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  • 1.
    Aiglsperger, Thomas
    et al.
    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.
    Proenza, Joaquin A.
    UB, Dept Mineral Petrol & Geol Aplicada, Barcelona, Spain.
    Villanova-de-Benavent, Cristina
    Univ Brighton, SET, Brighton, E Sussex, England.
    Torro, Lisard
    Pontifical Catholic Univ Peru PUCP, Fac Sci & Engn, Geol Engn Program, Lima, Peru.
    Ramirez, Australia
    Serv Geol Nacl, Santo Domingo, Dominican Rep.
    Rodriguez, Jesus
    Serv Geol Nacl, Santo Domingo, Dominican Rep.
    Geochemistry of REE-rich karst bauxite ore deposits from the Sierra de Bahoruco, Dominican Republic2019In: Proceedings of the 15th SGA Biennial Meeting, 27-30 August, University of Glasgow Publicity Services , 2019, Vol. 4, p. 1834-1836Conference paper (Refereed)
    Abstract [en]

    In this work the geochemistry of REE-rich karst bauxite ore from several deposits of the Sierra de Bahoruco (Dominican Republic) has been investigated. The bauxite ores are geochemically heterogenous and show differences with respect to major, minor and trace elements. According to their major element geochemistry, the studied ores classify mostly as Fe-rich bauxites. The minor elements Cr and Ni are in general relatively high (up to 1250 and 2370 ppm, respectively), hence pointing towards a (ultra-)mafic source for the bauxite formation. The sum of REE contents range from similar to 400 to similar to 5400 ppm (average similar to 1200 ppm) at varying LREE/HREE between similar to 1 and similar to 25 (average similar to 8). In general, REE chondrite-normalized patterns for studied bauxites show negative Ce and Eu anomalies with rather flat segments for HREE. However, three samples from different bauxite ore deposits with the highest REE contents show significant enrichment trends for heavier REE, particularly for Pr, Nd, Sm, Gd as well as for Tb and Dy (one sample). Mineralogical studies reveal that formation of secondary REE-bearing minerals (i.e. phosphates, carbonates and oxides) occurred. Karst bauxite ores hosted in the Sierra de Bahoruco represent an excellent natural laboratory to study the geochemical behaviour of REE in weathering systems.

  • 2.
    Aiglsperger, Thomas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, Barcelona, 08028, Spain.
    González-Jiménez, José M.
    Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, Granada, 18002, Spain; ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), GEMOC National Key Centre, Macquarie University, Sydney, 2109, NSW, Australia.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, Barcelona, 08028, Spain.
    Galí, Salvador
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, Barcelona, 08028, Spain.
    Longo, Francisco
    Faculty of Engineering, Universidad Catolica Tecnologica del Cibao (UCATECI), Ave. Universitaria, esq. Ave. Pedro Rivera, P.O. Box 401, La Vega, Dominican Republic.
    Griffin, William L.
    ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), GEMOC National Key Centre, Macquarie University, Sydney, 2109, NSW, Australia.
    O’Reilly, Suzanne Y.
    ARC Centre of Excellence for Core to Crust Fluid Systems (CCFS), GEMOC National Key Centre, Macquarie University, Sydney, 2109, NSW, Australia.
    Open system Re-Os isotope behavior in platinum-group minerals during laterization?2021In: Minerals, E-ISSN 2075-163X, Vol. 11, no 10, article id 1083Article in journal (Refereed)
    Abstract [en]

    In this short communication, we present preliminary data on the Re-Os isotopic systematics of platinum-group minerals (PGM) recovered from different horizons in the Falcondo Ni-laterite in the Dominican Republic. The results show differences in the Os-isotope composition in different populations of PGM: (i) pre-lateritic PGM yield 187 Os/188 Os varying from 0.11973 ± 0.00134 to 0.12215 ± 0.00005 (2σ uncertainty) whereas (ii) lateritic PGM are more radiogenic in terms of 187 Os/188 Os (from 0.12390 ± 0.00001 to 0.12645 ± 0.00005; 2σ uncertainty). We suggest that these differences reflect the opening of the Re-Os system in individual grains of PGM during lateritic weathering. The implications of these results are twofold as they will help to (1) elucidate the small-scale mobility of noble metals in the supergene setting and therefore the possible formation of PGM at these very low temperatures, (2) better refine the Os-isotopic datasets of PGM that are currently being used for defining dynamic models of core–mantle separation, crustal generation, and fundamental plate-tectonic processes such as the opening of oceans.

  • 3.
    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.

  • 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.
    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.

  • 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 .
    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.

  • 6.
    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, 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.

  • 7.
    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.

  • 8.
    Aydin, Faruk
    et al.
    Karadeniz Technical University, Department of Geological Engineering.
    Saka, Simge Oguz
    Karadeniz Technical University, Department of Geological Engineering.
    Sen, Cüneyt
    Karadeniz Technical University, Department of Geological Engineering.
    Dokuz, Abdurrahman
    Gümüşhane University, Department of Geological Engineering.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Uysal, Ibrahim
    Karadeniz Technical University, Department of Geological Engineering.
    Kandemir, Raif
    Recep Tayyip Erdoğan University, Department of Geological Engineering.
    Karsli, Orhan
    Recep Tayyip Erdoğan University, Department of Geological Engineering.
    Sari, Bilal
    Dokuz Eylül University, Department of Geological Engineering.
    Baser, Rasim
    Karadeniz Technical University, Department of Geological Engineering.
    Temporal, geochemical and geodynamic evolution of the Late Cretaceous subduction zone volcanism in the eastern Sakarya Zone, NE Turkey: Implications for mantle-crust interaction in an arc setting2020In: Journal of Asian Earth Sciences, ISSN 1367-9120, E-ISSN 1878-5786, Vol. 192, article id 104217Article in journal (Refereed)
    Abstract [en]

    The Late Cretaceous Artvin volcanic rocks (LCAVs) from the eastern Sakarya zone (ESZ) of NE Turkey are composed of mafic/basaltic (S1-Çatak and S2-Çağlayan) and felsic/acidic (S1-Kızılkaya and S2-Tirebolu) rock types that occurred in two successive stages: (i) first stage (S1: Turonian–Early Santonian) and (ii) second stage (S2: Late Santonian–Campanian). Clinopyroxene thermobarometric results point that the S2-Çağlayan basaltic rocks have crystallised at higher temperatures and under deeper crustal conditions than those of the S1-Çatak basaltic rocks.

    The LCAVs show a wide compositional spectrum, ranging from tholeiite to calc-alkaline/shoshonite and are typically represented by a geochemical composition resembling subduction-related arc rocks although the 87Sr/86Sr(i) (0.7044–0.7071) and ɛNd(i) values (−0.63 to + 3.47) as well as 206Pb/204Pb(i) (18.07–18.56), 207Pb/204Pb(i) (15.57–15.62) and 208Pb/204Pb(i) (37.12–38.55) ratios show very limited variation. The parent magmas of the S1-Çatak and S2-Çağlayan mafic volcanic rocks were derived from underplated basaltic melts that originated by partial melting of metasomatised spinel lherzolite and spinel-garnet lherzolite, respectively. It is proposed that the compositions of the S1-Kızılkaya (mainly dacitic) and S2-Tirebolu (rhyolitic to trachytic) felsic rocks were particularly controlled by metasomatised mantle–crust interaction and MASH zone + shallow crustal fractionation processes. Our data, together with data from previous studies, suggest that the S1- and S2-mafic and felsic rocks of the LCAVs (~95–75 Ma) are the products of two-stage volcanic event that took place during the northward subduction of the northern Neotethys Ocean (NNO).

  • 9.
    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.

  • 10.
    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.

