R. B. Pedersen

University of Bergen, Bergen, Hordaland, Norway

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Publications (89)135.02 Total impact

  • I. Okland, S. Huang, I.H. Thorseth, R.B. Pedersen
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    ABSTRACT: Hydrogen, methane and ammonium are important chemical species for chemolithotrophic microorganisms that sustain subsurface endolithic communities. It is well known that production of H2 through serpentinization of the primary Fe(II)-containing minerals, olivine and pyroxene, in ultramafic rocks and reduction of CO2 to CH4 are processes that occur at higher temperatures. Knowledge is, however, limited about these reactions under low-temperature conditions, and how they are affected by Fe(II)-containing secondary minerals, such as brucite and serpentine, which are commonly found in these environments. In this experimental study, we explored the formation of H2, CH4 and NH4 during low-temperature (25 °C) reactions between deionised water and 1) unaltered, 2) medium altered and 3) highly altered dunites, over a period of 99 days. Hydrogen was detected in all three experiments and the concentration increased over time. The O2 concentration decreased over time, but O2 was still present at significant levels when H2 started to form. This suggests that the H2 was formed locally at the surface of mineral grains rather than in the hypoxic solution. The highly altered dunite gave the highest and the unaltered dunite the lowest H2 concentrations, and while the O2 concentration decreased fast with the medium altered dunite, significant amounts of O2 still remained with the unaltered dunite at the end of the experiments. Both the medium and highly altered dunite gave O2 concentrations close to or below the detection limit during the last part of the experiment. Factors that likely affected the H2 production are Fe-content, mineralogy, dissolution rates and surface areas of the minerals as well as the presence of catalytic minerals such as chromite and magnetite. Methane was also detected and increased with time in all experiments. The results indicate that CH4 formation also occurred locally on the surface of minerals. Detection of both NH4 and NO3 in the aqueous solutions indicates that previously absorbed N-species were leached out during the experiment. Increasing NH4 and decreasing NO3 concentrations over time suggest NO3 reduction, likely catalysed by mineral surfaces. The results imply that low-temperature water–rock reactions in moderately to highly altered ultramafic rocks provide reduced chemical species that can be utilized as electron donors in energy-yielding metabolic processes by subsurface microorganisms. Such reactions could play an important role in sustaining subsurface microbial communities, particularly in ophiolites and near seafloor parts of the ultramafic oceanic lithosphere at slow-spreading mid-ocean ridges and possibly also in other rocks and sediments. The results suggest that brucite and possibly also serpentine may be more important sources of Fe(II) and thus H2 formation than olivine in low-temperature ultramafic systems. Formation of H2 in reducing microenvironments on mineral surfaces surrounded by oxic conditions increases the extent of H2 formation and the subsurface habitat for aerobic H2-oxidizing microorganisms.
    Chemical Geology 11/2014; 387:22–34. · 3.48 Impact Factor
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    ABSTRACT: Barite chimneys are known to form in hydrothermal systems where barium-enriched fluids generated by leaching of the oceanic basement are discharged and react with seawater sulfate. They also form at cold seeps along continental margins, where marine (or pelagic) barite in the sediments is remobilized because of subseafloor microbial sulfate reduction. We test the possibility of using multiple sulfur isotopes (δ34S, Δ33S, ∆36S) of barite to identify microbial sulfate reduction in a hydrothermal system. In addition to multiple sulfur isotopes, we present oxygen (δ18O) and strontium (87Sr/86Sr) isotopes for one of numerous barite chimneys in a low-temperature (~20 °C) venting area of the Loki's Castle black smoker field at the ultraslow-spreading Arctic Mid-Ocean Ridge (AMOR). The chemistry of the venting fluids in the barite field identifies a contribution of at least 10% of high-temperature black smoker fluid, which is corroborated by 87Sr/86Sr ratios in the barite chimney that are less radiogenic than in seawater. In contrast, oxygen and multiple sulfur isotopes indicate that the fluid from which the barite precipitated contained residual sulfate that was affected by microbial sulfate reduction. A sulfate reduction zone at this site is further supported by the multiple sulfur isotopic composition of framboidal pyrite in the flow channel of the barite chimney and in the hydrothermal sediments in the barite field, as well as by low SO4 and elevated H2S concentrations in the venting fluids compared with conservative mixing values. We suggest that the mixing of ascending H2- and CH4-rich high-temperature fluids with percolating seawater fuels microbial sulfate reduction, which is subsequently recorded by barite formed at the seafloor in areas where the flow rate is sufficient. Thus, low-temperature precipitates in hydrothermal systems are promising sites to explore the interactions between the geosphere and biosphere in order to evaluate the microbial impact on these systems.
