Punctuated,long-lived emplacement history of the Renard 2 kimberlite,Canada, revealed by new high precision U-Pb groundmass perovskite dating     

Ranger  Ilona M.  Heaman  Larry M.  Pearson  D. Graham  Muntener  Colleen  Zhuk  Volodymyr 《Mineralogy and Petrology》2018,112(2):639-651

Kimberlites are rare volatile-rich ultramafic magmas thought to erupt in short periods of time (<1 Myr) but there is a growing body of evidence that the emplacement history of a kimberlite can be significantly more protracted. In this study we report a detailed geochronology investigation of a single kimberlite pipe from the Renard cluster in north-central Québec. Ten new high precision ID-TIMS (isotope dilution – thermal ionization mass spectrometry) U-Pb groundmass perovskite dates from the main pipe-infilling kimberlites and several small hypabyssal kimberlites from the Renard 2 pipe indicate kimberlite magmatism lasted at least ~20 Myr. Two samples of the main pipe-infilling kimberlites yield identical weighted mean ²⁰⁶Pb/²³⁸U perovskite dates with a composite date of 643.8 ± 1.0 Myr, interpreted to be the best estimate for main pipe emplacement. In contrast, six hypabyssal kimberlite samples yielded a range of weighted mean ²⁰⁶Pb/²³⁸U perovskite dates between ~652-632 Myr. Multiple dates determined from these early-, syn- and late-stage small hypabyssal kimberlites in the Renard 2 pipe demonstrate this rock type (commonly used to date kimberlites) help to constrain the duration of kimberlite intrusion history within a pipe but do not necessarily reliably record the emplacement age of the main diatreme in the Renard cluster. Our results provide the first robust geochronological data on a single kimberlite that confirms the field relationships initially observed by Wagner (1914) and Clement (1982); the presence of antecedent (diatreme precursor) intrusions, contemporaneous (syn-diatreme) intrusions, and consequent (post-diatreme) cross-cutting intrusions. The results of this detailed U-Pb geochronology study indicate a single kimberlite pipe can record millions of years of magmatism, much longer than previously thought from the classical viewpoint of a rapid and short-duration emplacement history.

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Winter severity and snowiness and their multiannual variability in the Karkonosze Mountains and Jizera Mountains     

Grzegorz?UrbanEmail author  Dá?a?Richterová  Stanislava?Kliegrová  Ilona?Zusková  Piotr?Pawliczek 《Theoretical and Applied Climatology》2018,134(1-2):221-240

This paper analyses winter severity and snow conditions in the Karkonosze Mountains and Jizera Mountains and examines their long-term trends. The analysis used modified comprehensive winter snowiness (WSW) and winter severity (WOW) indices as defined by Paczos (1982). An attempt was also made to determine the relationship between the WSW and WOW indices. Measurement data were obtained from eight stations operated by the Institute of Meteorology and Water Management – National Research Institute (IMGW–PIB), from eight stations operated by the Czech Hydrological and Meteorological Institute (CHMI) and also from the Meteorological Observatory of the University of Wroc?aw (UWr) on Mount Szrenica. Essentially, the study covered the period from 1961 to 2015. In some cases, however, the period analysed was shorter due to the limited availability of data, which was conditioned, inter alia, by the period of operation of the station in question, and its type.Viewed on a macroscale, snow conditions in the Karkonosze Mountains and Jizera Mountains (in similar altitude zones) are clearly more favourable on southern slopes than on northern ones. In the study area, negative trends have been observed with respect to both the WSW and WOW indices—winters have become less snowy and warmer. The correlation between the WOW and WSW indices is positive. At stations with northern macroexposure, WOW and WSW show greater correlation than at ones with southern macroexposure. This relationship is the weakest for stations that are situated in the upper ranges (Mount ?nie?ka and Mount Szrenica).  相似文献   

The smoke is rising but where is the fire? Exploring effective online map design for wildfire warnings     

Yinghui Cao  Bryan J. Boruff  Ilona M. McNeill 《Natural Hazards》2017,88(3):1473-1501

