Change search
Refine search result
1 - 42 of 42
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Andrén, Margareta
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Stockmann, Gabrielle
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Skelton, Alasdair
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Sturkell, Erik
    Mörth, Carl-Magnus
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Guðrúnardóttir, Helga Rakel
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Keller, Nicole Simone
    Odling, Nic
    Dahrén, Börje
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Balic-Zunic, Tonci
    Hjartarson, Hreinn
    Siegmund, Heike
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Freund, Friedemann
    Kockum, Ingrid
    Coupling between mineral reactions, chemical changes in groundwater, and earthquakes in Iceland2016In: Journal of Geophysical Research - Solid Earth, ISSN 2169-9313, E-ISSN 2169-9356, Vol. 121, no 4, p. 2315-2337Article in journal (Refereed)
    Abstract [en]

    Chemical analysis of groundwater samples collected from a borehole at Hafralaekur, northern Iceland, from October 2008 to June 2015 revealed (1) a long-term decrease in concentration of Si and Na and (2) an abrupt increase in concentration of Na before each of two consecutive M 5 earthquakes which occurred in 2012 and 2013, both 76km from Hafralaekur. Based on a geochemical (major elements and stable isotopes), petrological, and mineralogical study of drill cuttings taken from an adjacent borehole, we are able to show that (1) the long-term decrease in concentration of Si and Na was caused by constant volume replacement of labradorite by analcime coupled with precipitation of zeolites in vesicles and along fractures and (2) the abrupt increase of Na concentration before the first earthquake records a switchover to nonstoichiometric dissolution of analcime with preferential release of Na into groundwater. We attribute decay of the Na peaks, which followed and coincided with each earthquake to uptake of Na along fractured or porous boundaries between labradorite and analcime crystals. Possible causes of these Na peaks are an increase of reactive surface area caused by fracturing or a shift from chemical equilibrium caused by mixing between groundwater components. Both could have been triggered by preseismic dilation, which was also inferred in a previous study by Skelton et al. (2014). The mechanism behind preseismic dilation so far from the focus of an earthquake remains unknown.

  • 2. Bark, Glenn
    et al.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Weihed, Pär
    Fluid chemistry of the Palaeoproterozoic Fäboliden hypozonal orogenic gold deposit, northern Sweden: evidence from fluid inclusions2007In: GFFArticle in journal (Refereed)
  • 3. Bengtson, S.
    et al.
    Ivarsson, M.
    Astolfo, A.
    Belivanova, V.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Marone, F.
    Stampanoni, M.
    Deep-biosphere consortium of fungi and prokaryotes in Eocene subseafloor basalts2014In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 12, no 6, p. 489-496Article in journal (Refereed)
    Abstract [en]

    The deep biosphere of the subseafloor crust is believed to contain a significant part of Earth's biomass, but because of the difficulties of directly observing the living organisms, its composition and ecology are poorly known. We report here a consortium of fossilized prokaryotic and eukaryotic micro-organisms, occupying cavities in deep-drilled vesicular basalt from the Emperor Seamounts, Pacific Ocean, 67.5m below seafloor (mbsf). Fungal hyphae provide the framework on which prokaryote-like organisms are suspended like cobwebs and iron-oxidizing bacteria form microstromatolites (Frutexites). The spatial inter-relationships show that the organisms were living at the same time in an integrated fashion, suggesting symbiotic interdependence. The community is contemporaneous with secondary mineralizations of calcite partly filling the cavities. The fungal hyphae frequently extend into the calcite, indicating that they were able to bore into the substrate through mineral dissolution. A symbiotic relationship with chemoautotrophs, as inferred for the observed consortium, may be a pre-requisite for the eukaryotic colonization of crustal rocks. Fossils thus open a window to the extant as well as the ancient deep biosphere.

  • 4. Billstrom, K.
    et al.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Jonsson, E.
    Recio, C.
    Boyce, A. J.
    Torssander, P.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Geochronological, stable isotopes and fluid inclusion constraints for a premetamorphic development of the intrusive-hosted Bjorkdal Au deposit, northern Sweden2009In: International journal of earth sciences, ISSN 1437-3254, E-ISSN 1437-3262, Vol. 98, no 5, p. 1027-1052Article in journal (Refereed)
    Abstract [en]

    The Bjorkdal gold deposit, bound to a quartz vein system which is mainly hosted by a quartz-monzodioritic intrusion, is situated at the easternmost part of the 1.9 Ga Skellefte base metal district in the Fennoscandian shield. Three fluid stages may be distinguished, referred to as a ""barren"" stage, a main gold stage, and a remobilization stage, respectively. From oxygen and hydrogen isotope evidence, it is argued that fluids of different origins (magmatic and surface waters) penetrated the ore zone at the inferred stages, but regional metamorphic fluids appear essentially only to have redistributed elements. Early quartz veining took place during a pre-metamorphic stage at ca. 1.88 Ga, as evidenced by unradiogenic galena data and an Sm-Nd scheelite errorchron of 1,915 +/- A 32 Ma (MSWD = 0.25). Temporarily, the main ore-forming stage was closely related to the first barren stage and took place during a major uplift event close to 1.88 Ga. Although other source rocks cannot be totally ruled out, available isotope data (O, S, Sr and Pb) are seemingly consistent with the view that these elements, and by inference other ore elements, were derived from the host intrusion.

  • 5. Billström, Kjell
    et al.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Jonsson, Erik
    Recio, Clemente
    Boyce, Adrian
    Torssander, Peter
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Isotopic, fluid inclusion and textural evidences for a multi-stage development of the Björkdal Au deposit, northern Sweden2008In: International Journal of Earth SciencesArticle in journal (Refereed)
  • 6.
    Boskabadi, Ahmad
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pitcairn, Iairn K.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Stern, R. J.
    Azer, M. K.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mohamed, F. H.
    Majka, J.
    Carbonatite crystallization and alteration in the Tarr carbonatite-albitite complex, Sinai Peninsula, Egypt2013In: Precambrian Research, ISSN 0301-9268, E-ISSN 1872-7433, Vol. - 239, p. 24-41Article in journal (Refereed)
    Abstract [en]

    Carbonate dykes occurring in the Arabian-Nubian Shield (ANS) are clearly intrusive in origin and carbonatites according to the IUGS classification, yet previous investigations refer to them as “intrusive carbonates”, due mainly to their low Sr, Ba, Nb, Y, Th and rare earth element (REE) contents. The Tarr carbonatite albitite complex (TCA) in SE Sinai, Egypt contains a series of small (<1.2 km2) albitite intrusions surrounded by small veins and dykes of carbonatite, which occur predominantly in a narrow zone of brecciation surrounding the intrusions. Fennitic alteration surrounding TCA has been reported but there is little consensus on the extent and origin of this alteration. Fennitic alteration surrounding the TCA carbonatites is not abundant. Alteration is dominated by precipitation of carbonates in the breccia zone surrounding the albitite intrusion with associated actinolite, chlorite, sericite and epidote. Geochemical compositions are consistent with addition of carbonates and associated secondary minerals because the altered rocks contain higher CaO, MgO, Fe2O3 and MnO and lower SiO2, Al2O3, Na2O and K2O compared to their less altered rocks. Fluid inclusion investigations show that the carbonatite magma contained a high-salinity H2O–CO2–NaCl–CaCl2 fluid, although the lack of fennitic alteration implies that this fluid was not abundant. The crystallization conditions of the carbonatite dykes and carbonatite matrix in the breccia zones have been constrained using Zr-in-rutile thermometry and fluid inclusion microthermometry. Crystallization of the carbonatite in the dykes and in the breccia zone occurred between 565 ± 38 °C and 420–480 °C, respectively and at 0.75–1.3 kbar, which corresponds to a depth of 2.8–4.9 km. Rutile hosted within the carbonatite crystallized earlier at high temperature and the carbonate matrix crystallized later after cooling. Immiscible fluid from carbonatite magma would have altered the surrounding country rocks at lower temperature (between 400 °C and 150 °C deduced from the fluid inclusion thermometry) after the intrusion of the carbonatite melt.

  • 7.
    Boskabadi, Arman
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. University of Texas at Dallas, USA.
    Pitcairn, Iain K.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Boyce, Adrian
    Teagle, Damon A. H.
    Cooper, Matthew J.
    Azer, Mokhles K.
    Stern, Robert J.
    Mohamed, Fathy H.
    Majka, Jaroslaw
    Carbonate alteration of ophiolitic rocks in the Arabian-Nubian Shield of Egypt: sources and compositions of the carbonating fluid and implications for the formation of Au deposits2017In: International Geology Review, ISSN 0020-6814, E-ISSN 1938-2839, Vol. 59, no 4, p. 391-419Article, review/survey (Refereed)
    Abstract [en]

    Ultramafic portions of ophiolitic fragments in the Arabian-Nubian Shield (ANS) show pervasive carbonate alteration forming various degrees of carbonated serpentinites and listvenitic rocks. Notwithstanding the extent of the alteration, little is known about the processes that caused it, the source of the CO2 or the conditions of alteration. This study investigates the mineralogy, stable (O, C) and radiogenic (Sr) isotope composition, and geochemistry of suites of variably carbonate altered ultramafics from the Meatiq area of the Central Eastern Desert (CED) of Egypt. The samples investigated include least-altered lizardite (Lz) serpentinites, antigorite (Atg) serpentinites and listvenitic rocks with associated carbonate and quartz veins. The C, O and Sr isotopes of the vein samples cluster between -8.1 parts per thousand and -6.8 parts per thousand for delta C-13, +6.4 parts per thousand and +10.5 parts per thousand for delta O-18, and Sr-87/Sr-86 of 0.7028-0.70344, and plot within the depleted mantle compositional field. The serpentinites isotopic compositions plot on a mixing trend between the depleted-mantle and sedimentary carbonate fields. The carbonate veins contain abundant carbonic (CO2 +/- CH4 +/- N-2) and aqueous-carbonic (H2O-NaCl-CO2 +/- CH4 +/- N-2) low salinity fluid, with trapping conditions of 270-300 degrees C and 0.7-1.1kbar. The serpentinites are enriched in Au, As, S and other fluid-mobile elements relative to primitive and depleted mantle. The extensively carbonated Atg-serpentinites contain significantly lower concentrations of these elements than the Lz-serpentinites suggesting that they were depleted during carbonate alteration. Fluid inclusion and stable isotope compositions of Au deposits in the CED are similar to those from the carbonate veins investigated in the study and we suggest that carbonation of ANS ophiolitic rocks due to influx of mantle-derived CO2-bearing fluids caused break down of Au-bearing minerals such as pentlandite, releasing Au and S to the hydrothermal fluids that later formed the Au-deposits. This is the first time that gold has been observed to be remobilized from rocks during the lizardite-antigorite transition.

