| 1. |
- Billström, Kjell, et al.
(författare)
-
Sandstone-hosted Pb-Zn deposits along the margin of the Scandinavian Caledonides and their possible relationship with nearby Pb-Zn vein mineralisation
- 2020
-
Ingår i: Ore Geology Reviews. - : Elsevier BV. - 0169-1368 .- 1872-7360. ; 127
-
Forskningsöversikt (refereegranskat)abstract
- Numerous sandstone-hosted Pb-Zn deposits occur along the present-day erosional front of the eastern Scandinavian Caledonides. The largest deposit is Laisvall (64.3 Mt at 4.0% Pb, 0.6% Zn and 9.0 g/t Ag) and since mineralisations generally share similar characteristics (reminding of both SEDEX and MVT-style) the term Laisvall-type has often been used. Typically, mineralised zones occur along sedimentary bedding and consist of disseminated galena and sphalerite and lesser amounts of calcite, fluorite, baryte, pyrite and sericite forming a cement that fill interstitial pores in Neoproterozoic/Eocambrian (e.g. Laisvall) to Cambrian (e.g. Vassbo) sandstones. Deposits occur both in autochtonous and allochtonous sedimentary rocks, and a broad consensus exists about their epigenetic nature, their spatial relationships to syn-sedimentary faults and that ore fluids have scavenged metals from the crystalline basement. However, the detailed ore depositional history and the timing of ore deposition have remained more controversial. New analyses aimed to complement earlier Rb-Sr data (crush-leach technique using sphalerite) fail to support a published three-point isochron age of 467 +/- 5 Ma. This is probably due to syn-ore mixing between fluids carrying isotopically variable strontium and inherited problems to analyse sphalerite grains that strictly were deposited from a single ore pulse. Tentatively, strontium in the ores originate from a mix of components derived from the basement, seawater and the local sedimentary host sequences. The lead component has highly radiogenic compositions, and data define sub-parallel linear arrays interpreted to essentially represent mixing of isotopically different types of lead released from regional basement rocks. There are obvious similarities when comparing features of deposits representing two Pb-Zn ore styles, the sandstone-hosted dissemination and the fracture-controlled mineralisation in the granite-dominated basement occurring further east of the Caledonian margin. These include low temperature brines responsible for mineral deposition, the mineralogy and the nature of Rb-Sr and Pb isotope data. We suggest that these types of mineralisation have a common origin and time of emplacement, but it is elusive to propose a well-constrained age. Nonetheless, field observations and other evidence suggest that ore formation is due to large-scale fluid flow triggered by the transition from an extensional to compressional tectonic setting at about 500 Ma. Connected to this mid-Cambrian stage was the development of syn-sedimentary faults and fractures in the basement and in overlying consolidated sandstones. The opening of such zones of weakness enabled a movement of ore-forming fluids infilling pore space in sandstones (disseminated ore) and fractures in the basement (vein ore).
|
|
| 2. |
- Charette, M, et al.
(författare)
-
Coastal ocean and shelf-sea biogeochemical cycling of trace elements and isotopes: lessons learned from GEOTRACES
- 2016
-
Ingår i: Philosopical Transactions of the Royal Society A. - : The Royal Society. - 1364-503X. ; 374:2081
-
Forskningsöversikt (refereegranskat)abstract
- Continental shelves and shelf seas play a central role in the global carbon cycle. However,their importance with respect to trace element and isotope (TEI) inputs to ocean basinsis less well understood. Here, we present major findings on shelf TEI biogeochemistryfrom the GEOTRACES programme as well as a proof of concept for a new method toestimate shelf TEI fluxes. The case studies focus on advances in our understanding of TEIcycling in the Arctic, transformations within a major river estuary (Amazon), shelf sedimentmicronutrient fluxes and basin-scale estimates of submarine groundwater discharge. Theproposed shelf flux tracer is 228-radium (T1/2 =5.75 yr), which is continuously supplied tothe shelf from coastal aquifers, sediment porewater exchange and rivers. Model-derived shelf228Ra fluxes are combined with TEI/ 228Ra ratios to quantify ocean TEI fluxes from thewestern North Atlantic margin. The results from this new approach agree well with previousestimates for shelf Co, Fe, Mn and Zn inputs and exceed published estimates of atmosphericdeposition by factors of approximately 3–23. Lastly, recommendations are made for additionalGEOTRACES process studies and coastal margin-focused section cruises that will help refinethe model and provide better insight on the mechanisms driving shelf-derived TEI fluxesto the ocean.This article is part of the themed issue ‘Biological and climatic impacts of ocean trace elementchemistry’.
