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1.
The use of magnetic measurements to investigate the mineralogy of Icelandic lake sediments and to study catchment processes 总被引：4，自引：0，他引：4
RICHARD BRADSHAW ROY THOMPSON 《Boreas: An International Journal of Quaternary Research》1985,14(3):203-215
Magnetic measurements made on sediment and catchment samples from two contrasting Icelandic lakes show how susceptibility and saturation isothermal remanent magnetisation alter as magnetic minerals pass from rock to soil to stream and into the lakes. There is no detectable growth of secondary magnetic minerals in Icelandic soil profiles and susceptibility peaks in the 62.5–1000 μm size range of mineral particles in the lake sediments. Changes in sediment source can be detected using combinations of magnetic measurements. 相似文献
2.
Geophysical methods are widely applied to soils for resolving different tasks in precision agriculture, pollution evaluation, erosion estimation, etc. Environmental magnetic methods were applied in our study on a collection of soil samples from area near Rosslau (Germany), which was gathered on the basis of a field electromagnetic induction study. Magnetic laboratory analyses include magnetic susceptibility, isothermal remanent magnetization (IRM), anhysteretic remanent magnetization (ARM), thermomagnetic analyses for determination of the kind of magnetic minerals present in soils. The results reveal the presence of statistically significant inverse correlations between magnetic susceptibility, as well as remanent magnetizations ARM and IRM, and conductivity values. This maybe ascribed to influence of topography and water regime on the iron oxide forms in soil and the influence of soil moisture on soil conductivity. Magnetic measurements on soil cores showed close correspondence between soil horizons outlined in 1 m-long cores, and depth changes in mass-specific magnetic susceptibility. Existing relationships between magnetic characteristics, soil reaction pH, and nutrients’ content (total nitrogen, carbon and sulphur) have been explored by cluster analysis and general regression model statistics. The results reveal the presence of significant correlations between nutrients’ content, magnetic susceptibility and the grain size sensitive ratio ARM/χ. These are expressed by numerical equations, representing pedotransfer functions, which predict the content of Nitrogen, Carbon and Sulphur through combination of magnetic parameters and soil pH. The obtained pedotransfer functions for the particular case of Gley soils and Fluvisols studied could be used for application of magnetic methods in agricultural practice as a fast and inexpensive proxy evaluation of the content of these nutrition elements. 相似文献
3.
Magnetic susceptibility measurements were conducted on 24 vibrocores obtained from an area located off the northeastern coast
of Lantau Island in Hong Kong. High intensities of magnetic susceptibility were detected in the uppermost sections of the
majority of the cores. Several magnetic parameters measured for one of the cores suggest that the variations in the magnetic
characteristics over depth are mainly due to varying concentrations of the magnetic minerals. Since a strong correlation has
been found between magnetic susceptibility and the heavy metals Pb, Cu, Zn and Cr, an anthropogenic contamination origin is
thought to be the cause. The present study shows that magnetic susceptibility is a fast, inexpensive and non-destructive method
for the detection and mapping of contaminated sediments.
Received: 12 August 1997 · Accepted: 18 November 1997 相似文献
4.
Correlation between magnetic susceptibility and heavy metals in urban topsoil: a case study from the city of Xuzhou, China 总被引：7，自引：0，他引：7
Anthropogenic influence, mainly due to urban and industrial activities and traffic exhaust, may affect urban topsoil via atmospheric contamination and solid waste. Magnetic susceptibility measurements were conducted on 21 urban topsoil samples from the city of Xuzhou, China. High intensities of magnetic susceptibility were detected in the majority of the samples. SEM analysis shows that magnetic minerals are in the form of spherules and mainly due to anthropogenic inputs. The heavy metals Pb, Cu, Zn, Se, Sc, Mo, Fe, and Bi show strong correlations with magnetic susceptibility, and Ag, Ba, Cd, Ni, Cr, Sb, and Sn, on the other hand, show a weak correlation with magnetic susceptibility. Whereas, of these metals studied, only Hg has no significant correlation with the susceptibility. The Tomlinson pollution load index (PLI) also shows significant correlation with the susceptibility (χ). The present study shows that magnetic susceptibility is a fast, inexpensive, and non-destructive method for the detection and mapping of contaminated soils. 相似文献
5.