  • 11.
    Domínguez-Carretero, Diego
    et al.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, Spain.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, Spain.
    González-Jiménez, José María
    Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Avda. de las Palmeras 4, 18100 Armilla, Granada, Spain.
    Llanes-Castro, Angélica I.
    Institute of Geology and Paleontology, Vía Blanca, Línea del Ferrocarril s/n, San Miguel del Padrón, Havana, 10200, Cuba.
    Torres, Harlison
    DataRock Ingeniería SAS, Calle 42 # 63A-198, Medellín, Colombia.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Torró, Lisard
    Geological Engineering Program, Faculty of Sciences and Engineering, Pontifical Catholic University of Peru (PUCP), Peru.
    Capote, Carbeny
    Institute of Geology and Paleontology, Vía Blanca, Línea del Ferrocarril s/n, San Miguel del Padrón, Havana, 10200, Cuba.
    de la Nuez, Deysy
    Institute of Geology and Paleontology, Vía Blanca, Línea del Ferrocarril s/n, San Miguel del Padrón, Havana, 10200, Cuba.
    Garcia-Casco, Antonio
    Instituto Andaluz de Ciencias de la Tierra, CSIC-Universidad de Granada, Avda. de las Palmeras 4, 18100 Armilla, Granada, Spain; Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Spain.
    Ultramafic-hosted volcanogenic massive sulfide deposits from Cuban ophiolites2022In: Journal of South American Earth Sciences, ISSN 0895-9811, E-ISSN 1873-0647, Vol. 119, article id 103991Article in journal (Refereed)
    Abstract [en]

    Ultramafic-hosted volcanogenic massive sulfide deposits (UM-VMS) located in the Havana-Matanzas ophiolite (Cuba) are the only known example of this type of mineralization in the Caribbean realm. UM-VMS from Havana-Matanzas are enriched in Cu, Ni, Co, Au, and Ag. The mineralization consists of massive sulfide bodies mostly composed of pyrrhotite and hosted by serpentinized upper mantle peridotites. Chemical composition of unaltered cores in Cr-spinel grains found within the massive sulfide mineralization and in the peridotite host indicates formation in the fore-arc region of the Greater Antilles volcanic arc. A first stage of serpentinization probably took place prior to the sulfide mineralization event. The UM-VMS mineralization formed by the near-complete replacement of the silicate assemblage of partially serpentinized peridotites underneath the seafloor. The sequence of sulfide mineralization has been divided into two stages. The first stage is characterized by a very reduced hydrothermal mineral assemblage consisting of pyrrhotite, Co–Ni–Fe diarsenides, chalcopyrite, Co-rich pentlandite, and electrum. In the second stage, pyrite and Co–Ni–Fe sulfarsenides partially replaced pyrrhotite and diarsenides, respectively, under a more oxidizing regime during the advanced stages of ongoing serpentinization. The proposed conceptual genetic model presented here can be useful for future exploration targeting this type of deposit in the Caribbean region and elsewhere.

  • 12.
    Farre-de-Pablo, Julia
    et al.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, C/ Martí i Franquès, s/n, 08028, Barcelona, Spain.
    Proenza, Joaquin A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, C/ Martí i Franquès, s/n, 08028, Barcelona, Spain.
    Gonzalez-Jimenez, Jose Maria
    Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Fuentenueva s/n, 18002, Granada, Spain; Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Avda. de las Palmeras 4, Armilla, E-18100, Granada, Spain.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Torro, Lisard
    Geological Engineering Program, Faculty of Sciences and Engineering, Pontifical Catholic University of Peru (PUCP), Av. Universitaria 1801, San Miguel, Lima, 15088, Peru.
    Domenech, Cristina
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona, C/ Martí i Franquès, s/n, 08028, Barcelona, Spain; Institut de Recerca de l’Aigua (IdRA), Universitat de Barcelona (UB), 08001, Barcelona, Spain.
    Garcia-Casco, Antonio
    Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Fuentenueva s/n, 18002, Granada, Spain; Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Avda. de las Palmeras 4, Armilla, E-18100, Granada, Spain.
    Low-temperature hydrothermal Pt mineralization in uvarovite-bearing ophiolitic chromitites from the Dominican Republic2022In: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 57, no 6, p. 955-976Article in journal (Refereed)
    Abstract [en]

    Platinum-group elements (PGEs) occur in ophiolitic chromitite in the Dominican Republic as platinum-group minerals (PGMs) in spatial association with hydrothermal uvarovite and chromian clinochlore. Bulk-rock total PGE content in a single analyzed chromitite sample is of 6.54 g/t. Three main PGM types are distinguished: euhedral magmatic laurite completely encased in chromite, subhedral to euhedral Ru-Os-Fe-(Ir) compounds partially encased in chromite, and anhedral Pt-Fe-Ni-rich grains exclusively embedded in uvarovite or chromian clinochlore. The Ru-Os-Fe-(Ir) compounds are interpreted as magmatic Ru-Os sulfides that experienced desulfurization during hydrothermal alteration of the chromitites, whereas the Pt-Fe-Ni-rich grains are hydrothermal in origin. We propose a model in which the Pt-Fe-Ni-rich PGMs formed via the accumulation of nanoparticles directly precipitated from the hydrothermal fluids. An estimation of the temperature of crystallization of uvarovite and chromian clinochlore suggests hydrothermal alteration of the chromitite within the thermal range of 150-350 degrees C. Thermodynamic modeling shows that, within this range of temperature, Pt could be mobilized as aqueous bisulfide complexes (HS-) by S-poor, highly reducing hydrothermal fluids originated during serpentinization of the host chromitite rock. The crystallization of Ni sulfides in the chromitite would drop the S concentration of the fluid, causing the precipitation of Pt as native element. Ultimately, this process contributes to constrain the conditions for the genesis of hydrothermal PGE mineralizations in ophiolitic chromitites.

  • 13.
    Farré-de-Pablo, Júlia
    et al.
    Departament de Mineralogia, Petrologia I Geologia Aplicada, Universitat de Barcelona, Barcelona, Spain.
    Proenza, Joaquin
    Departament de Mineralogia, Petrologia I Geologia Aplicada, Universitat de Barcelona, Barcelona, Spain.
    González-Jiménez, José María
    Departamento de Mineralogía y Petrología, Universidad de Granada, Facultad de Ciencias, Granada, Spain.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Garcia-Casco, Antonio
    Departamento de Mineralogía y Petrología, Universidad de Granada, Facultad de Ciencias, Granada, Spain. Instituto Andaluz de Ciencias de La Tierra (CSIC-UGR), Armilla, Granada, Spain.
    Escuder-Viruete, Javier
    Instituto Geológico y Minero de España, Madrid, Spain.
    Colás, Vanessa
    Instituto de Geología, Universidad Nacional Autónoma de México, Ciudad Universitaria, Ciudad de México, Mexico.
    Longo, Francisco
    Facultad de Ingeniería, Universidad Católica de Cibao, La Vega, Dominican Republic.
    Ophiolite hosted chromitite formed by supra-subduction zone peridotite –plume interaction2020In: Geoscience Frontiers, ISSN 1674-9871, Vol. 11, no 6, p. 2083-2102Article in journal (Refereed)
    Abstract [en]

    Chromitite bodies hosted in peridotites typical of suboceanic mantle (s.l. ophiolitic) are found in the northern and central part of the Loma Caribe Peridotite in the Cordillera Central of the Dominican Republic. These chromitites are massive pods of small size (less than a few meters across) and veins that intrude both dunite and harzburgite. Compositionally, they are high-Cr chromitites [Cr# = Cr/(Cr+Al) atomic ratio = 0.71–0.83] singularly enriched in TiO2 (up to 1.25 wt.%), Fe2O3 (2.77–9.16 wt.%) as well as some trace elements (Ga, V, Co, Mn, and Zn) and PGE (up to 4548 ppb in whole-rock). This geochemical signature is unknown for chromitites hosted in oceanic upper mantle but akin to those chromites crystallized from mantle plume derived melts. Noteworthy, the melt estimated to be in equilibrium with such chromite from the Loma Caribe chromitites is similar to basalts derived from different source regions of a heterogeneous Caribbean mantle plume. This mantle plume is responsible for the formation of the Caribbean Large Igneous Province (CLIP). Dolerite dykes with back-arc basin basalt (BABB) and enriched mid-ocean ridge basalt (E-MORB) affinities commonly intrude the Loma Caribe Peridotite, and are interpreted as evidence of the impact that the Caribbean plume had in the off-axis magmatism of the back-arc basin, developed after the Caribbean island-arc extension in the Late Cretaceous. We propose a model in which chromitites were formed in the shallow portion of the back-arc mantle as a result of the metasomatic reaction between the supra-subduction zone (SSZ) peridotites and upwelling plume-related melts.

