Constraining clastic input controls on magnetic susceptibility and trace element anomalies during the Late Devonian punctata Event in the Western Canada Sedimentary Basin     

Maciej G. Śliwiński  Michael T. Whalen  Franz J. Meyer  František Majs 《地学学报》2012,24(4):301-309

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Groundwater dating with 3H and SF6 in relation to mixing patterns,transport modelling and hydrochemistry     

A. Zuber  S. Witczak  K. Ra&#x;ski  I. liwka  M. Opoka  P. Mochalski  T. Kuc  J. Karlikowska  J. Kania  M. Jackowicz‐Korczy&#x;ski  M. Duli&#x;ski 《水文研究》2005,19(11):2247-2275

A comprehensive study of a sandy aquifer of deltaic origin in southern Poland included water chemistry, isotopes, dissolved trace gases and transport modelling. Tritium, sulphur hexafluoride (SF₆) and freons (F‐11, F‐12 and F‐113) showed the presence of modern waters in the recharge areas and shallow confined parts of the aquifer. The presence of older Holocene waters farther from the recharge areas was indicated by lack of ³H, SF₆ contents ≤0·02 fmol l⁻¹ and relatively low ¹⁴C values. The discharge from the system is by upward seepage in the valley of a major river. Pre‐Holocene waters of a cooler climate, identified on the basis of δ¹⁸O, δ²H, ¹⁴C, Ne and Ar data, were found in some distant wells. Concentrations of N₂, Ne and Ar determined by gas chromatography were used for calculating the noble gas temperatures, air excess needed for correction of SF₆, and nitrogen content released by denitrification process. The time series of ³H content available for some wells supplied quantitative information on age distributions and the total mean ages of flow through the unsaturated and saturated zones. The derived ³H age distributions turned out to be very wide, with mean values in the range of about 30 to 160 years. For each well with determined ³H age, the SF₆ data showed either a lower age range or the possibility of a lower age as expected due to shorter travel times of SF₆ through the unsaturated zone, which most probably also resulted in different types of age distributions of these tracers. Freons appeared to be of little use for individual age determinations. A quantitative estimation of two‐component mixing from SF₆ ³H relations is not possible unless the travel time of ³H through the unsaturated zone is comparable to that of SF₆. The ratio of integrals of the response function over the age range with tracer and the whole response function yields the ratio of water with tracer to total flow of water. That ratio is a tracer‐dependent function of time. Transport modelling of SF₆ tracer done with MT3D code yielded initially large discrepancies between calculated and measured tracer concentrations. Some discrepancies remained even after calibration of the transport model with SF₆. Simulation of tritium contents with a calibrated transport model yielded reasonable agreement with measured contents in some wells and indicated a need for further investigations, particularly in the eastern part of the aquifer. The existence of distinct hydrochemical zones is consistent with the tracer data; young waters with measurable ³H and SF₆ contents are aerobic and of HCO₃ Ca or HCO₃ SO₄ Ca types. Slightly elevated Na and Cl contents, as well as the highest concentrations of SO₄ and NO₃ within this zone are due to anthropogenic influences. Anaerobic conditions prevail in the far field, under the confining cover, where pre‐bomb era Holocene waters dominate. In that zone, dissolved oxygen, NO₃ and U contents are reduced, and Fe, Mn and NH₄ contents increase. In the third zone, early Holocene and glacial waters occur. They are of HCO₃ Ca Na or HCO₃ Na types, with TDS values higher than 1 g l⁻¹ and Na content higher than 200 mg l⁻¹, due to either small admixtures of ascending or diffusing older water or freshening of marine sediments, a process that is probably occurring till the present time. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Physics of accretion in the millisecond pulsar XTE J1751 − 305     

Marek Gierli&#;ski  Juri Poutanen † 《Monthly notices of the Royal Astronomical Society》2005,359(4):1261-1276