Marcos A. E. Chaparro Juan M. Lirio Héctor Nuñez Claudia S. G. Gogorza Ana M. Sinito 《Environmental Geology》2005,49(1):30-43
Magnetic properties of lagoon and stream sediments from Chascomús area (Buenos Aires Province) and the relevance of various magnetic parameters as giving pollution status are studied in the present work. This work is focussed on magnetic parameters, such as concentration-dependent (magnetic susceptibility, saturation anhysteric and isothermal remanent magnetisation) and feature-dependent parameters (S-ratio, coercivity of remanence, anhysteric susceptibility/magnetic susceptibility-ratio), as pollution indicators. Firstly and most importantly, different magnetic parameters and chemical measurements were correlated in order to investigate their goodness, obtaining the best results for feature-dependent magnetic parameters. Coercivity of remanence correlate very well with chemical variables, showing correlations at high level of significance up to 0.9094, and the anhysteric susceptibility/magnetic susceptibility-ratio also shows very good correlations (up to 0.8376). Some results and advantages of using a new experimental method in order to discriminate hard and soft magnetic phases are also shown. This method uses alternately backfield isothermal remanent magnetisation and alternating field demagnetisation. From the experimental separation, the presence of hard magnetic phases in some samples was confirmed. 相似文献
6.
We have applied techniques used in rock magnetism to the study of possible temporal changes in provenance and firing conditions of a collection of Etruscan bucchero pottery fragments representing the interval between 800 B.C. to 400 B.C. To our knowledge, this is the first time that such procedures have been applied to ancient ceramic wares. Our preliminary magnetic measurements demonstrate that this approach can provide useful archaeological information, as exemplified by the following results: (1) Bucchero ceramic styles sottile, spesso, and possibly pesante, contained magnetic particles of similar grain sizes, which suggested a common provenance and similar firing conditions for these pot typologies. (2) Ceramic styles buccheroid impasto and grey bucchero each had magnetic characteristics different from those in (1). However, too few samples of these were available for any definite conclusions. (3) The occurrence of magnetite, and not hematite, in all samples indicated that firing conditions were effectively reducing. (4) Variations in the amount of magnetite in different samples indicated that slight inhomogeneities must have existed in the iron oxide/hydroxide content of the local clay source. Most magnetic techniques are fast, easy, and generally nondestructive. Some magnetic properties, such as initial susceptibility, saturation remanent magnetization, and coercivity of remanence, can even be measured in the field. At the least, magnetic measurements can be used initially to discriminate among different groups of potsherds. Selected samples can then be analyzed with more elaborate methods of archaeometry. 相似文献
7.
磁化率是环境磁学研究中较常用、较易获得的指标之一,但其解释和意义又最为复杂.对采自中国东部从北到南涵盖中国主要气候带的风化-成壤成因的79个表层土壤样品进行高、低频磁化率和非磁滞剩磁测试并分析其与降水量、年均温等气候参数的关系.结果表明:(1)发育于不同类型母岩的风化-成壤成因表层土壤磁学性质之间存在显著差异,各磁化率参数与气候条件参数之间的关系大不一样,在大空间尺度进行磁学与气候条件的关系研究时,必须充分考虑地质背景与母岩类型的差异.(2)发育于花岗岩的表层土壤非磁滞剩磁磁化率与年降水量和年均温间呈显著负相关关系;而发育于玄武岩的表层土壤非磁滞剩磁磁化率与年降水量呈显著正相关关系.被广泛认可的黄土-古土壤序列磁化率与成壤的关系不一定适用于大空间尺度的其他气候区域.(3)在风化-成壤过程中,磁性颗粒有变细的趋势,但降水强度增大时,一些超细颗粒较易被搬运离开原地,单一磁学参数结果难以反映气候条件及环境变化.(4)风化-成壤成因表层土壤非磁滞剩磁磁化率能较好地反映风化成因土壤的风化程度,但风化-成壤表层土壤磁学性质变化的机制特别是对相应土壤剖面的磁性矿物迁移转化有待深入研究. 相似文献
8.