  • 14.
    Farré-de-Pablo, Júlia
    et al.
    Departament de Mineralogia, Petrologia i Geologia Aplicada. Facultat de Ciències de la Terra, Universitat de Barcelona. C/ Martí i Franquès, s/n, 08028, Barcelona, Spain.
    Pujol-Solà, Núria
    Departament de Mineralogia, Petrologia i Geologia Aplicada. Facultat de Ciències de la Terra, Universitat de Barcelona. C/ Martí i Franquès, s/n, 08028, Barcelona, Spain.
    Torres, Harlison
    Fundación Universitaria del Area Andina – Sede Valledupar. Transv 22 Bis 4-105, Valledupar, Colombia.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    González-Jiménez, José María
    Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada. Avda. Fuentenueva, s/n, 18002, Granada, Spain.
    Llanes-Castro, Angélica Isabel
    Departamento de Petrología y Mineralogía, Instituto de Geología y Paleontología. Vía Blanca 1002, San Miguel del Padrón, Cuba.
    Garcia-Casco, Antonio
    Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada. Avda. 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.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada. Facultat de Ciències de la Terra, Universitat de Barcelona. C/ Martí i Franquès, s/n, 08028, Barcelona, Spain.
    Orthopyroxenite hosted chromitite veins anomalously enriched in platinum-group minerals from the Havana-Matanzas Ophiolite, Cuba2020In: Boletín de la Sociedad Geológica Mexicana, ISSN 1405-3322, Vol. 72, no 3, article id A110620Article in journal (Refereed)
    Abstract [en]

    The Havana–Matanzas Ophiolite contains one of the few examples of ophiolitic platinum group minerals (PGM)-rich chromitites associated with orthopyroxenites in the mantle section of ophiolitic complexes. The chromitites occur as veins hosted by orthopyroxenite bands within mantle peridotites. The peridotites are mostly harzburgites and their accessory chromite shows high-Al compositions (Cr# [Cr/(Cr+Al), atomic ratio] = 0.39–0.50), which are typical of spinels in abyssal peridotites. Conversely, chromite from the chromitite veins and their host orthopyroxenite are high-Cr (Cr# = 0.72–0.73 and 0.62–0.69, respectively), with lower Mg# [Mg/(Mg+Fe2+), atomic ratio]. This suggests that both the chromitite and the orthopyroxenite formed from melts with boninitic affinity. The abundant PGM inclusions found in the chromitites are mainly Os-rich laurite grains, which is also characteristic of chromitites formed from magmas with boninitic affinity. Therefore, we propose that the chromitite veins and the orthopyroxenite bands probably formed contemporaneously in the fore-arc setting of an intra-oceanic arc during subduction. The chromitite-orthopyroxenite pair of the Havana-Matanzas Ophiolite could form after the reaction of a Si-rich melt with boninitic affinity and mantle harzburgite, with the orthopyroxenite bands preserving fingerprints of the infiltration of boninitic-affinity melts within the mantle. The small volume of forming chromitite could maximize the efficiency for the mechanical collection of the PGM forming in the parental melt of these rocks, resulting in the anomalous enrichment of primary PGM in the chromitites.

  • 15.
    García-Tudela, Matías A.
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, Carrer Martí i Franquès, s/n, 08028 Barcelona, Spain.
    Farré-de-Pablo, Júlia
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, Carrer Martí i Franquès, s/n, 08028 Barcelona, Spain.
    Aiglsperger, Thomas H.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Pujol-Solà, Núria
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, Carrer Martí i Franquès, s/n, 08028 Barcelona, Spain; Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Av. Fuentenueva s/n, 18071 Granada, Spain.
    González-Jiménez, José María
    Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Avda. de las Palmeras 4, E-18100 Armilla, Granada, Spain.
    A new look to the high-PGE chromitites from the Cabo Ortegal Complex (NW Spain)2023In: Proceedings of the 17th SGA Biennial Meeting, 28 August – 1 September 2023, The Society for Geology Applied to Mineral Deposits (SGA) , 2023, Vol. 3, p. 141-144Conference paper (Refereed)
  • 16.
    García-Tudela, Matías
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Proenza, J.A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, Martí i Franquès, s/n, 08028 Barcelona, Spain.
    González-Jiménez, J.M.
    Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR), Avda. de las Palmeras 4, E-18100 Armilla, Granada, Spain.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    New observations on PGM assemblages of the anomalously high PGE-rich chromitites from Cabo Ortegal (NW Spain)2023In: Abstract Volume: 14th International Platinum Symposium, Cardiff, Wales, 4-7 July, 2023, Cardiff University , 2023, p. 286-287Conference paper (Other academic)
  • 17.
    González-Jiménez, José M.
    et al.
    Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada.
    Proenza, Joaquin A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona.
    Pastor-Oliete, Miriam
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona.
    Saunders, Edward
    Division of Earth Sciences, School of Environmental and Rural Science, University of New England.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Pujol-Solà, Núria
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona.
    Melgarejo, Joan Carles
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona.
    Gervilla, Fernando
    Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada; Instituto Andaluz de Ciencias de la Tierra (IACT), CSIC-UGR.
    Garcia-Casco, Antonio
    Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada; Instituto Andaluz de Ciencias de la Tierra (IACT), CSIC-UGR.
    Precious metals in magmatic Fe-Ni-Cu sulfides from the Potosí chromitite deposit, eastern Cuba2020In: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 118, article id 103339Article in journal (Refereed)
    Abstract [en]

    The Moa-Baracoa ophiolite in eastern Cuba is one of the few known ophiolites that display sulfide mineralization attributable to a magmatic origin in association with podiform-chromite ores hosted in the mantle-crust transition. These sulfide ores chiefly consist of Fe-Ni-Cu sulfides, namely pyrrhotite, pentlandite, chalcopyrite and cubanite partly altered to valleriite. The sulfide mineralization is located along the contact between the podiform-like chromite ores and intruding pegmatitic gabroic dykes. The detailed mineralogical study of the sulfide mineralization coupled with the first ever laser ablation ICP-MS analysis reveals that this sulfide mineralization show contents of the precious metals (Os, Ir, Ru, Pt, Re, Au, Ag) and other (semi)-metals (Co, Ni, Cu, Se, Te, Bi, Pb, As Sb) comparable to those sulfides from the magmatic sulfide deposits associated with mafic complexes hosted in the continental crust. The results obtained from this study confirm that Fe-Ni-Cu sulfides at Potosí are magmatic in origin, and very likely derived from the solidification of droplets of sulfide melt segregated by immiscibility from the intruding mafic melts once they interacted with the pre-existing chromitite at the mantle-crust transition zone of the ophiolite. The immiscibility of sulfide melt was achieved as a result of a progressive increase of fS2, very likely triggered by a set of circumstances, including the progressive fractionation of the intruding mafic melt leading to increase of aSiO2 and accumulation of volatiles as well as the crystallization of oxides. Two main generations of pentlandite were observed. One generation is primary in origin and it was locally exsolved along with pyrrhotite from monosulfide solid solution (MSS) during low-temperature cooling. The second type of pentlandite resulted from the reaction of MSS with coexisting droplets of Cu-and Ni-rich sulfide melt. LA-ICP-MS analysis reveals that most precious metals (Ru, Os, Ir, Re, Au, Ag) were concentrated along with the base-metal sulfides (BMS), although their distribution among the different BMS (pyrrhotite, pentlandite, chalcopyrite and cubanite) does not strictly follow the expected distribution according to the known melt-solid and solid-solid partition coefficients. Unlike the other analyzed PGEs, Pt was not preferentially concentrated in BMS but as discrete micrometer-sized sperrylite grains. The crystallization of sperrylite took place before and contemporaneous to sulfide segregation, and Pt-As nanoparticles probably played an important role in the Pt uptake as nucleation seeds for the formation of micron-sized sperrylite grains. These observations highlight the open-system nature of the ore forming system as well as the important role of arsenic in concentrating PGE in high-temperature silicate and sulfide melts.