    Geobiology 04/2014; · 3.04 Impact Factor
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    ABSTRACT: Formation pathways of ancient siliceous iron formations and related Fe isotopic fractionation are still not completely understood. Investigating these processes, however, is difficult as good modern analogues to ancient iron formations are scarce. Modern siliceous Fe oxyhydroxide deposits are found at marine hydrothermal vent sites, where they precipitate from diffuse, low temperature fluids along faults and fissures on the seafloor. These deposits exhibit textural and chemical features that are similar to some Phanerozoic iron formations, raising the question as to whether the latter could have precipitated from diffuse hydrothermal fluids rather than from hydrothermal plumes. In this study, we present the first data on modern Fe oxyhydroxide deposits from the Jan Mayen hydrothermal vent fields, Norwegian-Greenland Sea. The samples we investigated exhibited very low δ56Fe values between −2.09‰ and −0.66‰. Due to various degrees of partial oxidation, the Fe oxyhydroxides are with one exception either indistinguishable from low-temperature hydrothermal fluids from which they precipitated (−1.84‰ and −1.53‰ in δ56Fe) or are enriched in the heavy Fe isotopes. In addition, we investigated Fe isotope variations in Ordovician jasper beds from the Løkken ophiolite complex, Norway, which have been interpreted to represent diagenetic products of siliceous ferrihydrite precursors that precipitated in a hydrothermal plume, in order to compare different formation pathways of Fe oxyhydroxide deposits. Iron isotopes in the jasper samples have higher δ56Fe values (−0.38‰ to +0.89‰) relative to modern, high-temperature hydrothermal vent fluids (ca. −0.40‰ on average), supporting the fallout model. However, formation of the Ordovician jaspers by diffuse venting cannot be excluded, due to lithological differences of the subsurface of the two investigated vent systems. Our study shows that reliable interpretation of Fe isotope variations in modern and ancient marine Fe oxyhydroxide deposits depends on comprehensive knowledge of the geological context. Furthermore, we demonstrate that very negative δ56Fe values in such samples might not be the result of microbial dissimilatory iron reduction, but could be caused instead by inorganic reactions.
    Geochimica et Cosmochimica Acta 01/2014; 126:422–440. · 3.88 Impact Factor
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    ABSTRACT: Deep-sea hydrothermal vents are unique environments on Earth, as they host chemosynthetic ecosystems fuelled by geochemical energy with chemolithoautotrophic microorganisms at the basis of the foodwebs. Whereas discrete high-temperature venting systems have been studied extensively, the microbiotas associated with low temperature diffuse venting are not well understood. We analysed the structure and functioning of microbial communities in two diffuse venting sediments from the Jan Mayen vent fields in the Norwegian-Greenland Sea, applying an integrated 'omics' approach combining meta-transcriptomics, -proteomics and -genomics. PCR-independent three-domain community profiling showed that the two sediments hosted highly similar communities dominated by Epsilon-, Delta- and Gamma-Proteobacteria, besides ciliates, nematodes and various archaeal taxa. Active metabolic pathways were identified through transcripts and peptides, with genes of sulfur and methane oxidation, and carbon fixation pathways highly expressed, in addition to genes of aerobic and anaerobic (nitrate and sulfate) respiratory chains. High expression of chemotaxis and flagella genes reflected a lifestyle in a dynamic habitat rich in physico-chemical gradients. The major metabolic pathways could be assigned to distinct taxonomic groups, thus enabling hypotheses about the function of the different pro- and eukaryotic taxa. This study advances our understanding of the functioning of microbial communities in diffuse hydrothermal venting sediments.