Two types of soil (fluvisols and anthrosols) were collected from different environmental settings (suburb and industrial area)
in Wuhan, central China, aiming to examine the applicability of magnetic mapping for heavy metal pollution of urban soil in
a large region. Magnetic measurements and chemical analysis indicated elevated magnetization and heavy metal concentrations
of topsoils in the industrial area. Magnetic susceptibility (χ), anhysteretic remanent magnetization (ARM) and saturation
isothermal remanent magnetization (SIRM) of fluvisols are much higher than those of anthrosols, but contrary for frequency-dependent
susceptibility, indicating that soil magnetism strongly depends on the soil type/condition. Predominant magnetic carrier in
topsoils in industrial area is pseudo-single-domain/multi-domain magnetite. Environmental scanning electron microscope/energy
dispersive X-ray examination of the magnetic extracts from these topsoils revealed abundant spherical particles with diameters
of 10–50 μm that are rich in iron-oxides, and could be attributed to the nearby industrial activities (e.g., steel work and
power generation). Significant correlations were observed between magnetic concentration-related parameters (e.g., χ, ARM
and SIRM) and concentrations of Cu, Pb, Zn, Hg and Tomlinson pollution load index. These results proposed that magnetic proxy
mapping of soil pollution is an effective, fast and inexpensive tool for delineation of heavy metal pollution. However, interpretation
of magnetic properties for such a purpose must be done on a site-specific basis, taking into account the possibilities of
pedogenic enhancement/depletion under the specific soil conditions. 相似文献
9.
10.
Evaluating magnetic lineations (AMS) in deformed rocks 总被引：3，自引：0，他引：3
Magnetic lineation in rocks is given by a cluster of the principal axes of maximum susceptibility (Kmax) of the Anisotropy of Magnetic Susceptibility (AMS) tensor. In deformed rocks, magnetic lineations are generally considered to be the result of either bedding and cleavage intersection or they parallel the tectonic extension direction in high strain zones. Our AMS determinations, based on a variety of samples that were taken from mudstones, slates and schists from the Pyrenees and Appalachians, show that strain is not the only factor controlling the development of magnetic lineation. We find that the development and extent to which the magnetic lineation parallels the tectonic extension direction depends on both the original AMS tensor, which in turn depends on the lithology, and the deformation intensity. Rocks having a weak pre-deformational fabric will develop magnetic lineations that more readily will track the tectonic extension. 相似文献
11.
《Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy》1999,24(6):541-543
A non-conventional way of utilizing magnetic susceptibility — soil kappametry — was tested in the area of a major metallurgical plant VSŽ Košice (East Slovakia). Magnetic susceptibility values above background in soil samples indicate higher concentrations of heavy metals in soil, i.e. the soil kappametry can be used as a preliminary quick and inexpensive method for detection of higher heavy metal contents in soils. 相似文献
12.
Sediment provenance in a tropical fluvial and marine context by magnetic 'fingerprinting' of transportable sand fractions 总被引：1，自引：0，他引：1
B. A. MAHER S. J. WATKINS G. BRUNSKILL† J. ALEXANDER‡ C. R. FIELDING§ 《Sedimentology》2009,56(3):841-861
The sources and fluxes of sediment to the Great Barrier Reef lagoon from north‐eastern Australian rivers have been the subject of much concern and study, with the large catchments of the Burdekin and Fitzroy Rivers thought to be the key sources at present. Here, the utility of newly developed magnetic ‘fingerprinting’ methods for identifying sediment provenance, both onshore and offshore, and in association with individual large flood events, is investigated. Within the Burdekin catchment, sediments are mobilized from different subcatchments by runoff generated by intense, localized rainfall events. Magnetic measurements were made on untreated and acid‐treated samples of river channel sediments within the Burdekin River subcatchments and from the estuarine and inner shelf depocentres of Burdekin River sediments. The acid treatment removes all discrete magnetic particles and coatings, and leaves magnetic inclusions (protected within host silicate grains) as the basis of the measured magnetic signature of a sample. The magnetic properties of the acid‐treated samples display statistically distinct sediment provenance groupings. Sand samples from the Upper Burdekin River appear magnetically distinct from samples from tributaries of the Burdekin (e.g. Hann Creek, Fanning River) and also from nearby coastal rivers, including the Haughton. Suspended sand samples from a Burdekin flood event in 2000 appear to have a different source compared with those from floods in 1998 and 1999. Comparisons of the terrestrial, acid‐treated sand fractions with the same, acid‐treated, sand‐size fractions from transects taken offshore suggest that the surface sediments in Upstart Bay and Bowling Green Bay have different sources. Some of these sources are as yet unidentified but may represent the unsampled, lower‐discharge south‐western Burdekin subcatchments, and/or along‐shore drift of sand from the south, perhaps even from the Fitzroy River, over millennial timescales of cyclone pumping. The magnetic inclusion method precludes any obfuscation or confounding of sediment source, which might arise from hydraulic sorting and/or post‐depositional magnetic diagenesis or authigenesis. 相似文献
13.