  • 18.
    Hernández-González, Juan S.
    et al.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, C/ Martí i Franquès s/n, 08028, Barcelona, Spain. Departamento de Mineralogia e Geotectônica, Instituto de Geociências (GMG-IGc), Universidade de São Paulo, Rua do Lago 562, 05508-080, São Paulo, Brazil.
    Butjosa, Lídia
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, C/ Martí i Franquès s/n, 08028, Barcelona, Spain.
    Pujol-Solà, Núria
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, C/ Martí i Franquès s/n, 08028, Barcelona, Spain.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Weber, Marion
    Departamento de Geociencias y Medio Ambiente, Facultad de Minas, Universidad Nacional de Colombia, Avenida 80 # 65-223, 050034, Medellín, Colombia.
    Escayola, Monica
    Instituto de Ciencias Polares y Ambientales ICPA, Universidad de Tierra del Fuego-CONICET, Fueguia Basket 251, 9410, Ushuaia, Tierra del Fuego, Argentina.
    Ramírez-Cárdenas, Carlos
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, C/ Martí i Franquès s/n, 08028, Barcelona, Spain.
    Blanco-Quintero, Idael F.
    Departamento de Ciencias de la Tierra y del Medio Ambiente, Universidad de Alicante, Carretera de San Vicente del Raspeig s/n, 03690, Alicante, Spain.
    González-Jiménez, José María
    Departamento de Mineralogía y Petrología, Facultad de Ciencias, Universidad de Granada, Avda. Fuentenueva s/n, 18002, Granada, Spain.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona, C/ Martí i Franquès s/n, 08028, Barcelona, Spain.
    Petrology and geochemistry of high-Al chromitites from the Medellín Metaharzburgitic Unit (MMU), Colombia2020In: Boletín de la Sociedad Geológica Mexicana, ISSN 1405-3322, Vol. 72, no 3, article id A120620Article in journal (Refereed)
    Abstract [en]

    The Medellin Metaharzburgitic Unit (MMU), emplaced onto the western continental margin of Pangea during Triassic time, is located in the Central Cordillera of Colombia and consists of metaharzburgites, minor metadunites and chromitite bodies (Patio Bonito and San Pedro ore deposits). The ultramafic rocks contain relicts of mantle-derived olivine, chromian spinel and minor orthopyroxene, and a later metamorphic mineral assemblage composed by tremolite, chlorite, talc, fine-grained recrystallized olivine, serpentine-group minerals, magnetite, and secondary chromian spinel, formed during the thermal evolution of the unit. The Cr# [Cr/(Cr+Al) atomic ratio] of the accessory primary chromian spinel in the metaperidotites ranges from 0.58 to 0.62 and overlaps those of supra-subduction peridotites from ophiolites. According to textural and compositional variations, the accessory chromian spinel in the metaperidotites can be classified into three groups: i) partially altered chromian spinel with an Al-rich core, ii) porous, Cr-Fe2+-enriched and Al-Mg-depleted chromian spinel, and iii) homogeneous Fe3+-rich chromian spinel. These variations can be related to superimposed medium-T metamorphism that reached amphibolite facies (ca. 600 ºC). Chromitite bodies associated with the metaperidotites have massive and semi-massive textures, and mainly consist of chromian spinel crystals, which show large unaltered cores surrounded by thin alteration rims of ferrian chromian spinel and chlorite. Chromitites are Al-rich (#Cr <0.6) and strongly depleted in platinum group elements (ΣPGE <41 ppb). The primary petrological and geochemical characteristics preserved in the metaperidotites and chromitites indicate that the MMU formed at shallow levels of a suboceanic lithospheric mantle related to a supra-subduction zone (back-arc basin/incipient arc scenario), and that the chromitites crystallized from a tholeiitic magma (back-arc basin basalt type).

  • 19.
    Jansson, Nils
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Hjorth, Ingeborg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Ivarsson, Filip
    Zinkgruvan Mining AB, 696 81 Zinkgruvan, Sweden.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Azim Zadeh, Amir M.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Kooijman, Ellen
    Department of Geosciences, Swedish Museum of Natural History, Frescativägen 40, SE-104 05 Stockholm, Sweden.
    Kielman-Schmitt, Melanie
    Department of Geosciences, Swedish Museum of Natural History, Frescativägen 40, SE-104 05 Stockholm, Sweden.
    Drakou, Foteini
    Department of Geology, School of Natural Sciences, Trinity College Dublin, Ireland.
    Kozub-Budzyń, Gabriela
    AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protecition, Al. Mickwiewicza 30, Kraków, Poland.
    Cobalt and REE distribution at the Zinkgruvan Zn-Pb-Ag and Cu deposit, Bergslagen, Sweden2022In: EGU General Assembly 2022, Copernicus GmbH , 2022, article id EGU22-1067Conference paper (Refereed)
    Abstract [en]

    The metamorphosed, stratiform, c. 1.9 Ga Zinkgruvan Zn-Pb-Ag deposit is one of Europe’s largest producers of Zn. Since 2010, disseminated Cu mineralization is also mined from dolomite marble in a hydrothermal vent-proximal position in the stratigraphic footwall. Local enrichments of Co and REE exist in the vent-proximal mineralization types, albeit their distribution is poorly known. This contribution provides new data on the distribution of Co and REE within the Zinkgruvan deposit.

    LA-ICP-MS analysis suggest that lattice-bound cobalt in sphalerite range between 44 ppm and 1372 ppm, with the lowest and highest values occurring in distal and proximal mineralization, respectively. Proximal Co-rich sphalerite is always Fe-rich. Lattice-bound Co also occur in pyrrhotite; ranging from 52 ppm in distal ore to 1608 ppm in proximal ore. There is a concurrent increase in lattice-bound Ni from 3 ppm to 529 ppm. In proximal ore, Co is also hosted by cobalt minerals such as costibite (27.37 wt.% Co), safflorite (16.21 wt.% Co), nickeline (7.54 wt.% Co), cobaltite (32.74 wt.% Co) and cobaltpentlandite (25.49 wt.% Co). Automated quantitative mineralogy suggest that these minerals are highly subordinate to sphalerite (<70.11%) and pyrrhotite (<14.69%), amounting to <2.88% cobalt minerals with safflorite being most common (up to 2.67%). Cobalt deportment calculations suggest that the proportion of whole-rock Co that is lattice-bound to sphalerite and pyrrhotite ranges from 7.80% to 100%, with sphalerite being the main host. Whole-rock As and Ni contents pose a strong control on whether Co occurs lattice-bound or as Co minerals.

