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101.
Magnetic properties of soils from sites with different geological and environmental settings 总被引:7,自引:0,他引:7
Hana Fialov Günter Maier Eduard Petrovský Ale Kapi
ka Tetyana Boyko Robert Scholger MAGPROX Team 《Journal of Applied Geophysics》2006,59(4):273-283
Measurements of magnetic susceptibility of soils, reflecting magnetic enhancement of topsoils due to atmospherically deposited magnetic particles of industrial origin, are used recently in studies dealing with outlining polluted areas, as well as with approximate determination of soil contamination with heavy metals. One of the natural limitations of this method is magnetic enhancement of soils caused by weathering magnetically rich parent rock material. In this study we compare magnetic properties of soils from regions with different geological and environmental settings. Four areas in the Czech Republic and Austria were investigated, representing both magnetically rich and poor geology, as well as point-like and diffuse pollution sources. Topsoil and subsoil samples were investigated and the effect of geology and pollution was examined. Magnetic data including mass and volume magnetic susceptibility, frequency-dependent susceptibility, and main magnetic characteristics such as coercivity (Hc and Hcr) and magnetization (Ms and Mrs) parameters are compared with heavy metal contents. The aim of the paper is to assess the applicability of soil magnetometry under different geological-environmental conditions in terms of magnetic discrimination of dominant lithogenic/anthropogenic contributions to soil magnetic signature. Our results suggest that lithology represents the primary effect on soil magnetic properties. However, in case of significant atmospheric deposition of anthropogenic particles, this contribution can be clearly recognized, independent of the type of pollution source (point-like or diffuse), and discriminated from the lithogenic one. Different soil types apparently play no role. Possible effects of climate were not investigated in this study. 相似文献
102.
Time-relative positioning makes use of observations taken at two different epochs and stations with a single global positioning
system (GPS) receiver to determine the position of the unknown station with respect to the known station. The limitation of
this method is the degradation over time of the positioning accuracy due to the temporal variation of GPS errors (ionospheric
delay, satellite clock corrections, satellite ephemerides, and tropospheric delay). The impact of these errors is significantly
reduced by adding to the one-way move from the known to the unknown station, a back move to the known station. A loop misclosure
is computed from the coordinates obtained at the known station at the beginning and at the end of the loop, and is used to
correct the coordinates of the unknown station. The field tests, presented in this paper, show that using the loop misclosure
corrections, time-relative positioning accuracy can be improved by about 60% when using single frequency data, and by about
40% with dual frequency data. For a 4-min processing interval (an 8-min loop) and a 95% probability level, errors remain under
20 cm for the horizontal components and 36 cm for the vertical component with single frequency data; and under 11 cm for the
horizontal components and 29 cm for the vertical component with dual frequency data. 相似文献
103.
We investigate the relative dispersion properties of the well-mixed class of Lagrangian stochastic models. Dimensional analysis
shows that, given a model in the class, its properties depend solely on a non-dimensional parameter, which measures the relative
weight of Lagrangian-to-Eulerian scales. This parameter is formulated in terms of Kolmogorov constants, and model properties
are then studied by modifying its value in a range that contains the experimental variability. Large variations are found
for the quantity, g* = 2gC0− 1, where g is the Richardson constant. 相似文献
104.
Layers with high magnetic susceptibility contain heavy minerals that are the most likely to preserve signatures of impact in metamorphosed Precambrian rocks. The following impact indicators are resistant to alteration and metamorphism and are likely to be found in heavy mineral layers: impact diamond, SiC, shocked zircon, high-pressure TiO2 phases, reidite, and high-pressure chromite. Coesite and stishovite could also be present but are not likely to be preserved in rocks metamorphosed above the greenschist facies. Looking for layers with high magnetic susceptibility will also identify layers that might contain concentrations of zircon for dating. 相似文献
105.
Li ChuanXin Guo ZhaoJie Meng ZiFang Li HaiYan Zhang ZhiCheng Wu ChaoDong 《中国科学D辑(英文版)》2007,50(4):544-554
Analyses of rock-magnetic properties of Neogene sediments of the Taxihe section, northern Tianshan Mountains, show that the section can be classified into three categories including lacustrine facies, fluvial facies and alluvial facies, which correspond to the lower, middle and upper of the Taxihe section respectively. The magnetic minerals of the lacustrine facies may be affected by the process of weath- ering, lithogenesis and biolithogenesis besides the source of the sediments. The natural remanence intensities are between 10-3 A/m and 10-2 A/m. The minerals are dominated by magnetite and the high coercive magnetic mineral may be goethite. The magnetic grains are the mixture of PSD SD or SD SP. The natural remanence intensities of the strata of fluvial facies are between 10-2 A/m and 10-1 A/m, about ten times that of the lacustrine facies. The magnetic minerals are mainly magnetite and hematite, and the magnetic grains are mainly PSD. The characteristic remanence (ChRM) carriers are magnetites. In the alluvial facies, the natural remanence intensities are mostly less than 1×10-2 A/m. The magnetic minerals of the series are dominated by magnetite and hematite, almost the same as the fluvial facies. But the difference is that most of the stepwise demagnetization can reveal two components and the ChRM carriers are hematites. The magnetic grains are PSD in terms of the hysteresis parameters. 相似文献
106.