Magnetic susceptibility anisotropy as a strain indicator in the sudbury basin, Ontario 总被引：2，自引：0，他引：2
The magnetic susceptibility anisotropy of 181 samples from the Chelmsford Formation, the Onaping Formation and the norite of the Sudbury Basin has been measured. Magnetic foliation planes are almost exactly parallel to the planar structural elements (slaty cleavage and foliation) that are axial planar to the Basin. Magnetic lineations, where present, are parallel to linear structural elements (mineral elongation lineations). The shapes of the susceptibility ellipsoids of individual samples and the grouping of their principal axes are used to classify each site according to one of nine possible anisotropy types. In the Chelmsford Formation there is dominantly one anisotropy type, but several are present in the norite. At each site there is a variation in shape of the anisotropy ellipsoids, which can be interpreted using magnetic susceptibility axial ratio plots analogous to the deformation plots used by structural geologists. Using this technique the measured anisotropy patterns are interpreted in terms of progressive modification of original predeformation magnetic fabrics by various types of strain. In the norite the shape of the susceptibility ellipsoid and the anisotropy type vary systematically with distance from the Grenville Front. 相似文献
14.
磁化率对土壤重金属污染的指示性研究——以沈阳新城子区为例 总被引：4，自引：0，他引：4
通过对399件表层土壤磁化率参数与化学组成的分析测试,较系统地总结了沈阳新城子区土壤磁化率特征,并初步进行了磁化率对土壤重金属污染的指示研究。结果表明:(1)不同土壤类型中磁化率差异较大,棕壤中由于人为作用较大,其均值最高。不同堆积类型中磁化率差别较大,洪积物和残坡积物中平均值最高,冲积物中最低。不同农作物对元素的需求不一样导致磁化率的含量变化范围存在着区别。(2)土壤的磁化率与土壤中Cd、Pb、Hg、Cu、Zn等重金属元素含量呈显著正相关,且与土壤pH值呈显著负相关关系,能反映出土壤酸化的状况,对土壤污染程度有较好的指示性。(3)利用磁化率可以快捷地划分污染区。 相似文献
15.
在胶东地区招远-平度断裂带上的大磨曲家金矿区选取了典型的构造区域进行岩石磁组构研究。沿着断裂带在不同构造部位的36个采样点钻取了112个定向岩心样品,所有样品均沿勘探线布置。磁组构研究显示,研究区以弱磁性岩石为主,总体上,胶东群变质岩的磁化率值较高,而玲珑黑云母花岗岩的磁化率值较低,尤以碎裂程度高的强蚀变岩的磁化率值最低;磁化率各向异性方位主要为NE向挤压,磁组构所指示的构造应力场与大磨曲家矿区的区域挤压应力方向是相同的;对具不同程度矿化的81线的Au含量与80线磁组构各向异性度(P值)进行对比研究发现,P值与金品位呈负相关关系;弱矿化糜棱岩中的金矿化在磁面理发育的岩石中较为发育,成矿晚期,Au元素含量随着岩石磁性的减弱而增加,特别是在强应变后弛豫阶段矿液充填于相对张性的石英脉中Au含量最高。 相似文献
16.
The anisotropy of magnetic susceptibility (AMS) of single crystals of biotite, muscovite and chlorite has been measured in order to provide accurate values of the magnetic anisotropy properties for these common rock-forming minerals. The low-field AMS and the high-field paramagnetic susceptibility are defined. For the high-field values, it is necessary to combine the paramagnetic deviatoric tensor obtained from the high-field torque magnetometer with the paramagnetic bulk susceptibility measured from magnetization curves of the crystals. This leads to the full paramagnetic susceptibility ellipsoid due to the anisotropic distribution of iron cations in the silicate lattice. The ellipsoid of paramagnetic susceptibility, which was obtained for the three phyllosilicates, is highly oblate in shape and the minimum susceptibility direction is subparallel to the crystallographic c-axes. The anisotropy of the susceptibility within the basal plane of the biotite has been evaluated and found to be isotropic within the accuracy of the instrumental measurements. The degree of anisotropy of biotite and chlorite is compatible with previously reported values while for muscovite the smaller than previously published values. The shape of the chlorite AMS ellipsoid for all the samples is near-perfect oblate in contrast with a wide distribution of oblate and prolate values reported in earlier studies. Reliable values are important for deriving models of the magnetic anisotropy where it reflects mineral fabrics and deformation of rocks. 相似文献
17.