The current study sought to offer guidance for developing effective web-based mapping tools for wildfire warnings by identifying (1) the important content for facilitating individuals’ decision-making, and (2) the optimal interface design for ensuring usability and ease of information access. A map-based warning tool was prototyped in the Australian context, followed by a usability and effectiveness evaluation through individual interviews and verbal protocol analysis to assess participants’ interaction with the mapping interface and information in response to the simulated warning scenario. The results demonstrated variations in participants’ approaches to wildfire warning response, revealing varied information needs. Specifically, most participants relied on their own assessment of the prospective threat, requiring specific wildfire-related information before eliciting a response. In contrast, the decision of a minority of the participants was motivated by response guidance from agencies, and accurate wildfire information was less important for their response. Imperative information for both types of residents therefore needs to be highlighted in a map-based warning tool to cater to a wide audience. Furthermore, a number of heuristics were identified for designing effective interactive functions to facilitate the control of, and access to, the various maps and textual information presented on the map-based warning interface.  相似文献   

Domestic and industrial water uses of the past 60 years as a mirror of socio-economic development: A global simulation study     

Martina Flörke  Ellen Kynast  Ilona Bärlund  Stephanie Eisner  Florian Wimmer  Joseph Alcamo 《Global Environmental Change》2013,23(1):144-156

To enhance global water use assessment, the WaterGAP3 model was improved for back-calculating domestic, manufacturing and thermoelectric water uses until 1950 for 177 countries. Model simulations were carried-out on a national scale to estimate water withdrawals and consumption as well as cooling water required for industrial processes and electricity production. Additionally, the amount of treated and untreated wastewater as generated by the domestic and manufacturing sectors was modeled. In the view of data availability, model simulations are based on key socio-economic driving forces and thermal electricity production. Technological change rates were derived from statistical records in order to consider developments in water use efficiency, which turned out to have a crucial role in water use dynamics. Simulated domestic and industrial water uses increased from ca. 300 km³ in 1950 to 1345 km³ in 2010, 12% of which were consumed and 88% of which were discharged back into freshwater bodies. The amount of domestic and manufacturing wastewater increased considerably over the last decade, but only half of it was untreated. The downscaling of the untreated wastewater volume to river basin scale indicates a matter of concern in East and Southeast Asia, Northern Africa, and Eastern and Southern Europe. In order to reach the Millennium Development Goals, securing water supply and the reduction of untreated wastewater discharges should be amongst the priority actions to be undertaken. Population growth and increased prosperity have led to increasing water demands. However, societal and political transformation processes as well as policy regulations resulting in new water-saving technologies and improvements counteract this development by slowing down and even reducing global domestic and industrial water uses.  相似文献   

Holocene environmental history in high‐Arctic North Greenland revealed by a combined biomarker and macrofossil approach     

Stephanie Kusch  Ole Bennike  Bernd Wagner  Matthias Lenz  Ilona Steffen  Janet Rethemeyer 《Boreas: An International Journal of Quaternary Research》2019,48(2):273-286

In this study, we use a combined biomarker and macrofossil approach to reconstruct the Holocene climate history recorded in Trifna Sø, Skallingen area, eastern North Greenland. Chronological information is derived from comparison of lithological, biogeochemical and macrofossil characteristics with a well‐dated record from nearby Lille Sneha Sø. Following local deglaciation around c. 8 cal. ka BP, the local peak warmth occurred between c. 7.4 and 6.2 cal. ka BP as indicated by maximum macrofossil abundances of warmth‐demanding plants (Salix arctica and Dryas integrifolia) and invertebrates (Daphnia pulex and Chironomidae). Warm conditions were dominated by terrestrial organic matter (OM) sedimentation as implied by the alkane‐based P_aq ratio, but increased aquatic productivity is indicated when temperature was highest around 6.5 cal. ka BP. The n‐C₂₉/n‐C₃₁ alkane ratio shows that vegetation in the catchment was dominated by shrubs after deglaciation, but shifted towards relatively more grassy/herbaceous vegetation during peak warmth. After 5.4 cal. ka BP, the disappearance of warmth‐demanding plant and invertebrate macrofossils indicates cooling in the Skallingen area. This cooling was characterized by a significant shift towards dominance of aquatic OM sedimentation in Trifna Sø as implied by high P_aq ratios. Cooling was also associated with a shift in vegetation type from dwarf‐shrub heaths towards relatively more herbaceous vegetation in the catchment, stronger erosion and more oligotrophic conditions in the lake. Our data show that mean air temperatures inferred using branched glycerol dialkyl glycerol tetraethers (brGDGTs) do not seem to accurately reflect the local climatic history. Irrespective of calibration, methylation of branched tetraethers (MBT) palaeothermometry cannot be reconciled with the macrofossil evidence and seems to be biased by either changing brGDGT sources (in situ vs. soil‐derived) or changing species assemblages and/or an unknown physiological response to changing environmental conditions at high latitude.  相似文献   