    Environmental Microbiology 09/2013; · 6.24 Impact Factor
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    ABSTRACT: The use of DNA as a marker for prey inside the gut of predators has been instrumental in further understanding of known and unknown interactions. Molecular approaches are in particular useful in unavailable environments like the deep sea. Trophic interactions in the deep sea are difficult to observe in situ, correct deep-sea experimental laboratory conditions are difficult to obtain, animals rarely survive the sampling, or the study organisms feed during the sampling due to long hauls. Preliminary studies of vent and seep systems in the Nordic Seas have identified the temperate-cold-water pelagic amphipod Themisto abyssorum as a potentially important predator in these chemosynthetic habitats. However, the prey of this deep-sea predator is poorly known, and we applied denaturing high performance liquid chromatography (DHPLC) to investigate the predator-prey interactions of T. abyssorum in deep-water vent and seep systems. Two deep-water hydrothermally active localities (The Jan Mayen and Loki's Castle vent fields) and one cold seep locality (The Håkon Mosby mud volcano) in the Nordic Seas were sampled, genomic DNA of the stomachs of T. abyssorum was extracted, and 18S rDNA gene was amplified and used to map the stomach content. We found a wide range of organisms including micro-eukaryotes, metazoans and detritus. Themisto abyssorum specimens from Loki's Castle had the highest diversity of prey. The wide range of prey items found suggests that T. abyssorum might be involved in more than one trophic level and should be regarded as an omnivore and not a strict carnivore as have previously been suggested.
    Molecular Ecology 09/2013; · 6.28 Impact Factor
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    ABSTRACT: The Epsilonproteobacteria, including members of the genus Sulfurovum, are regarded as important primary producers in hydrothermal systems. However, their in situ gene expression in this habitat has so far not been investigated. We report a metatranscriptomic analysis of a Sulfurovum-dominated biofilm from one of the chimneys at the Loki's Castle hydrothermal system, located at the Arctic Mid Ocean Ridge. Transcripts involved in hydrogen oxidation, oxidation of sulfur species, aerobic respiration and denitrification were abundant and mostly assigned to Sulfurovum, indicating that members of this genus utilize multiple chemical energy sources simultaneously for primary production. Sulfurovum also seemed to have a diverse expression of transposases, potentially involved in horizontal gene transfer. Other transcripts were involved in CO2 fixation by the reverse TCA cycle, the CRISPR-Cas system, heavy metal resistance, and sensing and responding to changing environmental conditions. Through pyrosequencing of PCR amplified 16S rRNA genes, the Sulfurovum-dominated biofilm was compared with another biofilm from the same chimney, revealing a large shift in the community structure of Epsilonproteobacteria-dominated biofilms over a few metres.
    Environmental Microbiology Reports 04/2013; 5(2):282-90. · 3.26 Impact Factor
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    ABSTRACT: Water-rock interactions in ultramafic lithosphere generate reduced chemical species such as hydrogen that can fuel subsurface microbial communities. Sampling of this environment is expensive and technically demanding. However, highly accessible, uplifted oceanic lithospheres emplaced onto continental margins (ophiolites) are potential model systems for studies of the subsurface biosphere in ultramafic rocks. Here, we describe a microbiological investigation of partially serpentinized dunite from the Leka ophiolite (Norway). We analysed samples of mineral coatings on subsurface fracture surfaces from different depths (10-160 cm) and groundwater from a 50-m-deep borehole that penetrates several major fracture zones in the rock. The samples are suggested to represent subsurface habitats ranging from highly anaerobic to aerobic conditions. Water from a surface pond was analysed for comparison. To explore the microbial diversity and to make assessments about potential metabolisms, the samples were analysed by microscopy, construction of small subunit ribosomal RNA gene clone libraries, culturing and quantitative-PCR. Different microbial communities were observed in the groundwater, the fracture-coating material and the surface water, indicating that distinct microbial ecosystems exist in the rock. Close relatives of hydrogen-oxidizing Hydrogenophaga dominated (30% of the bacterial clones) in the oxic groundwater, indicating that microbial communities in ultramafic rocks at Leka could partially be driven by H2 produced by low-temperature water-rock reactions. Heterotrophic organisms, including close relatives of hydrocarbon degraders possibly feeding on products from Fischer-Tropsch-type reactions, dominated in the fracture-coating material. Putative hydrogen-, ammonia-, manganese- and iron-oxidizers were also detected in fracture coatings and the groundwater. The microbial communities reflect the existence of different subsurface redox conditions generated by differences in fracture size and distribution, and mixing of fluids. The particularly dense microbial communities in the shallow fracture coatings seem to be fuelled by both photosynthesis and oxidation of reduced chemical species produced by water-rock reactions.