107.
Ruth Soto Antonio M. Casas-Sainz Juan J. Villalaín Beln Oliva-Urcia 《Tectonophysics》2007,445(3-4):373-394
In this work we analyse and check the results of anisotropy of magnetic susceptibility (AMS) by means of a comparison with palaeostress orientations obtained from the analysis of brittle mesostructures in the Cabuérniga Cretaceous basin, located in the western end of the Basque–Cantabrian basin, North Spain. The AMS data refer to 23 sites including Triassic red beds, Jurassic and Lower Cretaceous limestones, sandstones and shales. These deposits are weakly deformed, and represent the syn-rift sequence linked to basins formed during the Mesozoic and later inverted during the Pyrenean compression. The observed magnetic fabrics are typical of early stages of deformation, and show oblate, triaxial and prolate magnetic ellipsoids. The magnetic fabric seems to be related to a tectonic overprint of an original, compaction, sedimentary fabric. Most sites display a NE–SW magnetic lineation that is interpreted to represent the stretching direction of the Early Cretaceous extensional stage of the basin, without recording of the Tertiary compressional events, except for sites with compression-related cleavage.Brittle mesostructures include normal faults, calcite and quartz tension gashes and joints, related to the extensional stage. The results obtained from joints and tension gashes show a dominant N–S to NE–SW, and secondary NW–SE, extension direction. Paleostresses obtained from fault analysis (Right Dihedra and stress inversion methods) indicate NW–SE to E–W, and N–S extension direction. The results obtained from brittle mesostructures show a complex pattern resulting from the superposition of several tectonic processes during the Mesozoic, linked to the tectonic activity related to the opening of the Bay of Biscay during the Early Cretaceous. This work shows the potential in using AMS analysis in inverted basins to unravel its previous extensional history when the magnetic fabric is not expected to be modified by subsequent deformational events. Brittle mesostructure analysis seems to be more sensitive to far-field stress conditions and record longer time spans, whereas AMS records deformation on the near distance, during shorter intervals of time. 相似文献
108.
本文简介了康普顿背散射扫描仪(CBS)的基本原理,优点,阐述了便携式CBS的特点和对CBS多道分析器的要求,介绍了一种多道分析器的指标,电路原理,工作过程和稳峰技术。 相似文献
109.
清江神女洞岩溶洞穴沉积物的磁学研究 总被引:3,自引:0,他引:3
通过对清江神女洞岩溶沉积物的磁学研究,得出有关该洞沉积物形成环境的下列判断:岩溶洞穴沉积物形成于早更新世至中更新世;岩溶洞穴沉积物形成于湿暖、干冷交替的环境;岩溶洞穴沉积物形成于NE56°流向的古水流中。 相似文献
110.
LEI Xiangyi YUE LepingLoess Research Section Department of Geology Northwest University Xi'' an Shaanxi 《《地质学报》英文版》1998,72(4):420-431
The Fengzhou loess section is very typical in the Qinling Mountains. The section, which is about 82 m thick and underlain by Neogene red clays, consists of 33 layers of loess and 33 layers of palaeosol. It covers the Brunhes normal polarity zone and Matuyama reversed polarity zone, and the B/ M boundary is located in the middle part of loess layer 8 (L8). The loess of the Matuyama reversed polarity zone records the Jaramillo, Olduvai and Reunion normal polarity subchrons. The boundary between the Matuyama reversed polarity zone and Gauss normal polarity zone (M / Ga) appears on the lithological boundary between loess and Neogene red clays. Loess accumulation in the Fengzhou section started before 2.48 Ma B.P. Based on the stratigraphical structure, the material composition and magnetic susceptibility curve of the Fengzhou loess section, the palaeoclimatic changes during the last 2.48 Ma in the Qinling Mountains are subdivided into 66 cold-dry and warm-humid stages, equivalent to 33 climatic cycles. The 相似文献