  • 8.
    Broman, Curt
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Sturkell, Erik
    Fallick, Anthony E.
    Oxygen isotopes and implications for the cavity-grown quartz crystals in the Lockne impact structure, Sweden2011In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 133, no 02-jan, p. 101-107Article in journal (Refereed)
    Abstract [en]

    Well-developed quartz crystals are found in open cavities in the intensely fractured crystalline basement of the marine-target impact structure at Lockne in central Sweden. The 458 Ma impact structure has a well-preserved crater in Precambrian granitic basement rock that is covered by resurge deposits composed of breccias and fine-grained sedimentary units of mixed Ordovician limestone, Cambrian black bituminous shales and the basement granite. Directly after the impact, the resurge deposits formed when the seawater rushed back into the crater. The residual heat from the impact facilitated a short-lived hydrothermal system accompanied by the inflowing seawater, which resulted in mineral growth in fractures and open cavities of the granite basement. The oxygen isotope values of the first-precipitated minerals, the cavity-grown quartz crystals, range from +15.2 to +16.2 parts per thousand (Vienna Standard Mean Ocean Water) and differ from those of the hosting granite basement rock with delta(18)O quartz between +10.1 and +11.7 parts per thousand. The delta(18)O values of the quartz are more consistent with derivation from a fluid of relatively high delta(18)O probably attributable to oxygen isotope exchange during seawater-rock interactions in the resurge deposits. The occurrence of organic matter in association with the cavity-grown quartz strongly indicates a relationship to the black bituminous shale in the matrix of the breccia that rests on the crater floor. Comparing the results with previously obtained oxygen data on fracture-grown calcite from Lockne shows that oxygen isotope composition of the cavity-grown quartz crystals is less variable and probably more accurately reflects the original fluid source.

  • 9.
    Callac, Nolwenn
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Posth, Nicole R.
    Rattray, Jayne E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Yamoah, Kweku K. Y.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Wiech, Alan
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ivarsson, Magnus
    Hemmingsson, Christoffer
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kilias, Stephanos P.
    Argyraki, Ariadne
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Skogby, Henrik
    Smittenberg, Rienk H.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Chi Fru, Ernest
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Modes of carbon fixation in an arsenic and CO2-rich shallow hydrothermal ecosystem2017In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 7, article id 14708Article in journal (Refereed)
    Abstract [en]

    The seafloor sediments of Spathi Bay, Milos Island, Greece, are part of the largest arsenic-CO2-rich shallow submarine hydrothermal ecosystem on Earth. Here, white and brown deposits cap chemically distinct sediments with varying hydrothermal influence. All sediments contain abundant genes for autotrophic carbon fixation used in the Calvin-Benson-Bassham (CBB) and reverse tricaboxylic acid (rTCA) cycles. Both forms of RuBisCO, together with ATP citrate lyase genes in the rTCA cycle, increase with distance from the active hydrothermal centres and decrease with sediment depth. Clustering of RuBisCO Form II with a highly prevalent Zetaproteobacteria 16S rRNA gene density infers that ironoxidizing bacteria contribute significantly to the sediment CBB cycle gene content. Three clusters form from different microbial guilds, each one encompassing one gene involved in CO2 fixation, aside from sulfate reduction. Our study suggests that the microbially mediated CBB cycle drives carbon fixation in the Spathi Bay sediments that are characterized by diffuse hydrothermal activity, high CO2, As emissions and chemically reduced fluids. This study highlights the breadth of conditions influencing the biogeochemistry in shallow CO2-rich hydrothermal systems and the importance of coupling highly specific process indicators to elucidate the complexity of carbon cycling in these ecosystems.

  • 10.
    Chi Fru, Ernest
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Cardiff University, UK.
    Callac, Nolwenn
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Posth, Nicole R.
    Argyraki, Ariadne
    Ling, Yu-Chen
    Ivarsson, Magnus
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Kilias, Stephanos P.
    Arsenic and high affinity phosphate uptake gene distribution in shallow submarine hydrothermal sediments2018In: Biogeochemistry, ISSN 0168-2563, E-ISSN 1573-515X, Vol. 141, no 1, p. 41-62Article in journal (Refereed)
    Abstract [en]

    The toxicity of arsenic (As) towards life on Earth is apparent in the dense distribution of genes associated with As detoxification across the tree of life. The ability to defend against As is particularly vital for survival in As-rich shallow submarine hydrothermal ecosystems along the Hellenic Volcanic Arc (HVA), where life is exposed to hydrothermal fluids containing up to 3000 times more As than present in seawater. We propose that the removal of dissolved As and phosphorus (P) by sulfide and Fe(III)(oxyhydr)oxide minerals during sediment-seawater interaction, produces nutrient-deficient porewaters containing<2.0ppb P. The porewater arsenite-As(III) to arsenate-As(V) ratios, combined with sulfide concentration in the sediment and/or porewater, suggest a hydrothermally-induced seafloor redox gradient. This gradient overlaps with changing high affinity phosphate uptake gene abundance. High affinity phosphate uptake and As cycling genes are depleted in the sulfide-rich settings, relative to the more oxidizing habitats where mainly Fe(III)(oxyhydr)oxides are precipitated. In addition, a habitat-wide low As-respiring and As-oxidizing gene content relative to As resistance gene richness, suggests that As detoxification is prioritized over metabolic As cycling in the sediments. Collectively, the data point to redox control on Fe and S mineralization as a decisive factor in the regulation of high affinity phosphate uptake and As cycling gene content in shallow submarine hydrothermal ecosystems along the HVA.

  • 11.
    Chi Fru, Ernest
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Hemmingsson, Christoffer
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Callac, Nolwenn
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pérez, Nathalie
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Panova, Elena G.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    El Albani, Abderrazzak
    Atmospheric weathering of Scandinavian alum shales and the fractionation of C, N and S isotopes2016In: Applied Geochemistry, ISSN 0883-2927, E-ISSN 1872-9134, Vol. 74, p. 94-108Article in journal (Refereed)
    Abstract [en]

    Subaerial exposure and oxidation of organic carbon (C-org)-rich rocks is believed to be a key mechanism for the recycling of buried C and S back to Earth's surface. Importantly, processes coupled to microbial C-org oxidation are expected to shift new biomass delta C-13(org) composition towards more negative values relative to source. However, there is scarcity of information directly relating rock chemistry to oxidative weathering and shifting delta C-13(org) at the rock-atmosphere interface. This is particularly pertinent to the sulfidic, C-org-rich alum shale units of the Baltoscandian Basin believed to constitute a strong source of metal contaminants to the natural environment, following subaerial exposure and weathering. Consistent with independent support, we show that atmospheric oxidation of the sulfidic, C-org-rich alum shale sequence of the Cambrian-Devonian Baltoscandian Basin induces intense acid rock drainage at the expense of progressive oxidation of Fe sulfides. Sulfide oxidation takes priority over microbial organic matter decomposition, enabling quantitative massive erosion of C-org without producing a delta C-13 shift between acid rock drainage precipitates and shale. Moreover, C-13 enrichment in inorganic carbon of precipitates does not support microbial C-org oxidation as the predominant mechanism of rock weathering upon exposure. Instead, a Delta S-34 = delta S-34(shale) - delta S-34(precipitates) approximate to 0, accompanied by elevated S levels and the ubiquitous deposition of acid rock drainage sulfate minerals in deposited efflorescent precipitates relative to shales, provide strong evidence for quantitative mass oxidation of shale sulfide minerals as the source of acidity for chemical weathering. Slight delta N-15 depletion in the new surface precipitates relative to shale, coincides with dramatic loss of N from shales. Collectively, the results point to pyrite oxidation as a major driver of alum black shale weathering at the rock-atmosphere interface, indicating that quantitative mass release of C-org, N, S, and key metals to the environment is a response to intense sulfide oxidation. Consequently, large-scale acidic weathering of the sulfide-rich alum shale units is suggested to influence the fate and redistribution of the isotopes of C, N, and S from shale to the immediate environment.

