Mafic plutonic rocks in a continental‐arc setting: geochemistry of 1.87–1.78 Ga rocks from south‐central Sweden and models of their palaeotectonic setting

Mafic intrusive rocks (1.79–1.78 Ga) of the Transscandinavian Igneous Belt (TIB) and the c. 1.87 Ga Hedesunda Igneous Complex in the Fennoscandian Shield of south‐central Sweden were studied using whole‐rock and isotope geochemistry. Rock types vary from gabbros/norites (and leucogabbros) to quartz diorites, with Mg# between 76 and 49, and wt% SiO₂ between 43.6 and 59.7, indicating some variation in evolutionary levels and variable cumulus components. Geochemical signatures are calc‐alkaline to shoshonitic, large ion lithophile elements and light rare earth elements enriched and high‐field strength elements depleted of continental‐arc type. ε_Nd(t) ranges between +1.0 and +2.7, and ⁸⁷Sr/⁸⁶Sr(t) between 0.7020 and 0.7038. There is no systematic correlation between chemical parameters and isotope ratios. These isotopic data overlap with other mafic plutonic TIB rocks; samples from the Dala Province (DP) tend to overlap with the c. 1.7 Ga basic Dala lavas of TIB at slightly elevated relative Sr/Nd ratios. With two exceptions, the ε_Nd(t) of +1 to +2 conform to an isotopically ‘mildly depleted’ source, typical for mafic TIB rocks and many Svecofennian rocks in the region. Reported values above ε_Nd(t) +2.0 are scarce in the TIB. Mantle sources represent depleted mantle wedge material that was enriched by fluids/melts not long before (T_DM c. 2.0 Ga), that is during subduction in the preceding Svecofennian (2.0–1.87 Ga) and/or during the TIB‐0&1 event (1.85–1.78 Ga). The palaeotectonic settings inferred are active continental margins; N–S‐directed convergence at 1.87 Ga and E–W‐directed at 1.79–1.78 Ga. Copyright © 2008 John Wiley & Sons, Ltd.     

A large wet snow avalanche cycle in West Greenland quantified using remote sensing and in situ observations

Natural Hazards - On 11 April 2016 we observed high slushflow and wet snow avalanche activity at the environmental monitoring station Kobbefjord in W-Greenland. Snow avalanches released as a result...     

Determination of Trace Elements in the Quartz Reference Material UNS-SpS and in Natural Quartz Samples by ICP-MS

A procedure for the digestion and analysis of quartz samples was developed to measure trace element concentrations in natural quartz. The certified glass sand reference material UNS-SpS was chosen to assess the precision, accuracy and detection limit of the analytical method. Quartz was digested with HF/HNO₃ in a closed glassy carbon vessel and analysed by means of quadrupole ICP-MS with external calibration. Analyte concentrations of the sand UNS-SpS were compared with certified and other values from the literature. The abundances of a number of elements (Pr, Gd, Ho and Er) in the reference material are reported here for the first time. The procedure was then applied to three quartz samples from different geological settings to show that trace element data by ICP-MS can distinguish the origin of the sample.     

A Note on Velocity Spectra in the Marine Boundary Layer

Spectra of longitudinal and vertical velocity have been studied at a marine site, östergarnsholm, in the Baltic Sea during a period of six days with near-neutral or slightly unstable conditions, when the wave state gradually changed from pure wind sea to strong swell having approximately the same direction as the wind. During the pure wind sea phase, spectra are shown to adhere closely to general forms for the neutral atmospheric surface layer obtained from a new theory. As soon as the wave age goes slightly beyond that representative of pure wind sea conditions, the spectra deviate in shape from the ideal forms. The spectral modification appears to start at a frequency typical of the swell component. As the wave age increases, it progresses in frequency as a downscale cascade, which is particularly prominent in the spectrum of the vertical component but which is also observed in the longitudinal component. In addition, there is a strong effect in the low-frequency part of the spectra. It is interpreted as an indirect effect of large-scale inactive turbulence, which becomes progressively more important as wave-age increases. It is found that the ratio of the spectrum of the vertical component and the spectrum of the corresponding longitudinal component attains the theoretically predicted value of 4/3 for cases of developing sea (gale force wind) for frequencies above approximately 4 Hz but never much exceeds unity for cases with swell. It is argued that this is an indication of local anisotropy and that the inertial-dissipation method for determination of the momentum flux is inappropriate in the case of mixed seas or swell.     

