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  • 1. Alvarez, Belinda
    et al.
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    Clymans, Wim
    Fontorbe, Guillaume
    Conley, Daniel
    Assessing the Potential of Sponges (Porifera) as Indicators of Ocean Dissolved Si Concentrations2017In: Frontiers in Marine Science, ISSN 2296-2565, E-ISSN 2296-424X, Vol. 4, no 373Article in journal (Refereed)
    Abstract [en]

    We explore the distribution of sponges along dissolved silica (dSi) concentration gradients to test whether sponge assemblages are related to dSi and to assess the validity of fossil sponges as a palaeoecological tool for inferring dSi concentrations of the past oceans. We extracted sponge records from the publically available Global Biodiversity Information Facility (GBIF) database and linked these records with ocean physiochemical data to evaluate if there is any correspondence between dSi concentrations of the waters sponges inhabit and their distribution. Over 320,000 records of Porifera were available, of which 62,360 met strict quality control criteria. Our analyses was limited to the taxonomic levels of family, order and class. Because dSi concentration is correlated with depth in the modern ocean, we also explored sponge taxa distributions as a function of depth. We observe that while some sponge taxa appear to have dSi preferences (e.g., class Hexactinellida occurs mostly at high dSi), the overall distribution of sponge orders and families along dSi gradients is not sufficiently differentiated to unambiguously relate dSi concentrations to sponge taxa assemblages. We also observe that sponge taxa tend to be similarly distributed along a depth gradient. In other words, both dSi and/or another variable that depth is a surrogate for, may play a role in controlling sponge spatial distribution and the challenge is to distinguish between the two. We conclude that inferences about palaeo-dSi concentrations drawn from the abundance of sponges in the stratigraphic records must be treated cautiously as these animals are adapted to a great range of dSi conditions and likely other underlying variables that are related to depth. Our analysis provides a quantification of the dSi ranges of common sponge taxa, expands on previous knowledge related to their bathymetry preferences and suggest that sponge taxa assemblages are not related to particular dSi conditions. 

  • 2. Anand, Rajagopal
    et al.
    Balakrishnan, Srinivasan
    Kooijman, Ellen
    Swedish Museum of Natural History, Department of Geology.
    Mezger, Klaus
    Neoarchean crustal growth by accretionary processes: Evidence from combined zircon–titanite U–Pb isotope studies on granitoid rocks around the Hutti greenstone belt, eastern Dharwar Craton, India2014In: Journal of Asian Earth Sciences, ISSN 1367-9120, E-ISSN 1878-5786, Vol. 79, 72-85 p.Article in journal (Refereed)
    Abstract [en]

    The Neoarchean Hutti greenstone belt hosts mesothermal gold deposits and is surrounded by granitoid rocks on all sides. Combined U–Pb dating of zircon and titanite from the granitoid rocks constrains their emplacement history and subsequent geologic evolution. The Golapalli and Yelagatti granodiorites occurring to the north of the Hutti greenstone belt were emplaced at 2569 ± 17 Ma. The Yelagatti granodiorite yielded a younger titanite age of 2530 ± 6 Ma which indicates that it was affected by a post-crystallization thermal event that exceeded the titanite closure temperature. The western granodiorites from Kardikal have identical titanite and zircon ages of 2557 ± 6 Ma and 2559 ± 19 Ma, respectively. The eastern Kavital granodiorites yielded titanite ages of 2547 ± 6 Ma and 2544 ± 24 Ma which are identical to the published U–Pb zircon SHRIMP ages. These ages imply that the granitoid rocks surrounding the Hutti greenstone belt were formed as discrete batholiths within a short span of ca. 40 Ma between 2570 Ma and 2530 Ma ago. They were juxtaposed by horizontal tectonic forces against the supracrustal rocks that had formed in oceanic settings at the end of the Archean. The first phase of gold mineralization coincided with the last phase of granodiorite intrusion in the Hutti area. A metamorphic overprint occurred at ca. 2300 Ma ago that reset the Rb–Sr isotope system in biotites and possibly caused hydrothermal activity and enrichment of Au in the ore lodes. The eastern Dharwar Craton consists of quartz monzodiorite–granodiorite–granite suites of rocks that are younger than the greenstone belts that are older than ~2650 Ma reported from earlier studies. The granitoid magmatism took place between 2650 and 2510 Ma ago indicating accretionary growth of the eastern Dharwar Craton.

  • 3. Augustsson, Carita
    et al.
    Rüsing, Tobias
    Niemeyer, Hans
    Kooijman, Ellen
    Swedish Museum of Natural History, Department of Geology.
    Berndt, Jasper
    Bahlburg, Heinrich
    Zimmermann, Udo
    0.3 byr of drainage stability along the Palaeozoic palaeo-Pacific Gondwana margin; a detrital zircon study2015In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 172, 186-200 p.Article in journal (Refereed)
    Abstract [en]

    The palaeo-Pacific margin of Gondwana in the present-day south–central Andes is marked by tectonic activity related to subduction and terrane accretion. We present detrital zircon U–Pb data encompassing the Palaeozoic era in northern Chile and northwestern Argentina. Cathodoluminescence images reveal dominantly magmatic zircon barely affected by abrasion and displaying only one growth phase. The main age clusters for these zircon grains are Ediacaran to Palaeozoic with an additional peak at 1.3–0.9 Ga and they can be correlated with ‘Grenvillian’ age, and the Brasiliano, Pampean, and Famatinian orogenies. The zircon data reveal main transport from the nearby Ordovician Famatinian arc and related rocks. The Silurian sandstone units are more comparable with Cambrian units, with Brasiliano and Transamazonian ages (2.2–1.9 Ga) being more common, because the Silurian deposits were situated within or east of the (extinct) Famatinian arc. Hence, the arc acted as a transport barrier throughout Palaeozoic time. The complete suite of zircon ages does not record the accretions of exotic terranes or the Palaeozoic glacial periods. We conclude that the transport system along the palaeo-Pacific margin of Gondwana remained stable for c. 0.3 byr and that provenance data do not necessarily reflect the interior of a continent. Hence, inherited geomorphological features must be taken into account when detrital mineral ages are interpreted.

  • 4. Barão, Lúcia
    et al.
    Vandevenne, Floor
    Clymans, Wim
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    Ragueneau, Olivier
    Meire, Patrick
    Conley, Daniel J.
    Struyf, Eric
    Alkaline-extractable silicon from land to ocean: A challenge for biogenic silicon determination2015In: Limnology and Oceanography: Methods, ISSN 1541-5856, E-ISSN 1541-5856, n/a-n/a p.Article in journal (Refereed)
    Abstract [en]

    The biogeochemical cycling of silicon (Si) along the land-to-ocean continuum is studied by a variety of research fields and for a variety of scientific reasons. However, there is an increasing need to refine the methodology and the underlying assumptions used to determine biogenic silica (BSi) concentrations. Recent evidence suggests that contributions of nonbiogenic sources of Si dissolving during alkaline extractions, not corrected by standard silicate mineral dissolution correction protocols, can be substantial. The ratio between dissolved Si and aluminum (Al) monitored continuously during the alkaline extraction can be used to infer the origin of the Si fractions present. In this study, we applied both a continuous analysis method (0.5 M NaOH) and a traditional 0.1 M Na2CO3 extraction to a wide array of samples: (1) terrestrial vegetation, (2) soils from forest, cropland and pasture, (3) lake sediments, (4) suspended particulate matter and sediments from rivers, (5) sediments from estuaries and salt marshes and (6) ocean sediments. Our results indicate that the 0.1 M Na2CO3 extraction protocol can overestimate the BSi content, by simultaneously dissolving Si fractions of nonbiogenic origin that may represent up to 100% of the Si traditionally considered as biogenic, hampering interpretation especially in some deeper soil horizons, rivers and coastal oceanic sediments. Moreover, although the term amorphous Si was coined to reflect a growing awareness of nonbiogenic phases we show it is actually inappropriate in samples where silicate minerals may account for a large part of the extracted Si even after linear mineral correction.