Enhancement and inhibition of iron photoreduction by individual ligands in open ocean seawater     

Micha J.A. Rijkenberg  Loes J.A. Gerringa  Ilona Velzeboer 《Geochimica et cosmochimica acta》2006,70(11):2790-2805

In laboratory experiments, we investigated the effect of five individual Fe-binding ligands: phaeophytin, ferrichrome, desferrioxamine B (DFOB), inositol hexaphosphate (phytic acid), and protoporphyrin IX (PPIX) on the Fe(II) photoproduction using seawater of the open Southern Ocean. Addition of 10-100 nM Fe(III) to open Southern Ocean seawater without the model ligands and containing; 1.1 nM dissolved Fe(III), 1.75 ± 0.28 equivalents of nM Fe of natural ligands with a conditional stability constant (log K′) of 21.75 ± 0.34 and a concentration DOC of 86.8 ± 1.13 μM C leads to the formation of amorphous Fe(III) hydroxides. These amorphous Fe(III) hydroxides are the major source for the photoproduction of Fe(II). The addition of the model ligands changed the Fe(II) photoproduction considerably and in various ways. Phaeophytin showed higher Fe(II) photoproduction than ferrichrome and the control, i.e., amorphous Fe(III) hydroxides. Additions of phytic acid between 65 and 105 nM increased the concentration of photoproduced Fe(II) with 0.16 nM Fe(II) per nM phytic acid, presumably due to the co-aggregation of Fe(III) and phytic acid leading via an increasing colloidal surface to an increasing photoreducible Fe(III) fraction. DFOB and PPIX strongly decreased the photoproduced Fe(II) concentration. The low Fe(II) photoproduction with DFOB confirmed reported observations that Fe(III) complexed to DFOB is photo-stable. The PPIX hardly binds Fe(III) in the open Southern Ocean seawater but decreased the photoproduced Fe(II) concentration by complexing the Fe(II) with a binding rate constant of k_Fe(II)PPIX = 1.04 × 10⁻⁴ ± 1.53 × 10⁻⁵ s⁻¹ nM⁻¹ PPIX. Subsequently, PPIX is suggested to act as a photosensitizing producer of superoxide, thus increasing the dark reduction of Fe(III) to Fe(II). Our research shows that the photochemistry of Fe(III) and the resulting photoproduced Fe(II) concentration is strongly depending on the identity of the Fe-binding organic ligands and that a translation to natural conditions is not possible without further characterization of the natural occurring ligands.  相似文献   

European participatory scenario development: strengthening the link between stories and models     

Kasper Kok  Ilona Bärlund  Martina Flörke  Ian Holman  Marc Gramberger  Jan Sendzimir  Benjamin Stuch  Katharina Zellmer 《Climatic change》2015,128(3-4):187-200

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Dichotomy in host environments and signs of recycled active galactic nuclei     

Georgina V. Coldwell  Diego G. Lambas  Ilona K. Söchting  Sebastián Gurovich 《Monthly notices of the Royal Astronomical Society》2009,399(1):88-96

