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  • 1.
    Cámara, Fernando
    et al.
    Dipartimento di Scienze della Terra “Ardito Desio”, Università degli Studi di Milano, Via Luigi Mangiagalli 34, 20133, Milan, Italy.
    Holtstam, Dan
    Department of Geosciences, Swedish Museum of Natural History, Box 50007, 104 05 Stockholm, Sweden.
    Jansson, Nils
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Geosciences and Environmental Engineering.
    Jonsson, Erik
    Department of Mineral Resources, Geological Survey of Sweden, Villavägen 18, 752 36 Uppsala, Sweden; Department of Earth Sciences, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden .
    Karlsson, Andreas
    Department of Geosciences, Swedish Museum of Natural History, Box 50007, 104 05 Stockholm, Sweden.
    Langhof, Jörgen
    Department of Geosciences, Swedish Museum of Natural History, Box 50007, 104 05 Stockholm, Sweden.
    Majka, Jaroslaw
    Department of Earth Sciences, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden; Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków, Poland.
    Zetterqvist, Anders
    Zetterqvist Geokonsult AB, Kvarnbacksvägen 74, 168 74 Bromma, Sweden.
    Zinkgruvanite, Ba4Mn2+4Fe3+2(Si2O7)2(SO4)2O2(OH)2, a new ericssonite-group mineral from the Zinkgruvan Zn-Pb-Ag-Cu deposit, Askersund, Örebro county, Sweden2021In: European journal of mineralogy, ISSN 0935-1221, E-ISSN 1617-4011, Vol. 33, no 6, p. 659-673Article in journal (Refereed)
    Abstract [en]

    Zinkgruvanite, ideally Ba4Mn2+4Fe3+2(Si2O7)2(SO4)2O2(OH)2, is a new member of the ericssonite group, found in Ba-rich drill core samples from a sphalerite+galena- and diopside-rich metatuffite succession from the Zinkgruvan mine, Örebro county, Sweden. Zinkgruvanite is associated with massive baryte, barytocalcite, diopside and minor witherite, cerchiaraite-(Al) and sulfide minerals. It occurs as subhedral to euhedral flattened and elongated crystals up to 4 mm. It is almost black, semi-opaque with a dark brown streak. The luster is vitreous to sub-adamantine on crystal faces, resinous on fractures. The mineral is brittle with an uneven fracture. VHN100 = 539 and HMohs ~4½. In thin fragments, it is reddish-black, translucent and optically biaxial (+), 2Vz > 70°. Pleochroism is strong, deep brown-red (E ⊥ {001} cleavage) to olive-pale brown. Chemical point analyses by WDS-EPMA together with iron valencies determined from Mössbauer spectroscopy, yielded the empirical formula (based on 26 O+OH+F+Cl anions): (Ba4.02Na0.034.05(Mn1.79Fe2+1.56Fe3+0.42Mg0.14Ca0.10Ni0.01Zn0.014.03 (Fe3+1.74Ti0.20Al0.062.00Si4(S1.61Si0.32P0.071.99O24(OH1.63Cl0.29F0.082.00. The mineral is triclinic, space group P–1, with unit-cell parameters a = 5.3982(1) Å, b = 7.0237(1) Å, c = 14.8108(4) Å, α = 98.256(2)º, β = 93.379(2)º, γ = 89.985(2)º and V = 554.75(2) Å3 for Z = 1. The eight strongest X-ray powder diffraction lines are [d Å (I%; hkl)]: 3.508 (70; 103), 2.980(70; 11–4), 2.814 (68; 1–22), 2.777 (70; 121), 2.699 (714; 200), 2.680 (68; 20–1), 2.125 (100; 124, 204), 2.107 (96; –221). The crystal structure (R1 = 0.0379 for 3204 reflections) is an array of TS (titanium silicate) blocks alternating with intermediate blocks. The TS blocks consist of HOH sheets (H = heteropolyhedral, O = octahedral) parallel to (001). In the O sheet, the Mn2+-dominant MO(1,2,3) sites give ideally Mn2+4 pfu. In the H sheet, the Fe3+-dominant MH sites and AP(1) sites give ideally Fe3+2Ba2 pfu. In the intermediate block, SO4 oxyanions and eleven coordinated Ba atoms give ideally 2 × SO4Ba pfu. Zinkgruvanite is related to ericssonite and ferro-ericssonite in having the same topology and type of linkage of layers in the TS block. Zinkgruvanite is also closely compositionally related to yoshimuraite, Ba4Mn4Ti2(Si2O7)2(PO4)2O2(OH)2, via the coupled heterovalent substitution 2 Ti4+ + 2 (PO4)3- →2 Fe3+ + 2 (SO4)2-, but presents a different type of linkage. The new mineral probably formed during a late stage of regional metamorphism of a Ba-enriched, syngenetic protolith, involving locally generated oxidized fluids of high salinity. 