  • 5.
    Bellucci, Jeremy
    Swedish Museum of Natural History, Department of Geology.
    Pb Isotopic Composition of Panamanian Colonial Majolica by LA-ICP-MS2016In: Recent Advances in Laser Ablation ICP-MS for Archaeology / [ed] L. Dussubieux, Springer Berlin/Heidelberg, 2016Chapter in book (Refereed)
    Abstract [en]

    Panama ́ Viejo, founded in 1519 by the Spanish explorer Pedrarias Da ́vila, was the first permanent European settlement on the Pacific Ocean, and became a city, by royal decree, in 1521. Shortly after its creation, the city became an important base for trade with Spain. In 1671, the English pirate Henry Morgan waged an attack on Panama ́ Viejo, which resulted in a fire that destroyed the entire city. A new settlement built a few miles west, called Casco Antiguo or San Felipe, is now the historic district of modern Panama City. The Pb isotopic compositions of the glazes on the surface of sixteenth to seventeenth century majolica pottery sherds from Panama Viejo and Casco Antiguo (both in Panama), and Lima (Peru) were determined via non-destructive laser ablation multi-collector ICP-MS (LA-MC-ICP-MS). The contrast in Pb isotopic compositions in the glazes on ceramics recovered in different locations demonstrate that early majolica pottery production during this period used Pb obtained from the Andes. However, the Pb used in later majolica production in Panama is of Spanish origin. After Panama ́ Viejo was burned to the ground, Panamanian majolica production ended.

  • 6.
    Bellucci, Jeremy
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Whitehouse, Martin
    Swedish Museum of Natural History, Department of Geology.
    Snape, Joshua
    Swedish Museum of Natural History, Department of Geology.
    Halogen and Cl isotopic systematics in Martian phosphates: Implications for the Cl cycle and surface halogen reservoirs on Mars2017In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 458, 192-202 p.Article in journal (Refereed)
    Abstract [en]

    The Cl isotopic compositions and halogen (Cl, F, Br, and I) abundances in phosphates from eight Martian meteorites, spanning most rock types and ages currently available, have been measured in situ by Secondary Ion Mass Spectrometry (SIMS). Likewise, the distribution of halogens has been documented by x-ray mapping. Halogen concentrations range over several orders of magnitude up to some of the largest concentrations yet measured in Martian samples or on the Martian surface, and the inter-element ratios are highly variable. Similarly, Cl isotope compositions exhibit a larger range than all pristine terrestrial igneous rocks. Phosphates in ancient (>4 Ga) meteorites (orthopyroxenite ALH 84001 and breccia NWA 7533) have positive d37Cl anomalies (+1.1 to +2.5 ‰).  These samples also exhibit explicit whole rock and grain scale evidence for hydrothermal or aqueous activity. In contrast, the phosphates in the younger basaltic Shergottite meteorites (<600 Ma) have negative d37Cl anomalies (-0.2 to -5.6 ‰).  Phosphates with the largest negative d37Cl anomalies display zonation where the rims of the grains are enriched in all halogens and have significantly more negative d37Cl anomalies indicating interaction with the surface of Mars during the latest stages of basalt crystallization. The phosphates with no textural, major element, or halogen enrichment evidence for mixing with this surface reservoir have an average d37Cl of -0.6 ‰, which suggests a similar Cl isotope composition between Mars, the Earth, and the Moon. The only process known to fractionate Cl isotopes, both positively and negatively, is formation of perchlorate, which has been detected in weight percent concentrations on the Martian surface. The age range and obvious mixing history of the phosphates studied here suggest perchlorate formation and halogen cycling via brines, which have also been observed on the Martian surface, has been active throughout Martian history. 

  • 7.
    Biagion, Cristian
    et al.
    Università di Pisa, Italy.
    Bosi, Ferdinando
    Sapienza Università di Roma, Italy.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Pasero, Marco
    Università di Pisa, Italy.
    The crystal structure of turneaureite, Ca5(AsO4)3Cl, the arsenate analog of chlorapatite and its relationships with the arsenate apatites johnbaumite and svabite2017In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 102, 1981-1986 p.Article in journal (Refereed)
    Abstract [en]

    The crystal structure of turneaureite, ideally Ca5(AsO4)3Cl, was studied using a specimen from the Brattfors mine, Nordmark, Värmland, Sweden, by means of single-crystal X-ray diffraction data. The structure was refinedto R1 = 0.017 on the basis of 716 unique reflectios with Fo > 4σ(Fo) in the P63/m space group, with unit-cell parameters a = 9.9218(3), c = 6.8638(2) Å, V = 585.16(4) Å3. The chemical composition of the sample, determined by electron-microprobe analysis, is (in wt%; average of 10 spot analyses): SO3 0.22, P2O5 0.20, V2O5 0.01, As2O5 51.76, SiO2 0.06, CaO 41.39, MnO 1.89, SrO 0.12, BaO 0.52, PbO 0.10, Na2O 0.02, F 0.32, Cl 2.56, H2Ocalc 0.58, O(≡F+Cl) –0.71, total 99.04. On the basis of 13 anions per formula unit, the empirical formula corresponds to (Ca4.82Mn0.17Ba0.02Sr0.01)∑5.02 (As2.94P0.02S0.02Si0.01)∑2.99O12[Cl0.47(OH)0.42F0.11]∑1.00.Turneaureite is topologically similar to the other members of the apatite supergroup: columns of face-sharing M1 polyhedra running along c are connected through TO4 tetrahedra with channels hosting M2 cations and X anions. Owing to its particular chemical composition, the studied turneaureite can be considered as a ternary calcium arsenate apatite; consequently it has several partially filledanion sites within the anion columns. Polarized single-crystal FTIR spectra of the studied sample indicate stronger hydrogen bonding and less diverse short-range atom arrangements around (OH) groups in turneaureite as compared to the related minerals johnbaumite and svabite. An accurate knowledge of the atomic arrangement of this apatite-remediation mineral represents an improvement in our understanding of minerals able to sequester and stabilize heavy metals such as arsenic in polluted areas.

  • 8.
    Biagioni, Cristian
    et al.
    Università di Pisa, Italy.
    Bosi, Ferdinando
    Sapienza Università di Roma, Italy.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Pasero, Marco
    Università di Pisa, Italy.
    The crystal structure of svabite, Ca5(AsO4)3F, an arsenate member of the apatite supergroup2016In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 101, 1750-1755 p.Article in journal (Refereed)
    Abstract [en]

    The crystal structure of svabite, ideally Ca5(AsO4)3F, was studied using a specimen from the Jakobsberg mine, Värmland, Sweden, by means of single-crystal X‑ray diffraction data. The structure was refined to R1 = 0.032 on the basis of 928 unique reflections with Fo > 4s(Fo) in the P63/m space group, with unit-cell parameters a = 9.7268(5), c = 6.9820(4) Å, V = 572.07(5) Å3. The chemical composition of the sample, determined by electron-microprobe analysis, is (in wt%, average of 10 spot analyses): SO3 0.49, P2O5 0.21, V2O5 0.04, As2O5 51.21, SiO2 0.19, CaO 39.31, MnO 0.48, SrO 0.03, PbO 5.19, Na2O 0.13, F 2.12, Cl 0.08, H2Ocalc 0.33, O (≡ F+Cl) –0.91, total 98.90. On the basis of 13 anions per formula unit, the empirical formula corresponds to (Ca4.66Pb0.16Mn0.04Na0.03)Σ4.89(As2.96S0.04Si0.02P0.02)Σ3.04O12[F0.74(OH)0.24Cl0.01]. Svabite is topologically similar to the other members of the apatite supergroup: columns of face-sharing M1 polyhedra running along c are connected through TO4 tetrahedra with channels hosting M2 cations and X anions. The crystal structure of synthetic Ca5(AsO4)3F was previously reported as triclinic. On the contrary, the present refinement of the crystal structure of svabite shows no deviations from the hexagonal symmetry. An accurate knowledge of the atomic arrangement of this apatite-remediation mineral represents an improvement in our understanding of minerals able to sequester and stabilize heavy metals such as arsenic in polluted areas.