|
|
| 3. |
- Conley, Daniel J., et al.
(författare)
-
Biosilicification drives a decline of dissolved si in the oceans through geologic time
- 2017
-
Ingår i: Frontiers in Marine Science. - : Frontiers Media SA. - 2296-7745. ; 4:DEC
-
Forskningsöversikt (refereegranskat)abstract
- Biosilicification has driven variation in the global Si cycle over geologic time. The evolution of different eukaryotic lineages that convert dissolved Si (DSi) into mineralized structures (higher plants, siliceous sponges, radiolarians, and diatoms) has driven a secular decrease in DSi in the global ocean leading to the low DSi concentrations seen today. Recent studies, however, have questioned the timing previously proposed for the DSi decreases and the concentration changes through deep time, which would have major implications for the cycling of carbon and other key nutrients in the ocean. Here, we combine relevant genomic data with geological data and present new hypotheses regarding the impact of the evolution of biosilicifying organisms on the DSi inventory of the oceans throughout deep time. Although there is no fossil evidence for true silica biomineralization until the late Precambrian, the timing of the evolution of silica transporter genes suggests that bacterial silicon-related metabolism has been present in the oceans since the Archean with eukaryotic silicon metabolism already occurring in the Neoproterozoic. We hypothesize that biological processes have influenced oceanic DSi concentrations since the beginning of oxygenic photosynthesis.
|
|
| 4. |
- Dastoor, Ashu, et al.
(författare)
-
Arctic mercury cycling
- 2022
-
Ingår i: Nature Reviews Earth & Environment. - : Springer Nature. - 2662-138X. ; 3:4, s. 270-286
-
Forskningsöversikt (refereegranskat)abstract
- Anthropogenic mercury (Hg) emissions have driven marked increases in Arctic Hg levels,which are now being impacted by regional warming, with uncertain ecological consequences. This Review presents a comprehensive assessment of the present-day total Hg mass balance in the Arctic. Over 98% of atmospheric Hg is emitted outside the region and is transported to the Arctic via long-range air and ocean transport. Around two thirds of this Hg is deposited in terrestrial ecosystems, where it predominantly accumulates in soils via vegetation uptake. Rivers and coastal erosion transfer about 80 Mg year−1 of terrestrial Hg to the Arctic Ocean, in approximate balance with modelled net terrestrial Hg deposition in the region. The revised Arctic Ocean Hg mass balance suggests net atmospheric Hg deposition to the ocean and that Hg burial in inner-shelf sediments is underestimated (up to >100%), needing seasonal observations of sediment-oceanHg exchange. Terrestrial Hg mobilization pathways from soils and the cryosphere (permafrost, ice, snow and glaciers) remain uncertain. Improved soil, snowpack and glacial Hg inventories, transfer mechanisms of riverine Hg releases under accelerated glacier and soil thaw, coupled atmosphere– terrestrial modelling and monitoring of Hg in sensitive ecosystems such as fjords can help toanticipate impacts on downstream Arctic ecosystems.
|
|
| 5. |
- Fehr, Manuela A., et al.