    Geobiology 03/2013; · 3.04 Impact Factor
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    ABSTRACT: In marine sediments archaea often constitute a considerable part of the microbial community, of which the Deep Sea Archaeal Group (DSAG) is one of the most predominant. Despite their high abundance no members from this archaeal group have so far been characterized and thus their metabolism is unknown. Here we show that the relative abundance of DSAG marker genes can be correlated with geochemical parameters, allowing prediction of both the potential electron donors and acceptors of these organisms. We estimated the abundance of 16S rRNA genes from Archaea, Bacteria, and DSAG in 52 sediment horizons from two cores collected at the slow-spreading Arctic Mid-Ocean Ridge, using qPCR. The results indicate that members of the DSAG make up the entire archaeal population in certain horizons and constitute up to ~50% of the total microbial community. The quantitative data were correlated to 30 different geophysical and geochemical parameters obtained from the same sediment horizons. We observed a significant correlation between the relative abundance of DSAG 16S rRNA genes and the content of organic carbon (p < 0.0001). Further, significant co-variation with iron oxide, and dissolved iron and manganese (all p < 0.0000), indicated a direct or indirect link to iron and manganese cycling. Neither of these parameters correlated with the relative abundance of archaeal or bacterial 16S rRNA genes, nor did any other major electron donor or acceptor measured. Phylogenetic analysis of DSAG 16S rRNA gene sequences reveals three monophyletic lineages with no apparent habitat-specific distribution. In this study we support the hypothesis that members of the DSAG are tightly linked to the content of organic carbon and directly or indirectly involved in the cycling of iron and/or manganese compounds. Further, we provide a molecular tool to assess their abundance in environmental samples and enrichment cultures.
    Frontiers in Microbiology 01/2013; 4:299. · 3.90 Impact Factor
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    ABSTRACT: Microbial communities and their associated metabolic activity in marine sediments have a profound impact on global biogeochemical cycles. Their composition and structure are attributed to geochemical and physical factors, but finding direct correlations has remained a challenge. Here we show a significant statistical relationship between variation in geochemical composition and prokaryotic community structure within deep-sea sediments. We obtained comprehensive geochemical data from two gravity cores near the hydrothermal vent field Loki's Castle at the Arctic Mid-Ocean Ridge, in the Norwegian-Greenland Sea. Geochemical properties in the rift valley sediments exhibited strong centimeter-scale stratigraphic variability. Microbial populations were profiled by pyrosequencing from 15 sediment horizons (59,364 16S rRNA gene tags), quantitatively assessed by qPCR, and phylogenetically analyzed. Although the same taxa were generally present in all samples, their relative abundances varied substantially among horizons and fluctuated between Bacteria- and Archaea-dominated communities. By independently summarizing covariance structures of the relative abundance data and geochemical data, using principal components analysis, we found a significant correlation between changes in geochemical composition and changes in community structure. Differences in organic carbon and mineralogy shaped the relative abundance of microbial taxa. We used correlations to build hypotheses about energy metabolisms, particularly of the Deep Sea Archaeal Group, specific Deltaproteobacteria, and sediment lineages of potentially anaerobic Marine Group I Archaea. We demonstrate that total prokaryotic community structure can be directly correlated to geochemistry within these sediments, thus enhancing our understanding of biogeochemical cycling and our ability to predict metabolisms of uncultured microbes in deep-sea sediments.
    Proceedings of the National Academy of Sciences 10/2012; 109(42):E2846-55. · 9.81 Impact Factor
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    ABSTRACT: The present investigation uncovers various pieces of evidence for the possible biologically induced mineralization in iron mats associated with a pH-neutral spring in the Borra caves, Vishakhapatnam, India. Electron microscopy [scanning electron microscopy (SEM) and transmission electron microscopy (TEM)] demonstrated large numbers of (i) hollow tubes (diameter ∼1 μm) resembling sheaths of the iron-oxidizing bacteria Leptothrix, (ii) thin (diameter <1 μm) solid fibers of uncertain origin, (iii) nanoscale subspherical to irregularly shaped particles encrusting tubes and fibers, and (iv) aggregates of broken and partially disintegrated sheaths, fibers, and particles embedded in extracellular polymeric substances (EPS) occasionally including microbial cells. X-ray microanalyses by energy dispersive spectroscopy (EDS) revealed that the mat accumulated largely Fe but also smaller amounts of Si and traces of P and Ca. Particles rich in Si and Al (possibly kaolinite) and Ca (carbonate) were also observed. High-resolution TEM/EDS of unstained ultrathin sections suggests that microbial sheaths were highly mineralized by amorphous to cryptocrystalline Fe-rich phases and less frequently by other fine-grained and fibrous authigenic claylike minerals. Total number of microorganisms in the iron mats was 5.8×10(5) cells, g sed(-1) (wet weight). Analysis of the 16S rRNA gene diversity revealed microorganisms assigned to eight different phyla [Proteobacteria (62%), Chloroflexi (8%), Bacteroidetes (7%), Planctomycetes (1%), Actinobacteria (5%), Acidobacteria (6%), Nitrospira (1%), Firmicutes (5%)]. Within the Proteobacteria, Betaproteobacteria was the predominant class, which accounted for 28% of the sequences. Within this class some obvious similarities between the obtained sequences and sequences from other cave systems could be seen, especially sequences affiliated with Leptothrix, Siderooxidans, Crenothrix, Comamonadaceae, Dechloromonas, and many uncultured Betaproteobacteria. Four (4%) of the sequences could not be assigned to phylum level but were affiliating with the candidate division TM7 (2%), candidate division OP11 (1%), and candidate division WWE3 (1%). The results allow us to infer a possible relationship of microbial sheaths, EPS, and the iron precipitates to microbial community diversity in the Borra cave springs. Understanding biogenic iron oxides in caves has important astrobiological applications as it provides a potential tool for the detection of extraterrestrial life.