  • 9. Bolhar, R.
    et al.
    Hofmann, A.
    Kemp, A.I.S.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Wind, S.
    Kamber, B.S.
    Juvenile crust formation in the Zimbabwe Craton deduced from the O-Hf isotopic record of 3.8-3.0 Ga detrital zircons2017In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 215, 432-446 p.Article in journal (Refereed)
    Abstract [en]

    Hafnium and oxygen isotopic compositions measured in-situ on U-Pb dated zircon from Archaean sedimentary successions belonging to the 2.9–2.8 Ga Belingwean/Bulawayan groups and previously undated Sebakwian Group are used to characterize the crustal evolution of the Zimbabwe Craton prior to 3.0 Ga. Microstructural and compositional criteria were used to minimize effects arising from Pb loss due to metamorphic overprinting and interaction with low-temperature fluids. 207Pb/206Pb age spectra (concordance >90%) reveal prominent peaks at 3.8, 3.6, 3.5, and 3.35 Ga, corresponding to documented geological events, both globally and within the Zimbabwe Craton. Zircon δ18O values from +4 to +10‰ point to both derivation from magmas in equilibrium with mantle oxygen and the incorporation of material that had previously interacted with water in near-surface environments. In εHf-time space, 3.8–3.6 Ga grains define an array consistent with reworking of a mafic reservoir (176Lu/177Hf ∼0.015) that separated from chondritic mantle at ∼3.9 Ga. Crustal domains formed after 3.6 Ga depict a more complex evolution, involving contribution from chondritic mantle sources and, to a lesser extent, reworking of pre-existing crust. Protracted remelting was not accompanied by significant mantle depletion prior to 3.35 Ga. This implies that early crust production in the Zimbabwe Craton did not cause complementary enriched and depleted reservoirs that were tapped by later magmas, possibly because the volume of crust extracted and stabilised was too small to influence (asthenospheric) mantle isotopic evolution. Growth of continental crust through pulsed emplacement of juvenile (chondritic mantle-derived) melts, into and onto the existing cratonic nucleus, however, involved formation of complementary depleted subcontinental lithospheric mantle since the early Archaean, indicative of strongly coupled evolutionary histories of both reservoirs, with limited evidence for recycling and lateral accretion of arc-related crustal blocks until 3.35 Ga.

  • 10. Bollard, J.
    et al.
    Connelly, J.N.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Pringle, E.A.
    Bonal, E.A.
    Jørgensen, J.K.
    Nordlund, Å.
    Moynier, F.
    Bizzarro, M.
    Early formation of planetary building blocks inferred from Pb isotopic ages of chondrules.2017In: Science Advances, ISSN 2375-2548, Vol. 3, e1700407Article in journal (Refereed)
    Abstract [en]

    The most abundant components of primitive meteorites (chondrites) are millimeter-sized glassy spherical chondrules formed by transient melting events in the solar protoplanetary disk. Using Pb-Pb dates of 22 individual chondrules, we show that primary production of chondrules in the early solar system was restricted to the first million years after the formation of the Sun and that these existing chondrules were recycled for the remaining lifetime of the protoplanetary disk. This finding is consistent with a primary chondrule formation episode during the early high-mass accretion phase of the protoplanetary disk that transitions into a longer period of chondrule reworking. An abundance of chondrules at early times provides the precursor material required to drive the efficient and rapid formation of planetary objects via chondrule accretion.

  • 11.
    Bosi, Ferdinando
    et al.
    Sapienza Università di Roma.
    Andreozzi, Giovanni B.
    Sapienza Università di Roma.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Zn-O tetrahedral bond length variations in normal spinel oxides2011In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 96, 594-598 p.Article in journal (Refereed)
  • 12.
    Bosi, Ferdinando
    et al.
    Università di Roma, Italien.
    Andreozzi, Giovanni
    Università di Roma, Italien.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Experimental evidence for partial Fe2+ disorder at the Y and Z sites of tourmaline: a combined EMP, SREF, MS, IR and OAS study of schorl2015In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 79, no 3, 515-528 p.Article in journal (Refereed)
  • 13.
    Bosi, Ferdinando
    et al.
    Sapienza Università di Roma, Italy.
    Christy, Andrew
    Australian National University, Canberra, Australia.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Crystal-chemical aspects of the roméite group, A2Sb2O6Y, of the pyrochlore supergroup2017In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 81, no 6, 1287-1302 p.Article in journal (Refereed)
    Abstract [en]

    Four specimens of the roméite-group minerals oxyplumboroméite and fluorcalcioroméite from the Långban Mn-Fe deposit in Central Sweden were structurally and chemically characterized by single-crystal X-ray diffraction, electron microprobe analysis and infrared spectroscopy. The data obtained and those on additional roméite samples from literature show that the main structural variations within the roméite group are related to variations in the content of Pb2+, which is incorporated into the roméite structure via the substitution Pb2+ → A2+ where A2+ = Ca, Mn and Sr. Additionally, the cation occupancy at the six-fold coordinated B site, which is associated with the heterovalent substitution BFe3+ + Y□ → BSb5+ + YO2–, can strongly affect structural parameters.

    Chemical formulae of the roméite minerals group are discussed. According to crystal-chemical information, the species associated with the name ‘kenoplumboroméite’, hydroxycalcioroméite and fluorcalcioroméite most closely approximate end-member compositions Pb2(SbFe3+)O6□, Ca2(Sb5+Ti)O6(OH) and (CaNa)Sb2O6F, respectively. However, in accord with pyrochlore nomenclature rules, their names correspond to multiple end-members and are best described by the general formulae: (Pb,#)2(Sb,#)2O6□, (Ca,#)2(Sb,#)2O6(OH) and (Ca,#)Sb2(O,#)6F, where ‘#’ indicates an unspecified charge-balancing chemical substituent, including vacancies.

