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11.
V. Axelsson 《Geo-Marine Letters》2002,21(4):236-244
Spatial and temporal variations in sedimentation rate and the formation of cyclic and event types of stratification have been identified by the correlation of sedimentation units between sediment cores, which were sampled on the same day during different seasons and years, as well as before and after specific events. Some results are presented from a number of selected areas along the coast of Sweden. The cores were collected in rectangular, transparent coring tubes which were subsequently X-rayed (the uppermost part in stereo) before the cores were extruded from the tubes. The optical data obtained from the radiographic images were then quantified by the use of X-ray densitometric methods. The use of X-ray radiographic techniques, especially stereo-radiography and X-ray densitometry, simplifies the core-to-core correlation as well as the determination of sedimentary properties and the quantification of sedimentation rates. 相似文献
12.
Martin B. Kalinowski Anders Axelsson Marc Bean Xavier Blanchard Theodore W. Bowyer Guy Brachet Simon Hebel Justin I. McIntyre Jana Peters Christoph Pistner Maria Raith Anders Ringbom Paul R. J. Saey Clemens Schlosser Trevor J. Stocki Thomas Taffary R. Kurt Ungar 《Pure and Applied Geophysics》2010,167(4-5):517-539
A global monitoring system for atmospheric xenon radioactivity is being established as part of the International Monitoring System that will verify compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT) once the treaty has entered into force. This paper studies isotopic activity ratios to support the interpretation of observed atmospheric concentrations of 135Xe, 133mXe, 133Xe and 131mXe. The goal is to distinguish nuclear explosion sources from civilian releases. Simulations of nuclear explosions and reactors, empirical data for both test and reactor releases as well as observations by measurement stations of the International Noble Gas Experiment (INGE) are used to provide a proof of concept for the isotopic ratio based method for source discrimination. 相似文献
13.
Mikael D. Axelsson Ilia Rodushkin Douglas C. Baxter Johan Ingri Björn Öhlander 《Geochemical transactions》2002,3(1):40
A procedure was developed for the determination of element distributions in cross-sections of ferromanganese concretions using
laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The effects of carrier flow rates, rf forward power,
ablation energy, ablation spot size, repetition rate and number of shots per point on analyte intensity were studied. It is
shown that different carrier gas flow rates are required in order to obtain maximum sensitivities for different groups of
elements, thus complicating the optimisation of ICP parameters. On the contrary, LA parameters have very similar effects on
almost all elements studied, thus providing a common optimum parameter set for the entire mass range. However, for selected
LA parameters, the use of compromise conditions was necessary in order to compensate for relatively slow data acquisition
by ICP-MS and maintain high spatial resolution without sacrificing the multielemental capabilities of the technique. Possible
variations in ablation efficiency were corrected for mathematically using the sum of Fe and Mn intensities. Quantification
by external calibration against matrix-matched standards was successfully used for more than 50 elements. These standards,
in the form of pressed pellets (no binder), were prepared in-house using ferromanganese concentrates from a deep-sea nodule
reference material as well as from shallow-marine concretions varying in size and having different proportions of three major
phases: aluminosilicates, Fe- and Mn-oxyhydroxides. Element concentrations in each standard were determined by means of conventional
solution nebulisation ICP-MS following acid digestion. Examples of selected inter-element correlations in distribution patterns
along the cross-section of a concretion are given. 相似文献
14.
Björn Öhlander Barbara Müller Mikael Axelsson Lena Alakangas 《Journal of Geochemical Exploration》2007
Metals released from oxidation and weathering of sulphide minerals in mine tailings are to a high degree retained at deeper levels within the tailings themselves. To be able to predict what could happen in the future with these secondarily retained metals, it is important to understand the retention mechanisms. In this study an attempt to use laser ablation high-resolution ICP-MS (LA-ICP-SMS) to quantify enrichment of trace elements on pyrite surfaces in mine tailings was performed. Pyrite grains were collected from a profile through the pyrite-rich tailings at the Kristineberg mine in northern Sweden. At each spot hit by the laser, the surface layer was analyzed in the first shot, and a second shot on the same spot gave the chemical composition of the pyrite immediately below. The crater diameter for a laser shot was known, and by estimating the crater depth and total pyrite surface, the total enrichment on pyrite grains was calculated. Results are presented for As, Cd, Co, Cu, Ni and Zn. The results clearly show that there was an enrichment of As, Cd, Cu and Zn on the pyrite surfaces below the oxidation front in the tailings, but not of Co and Ni. Arsenic was also enriched on the pyrite grains that survived in the oxidized zone. Copper has been enriched on pyrite surfaces in unoxidized tailings in the largest amount, followed by Zn and As. However, only 1.4 to 3.1% of the Cd and Zn released by sulphide oxidation in the oxidized zone have been enriched on the pyrite surfaces in the unoxidized tailings, but for As and Cu corresponding figures are about 64 and 43%, respectively. There were many uncertainties in these calculations, and the results shall not be taken too literally but allowed the conclusion that enrichment on pyrite surfaces is an important process for retention of As and Cu below the oxidation front in pyrite rich tailings. Laser ablation is not a surface analysis technique, but more of a thin layer method, and gives no information on the type of processes resulting in enrichment on the pyrite surfaces. Although only pyrite grains that appeared to be fresh and without surface coatings were used in this study, the possibility that a thin layer of Fe-hydroxides occurred must be considered. Both adsorption to the pyrite directly or to Fe-oxyhydroxides may explain the enrichment of As, Cd, Cu and Zn on the pyrite surfaces, and, in the case of Cu, also the replacement of Fe(II) by Cu(II) in pyrite. 相似文献
15.