    Astrobiology 04/2012; 12(4):327-46. · 2.80 Impact Factor
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    ABSTRACT: The Mid-Cayman spreading centre is an ultraslow-spreading ridge in the Caribbean Sea. Its extreme depth and geographic isolation from other mid-ocean ridges offer insights into the effects of pressure on hydrothermal venting, and the biogeography of vent fauna. Here we report the discovery of two hydrothermal vent fields on the Mid-Cayman spreading centre. The Von Damm Vent Field is located on the upper slopes of an oceanic core complex at a depth of 2,300 m. High-temperature venting in this off-axis setting suggests that the global incidence of vent fields may be underestimated. At a depth of 4,960 m on the Mid-Cayman spreading centre axis, the Beebe Vent Field emits copper-enriched fluids and a buoyant plume that rises 1,100 m, consistent with >400 °C venting from the world's deepest known hydrothermal system. At both sites, a new morphospecies of alvinocaridid shrimp dominates faunal assemblages, which exhibit similarities to those of Mid-Atlantic vents.
    Nature Communications 01/2012; 3:620. · 10.74 Impact Factor
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    ABSTRACT: The Mid-Cayman spreading centre is an ultraslow-spreading ridge in the Caribbean Sea. Its extreme depth and geographic isolation from other mid-ocean ridges offer insights into the effects of pressure on hydrothermal venting, and the biogeography of vent fauna. Here we report the discovery of two hydrothermal vent fields on the Mid-Cayman spreading centre. The Von Damm Vent Field is located on the upper slopes of an oceanic core complex at a depth of 2,300 m. High-temperature venting in this off-axis setting suggests that the global incidence of vent fields may be underestimated. At a depth of 4,960 m on the Mid-Cayman spreading centre axis, the Beebe Vent Field emits copper-enriched fluids and a buoyant plume that rises 1,100 m, consistent with >400 °C venting from the world's deepest known hydrothermal system. At both sites, a new morphospecies of alvinocaridid shrimp dominates faunal assemblages, which exhibit similarities to those of Mid-Atlantic vents.
    Nature Communications 01/2012; 3:620. · 10.74 Impact Factor
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    ABSTRACT: Hydrothermal vent systems harbor rich microbial communities ranging from aerobic mesophiles to anaerobic hyperthermophiles. Among these, members of the archaeal domain are prevalent in microbial communities in the most extreme environments, partly because of their temperature-resistant and robust membrane lipids. In this study, we use geochemical and molecular microbiological methods to investigate the microbial diversity in black smoker chimneys from the newly discovered Loki's Castle hydrothermal vent field on the Arctic Mid-Ocean Ridge (AMOR) with vent fluid temperatures of 310–320 °C and pH of 5.5. Archaeal glycerol dialkyl glycerol tetraether lipids (GDGTs) and H-shaped GDGTs with 0–4 cyclopentane moieties were dominant in all sulfide samples and are most likely derived from both (hyper)thermophilic Euryarchaeota and Crenarchaeota. Crenarchaeol has been detected in low abundances in samples derived from the chimney exterior indicating the presence of Thaumarchaeota at lower ambient temperatures. Aquificales and members of the Epsilonproteobacteria were the dominant bacterial groups detected. Our observations based on the analysis of 16S rRNA genes and biomarker lipid analysis provide insight into microbial communities thriving within the porous sulfide structures of active and inactive deep-sea hydrothermal vents. Microbial cycling of sulfur, hydrogen, and methane by archaea in the chimney interior and bacteria in the chimney exterior may be the prevailing biogeochemical processes in this system.