  • 14.
    Bosi, Ferdinando
    et al.
    Sapienza Università di Roma, Italy.
    Cámara, Fernando
    Università di Torino, Italy.
    Ciriotti, Marco
    Associazione Micromineralogica Italiana, Torino, Italy.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Reznitskii, Leonid
    Russian Academy of Science, Irkutsk, Russia.
    Stagno, Vincenzo
    Sapienza Università di Roma, Italy.
    Crystal-chemical relations and classification problems in tourmalines belonging to the oxy-schorl—oxy-dravite—bosiite—povondraite series2017In: European journal of mineralogy, ISSN 0935-1221, E-ISSN 1617-4011, Vol. 29, no 3, 445-455 p.Article in journal (Refereed)
  • 15.
    Bosi, Ferdinando
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Andreozzi, Giovanni B.
    Sapienza Università di Roma.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Lucchesi, Sergio
    Sapienza Università di Roma.
    Structural refinement of Mn-doped spinel: a case for tetrahedrally coordinated Mn3+ in an oxygen-based structure2007In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 92, 27-33 p.Article in journal (Refereed)
  • 16.
    Bosi, Ferdinando
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    D'Ippolito, Veronica
    Sapienza Università di Roma.
    Andreozzi, Giovanni B.
    Sapienza Università di Roma.
    Blue spinel crystals in the MgAl2O4-CoAl2O4 series: II. Cation ordering over short range and long range scales2012In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 97, 1834-1840 p.Article in journal (Refereed)
  • 17.
    Bosi, Ferdinando
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Crystal chemistry of the magnetite-ulvöspinel series2009In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 94, 181-189 p.Article in journal (Refereed)
  • 18.
    Bosi, Ferdinando
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Crystal chemistry of the MgAl2O4-MgMn2O4-MnMn2O4 system: Analysis of structural distortion in spinel and hausmannite-type structures2010In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 95, 602-607 p.Article in journal (Refereed)
  • 19.
    Bosi, Ferdinando
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Crystal chemistry of the ulvöspinel-qandilite series2014In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 99, 847-851 p.Article in journal (Refereed)
  • 20.
    Bosi, Ferdinando
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Stoichiometry of synthetic ulvöspinel single crystals2008In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 93, 1312-1316 p.Article in journal (Refereed)
  • 21.
    Bosi, Ferdinando
    et al.
    Sapienza Università di Roma, Italy.
    Reznitskii, Leonid
    Russian Academy of Science, Irkutsk, Russia.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Crystal chemistry of Al-V-Cr oxy-tourmalines from Sludyanka complex, Lake Baikal, Russia2017In: European journal of mineralogy, ISSN 0935-1221, E-ISSN 1617-4011, Vol. 29, no 3, 457-472 p.Article in journal (Refereed)
  • 22.
    Bosi, Ferdinando
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Reznitskii, Leonid
    Russian Academy of Science.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Vanadio-oxy-chromium-dravite, NaV3(Cr4Mg2)(Si6O18)(BO3)3(OH)3O, a new mineral species of the tourmaline supergroup 2014In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 99, 1155-1162 p.Article in journal (Refereed)
  • 23.
    Bosi, Ferdinando
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Reznitskii, Leonid
    Russian Academy of Science, Irkutsk.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Vanadio-oxy-dravite, NaV3(Al4Mg2)(Si6O18)(BO3)3(OH)3O, a new mineral species of the tourmaline supergroup2014In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 99, 218-224 p.Article in journal (Refereed)
  • 24.
    Bosi, Ferdinando
    et al.
    Sapienza Università di Roma, Italy.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Fregola, Rosa Anna
    Università di Bari Aldo Moro, Italy.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Crystal chemistry of spinels in the system MgAl2O4-MgV2O4-Mg2VO42016In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 101, 580-586 p.Article in journal (Refereed)
    Abstract [en]

    Eight spinel single-crystal samples belonging to the spinel sensu stricto-magnesiocoulsonite series (MgAl2O4-MgV2O4) were synthesized and crystal-chemically characterized by X‑ray diffraction, electron microprobe and optical absorption spectroscopy. Site populations show that the tetrahedrally coordinated site (T) is populated by Mg and minor Al for the spinel sensu stricto compositions, and only by Mg for the magnesiocoulsonite compositions, while the octahedrally coordinated site (M) is populated by Al, V3+, minor Mg, and very minor amounts of V4+. The latter occurs in appreciable amounts in the Al-free magnesium vanadate spinel, T(Mg)M(Mg0.26V3+1.48V4+0.26)O4, showing the presence of the inverse spinel VMg2O4. The studied samples are characterized by substitution of Al3+ for V3+ and (Mg2++V4+) for 2V3+ described in the system MgAl2O4-MgV2O4-VMg2O4.

    The present data in conjunction with data from the literature provide a basis for quantitative analyses of two solid-solution series MgAl2O4-MgV23+O4 and MgV23+O4-V4+Mg2O4. Unit-cell parameter increases with increasing V3+ along the series MgAl2O4-MgV2O4 (8.085–8.432 Å), but only slightly increases with increasing V3+ along the series VMg2O4-MgV2O4 (8.386–8.432 Å). Although a solid solution could be expected between the MgAl2O4 and VMg2O4 end-members, no evidence was found. Amounts of V4+ are nearly insignificant in all synthetic Al-bearing vanadate spinels, but are appreciable in Al-free vanadate spinel.

    An interesting observation of the present study is that despite the observed complete solid-solution along the MgAl2O4-MgV2O4 and MgV2O4-VMg2O4 series, the spinel structure seems to be unable to stabilize V4+ in any intermediate members on the MgAl2O4-Mg2VO4 join even at high oxygen fugacities. This behavior indicates that the accommodation of specific V-valences can be strongly influenced by crystal-structural constraints, and any evaluation of oxygen fugacities during mineral formation based exclusively on V cation valence distributions in spinel should be treated with caution. The present study underlines that the V valency distribution in spinels is not exclusively reflecting oxygen fugacities, but also depends on activities and solubilities of all chemical components in the crystallization environment.

  • 25.
    Bosi, Ferdinando
    et al.
    Sapienza Università di Roma, Italy.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Oxy-foitite, □(Fe2+Al2)Al6(Si6O18)(BO3)3(OH)3O, a new mineral species of the tourmaline supergroup2017In: European journal of mineralogy, ISSN 0935-1221, E-ISSN 1617-4011, Vol. 29, no 5, 889-896 p.Article in journal (Refereed)
    Abstract [en]

    Oxy-foitite, □(Fe2+Al2)Al6(Si6O18)(BO3)3(OH)3O, is a new mineral of the tourmaline supergroup. It occurs in high-grade migmatitic gneisses of pelitic composition at the Cooma metamorphic Complex (New South Wales, Australia), in association with muscovite, K-feldspar and quartz. Crystals are black with a vitreous luster, sub-conchoidal fracture and gray streak. Oxy-foitite has a Mohs hardness of ∼7, and has a calculated density of 3.143 g/cm3. In plane-polarized light, oxy-foitite is pleochroic (O= dark brown and E = pale brown), uniaxial negative. Oxy-foitite belongs to the trigonal crystal system, space group R3ma = 15.9387(3) Å, c = 7.1507(1)Å and V = 1573.20(6)Å3,Z = 3. The crystal structure of oxy-foitite was refined to R1 = 1.48% using 3247 unique reflections from single-crystal X-ray diffraction using MoKα radiation. Crystal-chemical analysis resulted in the empirical structural formula: X(□0.53Na0.45Ca0.01K0.01)Σ1.00Y(Al1.53Fe2+1.16Mg0.22Mn2+0.05Zn0.01Ti4+0.03)Σ3.00Z(Al5.47Fe3+0.14Mg0.39)Σ6.00[(Si5.89Al0.11)Σ6.00O18](BO3)3V(OH)3W[O0.57F0.04(OH)0.39]Σ1.00. Oxy-foitite belongs to the X-site vacant group of the tourmaline-supergroup minerals, and shows chemical relationships with foitite through the substitution YAl3++WO2-YFe2++W(OH)1–.