We have undertaken an extensive study of X-ray data from the accreting millisecond pulsar XTE J1751 − 305 observed by RXTE and XMM–Newton during its 2002 outburst. In all aspects this source is similar to the prototypical millisecond pulsar SAX J1808.4 − 3658, except for the higher peak luminosity of 13 per cent of Eddington, and the optical depth of the hard X-ray source, which is larger by a factor ∼2. Its broad-band X-ray spectrum can be modelled by three components. We interpret the two soft components as thermal emission from a colder  ( kT ∼ 0.6 keV)  accretion disc and a hotter (∼1 keV) spot on the neutron star surface. We interpret the hard component as thermal Comptonization in plasma of temperature ∼40 keV and optical depth ∼1.5 in a slab geometry. The plasma is heated by the accretion shock as the material collimated by the magnetic field impacts on to the surface. The seed photons for Comptonization are provided by the hotspot, not by the disc. The Compton reflection is weak and the disc is probably truncated into an optically thin flow above the magnetospheric radius. Rotation of the emission region with the star creates an almost sinusoidal pulse profile with an rms amplitude of 3.3 per cent. The energy-dependent soft phase lags can be modelled by two pulsating components shifted in phase, which is naturally explained by a different character of emission of the optically thick spot and optically thin shock combined with the action of the Doppler boosting. The observed variability amplitude constrains the hotspot to lie within 3°–4° of the rotational pole. We estimate the inner radius of the optically thick accreting disc to be about 40 km. In that case, the absence of emission from the antipodal spot, which can be blocked by the accretion disc, gives the inclination of the system as ≳70°.  相似文献   

The Araucaria Project. Variable stars outside the Local Group: NGC 300     

R. E. Mennickent  G. Pietrzy&#;ski  W. Gieren 《Monthly notices of the Royal Astronomical Society》2004,350(2):679-684

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Averaging spectral shapes     

Piotr Lubi&#;ski 《Monthly notices of the Royal Astronomical Society》2004,350(2):596-608

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Phase-resolved X-ray spectroscopy of the millisecond pulsar SAX J1808.4−3658     

MarekGierlin´ski  ChrisDone  DidierBarret 《Monthly notices of the Royal Astronomical Society》2002,331(1):141-153

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Constraining the Galactic bar parameters with red clump giants     

Shude Mao  Bohdan Paczy&#;ski 《Monthly notices of the Royal Astronomical Society》2002,337(3):895-900

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The statistical effects of galactic tides on the Oort cloud     

Piotr A. Dybczyński  Halina Pretka 《Earth, Moon, and Planets》1996,72(1-3):13-18

This report is a comment on two papers by Matese and Whitman (1989, 1992). We discuss here the applicability of uniform probability densities for the orbital parameters of the Oort cloud comets.  相似文献   

Conditioning clayey soils with a dispersant agent for Deep Soil Mixing application: laboratory experiments and artificial neural network interpretation     

Salvatore  Erminio  Modoni  Giuseppe  Spagnoli  Giovanni  Arciero  Michela  Mascolo  Maria Cristina  Ochmański  Maciej 《Acta Geotechnica》2022,17(11):5073-5087

Acta Geotechnica - Plasticity of clays makes Deep Soil Mixing (DSM) problematic due to the tendency of the material to congest the rotating blades, reduce mixing efficiency and remain...  相似文献   

Tracing exhumation record in high-pressure micaschists: A new tectonometamorphic model of the evolution of the eastern part of the Fore Sudetic Block,Kamieniec Metamorphic Belt,NE Bohemian Massif,SW Poland     

Jacek Szczepański  Marcin Goleń 《Chemie der Erde / Geochemistry》2022,82(1):125859

The Kamieniec Metamorphic Belt comprises a volcano-sedimentary succession exposed within a collision zone between the Saxothuringian and Brunovistulian crustal domains of the European Variscides. The studied rocks recorded two metamorphic episodes. The first episode, M₁, occurred at conditions of c. 485 ± 25 °C and 18 ± 1.8 kbar related to burial within a subduction zone. The subsequent episode, M₂, was linked to the final phases of exhumation to mid-crustal level, associated with pressure and temperature (P–T) conditions ranging from c. 520 ± 26 °C and 6 ± 0.6 kbar through 555 ± 28 °C and 7 kbar ± 0.7 to ~590 ± 30 °C and 3–4 ± 0.4 kbar. The documented deformation record is ascribed to three events, D₁ to D₃, interpreted as related to the burial and subsequent exhumation of the Kamieniec Metamorphic Belt. The D₁ event must have witnessed the subduction of the Kamieniec Metamorphic Belt rock succession whereas the D₂ event was associated with the exhumation and folding of the Kamieniec Metamorphic Belt in an E-W-directed shortening regime. A subsequent folding related to the D₂ event was initiated at HP conditions, however, the planar fabric produced during a late stage of the D₂ event, defined by a low-pressure mineral assemblage M₂, indicates that the D₂ final stage was synchronous with the onset of the M₂ episode. Consequently, the entire D₂ event seems to have been associated with the exhumation of the Kamieniec Metamorphic Belt to mid crustal level. The third deformation event D₃, synchronous with the M₂ episode, marked the last stage of the exhumation, and was linked to emplacement of granitoid veins and lenses. The latter resulted in heating and rheological weakening of the entire rock succession and in the formation of non-coaxial shear zones.  相似文献