  • 12.
    Chi Fru, Ernest
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Swedish Museum of Natural History, Sweden.
    Ivarsson, M.
    Kilias, S. P.
    Frings, P. J.
    Hemmingsson, Christoffer
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bengtson, S.
    Chatzitheodoridis, E.
    Biogenicity of an Early Quaternary iron formation, Milos Island, Greece2015In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 13, no 3, p. 225-244Article in journal (Refereed)
    Abstract [en]

    A 2.0-million-year-old shallow-submarine sedimentary deposit on Milos Island, Greece, harbours an unmetamorphosed fossiliferous iron formation (IF) comparable to Precambrian banded iron formations (BIFs). This Milos IF holds the potential to provide clues to the origin of Precambrian BIFs, relative to biotic and abiotic processes. Here, we combine field stratigraphic observations, stable isotopes of C, S and Si, rock petrography and microfossil evidence from a 5-m-thick outcrop to track potential biogeochemical processes that may have contributed to the formation of the BIF-type rocks and the abrupt transition to an overlying conglomerate-hosted IF (CIF). Bulk C-13 isotopic compositions lower than -25 parts per thousand provide evidence for biological contribution by the Calvin and reductive acetyl-CoA carbon fixation cycles to the origin of both the BIF-type and CIF strata. Low S levels of 0.04 wt.% combined with S-34 estimates of up to 18 parts per thousand point to a non-sulphidic depository. Positive Si-30 records of up to +0.53 parts per thousand in the finely laminated BIF-type rocks indicate chemical deposition on the seafloor during weak periods of arc magmatism. Negative Si-30 data are consistent with geological observations suggesting a sudden change to intense arc volcanism potentially terminated the deposition of the BIF-type layer. The typical Precambrian rhythmic rocks of alternating Fe- and Si-rich bands are associated with abundant and spatially distinct microbial fossil assemblages. Together with previously proposed anoxygenic photoferrotrophic iron cycling and low sedimentary N and C potentially connected to diagenetic denitrification, the Milos IF is a biogenic submarine volcano-sedimentary IF showing depositional conditions analogous to Archaean Algoma-type BIFs.

  • 13. Chi Fru, Ernest
    et al.
    Ivarsson, Magnus
    Kilias, Stephanos P.
    Bengtson, Stefan
    Belivanova, Veneta
    Marone, Federica
    Fortin, Danielle
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Stampanoni, Marco
    Fossilized iron bacteria reveal a pathway to the biological origin of banded iron formation2013In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 4, p. 2050-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.

  • 14.
    Chi Fru, Ernest
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences. Cardiff University, UK.
    Kilias, Stephanos
    Ivarsson, Magnus
    Rattray, Jayne E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gkika, Katerina
    McDonald, Iain
    He, Qian
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Sedimentary mechanisms of a modern banded iron formation on Milos Island, Greece2018In: Solid Earth, ISSN 1869-9510, E-ISSN 1869-9529, Vol. 9, no 3, p. 573-598Article in journal (Refereed)
    Abstract [en]

    An early Quaternary shallow submarine hydrothermal iron formation (IF) in the Cape Vani sedimentary basin (CVSB) on Milos Island, Greece, displays banded rhythmicity similar to Precambrian banded iron formation (BIF). Field-wide stratigraphic and biogeochemical reconstructions show two temporal and spatially isolated iron deposits in the CVSB with distinct sedimentological character. Petrographic screening suggests the presence of a photoferrotrophic-like microfossil-rich IF (MFIF), accumulated on a basement consisting of andesites in a similar to 150 m wide basin in the SW margin of the basin. A banded nonfossiliferous IF (NFIF) sits on top of the Mn-rich sandstones at the transition to the renowned Mn-rich formation, capping the NFIF unit. Geochemical data relate the origin of the NFIF to periodic submarine volcanism and water column oxidation of released Fe(II) in conditions predominated by anoxia, similar to the MFIF. Raman spectroscopy pairs hematite-rich grains in the NFIF with relics of a carbonaceous material carrying an average delta C-13 org signature of similar to-25%0. A similar delta C-13 org signature in the MFIF could not be directly coupled to hematite by mineralogy. The NFIF, which postdates large-scale Mn deposition in the CVSB, is composed primarily of amorphous Si (opal-SiO2 center dot nH(2)O) while crystalline quartz (SiO2) predominates the MFIF. An intricate interaction between tectonic processes, changing redox, biological activity, and abiotic Si precipitation are proposed to have collectively formed the unmetamorphosed BIF-type deposits in a shallow submarine volcanic center. Despite the differences in Precambrian ocean-atmosphere chemistry and the present geologic time, these formation mechanisms coincide with those believed to have formed Algoma-type BIFs proximal to active seafloor volcanic centers.

  • 15. Drake, Henrik
    et al.
    Heim, Christine
    Roberts, Nick M. W.
    Zack, Thomas
    Tillberg, Mikael
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ivarsson, Magnus
    Whitehouse, Martin J.
    Åström, Mats E.
    Isotopic evidence for microbial production and consumption of methane in the upper continental crust throughout the Phanerozoic eon2017In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 470, p. 108-118Article in journal (Refereed)
    Abstract [en]

    Microorganisms produce and consume methane in terrestrial surface environments, sea sediments and, as indicated by recent discoveries, in fractured crystalline bedrock. These processes in the crystalline bedrock remain, however, unexplored both in terms of mechanisms and spatiotemporal distribution. Here we have studied these processes via a multi-method approach including microscale analysis of the stable isotope compositions of calcite and pyrite precipitated in bedrock fractures in the upper crust (down to 1.7 km) at three sites on the Baltic Shield. Microbial processes have caused an intriguing variability of the carbon isotopes in the calcites at all sites, with delta C-13 spanning as much as -93.1 parts per thousand (related to anaerobic oxidation of methane) to +36.5 parts per thousand (related to methanogenesis). Spatiotemporal coupling between the stable isotope measurements and radiometric age determinations (micro-scale dating using new high spatial methods: LA-ICP-MS U-Pb for calcite and Rb-Sr for calcite and co-genetic adularia) enabled unprecedented direct timing constraints of the microbial processes to several periods throughout the Phanerozoic eon, dating back to Devonian times. These events have featured variable fluid salinities and temperatures as shown by fluid inclusions in the calcite; dominantly 70-85 degrees C brines in the Paleozoic and lower temperatures (<50-62 degrees C) and salinities in the Mesozoic. Preserved organic compounds, including plant signatures, within the calcite crystals mark the influence of organic matter in descending surficial fluids on the microbial processes in the fracture system, thus linking processes in the deep and surficial biosphere. These findings substantially extend the recognized temporal and spatial range for production and consumption of methane within the upper continental crust.

  • 16. Drake, Henrik
    et al.
    Roberts, Nick M. W.
    Heim, Christine
    Whitehouse, Martin J.
    Siljeström, Sandra
    Kooijman, Ellen
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ivarsson, Magnus
    Åström, Mats E.
    Timing and origin of natural gas accumulation in the Siljan impact structure, Sweden2019In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 4736Article in journal (Refereed)
    Abstract [en]

    Fractured rocks of impact craters may be suitable hosts for deep microbial communities on Earth and potentially other terrestrial planets, yet direct evidence remains elusive. Here, we present a study of the largest crater of Europe, the Devonian Siljan structure, showing that impact structures can be important unexplored hosts for long-term deep microbial activity. Secondary carbonate minerals dated to 80 +/- 5 to 22 +/- 3 million years, and thus postdating the impact by more than 300 million years, have isotopic signatures revealing both microbial methanogenesis and anaerobic oxidation of methane in the bedrock. Hydrocarbons mobilized from matured shale source rocks were utilized by subsurface microorganisms, leading to accumulation of microbial methane mixed with a thermogenic and possibly a minor abiotic gas fraction beneath a sedimentary cap rock at the crater rim. These new insights into crater hosted gas accumulation and microbial activity have implications for understanding the astrobiological consequences of impacts.

  • 17. Drake, Henrik
    et al.
    Åström, Mats E.
    Heim, Christine
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Åström, Jan
    Whitehouse, Martin
    Ivarsson, Magnus
    Siljeström, Sandra
    Sjövall, Peter
    Extreme C-13 depletion of carbonates formed during oxidation of biogenic methane in fractured granite2015In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 6, article id 7020Article in journal (Refereed)
    Abstract [en]

    Precipitation of exceptionally C-13-depleted authigenic carbonate is a result of, and thus a tracer for, sulphate-dependent anaerobic methane oxidation, particularly in marine sediments. Although these carbonates typically are less depleted in C-13 than in the source methane, because of incorporation of C also from other sources, they are far more depleted in C-13 (delta C-13 as light as - 69% V-PDB) than in carbonates formed where no methane is involved. Here we show that oxidation of biogenic methane in carbon-poor deep groundwater in fractured granitoid rocks has resulted in fracture-wall precipitation of the most extremely C-13-depleted carbonates ever reported, delta C-13 down to - 125% V-PDB. A microbial consortium of sulphate reducers and methane oxidizers has been involved, as revealed by biomarker signatures in the carbonates and S-isotope compositions of co-genetic sulphide. Methane formed at shallow depths has been oxidized at several hundred metres depth at the transition to a deep-seated sulphate-rich saline water. This process is so far an unrecognized terrestrial sink of methane.