  • 26.
    Bosi, Ferdinando
    et al.
    Sapienza Università di Roma, Rome, Italy.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Thermally induced cation redistribution in Fe‑bearing oxy‑dravite and potential geothermometric implications2016In: Contributions to Mineralogy and Petrology, ISSN 0010-7999, E-ISSN 1432-0967, Vol. 171, no 5, 1-14 p., 47Article in journal (Refereed)
    Abstract [en]

    Iron-bearing oxy-dravite was thermally treated in air and hydrogen atmosphere at 800 °C to study potential changes in Fe, Mg and Al ordering over the octahedrally coordinated Y and Z sites and to explore possible applications to intersite geothermometry based on tourmaline. Overall, the experimental data (structural refinement, Mössbauer, infrared and optical absorption spectroscopy) show that heating Fe-bearing tourmalines results in disordering of Fe over Y and Z balanced by ordering of Mg at Y, whereas Al does not change appreciably. The Fe disorder depends on temperature, but less on redox conditions. The degree of Fe3+–Fe2+ reduction is limited despite strongly reducing conditions, indicating that the fO2 conditions do not exclusively control the Fe oxidation state at the present experimental conditions. Untreated and treated samples have similar short- and long-range crystal structures, which are explained by stable Al-extended clusters around the O1 and O3 sites. In contrast to the stable Al clusters that preclude any temperature-dependent Mg–Al order– disorder, there occurs Mg diffusion linked to temperaturedependent exchange with Fe. Ferric iron mainly resides around O2− at O1 rather than (OH), but its intersite disorder induced by thermal treatment indicates that Fe redistribution is the driving force for Mg–Fe exchange and that its diffusion rates are significant at these temperatures. With increasing temperature, Fe progressively disorders over Y and Z, whereas Mg orders at Y according to the order–disorder reaction: YFe + ZMg → ZFe + YMg. The presented findings are important for interpretation of the post-crystallization history of both tourmaline and tourmaline host rocks and imply that successful tourmaline geothermometers may be developed by thermal calibration of the Mg– Fe order–disorder reaction, whereas any thermometers based on Mg–Al disorder will be insensitive and involve large uncertainties.

  • 27.
    Bosi, Ferdinando
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Reznitskii, Leonid
    Russian Academy of Science, Irkutsk.
    Crystallographic and spectroscopic characterization of Fe-bearing chromo-alumino-povondraite and its relationships with oxy-chromium-dravite and oxy-dravite2013In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 98, 1557-1564 p.Article in journal (Refereed)
  • 28.
    Bruschini, Enrico
    et al.
    Sapienza Università di Roma.
    Speziale, Sergio
    Geoforschungszentrum, Potsdam.
    Andreozzi, Giovanni
    Sapienza Università di Roma.
    Bosi, Ferdinando
    Sapienza Università di Roma.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    The elasticity of MgAl2O4-MnAl2O4 spinels by Brillouin scattering and an empirical approach for bulk modulus prediction2015In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 100, 644-651 p.Article in journal (Refereed)
  • 29. Budd, D.A.
    et al.
    Troll, V.R.
    Deegan, F.M.
    Jolis, E.M.
    Smith, V.C.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Harris, C.
    Freda, C.
    Hilton, D.R.
    Halldorsson, S.A.
    Bindemann, I.N.
    Magma reservoir dynamics at Toba caldera, Indonesia, recorded by oxygen isotope zoning in quartz2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, 40624Article in journal (Refereed)
    Abstract [sv]

    Quartz is a common phase in high-silica igneous rocks and is resistant to post-eruptive alteration, thus offering a reliable record of magmatic processes in silicic magma systems. Here we employ the 75 ka Toba super-eruption as a case study to show that quartz can resolve late-stage temporal changes in magmatic δ18O values. Overall, Toba quartz crystals exhibit comparatively high δ18O values, up to 10.2‰, due to magma residence within, and assimilation of, local granite basement. However, some 40% of the analysed quartz crystals display a decrease in δ18O values in outermost growth zones compared to their cores, with values as low as 6.7‰ (maximum ∆core−rim = 1.8‰). These lower values are consistent with the limited zircon record available for Toba, and the crystallisation history of Toba quartz traces an influx of a low-δ18O component into the magma reservoir just prior to eruption. Here we argue that this late-stage low-δ18O component is derived from hydrothermally-altered roof material. Our study demonstrates that quartz isotope stratigraphy can resolve magmatic events that may remain undetected by whole-rock or zircon isotope studies, and that assimilation of altered roof material may represent a viable eruption trigger in large Toba-style magmatic systems.

  • 30. Cabral, R.A.
    et al.
    Jackson, M.G.
    Koga, K.T.
    Rose-Koga, E.F.
    Hauri, E.H.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Price, A.A:
    Day, J.M.D.
    Shimizu, N.
    Kelley, K.A.
    Volatile cycling of H2O, CO2, F, and Cl in the HIMU mantle: A new window provided by melt inclusions from oceanic hotspot lavas at Mangaia, Cook Islands.2014In: Geochemistry, Geophysics, Geosystems, ISSN 1525-2027, Vol. 15, 4445-4467 p.Article in journal (Refereed)
    Abstract [en]

    Mangaia hosts the most radiogenic Pb-isotopic compositions observed in ocean island basalts and represents the HIMU (high µ = 238U/204Pb) mantle end-member, thought to result from recycled oceanic crust. Complete geochemical characterization of the HIMU mantle end-member has been inhibited due to a lack of deep submarine glass samples from HIMU localities. We homogenized olivine-hosted melt inclusions separated from Mangaia lavas and the resulting glassy inclusions made possible the first volatile abundances to be obtained from the HIMU mantle end-member. We also report major and trace element abundances and Pb-isotopic ratios on the inclusions, which have HIMU isotopic fingerprints. We evaluate the samples for processes that could modify the volatile and trace element abundances postmantle melting, including diffusive Fe and H2O loss, degassing, and assimilation. H2O/Ce ratios vary from 119 to 245 in the most pristine Mangaia inclusions; excluding an inclusion that shows evidence for assimilation, the primary magmatic H2O/Ce ratios vary up to ∼200, and are consistent with significant dehydration of oceanic crust during subduction and long-term storage in the mantle. CO2 concentrations range up to 2346 ppm CO2 in the inclusions. Relatively high CO2 in the inclusions, combined with previous observations of carbonate blebs in other Mangaia melt inclusions, highlight the importance of CO2 for the generation of the HIMU mantle. F/Nd ratios in the inclusions (30 ± 9; 2σ standard deviation) are higher than the canonical ratio observed in oceanic lavas, and Cl/K ratios (0.079 ± 0.028) fall in the range of pristine mantle (0.02–0.08).

  • 31.
    Canfield, Donald E.
    et al.
    University of Southern Denmark.
    Ngombi Pemba, Lauriss
    Hammarlund, Emma
    Bengtson, Stefan
    Swedish Museum of Natural History, Department of Paleobiology.
    Chaussidon, Marc
    Gauthier Lafaye, François
    Meunier, Alain
    Riboulleau, Armelle
    Rollion Bard, Claire
    Rouxel, Olivier
    Asael, Dan
    Wickmann, Anne Catherine
    El Albani, Abderrazak
    Oxygen dynamics in the aftermath of the Great Oxidation of the Earth’s atmosphere.2013In: Proceedings of the National Academy of Sciences, ISSN 0027-8424, Vol. 110, no 42, 16736-16741 p.Article in journal (Refereed)
    Abstract [en]

    The oxygen content of Earth’s atmosphere has varied greatly through time, progressing from exceptionally low levels before about 2.3 billion years ago, to much higher levels afterward. In the absence of better information, we usually view the progress in Earth’s oxygenation as a series of steps followed by periods of relative stasis. In contrast to this view, and as reported here, a dynamic evolution of Earth’s oxygenation is recorded in ancient sediments from the Republic of Gabon from between about 2,150 and 2,080 million years ago. The oldest sediments in this sequence were deposited in well-oxygenated deep waters whereas the youngest were deposited in euxinic waters, which were globally extensive. These fluctuations in oxygenation were likely driven by the comings and goings of the Lomagundi carbon isotope excursion, the longest–lived positive ?13C excursion in Earth history, generating a huge oxygen source to the atmosphere. As the Lomagundi event waned, the oxygen source became a net oxygen sink as Lomagundi organic matter became oxidized, driving oxygen to low levels; this state may have persisted for 200 million years.