We analyse the relation between active galactic nuclei (AGN) host properties and large-scale environment for a representative red and blue AGN host galaxy sample selected from the Data Release 4 Sloan Digital Sky Survey. A comparison is made with two carefully constructed control samples of non-active galaxies, covering the same redshift range and colour baseline. The cross-correlation functions show that the density distribution of neighbours is almost identical for blue galaxies, either active or non-active. Although active red galaxies inhabit environments less dense compared to non-active red galaxies, both reside in environments considerably denser than those of blue hosts. Moreover, the radial density profile of AGN relative to galaxy group centres is less concentrated than galaxies. This is particularly evident when comparing red AGN and non-active galaxies.
The properties of the neighbouring galaxies of blue and red AGN and non active galaxies reflect this effect. While the neighbourhood of the blue samples is indistinguishable, the red AGN environs show an excess of blue-star-forming galaxies with respect to their non-active counterpart. On the other hand, the active and non-active blue systems have similar environments but markedly different morphological distributions, showing an excess of blue early-type AGN, which are argued to be late-stage mergers. This comparison reveals that the observable differences between active red and blue host galaxy properties including star formation history and AGN activity depends on the environment within which the galaxies form and evolve.  相似文献   

Is stress-insensitive chemical compaction responsible for high overpressures in deeply buried North Sea chalks?     

Hege M. Nordgrd Bols  Christian Hermanrud  Tomas A. Schutter  Gunn M. Grimsmo Teige 《Marine and Petroleum Geology》2008,25(7):565-587

Chalk compaction is often assumed to be controlled by a combination of mechanical and effective stress-related chemical processes, the latter commonly referred to as pressure solution. Such effective stress-driven compaction would result in elevated porosities in overpressured chalks compared with otherwise identical, but normally pressured chalks. The high porosities that are frequently observed in overpressured North Sea chalks have previously been reported to reflect such effective stress-dependent compaction.However, several wells with deeply buried chalk sequences also exhibit low porosities at high pore pressures. To investigate the possible origins of these overpressures, basin modeling was performed in a selected well (NOR 1/3-5) offshore Norway. This modeling was based on both effective stress-driven mechanical porosity reduction, which enables modeling of disequilibrium compaction, and on stress-insensitive chemical compaction where the porosity reduction is caused by thermally activated diagenesis.The modeling has demonstrated that the present day porosities and pore pressures of the chalks could be successfully replicated with mechanical porosity loss as the only process leading to chalk porosity reduction. However, the modeled porosity and fluid pressure history of the sediments deviated significantly from the porosity and pore pressure versus depth relationships observed in non-reservoir North Sea chalks today. To the contrary, modeling which was based on thermally activated porosity loss due to diagenesis (as a supplement to mechanical compaction), resulted in modeled chalk histories that are consistent with present day observations.It was therefore inferred that disequilibrium compaction could not account for all of the pore pressure development in overpressured chalks in the study area. The observation that modeling including temperature-controlled diagenetic porosity reduction gave plausible results, suggests that such porosity reduction may in fact be operating in chalks as well as in clastic rocks. If this is correct, then improved methods for pore pressure identification and fluid flow analysis in basins containing chalks should be developed.  相似文献   

Effect of modelling scale on the assessment of climate change impact on river runoff     

Mikołaj Piniewski  Frank Voss  Ilona Bärlund  Tomasz Okruszko  Zbigniew W. Kundzewicz 《水文科学杂志》2013,58(4):737-754

Abstract

The effect of using two distributed hydrological models with different degrees of spatial aggregation on the assessment of climate change impact on river runoff was investigated. Analyses were conducted in the Narew River basin situated in northeast Poland using a global hydrological model (WaterGAP) and a catchment-scale hydrological model (SWAT). Climate change was represented in both models by projected changes in monthly temperature and precipitation between the period 2040–2069 and the baseline period, resulting from two general circulation models: IPSL-CM4 and MIROC3.2, both coupled with the SRES A2 emissions scenario. The degree of consistency between the global and the catchment model was very high for mean annual runoff, and medium for indicators of high and low runoff. It was observed that SWAT generally suggests changes of larger magnitude than WaterGAP for both climate models, but SWAT and WaterGAP were consistent as regards the direction of change in monthly runoff. The results indicate that a global model can be used in Central and Eastern European lowlands to identify hot-spots where a catchment-scale model should be applied to evaluate, e.g. the effectiveness of management options.

Editor D. Koutsoyiannis; Associate editor F.F. Hattermann

Citation Piniewski, M., Voss, F., Bärlund, I., Okruszko, T., and Kundzewicz. Z.W., 2013. Effect of modelling scale on the assessment of climate change impact on river runoff. Hydrological Sciences Journal, 58 (4), 737–754.  相似文献