from extremely chromiferous (Cr/(Cr+Al)=0.81) to intermediate and aluminous(Cr/(Cr+Al)=0.54). This composition varies along a continuous trend, corresponding to calculated parental liquidswhich may have been derived from the differentiation of a single batch of boninitic magma with Cr-rich and(Al, Ti)-poor initial composition. Fractional precipitation of chromite probably occurred during differentiation ofthe boninitic melt and progressive metasomatic reaction with mantle peridotite. The distribution of platinum groupelements (PGE) displays the high (Os+Ir+Ru)/(Rh+Pt+Pd) ratio typical of ophiolitic chromitites and, consistently,the platinum group minerals (PGM) encountered are mainly Ru-Os-Ir sulfides and arsenides. Textural relations ofmost of the platinum group elements suggest crystallization at magmatic temperatures, possibly under relativelyhigh sulfur fugacity as indicated by the apparent lack of primary Os-Ir-Ru alloys.The chemical and mineralogical characteristics of chromitites from the Santa Elena ultramafic nappe have astrong affinity to podiform chromitites in the mantle section of supra-subduction-zone ophiolites. Calculatedparental melts of the chromitites are consistent with the differentiation of arc-related magmas, and do not supportthe oceanic spreading center geodynamic setting previously proposed by some authors.

  • 24.
    Zaccarini, Frederica
    et al.
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Tredoux, Marian
    Department of Geology, University of the Free State, Bloemfontein.
    Miller, Duncan E.
    2Department of Geology, University of the Free State, Bloemfontein.
    Garuti, Giorgio
    Department of Applied Geosciences and Geophysics, University of Leoben.
    Aiglsperger, Thomas
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona.
    Proenza, Joaquin A.
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona.
    The occurrence of platinum-group element and gold minerals in the Bon Accord Ni-oxide body, South Africa2014In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 99, no 8-9, p. 1774-1782Article in journal (Refereed)
    Abstract [en]

    Two samples from the enigmatic Ni-oxide body of Bon Accord (Barberton greenstone belt, South Africa) have been investigated with the hydroseparation technique to obtain heavy mineral concentrates. The concentrates contain abundant Pt, Pd, and gold minerals never reported before from the Bon Accord Ni-oxide body. The grains occur as: (1) minute inclusions (<3 μm) in trevorite (ideally NiFe3+O4) and (2) larger (5–70 μm) free aggregates liberated from the host phase. The first group comprises several PGM compounds of Pd-Sb, Pd-Sb-As, Pd-Cu-Sb, Pt-Sb, Pt-As-S, Ru-As-S, Ru-S, along with free grains of Ni-Fe-As. The second consists of sperrylite (PtAs2), members of the sobolevskite-kotulskite series, and electrum. These results are in good agreement with previous analyses of PGE-Au in bulk rock. Paragenetic relationships indicate that the PGM and electrum are of secondary origin, probably generated during low-temperature metamorphism of the Ni-rich mineralization. They have a terrestrial origin and are related with a low-sulfidation regime that usually accompanies hydrothermally driven serpentinization of mafic-ultramafic bodies. The ligands in the newly formed PGM (As, Sb, Bi, Te, and O) probably proceed from the same source of the hydrothermal solutions. In this model, the metals Ni-PGE-Au were original components of the primary mineral assemblage of the Bon Accord precursor, whereas As, Sb, Bi, Te, and O might have been contributed by the metasomatizing fluids, during near-surface evolution of the ore body. The data on the high-grade heavy mineral concentrates, obtained by hydroseparation, have provided new knowledge about the mineral deportment of Pd, Pt, and Au.

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