  • 32.
    Charette, M
    et al.
    Woods Hole Oceanographic Institution, USA.
    Lam, P.J.
    University of California Santa Cruz, USA.
    Lohan, M.C.
    University of Southhampton, UK.
    Kwon, E.Y.
    Seoul National University,Korea.
    Hatje, V
    Universidade Federal da Bahia, Brazil.
    Jeandel, C
    University of Toulouse, France.
    Shiller, A.M.
    University of Southern Mississippi, USA.
    Cutter, G.A.
    Old Dominion University, USA.
    Thomas, A
    University of Edinburgh, UK.
    Boyd, P.W.
    University of Tasmania, Australia.
    Homoky, W.B.
    University of Oxford, UK.
    Milne, A.
    Plymoth University, UK.
    Thomas, H.
    Dalhousie University, Canada.
    Andersson, P.S.
    Swedish Museum of Natural History, Department of Geology.
    Porcelli, D.
    University of Oxford,Uk.
    Tanaka, T
    University of Tokyo, Japan.
    Geibert, W
    Alfred Wegener Institute, Germany.
    Dehairs, F.
    Vrije Universiteit, Belgium.
    Garcia-Orellana, J.
    Universitat Autonoma de Barcelona, Spain.
    Coastal ocean and shelf-sea biogeochemical cycling of trace elements and isotopes: lessons learned from GEOTRACES2016In: Philosopical Transactions of the Royal Society A, ISSN 1364–503X, Vol. 374, no 2081Article, review/survey (Refereed)
    Abstract [en]

    Continental shelves and shelf seas play a central role in the global carbon cycle. However,

    their importance with respect to trace element and isotope (TEI) inputs to ocean basins

    is less well understood. Here, we present major findings on shelf TEI biogeochemistry

    from the GEOTRACES programme as well as a proof of concept for a new method to

    estimate shelf TEI fluxes. The case studies focus on advances in our understanding of TEI

    cycling in the Arctic, transformations within a major river estuary (Amazon), shelf sediment

    micronutrient fluxes and basin-scale estimates of submarine groundwater discharge. The

    proposed shelf flux tracer is 228-radium (T1/2 =5.75 yr), which is continuously supplied to

    the shelf from coastal aquifers, sediment porewater exchange and rivers. Model-derived shelf

    228Ra fluxes are combined with TEI/ 228Ra ratios to quantify ocean TEI fluxes from the

    western North Atlantic margin. The results from this new approach agree well with previous

    estimates for shelf Co, Fe, Mn and Zn inputs and exceed published estimates of atmospheric

    deposition by factors of approximately 3–23. Lastly, recommendations are made for additional

    GEOTRACES process studies and coastal margin-focused section cruises that will help refine

    the model and provide better insight on the mechanisms driving shelf-derived TEI fluxes

    to the ocean.

    This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element

    chemistry’.

  • 33. Chi Fru, Ernest
    et al.
    Ivarsson, Magnus
    Swedish Museum of Natural History, Department of Paleobiology.
    Kilias, Stephanos P
    Bengtson, Stefan
    Swedish Museum of Natural History, Department of Paleobiology.
    Belivanova, Veneta
    Swedish Museum of Natural History, Department of Paleobiology.
    Marone, Federica
    Paul Scherrer Institute.
    Fortin, Danielle
    Broman, Curt
    Stampanoni, Marco
    ETH Zürich.
    Fossilized iron bacteria reveal pathway to biological origin of banded iron formation.2013In: Nature Communications, ISSN 2041-1723, Vol. 4, no 2050, 1-7 p.Article in journal (Refereed)
    Abstract [en]

    Debates on the formation of banded iron formations in ancient ferruginous oceans are dominated by a dichotomy between abiotic and biotic iron cycling. This is fuelled by difficulties in unravelling the exact processes involved in their formation. Here we provide fossil environmental evidence for anoxygenic photoferrotrophic deposition of analogue banded iron rocks in shallow marine waters associated with an Early Quaternary hydrothermal vent field on Milos Island, Greece. Trace metal, major and rare earth elemental compositions suggest that the deposited rocks closely resemble banded iron formations of Precambrian origin. Well-preserved microbial fossils in combination with chemical data imply that band formation was linked to periodic massive encrustation of anoxygenic phototrophic biofilms by iron oxyhydroxide alternating with abiotic silica precipitation. The data implicate cyclic anoxygenic photoferrotrophy and their fossilization mechanisms in the construction of microskeletal fabrics that result in the formation of characteristic banded iron formation bands of varying silica and iron oxide ratios.

  • 34.
    Chi Fru, Ernest
    et al.
    Stockholm University, Department of Geological Sciences.
    Rodríguez, Nathalie
    Stockholm University Department of Geological Sciences.
    Partin, Camille
    University of Saskatchewan, Canada.
    Lalonde, Stefan
    Université de Bretagne Occidentale, France.
    Andersson, Per
    Swedish Museum of Natural History, Department of Geology.
    Weiss, Dominik
    Imperial College, London, UK.
    El Albani, Abderrazak
    Université de Poitiers, France.
    Rodushkin, Ilia
    ALS Scandinavia, Sweden.
    Konhauser, Kurt
    University of Alberta, Canada.
    Cu isotopes in marine black shales record the Great Oxidation Event2016In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 113, no 18, 4941-4946 p.Article in journal (Refereed)
    Abstract [en]

    The oxygenation of the atmosphere ∼2.45–2.32 billion years ago (Ga) is one of the most significant geological events to have affected Earth’s redox history. Our understanding of the timing and processes surrounding this key transition is largely dependent on the development of redox-sensitive proxies, many of which remain unexplored. Here we report a shift from negative to positive copper isotopic compositions (δ65CuERM-AE633) in organic carbon-rich shales spanning the period 2.66–2.08 Ga. We suggest that, before 2.3 Ga, a muted oxidative supply of weathering-derived copper enriched in 65Cu, along with the preferential removal of 65Cu by iron oxides, left seawater and marine biomass depleted in 65Cu but enriched in 63Cu. As banded iron formation deposition waned and continentally sourced Cu became more important, biomass sampled a dissolved Cu reservoir that was progressively less fractionated relative to the continental pool. This evolution toward heavy δ65Cu values coincides with a shift to negative sedimentary δ56Fe values and increased marine sulfate after the Great Oxidation Event (GOE), and is traceable through Phanerozoic shales to modern marine settings, where marine dissolved and sedimentary δ65Cu values are universally positive. Our finding of an important shift in sedimentary Cu isotope compositions across the GOE provides new insights into the Precambrian marine cycling of this critical micronutrient, and demonstrates the proxy potential for sedimentary Cu isotope compositions in the study of biogeochemical cycles and oceanic redox balance in the past.

  • 35. Conley, Daniel
    et al.
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    Fontorbe, Guillaume
    Clymans, Wim
    Stadmark, Johanna
    Hendry, Katherine
    Marron, Alan
    De La Rocha, Christina
    Biosilicification drives a decline of dissolved Si in the oceans through geologic time2017In: Frontiers in Marine Science, ISSN 2296-2565, E-ISSN 2296-424XArticle in journal (Refereed)
    Abstract [en]

    Biosilicification has driven variation in the global Si cycle over geologic time. The evolution of different eukaryotic lineages that convert dissolved Si (DSi) into mineralized structures (higher plants, siliceous sponges, radiolarians and diatoms) has driven a secular decrease in DSi in the global ocean leading to the low DSi concentrations seen today. Recent studies, however, have questioned the timing previously proposed for the DSi decreases and the concentration changes through deep time, which would have major implications for the cycling of carbon and other key nutrients in the ocean. Here, we combine relevant genomic data with geological data and present new hypotheses regarding the impact of the evolution of biosilicifying organisms on the DSi inventory of the oceans throughout deep time. Although there is no fossil evidence for true silica biomineralization until the late Precambrian, the timing of the evolution of silica transporter genes suggests that bacterial silicon-related metabolism has been present in the oceans since the Archean with eukaryotic silicon metabolism already occurring in the Neoproterozoic. We hypothesize that biological processes have influenced oceanic DSi concentrations since the beginning of oxygenic photosynthesis.