  • 18. Holtstam, Dan
    et al.
    Andersson, Ulf B.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Mansfeld, Joakim
    Origin of REE mineralization in the Bastnas-type Fe-REE-(Cu-Mo-Bi-Au) deposits, Bergslagen, Sweden2014In: Mineralium Deposita, ISSN 0026-4598, E-ISSN 1432-1866, Vol. 49, no 8, p. 933-966Article in journal (Refereed)
    Abstract [en]

    The Bastnas-type deposits, with mineral assemblages of Fe oxides, Ca-Mg silicates, rare earth element (REE) silicates, REE fluorocarbonates, and Cu-Fe-Mo-Bi sulfides, are associated with marble horizons in a strongly Na, K, and/or Mg altered, metavolcanic succession, over a distance of at least 80 km in a SW-NE trending zone in western Bergslagen. Two subtypes occur: (1) enriched (relative to the other type) in light REE (LREE) and Fe, exemplified by the Bastnas and Rodbergsgruvan deposits, and (2) enriched in heavy REE (HREE), Y, Mg, Ca, and F, represented by deposits in the Norberg district. Bastnasite hosts primary fluid H2O-CO2 inclusions with salinities of 6-29 eq. wt% CaCl2 and with total homogenization temperatures (Th-tot) of ca. 300-400 degrees C. Subtype 2 has late-stage fluorite with fluid inclusions that show 1-16 eq. wt% NaCl and Th-tot of ca. 90-150 degrees C. Molybdenite Re-Os ages obtained from three deposits are 1,904 +/- 6, 1,863 +/- 4, and 1,842 +/- 4 Ma. Nd isotopic data from five different REE minerals yielded no defined isochron, but a range in epsilon(Nd) (1.88 Ga) of +0.2 to +1.6. The oxygen isotope values (delta O-18(SMOW)) of dolomite and calcite from the associated REE-mineralized skarn and recrystallized carbonate assemblages lie in the range 6.1-8.6 parts per thousand, overlapping with those of the host marbles. Carbon isotope values (delta C-13(PDB)) show typical magmatic signatures of -6.7 to -4.4 parts per thousand, while the host marbles group around ca. -2.4 parts per thousand. The sulfur isotope (delta S-34(CDT)) values of associated sulfides range between -10.8 and +0.2 parts per thousand. The combined evidence suggests REE mineralization, beginning at 1.9 Ga, from mainly Svecofennian, juvenile magmatic (>400 degrees C) fluids carrying Si, F, Cl, S, CO2, and the REE in addition to other metals; mineralization occurred through reactions with dolomitic layers in the supracrustal units coevally with regional metasomatic alteration associated with fluid circulation through an extensive active volcano-plutonic complex.

  • 19. Ivarsson, M.
    et al.
    Bach, W.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Neubeck, Anna
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bengtson, S.
    Fossilized Life in Subseafloor Ultramafic Rocks2018In: Geomicrobiology Journal, ISSN 0149-0451, E-ISSN 1521-0529, Vol. 35, no 6, p. 460-467Article in journal (Refereed)
    Abstract [en]

    Ultramafic rocks are hypothesized to support a subseafloor hydrogen-driven biosphere because of extensive production of bioavailable energy sources like H-2 or CH4 from fluid-rock interactions. Hence, the apparent lack of microbial remains in subseafloor ultramafic rocks, in contrast to their frequent observation in subseafloor basalts, is somewhat of a paradox. Here we report fossilized microbial remains in aragonite veins in ultramafic rocks from the 15 degrees 20N Fracture Zone area on the Mid-Atlantic Ridge (MAR), collected during Ocean Drilling Program (ODP) Leg 209. The microbial remains consist of filamentous structures associated with biofilms. The young age (<1 Myr) and absence of diagenesis result in fossilized microbial communities with a pristine composition characterized by carbonaceous matter (CM) and the enrichment in trace elements such as Ni, Co, Mo and Mn. Our study confirms the presence of the hypothesized deep subseafloor biosphere hosted in ultramafic rocks. We further show that host rock composition may influence the microbial elemental composition, which is recorded during the fossilization.

  • 20. Ivarsson, Magnus
    et al.
    Bengtson, Stefan
    Skogby, Henrik
    Lazor, Peter
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Belivanova, Veneta
    Marone, Federica
    A Fungal-Prokaryotic Consortium at the Basalt-Zeolite Interface in Subseafloor Igneous Crust2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 10, article id e0140106Article in journal (Refereed)
    Abstract [en]

    We have after half a century of coordinated scientific drilling gained insight into Earth's largest microbial habitat, the subseafloor igneous crust, but still lack substantial understanding regarding its abundance, diversity and ecology. Here we describe a fossilized microbial consortium of prokaryotes and fungi at the basalt-zeolite interface of fractured subseafloor basalts from a depth of 240 m below seafloor (mbsf). The microbial consortium and its relationship with the surrounding physical environment are revealed by synchrotron-based X-ray tomographic microscopy (SRXTM), environmental scanning electron microscopy (ESEM), and Raman spectroscopy. The base of the consortium is represented by micro-stromatolites- remains of bacterial communities that oxidized reduced iron directly from the basalt. The microstromatolites and the surrounding basalt were overlaid by fungal cells and hyphae. The consortium was overgrown by hydrothermally formed zeolites but remained alive and active during this event. After its formation, fungal hyphae bored in the zeolite, producing millimetre-long tunnels through the mineral substrate. The dissolution could either serve to extract metals like Ca, Na and K essential for fungal growth and metabolism, or be a response to environmental stress owing to the mineral overgrowth. Our results show how microbial life may be maintained in a nutrient-poor and extreme environment by close ecological interplay and reveal an effective strategy for nutrient extraction from minerals. The prokaryotic portion of the consortium served as a carbon source for the eukaryotic portion. Such an approach may be a prerequisite for prokaryotic-eukaryotic colonisation of, and persistence in, subseafloor igneous crust.

  • 21. Ivarsson, Magnus
    et al.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Gustafsson, Håkan
    Holm, Nils G.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Biogenic Mn-Oxides in Subseafloor Basalts2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 6, article id e0128863Article in journal (Refereed)
    Abstract [en]

    The deep biosphere of the subseafloor basalts is recognized as a major scientific frontier in disciplines like biology, geology, and oceanography. Recently, the presence of fungi in these environments has involved a change of view regarding diversity and ecology. Here, we describe fossilized fungal communities in vugs in subseafloor basalts from a depth of 936.65 metres below seafloor at the Detroit Seamount, Pacific Ocean. These fungal communities are closely associated with botryoidal Mn oxides composed of todorokite. Analyses of the Mn oxides by Electron Paramagnetic Resonance spectroscopy (EPR) indicate a biogenic signature. We suggest, based on mineralogical, morphological and EPR data, a biological origin of the botryoidal Mn oxides. Our results show that fungi are involved in Mn cycling at great depths in the seafloor and we introduce EPR as a means to easily identify biogenic Mn oxides in these environments.

  • 22. Ivarsson, Magnus
    et al.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Holmström, Sara
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ahlbom, Marianne
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Lindblom, Sten
    Holm, Nils
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Putative fossilized fungi from the lithified volcaniclastic apron of Gran Canaria, Spain2011In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 11, no 7, p. 633-650Article in journal (Refereed)
    Abstract [en]

    We report the discovery of fossilized filamentous structures in samples of the lithified, volcaniclastic apron of Gran Canaria, which were obtained during Leg 157 of the Ocean Drilling Program (ODP). These filamentous structures are 2–15 μm in diameter and several hundred micrometers in length and are composed of Si, Al, Fe, Ca, Mg, Na, Ti, and C. Chitin was detected in the filamentous structures by staining with wheat germ agglutinin dye conjugated with fluorescein isothiocyanate (WGA-FITC), which suggests that they are fossilized fungal hyphae. The further elucidation of typical filamentous fungal morphological features, such as septa, hyphal bridges, and anastomosis and their respective sizes, support this interpretation. Characteristic structures that we interpreted as fossilized spores were also observed in association with the putative hyphae. The fungal hyphae were found in pyroxene phenocrysts and in siderite pseudomorphs of a basalt breccia. The fungal colonization of the basalt clasts occurred after the brecciation but prior to the final emplacement and lithification of the sediment at 16–14 Ma. The siderite appears to have been partially dissolved by the presence of fungal hyphae, and the fungi preferentially colonized Fe-rich carbonates over Fe-poor carbonates (aragonite). Our findings indicate that fungi may be an important geobiological agent in subseafloor environments and an important component of the deep subseafloor biosphere, and that hydrothermal environments associated with volcanism can support a diverse ecosystem, including eukaryotes.

  • 23.
    Ivarsson, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Lindblom, Sten
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Holm, Nils
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Fluid inclusions as a tool to constrain the preservation conditions of sub-seafloor cryptoendoliths2009In: Planetary and Space Science, Vol. 57, p. 477-490Article in journal (Refereed)
  • 24. Ivarsson, Magnus
    et al.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Sturkell, Erik
    Ormo, Jens
    Siljeström, Sandra
    van Zuilen, Mark
    Bengtson, Stefan
    Fungal colonization of an Ordovician impact-induced hydrothermal system2013In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, article id 3487Article in journal (Refereed)
    Abstract [en]

    Impacts are common geologic features on the terrestrial planets throughout the solar system, and on at least Earth and Mars impacts have induced hydrothermal convection. Impact-generated hydrothermal systems have been suggested to possess the same life supporting capability as hydrothermal systems associated with volcanic activity. However, evidence of fossil microbial colonization in impact-generated hydrothermal systems is scarce in the literature. Here we report of fossilized microorganisms in association with cavity-grown hydrothermal minerals from the 458 Ma Lockne impact structure, Sweden. Based on morphological characteristics the fossilized microorganisms are interpreted as fungi. We further infer the kerogenization of the microfossils, and thus the life span of the fungi, to be contemporaneous with the hydrothermal activity and migration of hydrocarbons in the system. Our results from the Lockne impact structure show that hydrothermal systems associated with impact structures can support colonization by microbial life.