    Geobiology 01/2012; 10(6):548-561. · 3.04 Impact Factor
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    ABSTRACT: The Island of Jan Mayen is situated at 71°N and 8.3°W in the north Atlantic at the southern edge of the Jan Mayen fracture zone. It is a volcanic island extending for about 53 km from SW towards NE. Maximum width of the island is 15.8 km at its northern tip, while minimum width is only 2.5 km at its centre. The island is built up by two main edifices that have erupted repeatedly, namely Sør-Jan and Nord-Jan or Beerenberg. Petrology of the two edifices is strikingly different. In the south volcanic products are characterized by evolved basalts and trackites to rhyolites. Crystals of ol, cpx, opx are small and in low portions in the rocks. Plg is however common. A 220 m thick plinian formation is found at Borga location in Sør Jan resting on top of a palaeo beach at the altitude of some 170-200 m. This we interpret as caldera formation on Sør Jan and the beach uplift a later stage resurgent activity within the caldera. Further the post caldera volcanic activity all indicates that magma has been stored for shorter or longer time before eruption on surface. Nord Jan or Beerenberg on the other hand shows more primitive magma evolution indicating its younger age. At the flanks of Beerenberg (e.g. Esk krater and Kapp Fishburn) volcanic activity is characterized by ankaramitic magma, with ol, opx and cpx (to lesser extent) in the size range of 1-4 cm and portions up 30% of the whole rock. Plg is absent in these rocks. Volcanic vents closer to the summit area of Beerenberg have smaller ol, cpx and opx (to a lesser extent) and in much lower portion than at the flank eruption sites. These rocks also all carry plg, indicating magma reservoir development and shallow magma residence towards the centre of Beerenberg. We will present a model for the evolution of the Jan Mayen Island, as a migrating volcanism from South towards North. At first the volcanism is characterized by mantle derived magma, namely ankaramites. Prolonged activity forms magma chambers in the crust that eventually lead to caldera formation at the volcano. Post caldera activity is characterized by evolved basalts and trackites.
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: Jan Mayen is a volcanic island situated at 71°N and 8°W. The Island is build up of two main edifices, Sør Jan and Nord Jan (Beerenberg). Volcanic activity on the island is little known, and however at least 4 eruptions are documented at the island since early 18th century. An expedition to the island in summer 2011 reveals that first of these eruptions formed the tuffcone Eggøyan in 1732 AD. The Eggøyan tuffcone is situated at the north east foot of Beerenberg volcano, about 2.5 km from the coastline marked by Valberget. The tuffcone is about 1.5 km in diameter and emerges from about 35 m depth to reach the altitude of at least 217 m above sea level. Pre Eggøyan Lava flows on the sandy coast west of the edifice are covered by up to 1.6 m of ash some 3 km from the vent. These lava flows have been suggested to be formed in the 1732 eruption and the 1818 eruption of Jan Mayen. However, they are covered with the Eggøyan tephra and thus considerable older. Volcanic tephra from the Eggøyan eruption forms the uppermost tephra layer on the Eastern flanks of Beerenberg. Contemporary description of the 1732 eruption, tell of violent explosive eruption at the east side of Beerenberg observed by German whalers for 28 hours, while sailing past the island in May that year. A Dutch wailer group arriving to the island in June that year, report fine ash covering the island in such a way they sink up to mid leg into it. Our study this summer shows that the only eruption these descriptions can report to are the Eggøyan eruption, dating it precisely to the spring 1732. The eruptive products are made up of frothy glass and ol, cpx and opx crystals, which characterize the flank eruptions of Beerenberg. In this presentation we shall present first results of intense fragmentation of deep gas rich ankaramitic magma from the Jan Mayen are and its interaction with seawater in shallow coastal settings.