    LA-ICP-MS analysis show that accessory apatite in proximal, marble-hosted Cu mineralization carries a few thousand ppm ∑REE, but locally up to c. 1.6 wt.% ∑REE. The apatite can be subdivided into two types. Type 1 apatite is characterized by dumbbell-shaped chondrite-normalized REE profiles with relative enrichment of in particular Sm-Tb, depletion of Yb-Lu relative to La-Pr, local positive Gd anomalies, and weak positive to negative Eu anomalies. Type 2 apatite is characterized by flat to negatively sloping REE profiles from La to Gd and relative HREE depletion. Additional REE is hosted by monazite. Type 1 apatite was only found as a gangue to Cu mineralization. The Type 1 apatite REE signature is characteristic of hydrothermal apatite, and a direct genetic association with vent-proximal Cu mineralization can be inferred.

    Comparison with published REE contents in apatite suggest that vent-proximal Zinkgruvan apatite is locally as REE-rich as apatite from Kiruna-type apatite iron oxide deposits, and more REE-rich than apatite in other metamorphosed sediment-hosted sulphide deposits in the world, such as the Gamsberg deposit (RSA).

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  • 20.
    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, 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.

  • 21.
    López-Males, Gladys G.
    et al.
    Department de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028, Barcelona, Spain.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Pujol-Solà, Núria
    Department de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028, Barcelona, Spain.
    Proenza, Joaquín A.
    Department de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028, Barcelona, Spain.
    New mineralogical data on platinum-group minerals from the Río Santiago alluvial placer, Esmeraldas province, Ecuador2020In: Boletín de la Sociedad Geológica Mexicana, ISSN 1405-3322, Vol. 72, no 3, article id A090720Article in journal (Refereed)
    Abstract [en]

    Mineralogical studies on platinum-group minerals found in placer deposits from the Río Santiago (Ecuador) are scarce. In this investigation, one sample collected from the Río Santiago alluvial placer was studied via a multi-disciplinary approach, including optical microscopy, scanning electron microscopy, electron microprobe, and Raman spectroscopy. Whole-rock geochemistry data of the sample confirms elevated Au and platinum-group elements contents and the chondrite-normalized pattern reveals pronounced positive Ir and Pt anomalies. Free grains of platinum-group minerals were separated via hydroseparation techniques and identified as: i) Pt-Fe alloy (Pt3Fe), ii) tulameenite (Pt2FeCu) and iii) hongshiite (PtCu). The most abundant platinum-group mineral is Pt-Fe alloy (85%) that occasionally hosts cuprorhodsite (CuRh2S4) inclusions. Although the primary source remains unknown, the geochemical and mineralogical data suggests that the source of platinum-group minerals in the Río Santiago alluvial placer is a mafic-ultramafic Ural-Alaska type complex. Possible primary sources are the mafic and ultramafic rocks found in the mafic basement of the coastal region and the Western Cordillera (Piñón, San Juan and Pallatanga units), which derive from the Late Cretaceous Caribbean Colombia Oceanic Plateau (CCOP).

  • 22.
    Melcher, Frank
    et al.
    Geology and Economic Geology, Montanuniversität Leoben, Peter-Tunnerstrasse 5, 8700 Leoben, Austria.
    Schwabl, Sonja
    Urtelgasse 4, 2620 Neunkirchen, Austria.
    Onuk, Peter
    Geology and Economic Geology, Montanuniversität Leoben, Peter-Tunnerstrasse 5, 8700 Leoben, Austria.
    Meisel, Thomas
    Analytical Chemistry, Montanuniversität Leoben, Franz-Josefstrasse 18, 8700 Leoben, Austria.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciènces de la Terra, Universitat de Barcelona, C/Marti i Franquès, s/n, 08028, Barcelona, Spain.
    The Haidbach deposit in the Central Tauern Window, Eastern Alps, Austria: a metamorphosed orthomagmatic Ni-Cu-Co-PGE mineralization in the Polymetallic Ore District Venediger Nappe System – Hollersbach Complex2021In: Austrian Journal of Earth Sciences, ISSN 0251-7493, Vol. 114, no 1, p. 1-26Article in journal (Refereed)
    Abstract [en]

    Cu-Ni-Co-PGE mineralization occurs at Haidbachgraben in the Early Palaeozoic, Subpenninic Hollersbach Complex of the Central Tauern Window, Austria. Massive sulfide ore formed from sulfide melt segregated from silicate melt during intrusion of pyroxenite into magmatic rocks formed in an MORB-type environment. Relics of magmatic minerals include chromian spinel and polyphase sulfide droplets composed of pyrrhotite, chalcopyrite and pentlandite preserved in recrystallized pyrite. Both ore and host rocks were multiply deformed and metamorphosed, leading to hornblendite carrying the ore, enveloped by chlorite-epidote schist. Conditions of – likely Variscan – amphibolite facies metamorphism are documented by relict pargasitic cores in hornblende and actinolite-tremolite, and by ternary sulfarsenide compositions in the Co-Ni-Fe solid solution series that are the most common accessory minerals found in the sulfide ore. Pyrrhotite, pentlandite, chalcopyrite and pyrite are the major sulfide minerals. Chalcopyrite is Cd-rich and retains a high-temperature magmatic signature. High Co/Sb and moderate Se/As ratios in pyrite also point to a magmatic environment of mineralization. The accessory mineral assemblage of small grain size (mostly <10 µm) comprises native Au-Ag alloy and petzite as Au-Ag minerals, sperrylite, a variety of Pd tellurides and bismuthotellurides with elevated Sb, irarsite, and Re sulfides such as tarkianite and a Pb-Re sulfide. In addition, minor molybdenite, bournonite, scheelite and selenides have been identified. Two precious metal assemblages are present in individual samples: (1) hessite associated with Pd tellurides, often accompanied by sphalerite and chalcopyrite; (2) tarkianite forming euhedral inclusions in pyrite. Sperrylite and Au-Ag native alloys are present throughout and were also detected in silicate matrix. Most of the precious metal-bearing phases must have formed during recrystallization of base metal sulfides after the magmatic, and probably during later metamorphic events terminating in the Neoalpine Tauern crystallization.

  • 23.
    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.

  • 24.
    Oğuz-Saka, Simge
    et al.
    Karadeniz Technical University, Department of Geological Engineering, Trabzon, Turkey; General Directorate of Mineral Research and Exploration, Ankara, Turkey.
    Aydin, Faruk
    Karadeniz Technical University, Department of Geological Engineering, Trabzon, Turkey.
    Karsli, Orhan
    Karadeniz Technical University, Department of Geological Engineering, Trabzon, Turkey.
    Dokuz, Abdurrahman
    Gümüşhane University, Department of Geological Engineering, Gümüşhane, Turkey.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Miggins, Daniel P.
    Oregon State University, College of Earth, Ocean and Atmospheric Sciences, Argon Geochronology Laboratory, Corvallis, USA.
    Şen, Cüneyt
    Karadeniz Technical University, Department of Geological Engineering, Trabzon, Turkey.
    Kandemir, Raif
    Recep Tayyip Erdoğan University, Department of Geological Engineering, Rize, Turkey.
    Sarı, Bilal
    Dokuz Eylül University, Department of Geological Engineering, İzmir, Turkey.
    Koppers, Anthony A.P.
    Oregon State University, College of Earth, Ocean and Atmospheric Sciences, Argon Geochronology Laboratory, Corvallis, USA.
    Two-stage bimodal volcanism in a Late Cretaceous arc/back-arc setting, NE Turkey: Constraints from volcano-stratigraphy, zircon U–Pb and 40Ar/39Ar geochronology and whole-rock elemental and Sr-Nd-Pb isotope geochemistry2023In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 440-441, article id 107018Article in journal (Refereed)
    Abstract [en]