V. Axelsson 《Geo-Marine Letters》2001,21(4):236-244
Spatial and temporal variations in sedimentation rate and the formation of cyclic and event types of stratification have been identified by the correlation of sedimentation units between sediment cores, which were sampled on the same day during different seasons and years, as well as before and after specific events. Some results are presented from a number of selected areas along the coast of Sweden. The cores were collected in rectangular, transparent coring tubes which were subsequently X-rayed (the uppermost part in stereo) before the cores were extruded from the tubes. The optical data obtained from the radiographic images were then quantified by the use of X-ray densitometric methods. The use of X-ray radiographic techniques, especially stereo-radiography and X-ray densitometry, simplifies the core-to-core correlation as well as the determination of sedimentary properties and the quantification of sedimentation rates. 相似文献
16.
An algorithm is outlined for the implicit integration of isotropic plasticity models for an arbitrary choice of mixed stress and strain control variables. Drained as well as undrained behaviour is considered. The closest-point-projection method in conjunction with a completely strain-driven format is used in a core algorithm. In the drained case strain response variables are determined via iterations to satisfy equilibrium of prescribed and calculated stresses that correspond to the strain response variables. In the undrained case, on the other hand, strains and pore pressure are determined via simultaneous iterations to satisfy equilibrium and the incompressibility condition. The algorithm is applied to a new generalized cam-clay model, and various iteration techniques are assessed. In particular, Newton iterations which employ the matrix of algorithmic tangent stiffness moduli are shown to compete favourably with more conventional methods. 相似文献
17.
V. Stefansson G. Axelsson O. Sigurdsson G. Gudmundsson B. Steingrimsson 《Journal of Geodynamics》1985,4(1-4)
The island Surtsey was created by a submarine volcanic eruption which started on the 14th of November 1963, 21 km southwest of the Westman Islands. Volcanic activity continued in this area for nearly 4 years. During the summer of 1979 a 181 m deep continuously cored borehole was drilled on the Surtsey island. Several temperature profiles have been measured in the hole since 1979. The results of these temperature measurements are used as the basis for a discussion of the thermal condition of Surtsey. The hypothesis that intrusions rather than pillow lavas are responsible for the excess heat content of Surtsey is favored. It is found that the 13 m thick discontinuous dike complex, observed in the drill core, is sufficient to explain the excess heat content in the vicinity of the borehole and the shape of the temperature profiles recorded. It is demonstrated that the heat transfer in Surtsey has been dominated by hydrothermal convection and that the system is vapor dominated above sea level. It is estimated that the permeability of a 40 m thick section of altered tuff below sea level is 4.1 × 10−13 m2, while the permeability of the unaltered tuff above sea level is estimated as 1.2 × 10−10 m2. 相似文献
18.
Determination of major and trace elements in sphalerite using laser ablation double focusing sector field ICP-MS 总被引：1，自引：0，他引：1
The analytical performance of laser ablation (LA) for the determination of Co, Fe, Cd, Ag, Mn, Cu and S in sphalerite was evaluated using double focusing sector field inductively coupled plasma mass spectrometry (ICP-SFMS). Samples were collected from Zinkgruvan, situated in the south central Sweden. The use of Zn for internal standardisation, together with correction for FeS impurities in sphalerite, allows straightforward quantification without using external methods for the determination of the actual Zn content. LA–ICP-SFMS results were compared with data obtained by conventional pneumatic nebulisation introduction of sample solutions following acid digestion. Good agreement between the two methods was obtained for homogeneously distributed elements. For the majority of the elements under consideration, LA–ICP-SFMS precision was better than 10% RSD. 相似文献
19.
Alexander Jarosch Magnus T. Gudmundsson Thrdís Hgnadttir Gudni Axelsson 《Journal of Volcanology and Geothermal Research》2008,170(3-4):218-229
In the subglacial eruption at Gjálp in October 1996 a 6 km long and 500 m high subglacial hyaloclastite ridge was formed while large volumes of ice were melted by extremely fast heat transfer from magma to ice. Repeated surveying of ice surface geometry, measurement of inflow of ice, and a full Stokes 2-D ice flow model have been combined to estimate the heat output from Gjálp for the period 1996–2005. The very high heat output of order 106 MW during the eruption was followed by rapid decline, dropping to 2500 MW by mid 1997. It remained similar until mid 1999 but declined to 700 MW in 1999–2001. Since 2001 heat output has been insignificant, probably of order 10 MW. The total heat carried with the 1.2 × 1012 kg of basaltic andesite erupted (0.45 km3 DRE) is estimated to have been 1.5 × 1018 J. About two thirds of the thermal energy released from the 0.7 km3 edifice in Gjálp occurred during the 13-day long eruption, 20% was released from end of eruption until mid 1997, a further 10% in 1997–2001, and from mid 2001 to present, only a small fraction remained. The post-eruption heat output history can be reconciled with the gradual release of 5 × 1017 J thermal energy remaining in the Gjálp ridge after the eruption, assuming single phase liquid convection in the cooling edifice. The average temperature of the edifice is found to have been approximately 240 °C at the end of the eruption, dropping to 110 °C after 9 months and reaching 40 °C in 2001. Although an initial period of several months of very high permeability is possible, the most probable value of the permeability from 1997 onwards is of order 10− 12 m2. This is consistent with consolidated/palagonitized hyaloclastite but incompatible with unconsolidated tephra. This may indicate that palagonitization had advanced sufficiently in the first 1–2 years to form a consolidated hyaloclastite ridge, resistant to erosion. No ice flow traversing the Gjálp ridge has been observed, suggesting that it has effectively been shielded from glacial erosion in its first 10 years of existence. 相似文献