(författare)
-
Iron isotope variations in Holocene sediments of the Gotland Deep, Baltic Sea
- 2008
-
Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 72:3, s. 807-826
-
Forskningsöversikt (refereegranskat)abstract
- Holocene sediments from the Gotland Deep basin in the Baltic Sea were investigated for their Fe isotopic composition in order to assess the impact of changes in redox conditions and a transition from freshwater to brackish water on the isotope signature of iron. The sediments display variations in delta Fe-56 (differences in the Fe-56/Fe-54 ratio relative to the IRMM-14 standard) from -0.27 +/- 0.09 parts per thousand to +0.21 +/- 0.08 parts per thousand. Samples deposited in a mainly limnic environment with oxygenated bottom water have a mean delta Fe-56 of +0.08 +/- 0.13 parts per thousand, which is identical to the mean Fe isotopic composition of igneous rocks and oxic marine sediments. In contrast, sediments that formed in brackish water under periodically euxinic conditions display significantly lighter Fe isotope signatures with a mean delta Fe-56 of -0.14 +/- 0.19 parts per thousand. Negative correlations of the delta Fe-56 values with the Fe/Al ratio and S content of the samples suggest that the isotopically light Fe in the periodically euxinic samples is associated with reactive Fe enrichments and sulfides. This is supported by analyses of pyrite separates from this unit that have a mean Fe isotopic composition of -1.06 +/- 0.20 parts per thousand for delta Fe-56. The supply of additional Fe with a light Fe isotopic signature can be explained with the shelf to basin Fe shuttle model. According to the Fe shuttle model, oxides and benthic ferrous Fe that is derived from dissimilatory iron reduction from shelves is transported and accumulated in euxinic basins. The data furthermore suggest that the euxinic water has a negative dissolved delta Fe-56 value of about -1.4 parts per thousand to -0.9 parts per thousand. If negative Fe isotopic signatures are characteristic for euxinic sediment formation, widespread euxinia in the past might have shifted the Fe isotopic composition of dissolved Fe in the ocean towards more positive delta Fe-56 values.
|
|
| 6. |
- Fång, Johan, et al.
(författare)
-
Spatial and temporal trends of the Stockholm Convention POPs in mothers' milk - a global review
- 2015
-
Ingår i: Environmental Science and Pollution Research. - : Springer Science and Business Media LLC. - 0944-1344 .- 1614-7499. ; 22:12, s. 8989-9041
-
Forskningsöversikt (refereegranskat)abstract
- Persistent organic pollutants (POPs) have been of environmental and health concern for more than half a century and have their own intergovernmental regulation through the Stockholm Convention, from 2001. One major concern is the nursing child's exposure to POPs, a concern that has led to a very large number of scientific studies on POPs in mothers' milk. The present review is a report on the assessment on worldwide spatial distributions of POPs and of their temporal trends. The data presented herein is a compilation based on scientific publications between 1995 and 2011. It is evident that the concentrations in mothers' milk depend on the use of pesticides and industrial chemicals defined as POPs. Polychlorinated biphenyls (PCBs) and dioxins are higher in the more industrialized areas, Europe and Northern America, whereas pesticides are higher in Africa and Asia and polybrominated diphenyl ethers (PBDEs) are reported in higher concentrations in the USA. POPs are consequently distributed to women in all parts of the world and are thus delivered to the nursing child. The review points out several major problems in the reporting of data, which are crucial to enable high quality comparisons. Even though the data set is large, the comparability is hampered by differences in reporting. In conclusion, much more detailed instructions are needed for reporting POPs in mothers' milk. Temporal trend data for POPs in mothers' milk is scarce and is of interest when studying longer time series. The only two countries with long temporal trend studies are Japan and Sweden. In most cases, the trends show decreasing concentrations of POPs in mothers' milk. However, hexabromocyclododecane is showing increasing temporal concentration trends in both Japan and Sweden.
|
|
| 7. |
- Holovachov, Oleksandr
(författare)
-
Nematodes from terrestrial and freshwater habitats in the Arctic
- 2014
-
Ingår i: Biodiversity Data Journal. - 1314-2836 .- 1314-2828. ; 2:e1165
-
Forskningsöversikt (refereegranskat)abstract
- We present an updated list of terrestrial and freshwater nematodes from all regions of the Arctic, for which records of properly identified nematode species are available: Svalbard, Jan Mayen, Iceland, Greenland, Nunavut, Northwest territories, Alaska, Lena River estuary, Taymyr and Severnaya Zemlya and Novaya Zemlya. The list includes 391 species belonging to 146 genera, 54 families and 10 orders of the phylum Nematoda.
|
|
| 8. |
- Ivarsson, Magnus, 1975-, et al.