  • 36.
    Cooper, Mark
    et al.
    University of Manitoba, Winnipeg, Canada.
    Hawthorne, Frank
    University of Manitoba, Winnipeg, Canada.
    Langhof, Jörgen
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Holtstam, Dan
    Swedish Museum of Natural History, Department of Geology.
    Wiklundite, ideally Pb2[4](Mn2+,Zn)3(Fe3+,Mn2+)2(Mn2+,Mg)19(As3+O3)2[(Si,As5+)O4]6 (OH)18Cl6, a new mineral from Långban, Filipstad, Värmland, Sweden: Description and crystal structure2017In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 81, no 4, 841-855 p.Article in journal (Refereed)
  • 37. Deegan, F.M.
    et al.
    Troll, V.R.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Jolis, E.M.
    Freda, C.
    Boron isotope fractionation in magma via crustal carbonate dissolution.2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, 30774Article in journal (Refereed)
    Abstract [en]

    Carbon dioxide released by arc volcanoes is widely considered to originate from the mantle and from subducted sediments. Fluids released from upper arc carbonates, however, have recently been proposed to help modulate arc CO2 fluxes. Here we use boron as a tracer, which substitutes for carbon in limestone, to further investigate crustal carbonate degassing in volcanic arcs. We performed laboratory experiments replicating limestone assimilation into magma at crustal pressure-temperature conditions and analysed boron isotope ratios in the resulting experimental glasses. Limestone dissolution and assimilation generates CaO-enriched glass near the reaction site and a CO2-dominated vapour phase. The CaO-rich glasses have extremely low δ11B values down to −41.5‰, reflecting preferential partitioning of 10B into the assimilating melt. Loss of 11B from the reaction site occurs via the CO2 vapour phase generated during carbonate dissolution, which transports 11B away from the reaction site as a boron-rich fluid phase. Our results demonstrate the efficacy of boron isotope fractionation during crustal carbonate assimilation and suggest that low δ11B melt values in arc magmas could flag shallow-level additions to the subduction cycle.

  • 38. Deegan, F.M.
    et al.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Troll, V.R.
    Budd, D.A.
    Harris, C.
    Geiger, H.
    Hålenius, U.
    Swedish Museum of Natural History, Department of Geology.
    Pyroxene standards for SIMS oxygen isotope analysis and their application to Merapi volcano, Sunda arc, Indonesia2016In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 447, 1-10 p.Article in journal (Refereed)
    Abstract [en]

    Measurement of oxygen isotope ratios in common silicate minerals such as olivine, pyroxene, feldspar, garnet, and quartz is increasingly performed by Secondary Ion Mass Spectrometry (SIMS). However, certain mineral groups exhibit solid solution series, and the large compositional spectrum of these mineral phases will result in matrix effects during SIMS analysis. These matrix effects must be corrected through repeated analysis of compositionally similar standards to ensure accurate results. In order to widen the current applicability of SIMS to solid solution mineral groups in common igneous rocks, we performed SIMS homogeneity tests on new augite (NRM-AG-1) and enstatite (NRM-EN-2) reference materials sourced from Stromboli, Italy and Webster, North Carolina, respectively. Aliquots of the standard minerals were analysed by laser fluorination (LF) to establish their δ18O values. Repeated SIMS measurements were then performed on randomly oriented fragments of the same pyroxene crystals, which yielded a range in δ18O less than ± 0.42 and ± 0.58‰ (2σ) for NRM-AG-1 and NRM-EN-2, respectively. Homogeneity tests verified that NRM-AG-1 and NRM-EN-2 do not show any crystallographic orientation bias and that they are sufficiently homogeneous on the 20 μm scale to be used as routine mineral standards for SIMS δ18O analysis. We subsequently tested our new standard materials on recently erupted pyroxene crystals from Merapi volcano, Indonesia. The δ18O values for Merapi pyroxene obtained by SIMS (n = 204) agree within error with the LF-derived δ18O values for Merapi pyroxene but differ from bulk mineral and whole-rock data obtained by conventional fluorination. The bulk samples are offset to higher δ18O values as a result of incorporation of mineral and glass inclusions that in part reflects crustal contamination processes. The Merapi pyroxene SIMS data, in turn, display a frequency peak at 5.8‰, which allows us to estimate the δ18O value of the primary mafic magma at Merapi to ~ 6.1‰ when assuming closed system differentiation.

  • 39.
    Dekov, Vesselin M.
    et al.
    University of Sofia.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Billström, Kjell
    Swedish Museum of Natural History, Department of Geology.
    Kamenov, George D.
    University of Florida.
    Munnik, Frans
    Forschungszentrum Dresden-Rossendorf.
    Eriksson, Lars
    Stockholms universitet.
    Dyer, Alan
    University of Salford.
    Schmidt, Mark
    Leibniz-Institut für Meeresforschung, IFM-GEOMAR.
    Botz, Reiner
    Universität Kiel.
    Native Sn-Pb droplets in a zeolitic amygdale (Isle of Mull, Inner Hebrides)2009In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 73, 2907-2919 p.Article in journal (Refereed)
  • 40.
    Dekov, Vesselin M.
    et al.
    IFREMER.
    Rouxel, Olivier
    Woods Hole Oceanographic Institution.
    Asael, Dan
    IFREMER.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Munnik, Frans
    Helmoholz-Zentrum Dresden-Rossendorf.
    Native Cu from the oceanic crust: Isotopic insights into native metal origin2013In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 359, 136-149 p.Article in journal (Refereed)
  • 41.
    D'Ippolito, Veronica
    et al.
    Sapienza Università di Roma.
    Andreozzi, Giovanni B.
    Sapienza Università di Roma.
    Bosi, Ferdinando
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Blue spinel crystals in the MgAl2O4-CoAl2O4 series: I. Flux growth and chemical characterisation2012In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 97, 1828-1833 p.Article in journal (Refereed)
  • 42.
    D'Ippolito, Veronica
    et al.
    Sapienza Università di Roma.
    Andreozzi, Giovanni B.
    Sapienza Università di Roma.
    Bosi, Ferdinando
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Mantovani, L.
    Università di Parma.
    Bersani, D.
    Università di Parma.
    Fregola, Rosa Anna
    Università di Bari.
    Crystallographic and spectroscopic characterisation of a natural Zn-rich spinel approaching the endmember gahnite (ZnAl2O4) composition2013In: Mineralogical magazine, ISSN 0026-461X, E-ISSN 1471-8022, Vol. 77, 2941-2953 p.Article in journal (Refereed)
  • 43.
    D'Ippolito, Veronica
    et al.
    Sapienza University, Rome, Italy.
    Andreozzi, Giovanni
    Sapienza University, Rome, Italy.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Hametner, Kathrin
    ETH, Zürich, Switzerland.
    Günther, Detlef
    ETH, Zürich, Swizerland.
    Color mechanisms in spinel: cobalt and iron interplay for the blue color2015In: Physics and chemistry of minerals, ISSN 0342-1791, E-ISSN 1432-2021, Vol. 42, no 6, 431-439 p.Article in journal (Refereed)
    Abstract [en]

    Six natural, blue colored spinel crystals were studied chemically by electron microprobe and laser ablation inductively coupled plasma mass spectrometry (LAICP-MS) techniques and optically by UV–VIS–NIR–MIR spectroscopy in the range 30,000–2,000 cm1  to investigate the causes of their blue color hues. The positions of the absorption bands vary only marginally with the principal composition of the samples (gahnite vs. spinel s.s .). Although blue colors in spinels are frequently the result of various electronic processes in Fe cations, we demonstrate by comparison with synthetic Co-bearing samplesthat Co acts as an important chromophore also in natural spinels. Already at concentration levels of a few ppm (e.g.,>10 ppm), cobalt gives rise to absorption bands at ~18,000, 17,000 and 16,000 cm1  that result in distinct blue coloration. In spinels with insignificant Co contents, different shades of paler blue (from purplish to greenish blue) colors are caused by electronic transitions in TFe2+, MFe2+, MFe3and Fe2+–Fe3 cation pairs.