    The eastern Blacksea magmatic arc (EBMA) in the eastern Sakarya Zone (ESZ) provides an excellent opportunity to investigate birth of an extensional intra-arc and back-arc settings in the Late Cretaceous over the Early Cretaceous northern passive margin of the Neotethys Ocean. Volcano-stratigraphy clearly shows that the Late Cretaceous volcanic activity of the EBMA occurred in two major phases. Bimodality, characterized by mafic/basaltic rocks at the base and felsic/silicic types on top of it, is a typical feature of the lower (LVS) and upper (UVS) volcanic successions in the Giresun region of the ESZ. U–Pb and Ar–Ar ages support the volcanic succession as two-stage (LVS: ca. 92–85 and UVS: ca. 83–67 Ma) bimodal volcanism. Both the volcanic successions are represented by similar rock types consisting of tholeiitic to calc-alkaline basalt-basaltic andesites and calc-alkaline to shoshonitic dacite-rhyolites. Basaltic (M1- and M2-series) and felsic/silicic (F1- and F2-series) samples of the LVS and UVS have an arc-like signature with enriched large ion lithophile elements (LILEs) and light rare earth elements (LREEs) and depleted high field strength elements (HFSEs). Also, the felsic/silicic samples of the F1- and F2-series show prominent negative Sr and Eu anomalies (Eu/Eu* = 0.4 to 0.9), suggesting that plagioclase fractionation played a key role on the evolution of both felsic series. Bimodal rock series in two phases have a wide range of 87Sr/86Sr(i) (0.7048–0.7075) and 143Nd/144Nd(i) (0.5123–0.5127) ratios with variable ɛNd(i) values of −3.8 to +3.0. 206Pb/204Pb(i), 207Pb/204Pb(i) and 208Pb/204Pb(i) isotope ratios of the Giresun volcanic rocks vary in the range of 17.97–18.52, 15.55–15.65 and 37.53–38.56, respectively.

    Geochemical and isotopic data suggest that the parental magma of the M1-basaltic rocks were probably derived from a shallow (spinel-bearing) mantle metasomatized by slab/sediment-derived fluids. In contrast, the M2-basalts seem to have been originated from a deeper mantle source (spinel-garnet transition zone) enriched by slab/sediment-derived fluids and hydrous melts (bulk sediment) metasomatism with some contributions of lower/upper crustal materials. The least evolved basaltic samples in two phases are consistent with moderate (∼10–15%) to high degree (∼20–30%) partial melting of the metasomatized mantle. The silicic melts of the F1- and F2-rocks series, on the other hand, were likely derived from melting of lower crustal materials consisting of meta-basalts/andesites and lesser amount of meta-sediments. Subsequently, these melts experienced FC ± AFC and mixing processes during their ascent and emplacement to generate high-silica (rhyolitic) melts. Our data, combined with previous studies, suggest that two-stage bimodal volcanic rocks of the Late Cretaceous in the ESZ were formed in the transition from an extensional continental intra-arc to a back-arc setting during the northward subduction of the northern branch of Neotethys Ocean.

  • 25.
    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.

  • 26.
    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).

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  • 27.
    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.

  • 28.
    Pujol-Sola, Nuria
    et al.
    Univ Barcelona, Dept Mineral Petrol & Geol Aplicada, Barcelona, Spain.
    Proenza, Joaquin A.
    Univ Barcelona, Dept Mineral Petrol & Geol Aplicada, Barcelona, Spain.
    Torres, Harlison
    Fdn Univ Area Andina, Sede Valledupar, Bogota, Colombia.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Maria Gonzales-Jimenez, Jose
    Univ Granada, Dept Mineral & Petrol, Granada, Spain.
    Garcia-Casco, Antonio
    Univ Granada, Dept Mineral & Petrol, Granada, Spain.
    Llanes Castro, Angelica Isabel
    Inst Geol & Paleontol, Dept Petrol & Mineral, Havana, Cuba.
    Olivine orthopyroxenite-hosted chromitite veins in the ophiolitic mantle, Havana-Matanzas, Cuba2019In: Proceedings of the 15th SGA Biennial Meeting, 27-30 August, University of Glasgow Publicity Services , 2019, p. 569-572Conference paper (Refereed)
    Abstract [en]

    The Havana-Matanzas ophiolite contains an example of chromitite veins hosted in olivine orthopyroxenites within mantle peridotites. Accessory Cr-spinei in the harzburgite and in the Ol-orthopyroxenite, and chromite in the chromitite vein show a wide range of composition (Cr# 0.39-0.75). However, the chromite in the vein and the Cr-spinel in the Ol-orthopyroxenite show similar composition with Cr#>0.7 (Cr-rich), probably related to crystallization from boninitic-like mantle melts. The study of platinum-group minerals hosted in the chromite shows that Os-rich laurite is the main mineral phase, as it is typically observed in chromitites that formed from magmas of boninitic affinity. The Ol-orthopyroxenite bands are believed to represent melt channels that formed after replacement of peridotites by a Si-rich melt with boninitic affinity. This is supported by the Cr-spinel composition of the pyroxenites (Cr#>0.7) and the low Al, Ca and Cr content of orthopyroxene. The interaction between a Si-rich melt with harzburgite/dunite formed Ol-orthopyroxenite and a Cr-saturated melt, which also circulated through the pyroxenite channels and formed the chromitite veins.

  • 29.
    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, 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.

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    Reinhardt et al. 2018
  • 30.
    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.

  • 31.
    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).

  • 32.
    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.

  • 33.
    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.

  • 34.
    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.
    Alakangas, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Biogeochemical Controls on 13CDIC Signatures from Circum-Neutral pH Groundwater in Cu–W–F Skarn Tailings to Acidic Downstream Surface Waters2020In: Minerals, E-ISSN 2075-163X, Vol. 10, no 9, article id 758Article in journal (Refereed)
    Abstract [en]

    Regular features of ground and surface waters affected by drainage from mine waste include their acidity and elevated concentrations of dissolved metals, with their attendant negative effects on drinking water quality and aquatic life. One parameter that aids in buffering these waters against acidity and sustains aquatic life is dissolved inorganic carbon (DIC). In this study, the chemical and isotopic (δ13C) composition of primary calcite and DIC (δ13CDIC) in groundwater and surface waters within and downstream, respectively, of abandoned Cu–W–F skarn tailings at Yxsjöberg, Sweden, were used to trace the biogeochemical processes controlling their respective δ13CDIC signatures. In addition, the δ13C signatures of the inorganic (carbonate) fractions of the tailings were used to verify the formation of secondary carbonates within the tailings. Lower average δ13C values of the carbonate fractions (δ13Ccarb = −2.7‰) relative to those of the primary calcite (δ13C = +0.1‰) from the orebodies from which the tailings originated pointed to the precipitation of secondary carbonates. These lower δ13Ccarb signatures were assumed to represent mixed-source C signals involving isotopically light CO2 from the atmosphere, the degradation of organic matter in the upper part of the tailings and HCO3 from calcite dissolution. The groundwater δ13CDIC values (−12.6‰ to −4.4‰) were far lower than the hypothetical range of values (−4.6‰ to +0.7‰) for primary calcite and secondary carbonate dissolution. These signatures were attributed to carbonate (calcite and secondary carbonate) dissolution and the degradation of dissolved organic carbon (DOC) from various organic sources such as peat underneath the tailings and the surrounding forests. Downstream surface water samples collected in May had low δ13CDIC values (−16‰) and high DOC (14 mg C/L) compared to the groundwater samples. These signatures represented the oxidation of the DOC from the wash out of the mires and forests during the snowmelt and spring flood. The DOC and δ13CDIC values of the surface waters from June to September ranged from 6–15 mg·C/L and −25‰ to −8.6‰, respectively. These signatures were interpreted to reflect mixed C sources, including carbonate dehydration by acidity from Fe3+ hydrolysis due to the mixing of groundwater with surface waters and the subsequent diffusive loss of CO2 (g), aquatic photosynthesis, photooxidation, DOC degradation, as well as microbial respiration. Although the 13CDIC signatures of the downstream surface waters seemed to be seasonally controlled and influenced by variable groundwater contributions, the lack of data with respect to DIC concentrations, coupled with multiple potential biogeochemical processes that could influence the DIC pool and 13CDIC values, made it difficult to identify the major regulating process of the 13CDIC signatures. Therefore, other complimentary isotopes and elemental concentrations are recommended in order to decipher the dominant biogeochemical process.