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  • 2.
    Gonzalez-Jimenez, José Maria
    et al.
    Departamento de Mineralogía y Petrología (Universidad de Granada), Facultad de Ciencias, Spain.
    Plissart, Gaelle
    Instituto de Ciencias de la Tierra, Universidad Austral de Chile, Valdivia, Chile.
    Garrido, Leonardo N.
    Department of Geology and Andean Geothermal Center of Excellence (CEGA), Universidad de Chile, Santiago, Chile.
    Padron-Navarta, Jose Alberto
    Géosciences Montpellier, CNRS and Univ. Montpellier (UMR5243), Montpellier, France.
    Aiglsperger, Thomas
    Departament de Mineralogia, Petrologia i Geologia Aplicada, Universidad de Barcelona (UB), Barcelona, Spain.
    Romero, Rurik
    Department of Geology and Andean Geothermal Center of Excellence (CEGA), Universidad de Chile, Santiago, Chile.
    Marchesi, Claudio
    Departamento de Mineralogía y Petrología (Universidad de Granada), Facultad de Ciencias, Spain.
    Moreno-Abril, Antonio Jesus
    Departamento de Mineralogía y Petrología (Universidad de Granada), Facultad de Ciencias, Spain.
    Reich, Martin
    Department of Geology and Andean Geothermal Center of Excellence (CEGA), Universidad de Chile, Santiago, Chile.
    Barra, Fernando
    Department of Geology and Andean Geothermal Center of Excellence (CEGA), Universidad de Chile, Santiago, Chile.
    Morata, Diego
    Department of Geology and Andean Geothermal Center of Excellence (CEGA), Universidad de Chile, Santiago, Chile.
    Titanian clinohumite and chondrodite in antigorite serpentinites from Central Chile: evidence for deep and cold subduction2017In: European journal of mineralogy, ISSN 0935-1221, E-ISSN 1617-4011, Vol. 29, no 6, p. 959-970Article in journal (Refereed)
    Abstract [en]

    Humite minerals, including Ti-rich, hydroxyl-dominant chondrodite and clinohumite, occur in Paleozoic antigorite serpentinite in the La Cabaña area, in the Chilean Coastal Cordillera (~38° 30 ′ S–73° 15 ′ W). This may be the first report from South America. Humite minerals are intergrown with Mn-rich olivine hosting antigorite blades in textural equilibrium, indicating a metamorphic origin. A comparison with previous results from piston-cylinder experiments and petrological studies of other high-P serpentinites constrains the formation conditions of the humite + olivine + antigorite assemblage to ca. 2.0–2.5 GPa and <600°C. Thus, the assemblage is interpreted as having formed during cold subduction of a segment of oceanic lithosphere to a depth >60 km, suggesting that the Paleozoic serpentinites were entrained into the mantle at higher P T conditions than those experienced by the spatially associated olivine–lizardite metadunites and enclosing metasedimentary rocks (subducted to < 30 km). During exhumation along the subduction channel, high- P serpentinites together with metadunites underwent tectonic mingling with metasediments of the accretionary prism, preserving their signature of distinct metamorphic trajectories. This could be similar to the tectonic evolution of blueschists and high-P amphibolites found as isolated blocks in the metasediments of the Chilean Coastal Cordillera.

  • 3.
    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.

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