Soil frost effects on soil water and runoff dynamics along a boreal forest transect: 1. Field investigations

To determine how soil frost changes flowpaths of runoff water along a hillslope, a transect consisting of four soil profiles directed towards a small stream in a mature forest stand was investigated at Svartberget, near Vindeln in northern Sweden. Soil temperature, unfrozen water content, groundwater level and snow depth were investigated along the transect, which started at the riparian peat, and extended 30 m upslope into mineral soils. The two, more organic‐rich profiles closest to the stream had higher water retention and wetter autumn conditions than the sandy mineral soils further upslope. The organic content of the soil influenced the variation in frost along the transect. The first winter (1995–96) had abnormally low snow precipitation, which gave a deep frost down to 40–80 cm, whereas the two following winters had frost depths of 5–20 cm. During winter 1995–96, the two organic profiles close to the stream had a shallower frost depth than the mineral soil profile higher upslope, but a considerably larger amount of frozen water. The fraction of water that did not freeze despite several minus degrees in the soil was 5–7 vol.% in the mineral soil and 10–15 vol.% in the organic soil. From the measurements there were no signs of perched water tables during any of the three snowmelt periods, which would have been strong evidence for changed water flowpaths due to soil frost. When shallow soil layers became saturated during snowmelt, especially in 1997 and 1998, it was because of rising groundwater levels. Several rain on frozen ground events during spring 1996 resulted in little runoff, since most of the rain either froze in the soil or filled up the soil water storage. Copyright © 2001 John Wiley & Sons, Ltd.     

Some investigations in hydrological forecasting

Summary In the northern parts of Sweden precipitation falls during the winter as snow which melts only in spring, i. e. in April and May, or in the northern mountainous regions in June or even in July. Under natural conditions the water level and the flow are high during late spring and summer and low in winter. In order to reach a better utilization of the water power storage magazines have been created and thus the flow can be regulated in order to obtain more power during the winter time. To be able to do this in the most profitable way it is necessary to find the relations between the net influx and the relevant meteorological factors and then to make forecasts concerning the water supply for rather long periods. Some results from such already established forecast relations are discussed. There forecasts are concerned with the total flow of water during the spring time and are based only upon the amount of precipitation during the winter. Some preliminary results are also given from trials, just being started and aiming at forecasts of the variation with time of the flow during the spring.