  • 35.
    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.

  • 36.
    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.
    Mörth, Carl-Magnus
    Department of Geological Sciences, Stockholm University, Stockholm, Sweden.
    Alakangas, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Stable sulphur and oxygen isotopes as indicators of sulphide oxidation reaction pathways and historical environmental conditions in a Cu–W–F skarn tailings piles, south-central Sweden2019In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 110, article id 104426Article in journal (Refereed)
    Abstract [en]

    Improved remediation strategies or predictive modelling of acid mine drainage (AMD) sites, require detailed understanding of the sulphide oxidation reaction pathways, as well as pollutant-source characterisation. In this study, ore minerals, solids and water-soluble fractions of an oxidising Cu–W–F skarn tailings in Yxsjöberg, Sweden, were chemically and isotopically (δ34S and δ18O) characterised to reveal sulphate (SO42−) sources, sulphide oxidation reaction pathways and historical environmental conditions in the tailings. δ34S was additionally used to trace the weathering of danalite [(Fe,Mn,Zn)4Be3(SiO4)3S], a rare and unstable sulphur-bearing silicate mineral containing high concentrations of beryllium (Be) and zinc (Zn). Eighteen subsamples from a drill core of the tailings were subjected to batch leaching tests to obtain water-soluble fractions, which reflected both existing pore-waters and easily-soluble secondary minerals. The tailings were categorised into three geochemical zones: (i) oxidised zone (OZ), (ii) transition zone (TZ) and (iii) unoxidised zone (UZ), based on prevailing pH, elemental concentrations and colour. The upper OZ (UOZ) showed a sharp depletion of sulphur (S) and relatively higher δ18OSO4 values (−3.0 to +0.1‰) whereas the underlying lower OZ (LOZ) showed S accumulation and lower δ18OSO4 values (−4.6 to −4.2‰). The higher δ18OSO4 suggested the role of atmospheric oxygen, O2 (as oxidant), contribution of evaporated rainwaters and/or evaporation in the upper zones of the tailings. The lower δ18OSO4 values were indicative of ferric iron (Fe3+) as oxidant and the possible incorporation of 16O into SO42− during its formation, most probably from snow melt or depleted rainwater. The δ34SSO4 values in the OZ (+2.3 to +2.4‰) suggested SO42− from pyrrhotite oxidation in the UOZ which has been subsequently mobilised to the LOZ. Low δ34S fractionation (+0.2 to +1.9‰) between SO42− in the OZ and pyrrhotite, as well as the low δ18OSO4 values in the LOZ suggested the complete oxidation of pyrrhotite by Fe3+, signalling that previously, a low pH (<3) prevailed in the tailings. Mineralogical observations confirmed that pyrrhotite was completely oxidised in the UOZ, with the formation of hydrous ferric oxides (HFOs) coatings. The observed current high δ18OSO4 and pH (3.9–4.5) values in the UOZ were attributed to decreased oxidation rate and silicate buffering, limiting the availability of aqueous Fe3+ and subsequent formation of HFOs. The δ34SSO4 signatures of the water-soluble SO42− in the TZ and UUZ suggested the dissolution of gypsum which precipitated from a leachate from the weathering of danalite in the UOZ. In the middle UZ, the δ34SSO4 (−0.8 to +0.6‰) and δ18OSO4 (−1.8 to −1.0‰) signatures corresponded to SO42− from a mixture of pyrite, pyrrhotite and chalcopyrite oxidation by O2 at the LOZ (i.e. oxidation front). Negative δ34S fractionation values (−3.0 to −1.6‰) between these minerals and the water-soluble SO42− were attributed to the potential formation of intermediate S species, due to the partial oxidation of the sulphides. Consequently, the S accumulation in the LOZ could be due to the likely formation of the intermediate S species and secondary pyrite identified in this zone. The lower UZ coincided with the groundwater table and registered consistent negative δ34SSO4 (−2.6 to −1.8‰) and δ18OSO4 (−7.6 to −4.4‰) values. These signatures were hypothesised to be controlled by SO42− from the mineralisation of organic S in peat underneath the tailings and/or H2S oxidation, with possible contribution from sulphide oxidation in the tailings. This study highlights the usefulness of δ34S and δ18O as tracers of geochemical processes and environmental conditions that have existed in the tailings.

  • 37.
    Salifu, Musah
    et al.
    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.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Mörth, Carl-Magnus
    Department of Geological Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
    Alakangas, Lena
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    A simple model for evaluating isotopic (18O, 2H and 87Sr/86Sr) mixing calculations of mine: Impacted surface waters2020In: Journal of Contaminant Hydrology, ISSN 0169-7722, E-ISSN 1873-6009, Vol. 232, article id 103640Article in journal (Refereed)
    Abstract [en]

    This study was aimed at identifying and quantifying mixing proportions in surface waters downstream of historical Cu-W-F skarn mine tailings at Yxsjöberg, Sweden, using 18O, 2H, and 87Sr/86Sr isotopes. In addition, a simple mathematical model was developed to evaluate the consistency of the mixing calculations. Hydrochemical and isotopic data from 2 groundwater wells, 6 surface water and 2 rainwater sampling sites, spanning 6 sampling campaigns between May and October were used. Three mixed surface waters downstream of the tailings were identified, namely: C7, C11 and C14. C7 was directly influenced by groundwater from the tailings whereas C11 was also subsequently influenced by C7. C14 on the other hand, had contributions from C11. Sequential mixing calculations indicated that the contribution of the groundwater to C7 ranges from 1 to 17%. The subsequent contribution of C7 to C11 varied from 49 to 91% whereas C14 had contributions of C11 ranging between 16 and 56%. A strong agreement between the model data (MD) and measured raw data (RD) for C11 and C14 indicated the accuracy of the mixing calculations. Variations between the MD and RD at C7, however, was mainly due to sorption and reductive processes underneath the tailings, which tend to attenuate the amount of dissolved ions reaching the surface waters, resulting in a low ionic contribution of the tailings groundwater to the surface water. The low ionic contribution of the groundwater to C7 suggested that although the tailings impoundment is of environmental concern, its impact on the downstream surface waters is small. The results of this study suggest that mixing calculations in surface waters involving a closed system such as groundwater (as an end-member) must be treated with caution. It is recommended that the interpretation of such mixing results must be coupled with detailed knowledge of the potential hydrogeochemical processes along its flow paths.

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  • 38.
    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.