(författare)
-
Är magmatiska bergarterfossilförande?
- 2017
-
Ingår i: Geologiskt Forum. - Stockholm. - 1104-4721. ; :94, s. 20-23
-
Forskningsöversikt (populärvet., debatt m.m.)abstract
- Förekomsten av fossil är lika starkt sammankopplad till sedimentära bergarter som magmatiska bergarter är till frånvaron av fossil. Detta har varit ett obestridbart faktum sedan geovetenskapernas gryning. Men nu börjar detta synsätt att ändra sig. Forskare vid Naturhistoriska riksmuseet utforskar ett fossilt arkiv som påträffas i sprickor och håligheter i magmatiska och vulkaniska bergarter. Detta kan spela stor roll framöver för studiet av djupbiosfären och det tidiga livet på jorden samt även för sökandet efter liv på Mars.
|
|
| 9. |
- Kitchener, A.C., et al.
(författare)
-
A revised taxonomy of the Felidae : The final report of the Cat Classification Task Force of the IUCN Cat Specialist Group
- 2017
-
Ingår i: Cat News. - Muri, Switzerland. - 1027-2992.
-
Forskningsöversikt (övrigt vetenskapligt/konstnärligt)abstract
- 1. The current classification of the Felidae was reviewed by a panel of 22 experts divided into core, expert and review groups, which make up the Cat Classification Task Force CCTF of the IUCN Cat Specialist Group.2. The principal aim of the CCTF was to produce a consensus on a revised classification of the Felidae for use by the IUCN.3. Based on current published research, the CCTF has fully revised the classification of the Felidae at the level of genus, species and subspecies.4. A novel traffic-light system was developed to indicate certainty of each taxon based on morphological, molecular, biogeographical and other evidence. A concordance of good evidence in the three principal categories was required to strongly support the acceptance of a taxon.5. Where disagreements exist among members of the CCTF, these have been highlighted in the accounts for each species. Only further research will be able to answer the potential conflicts in existing data.6. A total of 14 genera, 41 species and 80 subspecies are recognised by most members of the CCTF, which is a considerable change from the classification proposed by Wozencraft (2005), the last major revision of the Felidae.7. Future areas of taxonomic research have been highlighted in order to answer current areas of uncertainty.8. This classification of the Felidae will be reviewed every five years unless a major new piece of research requires a more rapid revision for the conservation benefit of felid species at risk of extinction.
|
|
| 10. |
- Kronestedt, Torbjörn, 1942-, et al.
(författare)
-
Fixation of Lycosa fidelis =. Pickard-Cambridge, 1872 as the type species for the genus Wadicosa Zyuzin, 1985 (Araneae: Lycosiadae), with a redescription of the species
- 2009
-
Ingår i: Contributions to Natural History. - Bern. - 1660-9972. ; 12, s. 813-828
-
Forskningsöversikt (refereegranskat)abstract
- The name Lycosa or Pardosa venatrix has been used since Simon in 1882 to denote a widespread Palearctic species. The nominal species Lycosa venatrix Lucas, 1846 was originally designed as the type species for the genus Wadicosa Zyuzin, 1985. It has, however, been recognized that the species long known as venatrix was misidentified: the species so named by Lucas is evidently not a species of Wadicosa. Therefore, we now fix Lycosa fidelis O. P.-Cambridge, 1872, the species actually involved in the misidentification, as the type species for Wadicosa. An emended diagnosis for the genus Wadicosa is given, as well as a redescription of W. fidelis. The presence of some hitherto unrecorded structures in the male palp is emphasized. A hypothetic view on the mating mechanism in W. fidelis is presented.
|
|