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Zusammenfassung Der Niederschlag in den n?rdlichen Teilen von Schweden f?llt w?hrend des Winterhalbjahres in Form von Schnee, der erst im Frühling, d. h. im April und Mai oder in den n?rdlichen Gebirgslagen sogar erst im Juni oder Juli, schmilzt. In den natürlichen Wasserl?ufen sind Wasserstand und Abflu? hoch w?hrend des Sp?tfrühlings und des Sommers, niedrig w?hrend des Winters. Um die Wasserkraft besser ausnutzen zu k?nnen, wurden Wasserreservoire geschaffen, wodurch die Wassermenge reguliert und die Energie auch im Winter ausgenützt werden kann. Um diese Wasserkraft in der günstigsten Weise ausnützen zu k?nnen, ist es notwendig, die Beziehungen zwischen dem Zuflu? und den wirksamen meteorologischen Faktoren festzulegen und nach M?glichkeit Prognosen über die Wasserausbeute auf l?ngere Sicht zu machen. Im vorliegenden Aufsatz werden die Ergebnisse von einigen solchen Prognoseversuchen er?rtert, die nur auf dem Winterniederschlag basieren und den totalen Abflu? ergeben. Weiterhin werden einige vorl?ufige Ergebnisse von neuerdings angefangenen Versuchen berichtet, die zeitlichen Schwankungen des Frühjahrshochwassers vorauszusagen. Résumé Dans les parties septentrionales de la Suède, les précipitations tombent, pendant la saison hivernale sous la forme de neige, qui ne se fond qu'au printemps, c'est-à-dire en avril et mai ou, dans les parties montagneuses du nord, même en juin ou juillet. Dans les courants d'eau naturels la hauteur d'eau et le débit sont élevés vers la fin du printemps et en été, bas pendant l'hiver. Pour mieux exploiter les forces hydrauliques, des réservoirs d'eau ont été construits, par lesquelles le débit peut être réglé et la force hydraulique peut être exploitée aussi pendant la saison d'hiver. Pour arriver à des résultats plus favorables il est nécessaire d'étudier les relations entre l'afflux et les facteurs météorologiques et de faire dans la mesure du possible des prévisions de l'évolution du débit d'eau à plus longue échéance. Quelques résultats de tels essais de prognostics établis, basés uniquement sur la précipitation d'hiver et donnant le volume total d'eau, sont discutés. En outre, on donne des résultats provisoires des essais qui ont été commencés récemment et qui concernent les possibilités de la prévision des variations temporaires des grandes crues de printemps.

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With 2 Figures

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Dedicated to Dr.Anders K. ?ngstr?m on the occasion of his 70th birthday.     

An EELS study of near edge structures of the oxygen K-edge in spinels

Spectra of seven aluminate, ferrite and chromate spinels were collected at the oxygen K-edge in order to examine the effect of octahedral ion composition on the near edge structures and explore whether these may shed some light on previously reported major variations in the optical absorption coefficient (ε) for the spin-allowed d–d band transitions due to tetrahedrally coordinated Fe²⁺ in optical spectra of oxide spinels. Interpretation of the energy loss near edge structure (ELNES) spectra was aided using the multiple scattering code FEFF8.40. For the chromate samples spin polarised calculations were included. Gold’s iterative deconvolution method was utilized to improve on energy resolution, resulting in spectra equal in merit to those recorded by technically superior instruments. Results include absolute energy positions and interpretation of ELNES features in terms of transitions to available states. We conclude that the major causes of differences in the optical absorption coefficient mentioned above are hybridization between oxygen p- and octahedral metal orbitals. Our study does not support the idea presented by other authors that there exists a local antiferromagnetic ordering in MgCr₂O₄ at room temperature.     

First U–Pb geochronology on detrital zircons from Early-Middle Cambrian strata of the Torgau-Doberlug Syncline (eastern Germany) and palaeogeographic implications

International Journal of Earth Sciences - LA-ICP-MS U–Pb data from detrital zircons of the Ediacaran to Cambrian siliciclastic sequence of the Torgau-Doberlug Syncline (TDS, Saxo-Thuringia,...     

Modelling multi-species interactions in the Barents Sea ecosystem with special emphasis on minke whales and their interactions with cod, herring and capelin

The Barents Sea ecosystem, one of the most productive and commercially important ecosystems in the world, has experienced major fluctuations in species abundance the past five decades. Likely causes are natural variability, climate change, overfishing and predator–prey interactions. In this study, we use an age-length structured multi-species model (Gadget, Globally applicable Area-Disaggregated General Ecosystem Toolbox) to analyse the historic population dynamics of major fish and marine mammal species in the Barents Sea. The model was used to examine possible effects of a number of plausible biological and fisheries scenarios. The results suggest that changes in cod mortality from fishing or cod cannibalism levels have the largest effect on the ecosystem, while changes to the capelin fishery have had only minor effects. Alternate whale migration scenarios had only a moderate impact on the modelled ecosystem. Indirect effects are seen to be important, with cod fishing pressure, cod cannibalism and whale predation on cod having an indirect impact on capelin, emphasising the importance of multi-species modelling in understanding and managing ecosystems. Models such as the one presented here provide one step towards an ecosystem-based approach to fisheries management.