  • 25.
    Ivarsson, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Lausmaa, Jukka
    Lindblom, Sten
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Holm, Nils
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Fossilized microorganisms from the Emperor Seamounts: implications for the search for a sub-surface fossil record on Earth and Mars2008In: AstrobiologyArticle in journal (Refereed)
  • 26.
    Ivarsson, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Lindblom, Sten
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Broman, Curt
    Naturhistoriska riksmuseet.
    Holm, Nils
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Fossilized microorganisms associated with zeolite-carbonate interfaces in sub-seafloor hydrothermal environments2008In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 6, no 2, p. 155-170Article in journal (Refereed)
    Abstract [en]

    In this paper we describe carbon-rich filamentous structures observed in association with the zeolite mineral phillipsite from sub-seafloor samples drilled and collected during the Ocean Drilling Program (ODP) Leg 197 at the Emperor Seamounts. The filamentous structures are ~5 µm thick and ~100–200 µm in length. They are found attached to phillipsite surfaces in veins and entombed in vein-filling carbonates. The carbon content of the filaments ranges between ~10 wt% C and 55 wt% C. They further bind to propidium iodide (PI), which is a dye that binds to damaged cell membranes and remnants of DNA.

    Carbon-rich globular microstructures, 1–2 µm in diameter, are also found associated with the phillipsite surfaces as well as within wedge-shaped cavities in phillipsite assemblages. The globules have a carbon content that range between ~5 wt% C and 55 wt% C and they bind to PI. Ordinary globular iron oxides found throughout the samples differ in that they contain no carbon and do not bind to the dye PI. The carbon-rich globules are mostly concentrated to a film-like structure that is attached to the phillipsite surfaces. This film has a carbon content that ranges between ~25 wt% C and 75 wt% C and partially binds to PI. EDS analyses show that the carbon in all structures described are not associated with calcium and therefore not bound in carbonates. The carbon content and the binding to PI may indicate that the filamentous structures could represent fossilized filamentous microorganisms, the globules could represent fossilized microbial cells and the film-like structures could represent a microbially produced biofilm.

    Our results extend the knowledge of possible habitable niches for a deep biosphere in sub-seafloor environments and suggests, as phillipsite is one of the most common zeolite mineral in volcanic rocks of the oceanic crust, that it could be a common feature in the oceanic crust elsewhere.

  • 27. Ivarsson, Magnus
    et al.
    Peckmann, Joern
    Tehler, Anders
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Bach, Wolfgang
    Behrens, Katharina
    Reitner, Joachim
    Boettcher, Michael E.
    Ivarsson, Lena Norback
    Zygomycetes in Vesicular Basanites from Vesteris Seamount, Greenland Basin - A New Type of Cryptoendolithic Fungi2015In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 10, no 7, article id e0133368Article in journal (Refereed)
    Abstract [en]

    Fungi have been recognized as a frequent colonizer of subseafloor basalt but a substantial understanding of their abundance, diversity and ecological role in this environment is still lacking. Here we report fossilized cryptoendolithic fungal communities represented by mainly Zygomycetes and minor Ascomycetes in vesicles of dredged volcanic rocks (basanites) from the Vesteris Seamount in the Greenland Basin. Zygomycetes had not been reported from subseafloor basalt previously. Different stages in zygospore formation are documented in the studied samples, representing a reproduction cycle. Spore structures of both Zygomycetes and Ascomycetes are mineralized by romanechite-like Mn oxide phases, indicating an involvement in Mn(II) oxidation to form Mn(III, VI) oxides. Zygospores still exhibit a core of carbonaceous matter due to their resistance to degradation. The fungi are closely associated with fossiliferous marine sediments that have been introduced into the vesicles. At the contact to sediment infillings, fungi produced haustoria that penetrated and scavenged on the remains of fragmented marine organisms. It is most likely that such marine debris is the main carbon source for fungi in shallow volcanic rocks, which favored the establishment of vital colonies.

  • 28.
    Lewerentz, Alexander
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Skelton, Alasdair
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Graham, Colin
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Däcker, Elisabeth
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Post-peak metamorphic kyanite stabilisation in greenschist facies metasedimentary rocks on the Isle of Islay, SW Scottish HighlandsManuscript (preprint) (Other academic)
  • 29.
    Lindgren, Paula
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ivarsson, Magnus
    Naturhistoriska riksmuséet.
    Neubeck, Anna
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Henkel, Herbert
    Kungliga tekniska högskolan.
    Holm, Nils
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Putative fossil life in a hydrothermal system of the Dellen impact structure, Sweden2010In: International Journal of Astrobiology, ISSN 1473-5504, E-ISSN 1475-3006, Vol. 9, no 3, p. 137-146Article in journal (Refereed)
    Abstract [en]

    The role of muscarinic acetylcholine receptors (mAChRs) in regulating glucose uptake in L6 skeletal muscle cells was investigated. [H-3]-2-Deoxyglucose uptake was increased in differentiated L6 cells by insulin, acetylcholine, oxotremorine-M and carbachol. mAChR-mediated glucose uptake was inhibited by the AMPK inhibitor Compound C. Whole cell radioligand binding using [H-3]-N-methyl scopolamine chloride identified mAChRs in differentiated but not undifferentiated L6 cells and M-3 mAChR mRNA was detected only in differentiated cells. M-3 mAChRs are Gq-coupled, and cholinergic stimulation by the rnAChR agonists acetylcholine, oxotremorine-M and carbachol increased Ca2+ in differentiated but not undifferentiated L6 cells. This was due to muscarinic but not nicotinic activation as responses were antagonised by the muscarinic antagonist atropine but not the nicotinic antagonist tubocurarine. Western blotting showed that both carbachol and the AMPK activator AICAR increased phosphorylation of the AMPK alpha subunit at Thr172, with responses to carbachol blocked by Compound C and the CaMKK inhibitor STO609 but not by the PI3K inhibitor wortmannin. AICAR-stimulated AMPK phosphorylation was not sensitive to STO-609, confirming that this compound inhibits CaMKK but not the classical AMPK kinase LKB1. The TAK1 inhibitor (5Z)-7-oxozeaenol and the G(i) inhibitor pertussis toxin both failed to block AMPK phosphorylation in response to carbachol. Using CHO-K1 cells stably expressing each of the mAChR subtypes (M-1-M-4), it was determined that only the M-1 and M-3 mAChRs phosphorylate AMPK, confirming a G(q)-dependent mechanism. This study demonstrates that activation of M-3 mAChRs in L6 skeletal muscle cells stimulates glucose uptake via a CaMKK-AMPK-dependent mechanism, independent of the insulin-stimulated pathway.

  • 30. Martinsson, Olof
    et al.
    Billström, Kjell
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Weihed, Pär
    Wanhainen, Christina
    Metallogeny of the Northern Norrbotten Ore Province, northern Fennoscandian Shield with emphasis on IOCG and apatite-iron ore deposits2016In: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 78, p. 447-492Article, review/survey (Refereed)
    Abstract [en]