    AGU Fall Meeting Abstracts. 12/2011;
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    ABSTRACT: Detrital zircon U–Pb and Lu–Hf isotope data from Neoproterozoic to Cretaceous sandstones exposed in eastern Greenland, 70°30′–74°N, are reported to characterize and evaluate the provenance from Greenland during pre-breakup and post-breakup sedimentation in the Norwegian–Greenland Sea. Middle Devonian to Lower Cretaceous samples all show similar detrital zircon age distributions characterized by variable Archean populations, abundant Proterozoic populations ranging from ca. 2000 to 900Ma and a Caledonian population peaking at ca. 440Ma. Neoproterozoic sediments of the Eleonore Bay Supergroup give a more narrow age distribution with a dominant age peak at 1100 to 1000Ma, a secondary peak at 1700–1400Ma, and rare Archean to Paleoproterozoic ages. We suggest that the Neoproterozoic metasediments of the Krummedal and Smallefjord sequences and the Eleonore Bay Supergroup together with Caledonian rocks of age ca. 440Ma and variable amounts of Paleoproterozoic basement were the main sources for the analyzed Middle Devonian to Lower Cretaceous sandstones. The scarcity of Archean zircons could indicate a rather limited role of the Archean basement rocks of the eastern Greenland Caledonian orogenic belt as a source for some of the analyzed younger sedimentary rocks.The composite age distribution of the zircons from the Phanerozoic eastern Greenland samples, i.e., a minor Archean to Paleoproterozoic (Siderian and Rhyacian) component, abundant Paleoproterozoic (Orosian) to Neoproterozoic (Tonian) ages, and a significant Lower Silurian (Caledonian) signal, is very similar to zircon age distributions reported for Upper Cretaceous turbidite sandstones from large parts of the Norwegian Sea, and to the age distributions determined in this study for three Oligocene sandstone samples from east of Jan Mayen Island. Upper Cretaceous to Paleocene Norwegian Sea sandstones, known to be derived from Norway, differ from this eastern Greenland-derived pattern by a near total lack of Archean zircon ages and a less pronounced Caledonian component. Wide detrital zircon age spectra with a distinct Silurian group and a population of Neoarchean zircons is thus suggested as indicative of sediments sourced from the studied area of eastern Greenland.The Hf isotopic compositions of detrital zircons suggest that Eoarchean crust derived from a source with chondritic Lu/Hf ratios at ca. 3900–3700Ma contributed to zircon-forming processes in the source area for the eastern Greenland sandstones until ca. 2300Ma. The Caledonian orogeny in this area was probably a crust reworking event with a limited contribution from depleted mantle.
    Sedimentary Geology 01/2011; 238(3):254-267. · 1.80 Impact Factor
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    ABSTRACT: The incipient alteration of basaltic glass to palagonite in recent seafloor lavas from the arctic Mohns Ridge was studied by complimentary high-spatial-resolution geochemical techniques: TEM-EDS (transmission electron microscopy energy dispersive X-ray spectroscopy) and NanoSIMS (nano-scale secondary ion mass spectrometry). Rounded to elongated pores 0.5–2μm across were found embedded in compact palagonite that have sizes and shapes comparable to microbial cells. In-situ elemental mapping revealed that the micropore rims are comparable in composition to the bulk palagonite and that some are enriched in manganese. Elevated concentrations of carbon and nitrogen were also found in some of the micropores. Hence these structures are interpreted as fossilised bacteriomorphs of endolithic microorganisms that inhabited fractures in the basaltic glass. The preferential accumulation of Mn in some of the cell encrustations suggests the mineralisation of Mn-oxidising bacteria. These data provide further evidence for the involvement of microorganisms in the colonisation and chemical alteration of recent seafloor volcanic glass and identify micro-scale Mn enrichments associated with micropores as a promising biosignature in such rocks.
    Chemical Geology - CHEM GEOL. 01/2011; 289(1):154-162.
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    ABSTRACT: Newly acquired, sequentially spaced, high-resolution near-infrared spectra across the central section of crater Copernicus’ interior have been analyzed using a range of complementary techniques and indexes.We have developed a new interpretative method based on a multiple stage normalization process that appears to both confirm and expand on previous mineralogical estimations and mapping. In broad terms, the interpreted distribution of the principle mafic species suggests an overall composition of surface materials dominated by calcium-poor pyroxenes and minor olivine but with notable exceptions: the southern rim displays strong ca-rich pyroxene absorption features and five other locations, the uppermost northern crater wall, opposite rim sections facing the crater floor, and the central peak Pk1 and at the foot of Pk3, show instead strong olivine signatures.We also propose impact glass an alternative interpretation to the source of the weak but widespread olivine-like spectral signature found in low-reflectance samples, since it probably represents a major regolith constituent and component in large craters such as Copernicus.The high quality and performance of the SIR-2 data allows for the detection of diagnostic key mineral species even when investigating spectral samples with very subdued absorption features, confirming the intrinsic high-quality value of the returned data.