  • 39.
    Tobón, Mónica
    et al.
    Departamento de Materiales y Minerales, Facultad de Minas, Universidad Nacional de Colombia, Carrera 80 # 65-223, Medellín, Colombia.
    Weber, Marion
    Departamento de Materiales y Minerales, Facultad de Minas, Universidad Nacional de Colombia, Carrera 80 # 65-223, Medellín, Colombia.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Betancur, Sebastián
    Departamento de Materiales y Minerales, Facultad de Minas, Universidad Nacional de Colombia, Carrera 80 # 65-223, Medellín, Colombia.
    Farré-de-Pablo, Júlia
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Ramírez, Carlos
    Departamento de Materiales y Minerales, Facultad de Minas, Universidad Nacional de Colombia, Carrera 80 # 65-223, Medellín, Colombia.
    Pujol-Solà, Núria
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Geochemistry of Platinum-Group Elements (PGE) in the Cerro Matoso and Planeta Rica Ni-Laterite deposits, Northern Colombia2020In: Boletín de la Sociedad Geológica Mexicana, ISSN 1405-3322, Vol. 72, no 3, article id A201219Article in journal (Refereed)
    Abstract [en]

    Platinum-group elements (PGE) are included among the so-called critical metals, and are essential metals for the technological industry. However, there are very few deposits in the world from which these metals can be extracted. The present work investigates three Ni-laterite profiles (hydrous Mg silicate type) formed over the ultramafic rocks of Cerro Matoso and Planeta Rica in Colombia. The main goal is to determine their PGE concentration and distribution, as well as to identify the carrier phases of these noble metals. The highest PGE contents in Cerro Matoso and Planeta Rica are concentrated in the limonite horizon (141–272 ppb), showing a strong decrease towards the saprolite and the underlying serpentinized peridotite (parent rock; < 50 ppb). The highest concentrations correspond to Pt>Ru>Pd and the lowest to Rh<Os<Ir. Such distribution indicates that PGE are mobilized in different proportions by the laterization processes. The high affinity between PGE and Fe favors the formation of PGE-Fe mineral alloys such as the Pt-Ir-Fe-Ni minerals hosted by Fe-oxyhydroxide found in the limonite–saprolite transition zone in Planeta Rica. In addition, in the same zone, nanoparticles of Pt (< 1 μm) were found within framboidal pyrite. Both types of platinum group minerals (PGM) are secondary in origin. In the case of Pt-Ir-Fe-Ni alloys, this interpretation is supported by their morphology and chemical composition, which is comparable with PGE-Fe-Ni alloys found in laterites of Dominican Republic. In the case of Pt nanoparticle, textural relations suggest the neoformation of PGM adhered to the porous edges of altered pyrite. Cerro Matoso and Planeta Rica should be considered as unconventional PGE deposits, if adequate recovery processes can be applied for their recoveryas by-products during Ni (+Co) production.

  • 40.
    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.

  • 41.
    Villanova-de-Benavent, Cristina
    et al.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Proenza, Joaquín A.
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Torró, Lisard
    Geological Engineering Program, Faculty of Sciences and Engineering, Pontifical Catholic University of Peru, Lima, Peru.
    Aiglsperger, Thomas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Domènech, Cristina
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Domínguez-Carretero, Diego
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Llovet, Xavier
    Centres Científics i Tecnològics, Universitat de Barcelona, Lluís Solé i Sabarís, 1-3, 08028 Barcelona, Spain.
    Suñer, Pol
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Facultat de Ciències de la Terra, Universitat de Barcelona (UB), Martí i Franquès s/n, 08028 Barcelona, Spain.
    Ramírez, Australia
    Servicio Geológico Nacional, Av. Winston Churchill 75, Edificio “J. F. Martínez”, Santo Domingo, Dominican Republic.
    Rodríguez, Jesús
    Servicio Geológico Nacional, Av. Winston Churchill 75, Edificio “J. F. Martínez”, Santo Domingo, Dominican Republic.
    REE ultra-rich karst bauxite deposits in the Pedernales Peninsula, Dominican Republic: Mineralogy of REE phosphates and carbonates2023In: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 157, p. 105422-105422, article id 105422Article in journal (Refereed)
    Abstract [en]

    Karst bauxites have recently received renewed attention for their potential as non-conventional REE sources. Karst bauxites from the Pedernales Peninsula in the Dominican Republic stand among the world’s richest in REE. Bauxite ore from two deposits from this bauxite district, Aceitillar and El Turco, have been selected for this study due to their outstanding REE contents and contrasting mineralogy. REE (La to Lu) contents in Aceitillar, range from 0.07 to 0.16 wt%, and Y from 0.01 to 0.13 wt%, whereas El Turco contains between 0.28 and 1.40 wt% REE, and 0.33 to 1.48 wt% Y. The characterisation of REE mineralisation was performed through powder and monocrystal XRD, SEM-EDS, and EMP analyses. REE phosphates and carbonates reveal textural features that suggest significant REE mobilisation and re-deposition within the bauxite profile. The identified REE minerals can be classified into: i) primary monazite(-Ce) and minor monazite(-La); ii) secondary Y- and Nd-dominant phosphates; and iii) secondary Gd- and Nd-carbonates of the (hydroxyl)bastnäsite group. While monazites are ubiquitous in the two studied deposits, secondary phosphates are predominant in El Turco while secondary carbonates are exclusive of Aceitillar. This contrasting mineralogy is explained by the total concentration of carbonate and/or phosphate in the karst bauxite groundwater solutions. REE phosphates are the most stable phases at [CO32−]total/[PO43-]total ≤ 2; whereas REE carbonates are stable at near neutral pH when the total aqueous carbonate concentration is two orders of magnitude higher than that of phosphate. Results of this investigation contribute to a better understanding of the formation REE minerals in the supergene environment and can be applied in REE separation methods.

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  • 42.
    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.

  • 43. 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.

  • 44.
    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.

  • 45.
    Zaccarini, Frederica
    et al.
    Department of Applied Geosciences and Geophysics, University of Leoben, A 8700, Leoben, Austria.
    Tredoux, Marian
    Department of Geology, University of the Free State, Bloemfontein 9300, South Africa.
    Miller, Duncan E.
    Department of Geology, University of the Free State, Bloemfontein 9300, South Africa.
    Garuti, Giorgio
    Department of Applied Geosciences and Geophysics, University of Leoben, A 8700, Leoben, Austria.
    Aiglsperger, Thomas
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona, 08028 Barcelona, Spain.
    Proenza, Joaquin A.
    Department of Crystallography, Mineralogy, and Ore Deposits, University of Barcelona, 08028 Barcelona, Spain.
    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.

  • 46.
    Zwahlen, Carmen
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. University of Bern, Switzerland.
    Rehn, Andreas
    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.
    Dold, Bernhard
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering. SUMIRCO, Konstanz, Germany.
    Geochemical and mineralogical aspects of acid mine drainage associated with 100 years of coal mining in the arctic, Svalbard (78°N)2023In: Journal of Geochemical Exploration, ISSN 0375-6742, E-ISSN 1879-1689, Vol. 252, article id 107266Article in journal (Refereed)
    Abstract [en]

    Acid mine drainage (AMD) is a pressing issue due to increasing mining activities in arctic climate zones. Over 100 years of coal mining in Svalbard presents an ideal study case for the development of AMD in arctic regions.

    The mined coal (low liptinite type oil prone coal) has less than 1.1 wt% sulphur with micro inclusions of pyrite but the contacting silt and sandstones contain pyrite nodules of centimeter size. These forms of pyrite are left to oxidize on multiple large waste rock piles. Simple accounting of the acid producing and neutralizing potential reveals that all studied lithologies are prone to produce acid waters despite a relatively low pyrite content but with an almost absent neutralization potential.

    During spring and summer, there are small streams draining the waste rock piles with a pH of 2.5 to 3.7, buffered by an iron hydroxide assemblage. The sulphate concentration of the water samples correlates well with the sum of the cations, indicating that pyrite oxidation is the dominant weathering process. There is no correlation between the age of the waste rock piles and the acidity of the effluents and the system might be controlled by the geometry of the waste rock piles combined with the local hydrology.

    Mass balance calculations for one of the mine sites estimates that AMD will continue for another 150 years. The sole operating mine site to date is likely to face a similar prospect once lime buffering measures seize.

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