    The Northern Norrbotten Ore Province in northernmost Sweden includes the type localities for Kiruna-type apatite iron deposits and has been the focus for intense exploration and research related to Fe oxide-Cu-Au mineralisation during the last decades. Several different types of Fe-oxide and Cu-Au +/- Fe oxide mineralisation occur in the region and include: stratiform Cu +/- Zn +/- Pb +/- Fe oxide type, iron formations (including BIF's), Kiruna-type apatite iron ore, and epigenetic Cu +/- Au +/- Fe oxide type which may be further subdivided into different styles of mineralisation, some of them with typical IOCG (Iron Oxide-Copper-Gold) characteristics. Generally, the formation of Fe oxide +/- Cu +/- Au mineralisation is directly or indirectly dated'between-2.1 and 1.75 Ga, thus spanning about 350 m.y. of geological evolution. The current paper will present in more detail the characteristics of certain key deposits, and aims to put the global concepts of Fe-oxide Cu-Au mineralisation into a regional context. The focus will be on iron deposits and various types of deposits containing Fe-oxides and Cu-sulphides in different proportions which generally have some characteristics in common with the IOCG style. In particular, ore fluid characteristics (magmatic versus non magmatic) and new geochronological data are used to link the ore-forming processes with the overall crustal evolution to generate a metallogenetic model. Rift bounded shallow marine basins developed at similar to 2.1-2.0 Ga following a long period of extensional tectonics within the Greenstone-dominated, 2.5-2.0 Ga Karelian craton. The similar to 1.9-1.8 Ga Svecofennian Orogen is characterised by subduction and accretion from the southwest. An initial emplacement of calc-alkaline magmas into similar to 1.9 Ga continental arcs led to the formation of the Haparanda Suite and the Porphyrite Group volcanic rocks. Following this early stage of magmatic activity, and separated from it by the earliest deformation and metamorphism, more alkali-rich magmas of the Perthite Monzonite Suite and the Kiirunavaara Group volcanic rocks were formed at similar to 1.88 Ga. Subsequently, partial melting of the middle crust produced large volumes of similar to 1.85 and 1.8 Ga S-type granites in conjunction with subduction related A-/I-type magmatism and associated deformation and metamorphism. In our metallogenetic model the ore formation is considered to relate to the geological evolution as follows. Iron formations and a few stratiform sulphide deposits were deposited in relation to exhalative processes in rift bounded marine basins. The iron formations may be sub-divided into BIF-(banded iron formations) and Mg rich types, and at several locations these types grade into each other. There is no direct age evidence to constrain the deposition of iron formations, but stable isotope data and stratigraphic correlations suggest a formation within the 2.1-2.0 Ga age range. The major Kiruna-type ores formed from an iron-rich magma (generally with a hydrothermal over-print) and are restricted to areas occupied by volcanic rocks of the Kiirunavaara Group. It is suggested here that 1.89-1.88 Ga tholeiitic magmas underwent magma liquid immiscibility reactions during fractionation and interaction with crustal rocks, including metaevaporites, generating more felsic magmatic rocks and Kiruna-type iron deposits. A second generation of this ore type, with a minor economic importance, appears to have been formed about 100 Ma later. The epigenetic Cu-Au +/- Fe oxide mineralisation formed during two stages of the Svecofennian evolution in association with magmatic and metamorphic events and crustal scale shear zones. During the first stage of mineralisation, from 1.89-1.88 Ga, intrusion-related (porphyry style) mineralisation and Cu-Au deposits of IOCG affinity formed from magmatic-hydrothermal systems, whereas vein-style and shear zone deposits largely formed at c. 1.78 Ga. The large range of different Fe oxide and Cu-Au +/- Fe oxide deposits in Northern Norrbotten is associated with various alteration systems, involving e.g. scapolite, albite, K feldspar, biotite, carbonates, tourmaline and sericite. However, among the apatite iron ores and the epigenetic Cu-Au +/- Fe oxide deposits the character of mineralisation, type of ore- and alteration minerals and metal associations are partly controlled by stratigraphic position (i.e. depth of emplacement). Highly saline, NaCl + CaCl2 dominated fluids, commonly also including a CO2-rich population, appear to be a common characteristic feature irrespective of type and age of deposits. Thus, fluids with similar characteristics appear to have been active during quite different stages of the geological evolution. Ore fluids related to epigenetic Cu-Au Fe oxides display a trend with decreasing salinity, which probably was caused by mixing with meteoric water. Tentatively, this can be linked to different Cu-Au ore paragenesis, including an initial (magnetite)-pyrite-chalcopyrite stage, a main chalcopyrite stage, and a late bornite stage. Based on the anion composition and the Br/Cl ratio of ore related fluids bittern brines and metaevaporites (including scapolite) seem to be important sources to the high salinity hydrothermal systems generating most of the deposits in Norrbotten. Depending on local conditions and position in the crust these fluids generated a variety of Cu-Au deposits. These include typical IOCG-deposits (Fe-oxides and Cu-Au are part of the same process), IOCG of iron stone type (pre-existing Fe-oxide deposit with later addition of Cu-Au), IOCG of reduced type (lacking Fe-oxides due to local reducing conditions) and vein-style Cu-Au deposits. From a strict genetic point of view, IOCG deposits that formed from fluids of a mainly magmatic origin should be considered to be a different type than those deposits associated with mainly non-magmatic fluids. The former tend to overlap with porphyry systems, whereas those of a mainly non-magmatic origin overlap with sediment hosted Cu-deposits with respect to their origin and character of the ore fluids.

  • 31. Maskenskaya, O. M.
    et al.
    Drake, H.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Hogmalm, J. K.
    Czuppon, G.
    Astrom, M. E.
    Source and character of syntaxial hydrothermal calcite veins in Paleoproterozoic crystalline rocks revealed by fine-scale investigations2014In: Geofluids, ISSN 1468-8115, E-ISSN 1468-8123, Vol. 14, no 4, p. 495-511Article in journal (Refereed)
    Abstract [en]

    Calcite veins in Paleoproterozoic granitoids on the Baltic Shield are the focus of this study. These veins are distinguished by their monomineralic character, unusual thickness and closeness to Neoproterozoic dolerite dykes and therefore have drawn attention. The aim of this study was to define the source of these veins and to unravel their isotopic and chemical nature by carrying out fine-scale studies. Seven calcite veins covering a depth interval of 50-420m below the ground surface and composed of breccias or crack-sealed fillings typically expressing syntaxial growth were sampled and analysed for a variety of physicochemical variables: homogenization temperature (T-h) and salinity of fluid inclusions, and stable isotopes (Sr-87/Sr-86, C-13/C-12, O-18/O-16), trace-element concentrations (Fe, Mn, Mg, Sr, rare earth elements) and cathodoluminescence (CL) of the solid phase. The fluid-inclusion data show that the calcites were precipitated mainly from relatively low-temperature (T-h=73-106 degrees C) brines (13.4-24.5wt.% CaCl2), and the Sr-87/Sr-86 is more radiogenic than expected for Rb-poor minerals precipitated from Neoproterozoic fluids. These features, together with the distribution of C-13 and O-18 values, provide evidence that the calcite veins are not genetic with the nearby Neoproterozoic dolerite dykes, but are of Paleozoic age and were precipitated from warm brines expressing a rather large variability in salinity. Whereas the isotopic and chemical variables express rather constant average values among the individual veins, they vary considerably on fine-scale across individual veins. This has implications for understanding processes causing calcite-rich veins to form and capture trace metals in crystalline bedrock settings.

  • 32.
    Neubeck, Anna
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Sun, Li
    Müller, Bettina
    Ivarsson, Magnus
    Hosgörmez, Hakan
    Özcan, Dogacan
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Schnürer, Anna
    Microbial Community Structure in a Serpentine-Hosted Abiotic Gas Seepage at the Chimaera Ophiolite, Turkey2017In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 83, no 12, article id UNSP e03430Article in journal (Refereed)
    Abstract [en]

    The surface waters at the ultramafic ophiolitic outcrop in Chimaera, Turkey, are characterized by high pH values and high metal levels due to the percolation of fluids through areas of active serpentinization. We describe the influence of the liquid chemistry, mineralogy, and H-2 and CH4 levels on the bacterial community structure in a semidry, exposed, ultramafic environment. The bacterial and archaeal community structures were monitored using Illumina sequencing targeting the 16S rRNA gene. At all sampling points, four phyla, Proteobacteria, Actinobacteria, Chloroflexi, and Acidobacteria, accounted for the majority of taxa. Members of the Chloroflexi phylum dominated low-diversity sites, whereas Proteobacteria dominated high-diversity sites. Methane, nitrogen, iron, and hydrogen oxidizers were detected as well as archaea and metal-resistant bacteria. IMPORTANCE Our study is a comprehensive microbial investigation of the Chimaera ophiolite. DNA has been extracted from 16 sites in the area and has been studied from microbial and geochemical points of view. We describe a microbial community structure that is dependent on terrestrial, serpentinization-driven abiotic H-2, which is poorly studied due to the rarity of these environments on Earth.

  • 33. Petersson, Jesper
    et al.
    Fallick, Anthony E.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Eliasson, Thomas
    Imprints of multiple fluid regimes on episyenites in the Bohus granite, Sweden2014In: Lithos, ISSN 0024-4937, E-ISSN 1872-6143, Vol. 196, p. 99-114Article in journal (Refereed)
    Abstract [en]

    A number of episyenite occurrences within the Neoproterozoic Bohus granite, southwestern Sweden, were investigated in order to elucidate their genesis and past associated fluid regimes. Fluid inclusion microthermometry and O-H isotope systematics integrated with information from detailed mineralogy reveal a paragenetic succession within individual episyenites, including: (1) albitization of plagioclase, accompanied by dissolution of quartz, with a vuggy feldspathic reservoir rock as a result; (2) resumed infilling and replacement of igneous Fe-Ti-phases by various phyllosilicates (muscovite, chlorite and/or illite) +/- hematite assemblages and quartz, due to rift-related reactivation and (3) sporadic argillitic alteration and precipitation of fracture calcite. Although sparse owing to later overprinting, there are a few remnants that provide arguments for the involvement of meteoric water, shifted to a more O-18-rich composition, during the initial stage of dissolution and albitization. The main vug-filling phase is proposed to be associated with the ingress of surface-derived fluids with negative delta O-18 values, during the regional thermal anomaly accompanying the development of the nearby Permo-Carboniferous Oslo Rift at similar to 250 Ma The fluids involved during this event show consistently a marked, but variable O-18-depletion and resemble the modern-day shield brines, with modal salinities of 11-24 wt.% NaCl eq., low NaCl/(NaCl + CaCl2) weight ratios and no discernible CO2. Even though no P-T path can be defined for this phase, the fluid pressure can be restricted to 03-0.8 kbar and temperature to 160-280 degrees C, assuming a sedimentary overburden of similar to 3 km. An overall variability in the delta O-18 and delta D data can mainly be ascribed to (1) precipitation from fluids affected by isotopic exchange with the host rock and/or sedimentary overburden under highly variable water/rock ratios, and to some extent with (2) varying degrees of partial re-equilibration during subsequent hydrothermal interaction at lower temperatures, as emphasized by the presence of fluid inclusions of suspected secondary origin in quartz.