    Icarus 01/2011; 213(1):43-63. · 3.16 Impact Factor
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    ABSTRACT: Detrital zircon grains in coarse-grained sedimentary rocks of the Noisy formation, (traditionally considered as the H6 unit of the uppermost Hooggenoeg Formation) in the Paleoarchean Barberton Greenstone Belt (BGB) South Africa, are investigated by laser ablation (LA)-ICP-MS to constrain their U–Pb and 207Pb/206Pb ages for depositional age and provenance determination. Drill core and field observations indicate that these rocks are clastic polymictitic diamictites and sandstones. A wide range in 207Pb/206Pb ages between ca. 3600 and 3430Ma is reported. The youngest detrital zircon grain identified has an age of 3432±10Ma, constraining the maximum depositional age of the sedimentary sequence and the formation of a major underlying erosional unconformity. The youngest grains correspond in age to the ca. 3460–3430Ma tonalite–trondjemite–granodiorite (TTG) gneisses of the Stoltzburg terrane and felsic intrusions of the uppermost Hooggenoeg Formation that constitute most of the Songimvelo Block of the BGB on the Kaapvaal craton. The 207Pb/206Pb ages of the oldest grains identified corresponds to plutonic sources identified in older proto-continental blocks of the Kaapvaal craton, namely the ca. 3509Ma Steynsdorp Block and ca. 3667–3223Ma Ancient Gneiss Complex (AGC). This new data indicates provenancial linkage between the Songimvelo Block and older proto-continental blocks exposed on the Kaapvaal craton at ca. 3432Ma. It is argued here, that the Noisy formation is a remnant of the earliest tectonic basin in the BGB, that developed during major tectonic accretion and uplift at ca. 3432Ma that lead to formation of the erosional unconformity. In conjunction with new drill core and field observations, the geochronological constraints presented here support plate-tectonic processes operating in the proto-Kaapvaal craton that resulted in its formation as a stable continental landmass as early as ca. 3432Ma.
    Precambrian Research - PRECAMBRIAN RES. 01/2011; 191(1):85-99.
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    ABSTRACT: The chemical composition as well as the stable and radiogenic isotope signatures of hydrothermal fluids from the Loki's Castle vent field, located at the Mohns-Knipovich bend in the Norwegian-Greenland Sea (73°N), are substantially different from sediment-starved mid-ocean ridge hydrothermal systems. Geochemical studies of the hydrothermal vent fluids and the adjacent rift valley sediments provide insights into the influence of sediments on the hydrothermal fluid composition and provide constraints on acting redox conditions. Additionally, they reflect the degree of fluid-rock-sediment interaction at this arctic hydrothermal vent field. Here we present an overview of the geochemical characteristics of the hydrothermal and sedimentary components at Loki's Castle, obtained during expeditions in 2008, 2009 and 2010, with emphasis on the stable and radiogenic isotope signatures. We compare these data with other sediment-influenced and sediment-starved mid-ocean ridge hydrothermal systems. The hydrothermal vent fluids are characterized by a pH of ˜ 5.5 and by elevated concentrations of methane, hydrogen and ammonia, which reflect a sedimentary contribution. delta13CDIC (dissolved inorganic carbon) are depleted relative to mantle carbon values, consistent with an organic carbon input. The delta18OH2O values of the vents fluids are enriched compared to background bottom seawater, whereas the deltaD values are not. 87Sr/86Sr ratios are more radiogenic than those characteristic of un-sedimented mid-ocean ridge vent fluids. S-isotope data reflect mixing of a MORB source with sulphide derived from reduced seawater sulphate. To document the background sediment input of the ridge system, short gravity cores and up to 18 m long piston cores were recovered from various localities in the rift valley. The pore-fluid isotope chemistries of the sediments show vertical gradients that primarily reflect diagenesis and degradation of organic matter. The vertical gradient is locally enhanced as a consequence of elevated temperature or higher organic carbon sediment concentrations. Our data suggests that buried rift valley sediments may significantly contribute to the Loki's Castle hydrothermal fluids leading to hydrothermal fluids distinct from un-sedimented mid-ocean ridge systems.
    AGU Fall Meeting Abstracts. 12/2010;

Publication Stats

396 Citations
135.02 Total Impact Points

Institutions

  • 2002–2014
    • University of Bergen
      • • Centre for Geobiology
      • • Department of Earth Science
      Bergen, Hordaland, Norway
  • 2007
    • Academy of Sciences of the Czech Republic
      Praha, Praha, Czech Republic
  • 2005
    • Oregon State University
      Corvallis, Oregon, United States