灵台红粘土—黄土—古土壤序列频率磁化率的古气候意义 总被引：10，自引：0，他引：10
通过对甘肃灵台晚新生代红粘土－黄土－古土壤序列的磁化率测量和频率磁化率分析，发现红粘土及黄土－古土壤的磁化率和频率磁化率化率存有良好的正相关关系，表明两套沉积在成壤过程中由生物作用或化学作用而形成的超顺磁性矿物含量，对磁化率和频率磁化率增大有重要的贡献。相比化率而言，受影响因素较少的频率磁化率变化，反映了不同气候条件下形成的超顺磁粒级铁磁矿物的相对含量，能更真实、敏感地记录不同时间尺度的古气候波动。灵台红粘土－黄土－古土壤序列的频率磁化等在2．6MaBP前后不同的变率特征，揭示了大冰期来临前后黄土高原的冷暖、干湿反差产生了显著变化，而与此相关的冬、夏季风变迁则表现出不同的组合特征。 相似文献
18.
Aleksandra Stachowska Maciej Łoziński Michał Śmigielski Anna Wysocka Leszek Jankowski Piotr Ziółkowski 《Sedimentology》2020,67(7):3783-3808
The anisotropy of magnetic susceptibility is a well-known geological proxy in revealing the directional tectonic and sedimentological features of rocks, although it can be ambiguous in situations where these two factors co-occur. This paper demonstrates the usefulness of the anisotropy of magnetic susceptibility in determining palaeotransport directions in turbiditic rocks that underwent subsequent thrusting and folding. This study demonstrates that the magnetic lineation is largely unsuitable as a palaeocurrent direction proxy, and suggests that the imbrication of magnetic foliation is better in such cases. Moreover, the anisotropy of magnetic susceptibility results were analyzed in reference to a joint and fold study within the framework of the regional structural geology. Magnetic fabric investigations were conducted in the eastern part of the Outer Western Carpathians (south-east Poland). During the study, a total of 191 oriented palaeomagnetic samples were collected from three outcrops (Nasiczne, Dwernik and Hoczew) in the Krosno Beds, Silesian Unit. For the purpose of sedimentological analysis, 121 m of turbidite successions were documented and 126 directional sedimentary structures were measured. The magnetic anisotropy of sandstones revealed typical sedimentary fabrics, often overprinted by variably intense tectonic deformation. Oblate susceptibility ellipsoids from Nasiczne showed tilt coherent with the palaeoflow direction, whereas the rocks from Dwernik and Hoczew contained triaxial magnetic fabric developed during compressional palaeostress. This paper suggests that medium-grained and coarse-grained sandstones, preferably with high mica content, are the most suitable for palaeotransport reconstructions among the studied lithologies. 相似文献
19.
Time dependence of magnetic susceptibility of soil chronosequences on the California coast 总被引：1，自引：0，他引：1
As the age of the soils in a chronosequence on the California coast increases, the difference between the magnetic susceptibility of eluvial and illuvial horizons increases, and the residual susceptibility after extraction with citrate-bicarbonate-dithionite (CBD) decreases. Enhanced susceptibility results from the conversion of nonferrimagnetic minerals to secondary ferrimagnetic forms (most likely maghemite) and the preferential accumulation of inherited and pedogenic magnetic minerals. Little enhancement occurs for pedons younger than 40,000 yr. By 124,000 yr, most of the magnetic susceptibility can be attributed to forms soluble in CBD. Magnetic susceptibility appears to vary systematically over time for three chronosequences from areas with mean annual precipitation ranging from 650 to 1500 mm yr−1. Magnetic susceptibility enhancement may be a useful parameter for estimating soil age in certain climates. 相似文献
20.
F. Di Benedetto G. B. Andreozzi G. P. Bernardini M. Borgheresi A. Caneschi C. Cipriani D. Gatteschi M. Romanelli 《Physics and Chemistry of Minerals》2005,32(5-6):339-348
An extensive study of natural and synthetic Fe-bearing sphalerites (Fe-content ranging from 0.005 afu to 0.250 afu) has been carried out through the combined investigations of the temperature dependence of the magnetic susceptibility and of the 57Fe Mössbauer spectroscopic features. Magnetic susceptibility measurements evidence, in the low temperature regime, the presence of clustered Fe even in the most diluted samples, whereas all the Mössbauer spectra are described in terms of variable proportions of three components, namely one single and two doublets absorption, centred at the same isomer shift, relative to Fe ions and to different Fe clusters, respectively. The comparison of all the experimental results points out a self-affinity of Fe ions in sphalerite favoured by the superexchange interaction, which stabilises the formation of clusters even in diluted samples and may be related to both macroscopic inhomogeneous distribution and crystal zoning. 相似文献