  • 34.
    Pitcairn, Iain K.
    et al.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Skelton, Alasdair D. L.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Arghe, Fredrik
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Boyce, Adrian
    Structurally focused fluid flow during orogenesis: the Islay Anticline, SW Highlands, Scotland2010In: Journal of the Geological Society, ISSN 0016-7649, E-ISSN 2041-479X, Vol. 167, no 4, p. 659-674Article in journal (Refereed)
    Abstract [en]

    Displacement of isotopic compositions at boundary layers across strata of contrasting composition is commonly used to investigate hydrothermal fluid flow during orogeny. This study investigates whether hydrothermal fluid flow was focused along the Islay Anticline, Islay, SW Highlands of Scotland, as shown in the axial zone of the neighbouring Ardrishaig Anticline. Four localities from the limb to the axial plane of the Islay Anticline were investigated for isotopic homogenization of metacarbonate units to silicate values. At Mull of Oa on the limb of the anticline, metacarbonate samples show limited isotopic resetting and the fluid flux is estimated to be <1 m(3) m(-2). Within the axial zone of the Islay Anticline, metacarbonate units from Port a' Chotain and Bagh an Da Dhoruis show complete isotopic homogenization to silicate values indicating higher fluid fluxes. Fluid flow was enhanced along localized parasitic folds such as at Port an t-Sruthain, where metacarbonates have been isotopically reset, and there are abundant quartz-carbonate veins that precipitated during D-1-D-2 deformation. Metamorphic fluid flow was higher in the axial zone of the Islay Anticline and in localized antiformal structures. Fluid fluxes are estimated to be considerably lower than at the neighbouring Ardrishaig Anticline.

  • 35.
    Siljeström, Sandra
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Lausmaa, Juka
    SP Sveriges Tekniska Forskningsinstitut.
    Sjövall, Peter
    SP Sveriges Tekniska Forskningsinstitut.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Thiel, Volker
    University of Göttingen.
    Hode, Tomas
    Portland State University.
    Detection of hopanes and steranes in single oil-bearing fluid inclusions using ToF-SIMS2009In: IMOG 24th International Meeting of Organic Geochemistry, Book of Abstract, www.imog2009.org, 2009, p. 6-Conference paper (Other academic)
    Abstract [en]

    Hopanes and steranes are key biomarkers when tracking early evolution of life on Earth. A potential contamination-free source of Precambrian biomarkers is oil-bearing fluid inclusions as the oil has been secluded from the environment since the formation of the inclusion. Due to presence of often several generations of inclusions it can be problematic to assign the biomarkers to specific inclusions. It has, however, because of the small size of inclusions (5-30 µm), not been possible to analyse single oil-bearing fluid inclusions. We present here an approach employing time-of-flight secondary ion mass spectrometry (ToF-SIMS) to selectively open individual oil inclusions in situ by ion etching, and precisely analyse their picoliter content for steranes and hopanes.

    A number of oil-bearing inclusions from hydrothermal veins in the Siljan impact structure in south-central Sweden were analysed. The approach used for analysis of a single inclusion consisted of the following steps i) localization of suitable inclusion in double polished thin section with optical microscopy, ii) opening of inclusion by ion etching with C60+ gun inside the ToF-SIMS instrument while recording in real-time the opening of the inclusion and, iii) analysis of the exposed inclusion contents with ToF-SIMS. The micrographs and the ToF-SIMS ion images collected before, during and after analysis ensured the correct inclusion had been analysed. ToF-SIMS spectra reconstructed from analysis times and 2D regions of interest with increased organic ion signal showed a large number of organic peaks (up to m/z 500) that are characteristic for a crude oil. Comparison of the reconstructed spectra with those of a Siljan seep oil, which has previously been analysed with ToF-SIMS, showed a high degree of resemblance, as expected from the geological interpretation of the origin on the oils. All major characteristic peaks for several hopanes and steranes were detected in the mass spectra from the single fluid inclusion (Fig. 1). The agreement with respect to mass accuracy (< 50 ppm), fragment pattern and isotope distributions between these peaks and those observed in spectra from standard samples and from hopanes and steranes in the Siljan seep oil, provide strong evidence for the presence of hopanes and steranes in the analysed single fluid inclusions. The results thus demonstrate that the approach presented here has the capability to detect specific biomarkers in individual single oil inclusions.

    It is to our knowledge the first time hopanes and steranes have been detected in single oil-bearing fluid inclusins and the next step will be to analyse single oil-bearing fluid inclusions in Precambrian rocks with ToF-SIMS in search for organic biomarkers. Detection of hopanes and steranes in such an inclusion could help to answer questions regarding early evolution of life on Earth, including the first appearance of the eukaryotes on Earth.

  • 36.
    Siljeström, Sandra
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Lausmaa, Jukka
    Sjövall, Peter
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Thiel, Volker
    ToF-SIMS analysis of oil-bearing fluid inclusions2008In: SIMS Europe 2008, 2008Conference paper (Other (popular science, discussion, etc.))
  • 37.
    Siljeström, Sandra
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Lausmaa, Jukka
    Sjövall, Peter
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Thiel, Volker
    Hode, Tomas
    Analysis of hopanes and steranes in single oil-bearing fluid inclusions using time-of-flight secondary ion mass spectrometry (ToF-SIMS)2010In: Geobiology, ISSN 1472-4677, E-ISSN 1472-4669, Vol. 8, no 1, p. 37-44Article in journal (Refereed)
    Abstract [en]

    Steranes and hopanes are organic biomarkers used as indicators for the first appearance of eukaryotes and cyanobacteria on Earth. Oil-bearing fluid inclusions may provide a contamination-free source of Precambrian biomarkers, as the oil has been secluded from the environment since the formation of the inclusion. However, analysis of biomarkers in single oil-bearing fluid inclusions, which is often necessary due to the presence of different generations of inclusions, has not been possible due to the small size of most inclusions. Here, we have used time-of-flight secondary ion mass spectrometry (ToF-SIMS) to monitor in real time the opening of individualinclusions trapped in hydrothermal veins of fluorite and calcite and containing oil from Ordovician source rocks. Opening of the inclusions was performed by using a focused C60+ ion beam and the in situ content was preciselyanalysed for C27–C29 steranes and C29–C32 hopanes using Bi3+ as primary ions. The capacity to unambiguouslydetect these biomarkers in the picoliter amount of crude oil from a single, normal-sized (15–30 µm in diameter)inclusion makes the approach promising in the search of organic biomarkers for life’s early evolution on Earth.

  • 38.
    Siljeström, Sandra
    et al.
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Lausmaa, Jukka
    SP Sveriges Tekniska Forskningsinstitut.
    Sjövall, Peter
    SP Sveriges Tekniska Forskningsinstitut.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Thiel, Volker
    University of Göttingen.
    Hode, Tomas
    Portland State University.
    ToF-SIMS analysis of hopanes and steranes in single oil-bearing fluid inclusions2009In: Geochimica et Cosmochimica Acta, vol  73, A1223, 2009Conference paper (Other academic)
    Abstract [en]

    Hopanes and steranes are key biomarkers when tracking early evolution of life on Earth. A potential contamination-free source of such biomarkers is oil-bearing fluid inclusions as the oil has been secluded from the environment since the the inclusion was trapped. Using extraction-based techniques (GC/MS, LC/MS), it is, however, problematic to assign the extracted biomarkers to specific inclusions, due to the presence of often several generations of inclusions. As yet, it has not been possible to selectively analyse syngenetic inclusions for their biomarker content, because of their small size (5-30 µm in diameter). Here we present an approach employing time-of-flight secondary ion mass spectrometry (ToF-SIMS) to open and directly analyse the picoliter content of individual oil inclusions in petrographic thin sections of the target rocks.

    A number of oil-bearing inclusions (20-30 µm in diameter) from hydrothermal veins in the Siljan impact structure, Sweden, were analysed. The approach consisted of the following steps; i) localization of a suitable inclusion in a thin section using optical microscopy, ii) opening of the inclusion by ion etching with a C60+ sputter gun inside the ToF-SIMS instrument while recording in real-time the opening of the inclusion and, iii) analysis of the exposed inclusion contents with ToF-SIMS. ToF-SIMS spectra from the analysed inclusions showed a large number of organic peaks that are characteristic for crude oils, including all major diagnostic peaks for several hopanes and steranes.

    To our knowledge, it is the first time hopanes and steranes have been detected in single oil-bearing fluid inclusions. We are currently using this approach for analysing single inclusions in Precambrian rocks, in search of organic biomarkers that could help to answer questions regarding early evolution of life on Earth.

  • 39. Sjoqvist, Axel S. L.
    et al.
    Lindgren, Paula
    Sturkell, Erik F. F.
    Hogmalm, K. Johan
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Ivarsson, Magnus
    Lee, Martin R.
    Shock metamorphism and hydrothermal alteration of mafic impact ejecta from the Lockne impact structure, Sweden2017In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 139, no 2, p. 119-128Article in journal (Refereed)
    Abstract [en]

    The local geology at Kloxasen is characterised by ejecta deposits from the 458 Ma Lockne marine impact. The Kloxasen ejecta are located on a Caledonian parautochthonous unit, approximately 7 km from the centre of the 7.5-km-wide Lockne crater structure. The ejecta were deposited on the seafloor and were covered with seawater immediately after the impact event. Of special interest is a mafic impact breccia within the ejecta, which before the impact was angstrom sby dolerite that belongs to the Jamtland suite of the 1.25 Ga Central Scandinavian Dolerite Group. The mafic impact breccia occurs mainly as a coherent thin domain within a larger block of granitic breccia, which we interpret as a result of the in situ brecciation of a dolerite sill within granitic bedrock. Shock pressure in the doleritic breccia was low, in the order of 0.4 GPa, constrained by the presence of mechanically twinned clinopyroxene. Low shock pressure and brecciation corresponds well to the spall zone of an impact crater, where ejecta originate from. Whereas spalled ejecta can also show signs of having been exposed to high shock pressures, including shocked quartz, evidence for this was not found in the Kloxasen ejecta. The breccia has been hydrothermally altered, but the ejecta are too far removed from the crater to have been affected by hydrothermal circulation in relation to Lockne's impact event. Fluid inclusion analyses suggest that most of the alteration happened later, during the Caledonian orogeny. Geochemical analyses reflect observed mineral alterations well, such as serpentinisation of olivine.