  • 44. Drake, H.
    et al.
    Tullborg, E.L.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Sandberg, B.
    Blomfeldt, T.
    Åström, M.E.
    Extreme fractionation and micro-scale variation of sulphur isotopes during bacterial sulphate reduction in deep groundwater systems.2015In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 161, 1-18 p.Article in journal (Refereed)
    Abstract [en]

    This study conducted at the Äspö Hard Rock Laboratory, SE Sweden, determines the extent and mechanisms of sulphur-isotope fractionation in permanently reducing groundwater in fractured crystalline rock. Two boreholes >400 m below the ground surface were investigated. In the 17-year-old boreholes, the Al instrumentation pipes had corroded locally (i.e., Al-[oxy]hydroxides had formed) and minerals (i.e., pyrite, iron monosulphide, and calcite) had precipitated on various parts on the equipment. By chemically and isotopically comparing the precipitates on the withdrawn instrumentation and the borehole waters, we gained new insight into the dynamics of sulphate reduction, sulphide precipitation, and sulphur-isotope fractionation in deep-seated crystalline-rock settings. An astonishing feature of the pyrite is its huge variability in δ34S, which can exceed 100‰ in total (i.e., −47.2 to +53.3‰) and 60‰ over 50 μm of growth in a single crystal. The values at the low end of the range are up to 71‰ lower than measured in the dissolved sulphate in the water (20–30‰), which is larger than the maximum difference reported between sulphate and sulphide in pure-culture experiments (66‰) but within the range reported from natural sedimentary settings. Although single-step reduction seems likely, further studies are needed to rule out the effects of possible S disproportionation. The values at the high end of the range (i.e., high δ34Spy) are much higher than could be produced from the measured sulphate under any biogeochemical conditions. This strongly suggests the development of closed-system conditions near the growing pyrite, i.e., the rate of sulphate reduction exceeds the rate of sulphate diffusion in the local fluid near the pyrite, causing the local aqueous phase (and thus the forming pyrite) to become successively enriched in heavy S (34S). Consequently, the δ34S values of the forming pyrite become exceptionally high and strongly decoupled from the δ34S values of the sulphate in the bulk fluid. The Al-(oxy)hydroxide and calcite precipitates are explained by a combination of deposit and galvanic corrosion initiated by Al corrosion by H2S produced by sulphate-reducing microorganisms.

  • 45. Eyal, Moshe
    et al.
    Be'eri-Shlevin, Yaron
    Eyal, Yehuda
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Litvinovsky, Boris
    Three successive Proterozoic island arcs in the Northern Arabian–Nubian Shield: Evidence from SIMS U–Pb dating of zircon2014In: Gondwana Research, ISSN 1342-937X, E-ISSN 1878-0571, Vol. 25, 338-357 p.Article in journal (Refereed)
  • 46.
    Fehr, Manuela A.
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Andersson, Per S.
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Gustafsson, Örjan
    Stockholms universitet.
    Mörth, Carl-Magnus
    Stockholms universitet.
    Iron enrichments and Fe isotopic compositions of surface sediments from the Gotland Deep, Baltic Sea2010In: Chemical Geology, ISSN 0009-2541, E-ISSN 1872-6836, Vol. 277, 310-322 p.Article in journal (Refereed)
  • 47.
    Fehr, Manuela
    et al.
    Swedish Museum of Natural History, Department of Geology.
    Andersson, Per S.
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Mörth, Carl-Magnus
    Stockholms universitet.
    Iron isotope variations in Holocene sediments of the Gotland deep, Baltic Sea2008In: Geochimica et Cosmochimica Acta, ISSN 0016-7037, E-ISSN 1872-9533, Vol. 72, 807-826 p.Article in journal (Refereed)
  • 48. Fisher, C.M.
    et al.
    Hanchar, J.M.
    Miller, C.M.
    Phillips, S.
    Vervoort, J.D.
    Whitehouse, Martin J.
    Swedish Museum of Natural History, Department of Geology.
    Combining Nd isotopes in monazite and Hf isotopes in zircon to understand complex open-system processes in granitic magmas.2017In: Geology, Vol. 45, 267-270 p.Article in journal (Refereed)
    Abstract [en]

    Mapping the age and trace element and Sm-Nd isotope compositions of monazite grains from a peraluminous Cretaceous granite using laser ablation–split stream analysis reveals a wide range in Nd isotope and rare earth element (REE) compositions within and between single grains. These data corroborate isotopic variability indicated by Hf isotope analysis of zircon in the same granite sample. The REE variations indicate that monazite grew during fractional crystallization. Hf and Nd isotopes indicate that the granitic magma was generated from at least two distinct Proterozoic sources of approximately the same age: one component that had highly radiogenic initial 176Hf/177Hf and 143Nd/144Nd and a second component that was notably less radiogenic. This study highlights the utility of in situ REE and Sm-Nd isotope data in monazite in magmatic systems. Further, it refines the zircon-based constraints on magmatic processes because of sensitivity of light REEs to fractional crystallization, lower probability of complications owing to inheritance, and smaller analytical volumes required.

  • 49. Fontorbe, Guillaume
    et al.
    Frings, Patrick J
    Swedish Museum of Natural History, Department of Geology.
    De La Rocha, Christina
    Hendry, Kate
    Carstensen, Jacob
    Conley, Daniel
    Enrichment of dissolved silica in the deep equatorial Pacific during the Eocene-Oligocene2017In: Paleoceanography, ISSN 0883-8305, E-ISSN 1944-9186, Vol. 32, 848-863 p.Article in journal (Refereed)
    Abstract [en]

    Silicon isotope ratios (expressed as δ30Si) in marine microfossils can provide insights into silica cycling over geologic time. Here we used δ30Si of sponge spicules and radiolarian tests from the Paleogene Equatorial Transect (Ocean Drilling Program Leg 199) spanning the Eocene and Oligocene (~50–23 Ma) to reconstruct dissolved silica (DSi) concentrations in deep waters and to examine upper ocean δ30Si. The δ30Si values range from 3.16 to +0.18‰ and from 0.07 to +1.42‰ for the sponge and radiolarian records, respectively. Both records show a transition toward lower δ30Si values around 37 Ma. The shift in radiolarian δ30Si is interpreted as a consequence of changes in the δ30Si of source DSi to the region. The decrease in sponge δ30Si is interpreted as a transition from low DSi concentrations to higher DSi concentrations, most likely related to the shift toward a solely Southern Ocean source of deep water in the Pacific during the Paleogene that has been suggested by results from paleoceanographic tracers such as neodymium and carbon isotopes. Sponge δ30Si provides relatively direct information about the nutrient content of deep water and is a useful complement to other tracers of deep water circulation in the oceans of the past. 

  • 50.
    Fregola, Rosa Anna
    et al.
    Università di Bari.
    Bosi, Ferdinando
    Swedish Museum of Natural History, Department of Geology.
    Skogby, Henrik
    Swedish Museum of Natural History, Department of Geology.
    Hålenius, Ulf
    Swedish Museum of Natural History, Department of Geology.
    Cation ordering over short range and long range scales in the MgAl2O4-CuAl2O4 series2012In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 97, 1821-1827 p.Article in journal (Refereed)
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