  • 40. Sosnicka, Marta
    et al.
    Bakker, Ronald J.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Pitcairn, Iain
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Paranko, Ihor
    Burlinson, Kingsley
    Fluid types and their genetic meaning for the BIF-hosted iron ores, Krivoy Rog, Ukraine2015In: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 68, p. 171-194Article in journal (Refereed)
    Abstract [en]

    This paper contributes to the understanding of the genesis of epigenetic, hypogene BIF-hosted iron deposits situated in the eastern part of Ukrainian Shield. It presents new data from the Krivoy Rog iron mining district (Skelevatske-Magnetitove deposit, Frunze underground mine and Balka Severnaya Krasnaya outcrop) and focuses on the investigation of ore genesis through application of fluid inclusion petrography, micro-thermometry, Raman spectroscopy and baro-acoustic decrepitation of fluid inclusions. The study investigates inclusions preserved in quartz and magnetite associated with the low-grade iron ores (31-37% Fe) and iron-rich quartzites (38-45% Fe) of the Saksaganskaya Suite, as well as magnetite from the locally named high-grade iron ores (52-56% Fe). These high-grade ores resulted from alteration of iron quartzites in the Saksaganskiy thrust footwall (Saksaganskiy tectonic block) and were a precursor to supergene martite, high-grade ores (60-70% Fe). Based on the new data two stages of iron ore formation (metamorphic and metasomatic) are proposed. The metamorphic stage, resulting in formation of quartz veins within the low-grade iron ore and iron-rich quartzites, involved fluids of four different compositions: CO2-rich, H2O, H2O-CO2(+/- N-2-CH4)-NaCl(+/- NaHCO3) and H2O-CO2(+/- N-2-CH4)-NaCl. The salinities of these fluids were relatively low (up to 7 mass% NaCl equiv.) as these fluids were derived from dehydration and decarbonation of the BIF rocks, however the origin of the nahcolite (NaHCO3) remains unresolved. The minimum P-T conditions for the formation of these veins, inferred from microthermometry are T-min = 219-246 degrees C and P-min = 130-158 MPa. The baro-acoustic decrepitation analyses of magnetite bands indicated that the low-grade iron ore from the Skelevatske-Magnetitove deposit was metamorphosed at T = similar to 530 degrees C. The metasomatic stage post-dated and partially overlapped the metamorphic stage and led to the upgrade of iron quartzites to the high-grade iron ores. The genesis of these ores, which are located in the Saksaganskiy tectonic block (Saksaganskiy ore field), and the factors controlling iron ore-forming processes are highly controversial. According to the study of quartz-hosted fluid inclusions from the thrust zone the metasomatic stage involved at least three different episodes of the fluid flow, simultaneous with thrusting and deformation. During the 1st episode three types of fluids were introduced: CO2-CH4-N-2(+/- C), CO2(+/- N-2-CH4) and low salinity H2O-N-2-CH4-NaCl (6.38-7.1 mass% NaCl equiv.). The 2nd episode included expulsion of the aqueous fluids H2O-N2CH4-NaCl(+/- CO2, +/- C) of moderate salinities (15.22-16.76 mass% NaCl equiv.), whereas the 3rd event involved high salinity fluids H2O-NaCl(+/- C) (20-35 mass% NaCl equiv.). The fluids most probably interacted with country rocks (e.g. schists) supplying them with CH4 and N-2. The high salinity fluids were most likely either magmatic-hydrothermal fluids derived from the Saksaganskiy igneous body or heated basinal brines, and they may have caused pervasive leaching of Fe from metavolcanic and/or the BIF rocks. The baro-acoustic decrepitation analyses of magnetite comprising the high-grade iron ore showed formation T = similar to 430-500 degrees C. The fluid inclusion data suggest that the upgrade to high-grade Fe ores might be a result of the Krivoy Rog BIF alteration by multiple flows of structurally controlled, metamorphic and magmatic-hydrothermal fluids or heated basinal brines.

  • 41. Tillberg, Mikael
    et al.
    Maskenskaya, Olga M.
    Drake, Henrik
    Hogmalm, Johan K.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Fallick, Anthony E.
    Åström, Mats E.
    Fractionation of Rare Earth Elements in Greisen and Hydrothermal Veins Related to A-Type Magmatism2019In: Geofluids, ISSN 1468-8115, E-ISSN 1468-8123, Vol. 2019, article id 4523214Article in journal (Refereed)
    Abstract [en]

    This study focuses on concentrations and fractionation of rare earth elements (REE) in a variety of minerals and bulk materials of hydrothermal greisen and vein mineralization in Paleoproterozoic monzodiorite to granodiorite related to the intrusion of Mesoproterozoic alkali- and fluorine-rich granite. The greisen consists of coarse-grained quartz, muscovite, and fluorite, whereas the veins mainly contain quartz, calcite, epidote, chlorite, and fluorite in order of abundance. A temporal and thus genetic link between the granite and the greisen/veins is established via high spatial resolution in situ Rb-Sr dating, supported by several other isotopic signatures (delta S-34, Sr-87/Sr-86, delta O-18, and delta C-13). Fluid-inclusion microthermometry reveals that multiple pulses of moderately to highly saline aqueous to carbonic solutions caused greisenization and vein formation at temperatures above 200-250 degrees C and up to 430 degrees C at the early hydrothermal stage in the veins. Low calculated Sigma REE concentration for bulk vein (15ppm) compared to greisen (75ppm), country rocks (173-224ppm), and the intruding granite (320ppm) points to overall low REE levels in the hydrothermal fluids emanating from the granite. This is explained by efficient REE retention in the granite via incorporation in accessory phosphates, zircon, and fluorite and unfavorable conditions for REE partitioning in fluids at the magmatic and early hydrothermal stages. A noteworthy feature is substantial heavy REE (HREE) enrichment of calcite in the vein system, in contrast to the relatively flat patterns of greisen calcite. The REE fractionation of the vein calcite is explained mainly by fractional crystallization, where the initially precipitated epidote in the veins preferentially incorporates most of the light REE (LREE) pool, leaving a residual fluid enriched in the HREE from which calcite precipitated. Fluorite occurs throughout the system and displays decreasing REE concentrations from granite towards greisen and veins and different fractionation patterns among all these three materials. Taken together, these features confirm efficient REE retention in the early stages of the system and minor control of the REE uptake by mineral-specific partitioning. REE-fractionation patterns and fluid-inclusion data suggest that chloride complexation dominated REE transport during greisenization, whereas carbonate complexation contributed to the HREE enrichment in vein calcite.

  • 42. Wanhainen, C.
    et al.
    Broman, Curt
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Martinsson, O.
    Magnor, B.
    Modification of a Palaeoproterozoic porphyry-like system: Integration of structural, geochemical, petrographic, and fluid inclusion data from the Aitik Cu-Au-Ag deposit, northern Sweden2012In: Ore Geology Reviews, ISSN 0169-1368, E-ISSN 1872-7360, Vol. 48, p. 306-331Article, review/survey (Refereed)
    Abstract [en]

    The Aitik Cu-Au-Ag deposit in the Gallivare area in northern Sweden is Sweden's largest sulphide mine with an annual production of 35 Mt of ore, and the biggest open pit operation in northern Europe. It is proposed in the present study that the Aitik deposit represents a Palaeoproterozoic, strongly metamorphosed porphyry copper deposit that was affected ca. 100 Ma later by a regional IOCG-type hydrothermal event. Consequently, the Aitik deposit might represent a mixed ore system where an early copper mineralisation of porphyry type has been overprinted by later regional IOCG mineralisation. Several attempts have previously been made to genetically classify the Aitik Cu-Au-Ag deposit as a distinct ore type. New geochemical, petrographic, structural, and fluid inclusion results combined with published data have provided the opportunity to present new ideas on the genesis and evolution of the Aitik Cu-Au-Ag deposit. The emplacement of a ca. 1.9 Ga quartz monzodiorite that host the ore at Aitik was related to subduction processes and volcanic arc formation, and synchronous with quartz vein stockwork formation and porphyry copper mineralisation. Highly saline aqueous (38 wt.% NaCl) fluid inclusions in the stockwork veins suggest entrapment at 300 degrees C and a pressure of nearly 3 kbar, a high pressure for a typical porphyry copper ore, but consistent with conditions at associated deep root zones of intrusion-related magmatic-hydrothermal systems. The highly saline fluid formed disseminated and vein-type ore of mainly chalcopyrite and pyrite within comagmatic volcaniclastic rocks, and caused potassic alteration (biotite, microcline) of the host rocks. The early porphyry copper mineralising event was followed, and largely overprinted, by CO2 and aqueous medium- to high-salinity (16-57 wt.% salts) fluids related to a ca. 1.8 Ga tectonic and metamorphic event (peak conditions 500-600 degrees C and 4-5 kbar). Extensive deformation of rocks and redistribution of metals occurred. Magnetite enrichment locally found within late veins, and late amphibole-scapolite and K feldspar alterations within the deposit, are some of the features at Aitik implying that aqueous fluids responsible for IOCG-mineralisation (200-500 degrees C and similar to 1 kbar) and extensive Na-Ca alteration in the region during the 1.8 Ga tectonic event also affected the Aitik rocks, possibly leading to addition of copper +/- gold.

1 - 42 of 42
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf