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1.
Ferrimagnetic minerals in red paleosols of Pleistocene Epoch, eastern China   总被引：1，自引：1，他引：0  
The type,grain size and origin of ferimagnetic minerals separated from red paleosols of pleistocene Epoch(Q2)in eastern China ,were studied by using mineral magnetic measurement,X-ray powder diffraction and electron microscopy.Results showed that the iron oxider in red paleosols were composed of hematite(α-Fe2O3),maghemite(γ-Fe2O3) and goethite(α-FeOOH),Mineral magnetic parameters and X-ray diffraction patterns indicated that maghemite was the dominant remanence carrier in red paleosols,which is characterized by superparamagnetic(SP) and stable single domain(SSD) grains,The variations of magnetic susceptibility(χ） ,anhysteretic magnetic susceptibility(χRAM）and saturation isothermal remanent magnetization(SIRM) for red paleosols following heating to various temperatures showed two peak values at 700℃ and 900℃.The spherulitic magnetic particles measuring 250-1000μm in diameter in red paleosols were separated by the magnetic separation method,indicating that these magnetic particles were an assemblage of superparamagnetic and stable single domain ferrimagnetic grains,It is suggested that the ferrimagnetic minerals of red paleosols be a pedogenic ferrimagnetic component under high temperature and high humid conditions in the Pleistocene Fpoch(Q2).It is concluded that the magnetism characteristics of red paleosols can be used to evaluate the environmental changes of Quaternary in eastern China.  相似文献   

2.
Magnetic parameters have been widely used as a rapid, cost-effective, and non-destructive method. To assess whether their magnetic properties reflect the development history in the Pearl River Delta, three sediment cores collected from South China coastal waters were selected for magnetic research. The results indicate that the predominant ferrimagnetic mineral is magnetite, with an additional smaller amount of surprisingly high-coercive greigite. Fine-grained superparamagnetic and single-domain particles of magnetite and the relative contribution of greigite are increased when the total concentration of ferrimagnetic minerals is higher. Three well-known stages of the Chinese history, i.e., iron smelting, cultural revolution, and the latest phase of opening and reforming were identified in the vertical variation of magnetic concentration parameters. Although the record of the three cores is not completely consistent, the results point out that magnetic concentration parameters can reflect the development and pollution history in surrounding coastal areas.  相似文献   

3.
The use of mineral magnetic techniques as pollution proxy for road deposited sediment was explored using various statistical approaches. Standard techniques were adopted for measurement of mineral magnetic and geochemical parameters. The analyses of magnetic parameters revealed that the samples were dominated by ferrimagnetic minerals and multidomain grains. This implied that the magnetic fractions in the samples might be of anthropogenic origin. Results also indicate that the samples were dominated by low coercive, magnetically soft minerals. Thermomagnetic curves confirmed magnetite as the remanence bearing magnetic mineral having a Curie point temperature of ~580 °C. The strong association observed between magnetic susceptibility, susceptibility of anhysteric remanent magnetization and saturation isothermal remanent magnetization and aluminum, titanium, manganese, iron, chromium and lead demonstrated that these metals occurred as ferrimagnetic particles of technogenic origin resulting from vehicular sources. Assessment of pollution status of the road deposited sediment identified silicon and lead as the priority pollutants of concern. Generally, pollution load index was <1 (mean, 0.66 ± 0.14), indicating that the samples were not polluted in the overall, but the metals were in the buildup stage requiring constant monitoring. The sources of pollutants from principal component and cluster analyses identified the sources of pollution to be mainly from vehicular emissions such as brake linings, exhaust materials, tire wear, corroded metal parts, abrasion of lubricating oil and road construction materials. This study found that mineral magnetic techniques offer great potential as pollution proxy for soil pollution studies.  相似文献   

4.
Intense primary biologic productivity in the surface waters of the Benguela upwelling system provides a high supply of organic matter to the sea floor at the continental slope off Namibia and sustains extreme concentrations of magnetite producing bacteria in the top sediment layers. Biogenic magnetite is thus by far the dominant carrier of the magnetic signal in these deposits also because of a very minor input of terrigenous ferrimagnetic minerals. Reducing conditions in the sediment column cause a selective dissolution of the bacterial magnetite fraction just a few centimeters below the main mineralization horizon. This diagenetic process is documented in detail by high-resolution rock magnetic analyses and transmission electron microscopy. Concentration dependent and grain-size sensitive magnetic parameters, such as susceptibility, laboratory imparted remanences, and hysteresis data, reveal a significant drop in ferrimagnetic mineral content within the upper 10 cm of the sediments accompanied by a gradual downward coarsening of the ferrimagnetic mineral assemblage from primarily magnetic single-domain particles in the top centimeters to multi-domain grains in deeper strata. Electron microscope observations enable both an unequivocal identification of bacterial magnetite on the basis of shape and grain-size and to trace dissolution effects on the biogenic magnetic mineral component to depth. Received: 9 November 1998 / Accepted: 10 October 1999  相似文献   

5.
以嘉峪关市为研究靶区,系统采集城区表土样品58件,对其进行环境磁学和重金属元素（Cd、Cr、Cu、Mn、Pb、V、Zn、Fe）质量分数分析。结果表明：嘉峪关市表土以低矫顽力磁铁矿为主导,磁晶粒度以较粗的假单畴（PSD）和多畴（MD）颗粒为主;城区表土亚铁磁性矿物浓度和磁性颗粒大小远高于国内综合型大城市表土;市区反映磁性矿物含量的参数呈现出以酒钢厂和废渣场为中心的高值区域,并随着污染源距离的增加向周围递减;嘉峪关市表土重金属Cd、Cr、Cu、Mn、Pb、V、Zn、Fe质量分数与反映磁性矿物含量的参数具有显著共变性,二者的高值分布与反映磁晶粒度参数的高值分布成盈缺呼应关系。然而嘉峪关市土壤母质磁性颗粒本底值较粗,与污染土壤特征相似,因此对西北地区而言,亚铁磁性矿物浓度相对磁晶粒度可以更好地指示钢铁厂周边土壤重金属的污染程度。  相似文献   

6.
Mumbai metropolitan region (MMR) in India represents one of the most industrialized and thickly populated areas of the monsoon dominated Asian region. We present here pre- and post-monsoon magnetic susceptibility variations in the top-soils representing sampling domains of industrial, heavy traffic and forested areas within MMR. The rock magnetic studies (including isothermal and anhysteric remanent magnetization and hysteresis loop analysis) infer predominant pseudo single domain to multi domain grains in an overall ferrimagnetic dominant mineralogy of the soils. The susceptibility-temperature variations (from ?190 to 700°C) infer maghemite (??-Fe2O3) as the chief mineral component of pedogenic origin, and the pure magnetite (Fe3O4) is of anthropogenic nature. Spatial distribution of ferrimagnetic concentration is in agreement with polluting sources. The post-monsoon redistribution pattern is greatly controlled by the surface runoff and topographic conditions. The study demonstrates that in a ferrimagnetically reach substrate like MMR, the spatial distribution patterns derived from routine concentration- and grain-size-dependent rock magnetic parameters integrated with topographic and seasonal attributes yield significant information on the style and surface re-distribution of anthropogenically loaded soils and sediments to identify its seasonal dumping. Alternatively, knowing the source of signal, the magnetic susceptibility can be further used as a robust parameter to produce detailed maps to monitor the pollutions in urban areas.  相似文献   

7.
Magnetic analysis and 57Fe Mössbauer spectroscopy were used to find characteristic properties of obsidian samples collected from various localities in the Mediterranean area. Magnetic hysteresis parameters of ≈ 30 different obsidian samples, recorded at 294 K, and plotted in the form σ r /σ s versus H c /H cr (σ r =saturation remanent magnetization, σ s =saturation magnetization of ferrimagnetic phases in the obsidian samples, H c =coercive force, H cr =remanent coercive force) cluster in certain areas of the plot for obsidian samples of a given region. This property results from the formation of ferrimagnetic ore grains of various grain sizes, which appear to be Fe3O4-rich spinels (Curie temperatures T c ≈520–580°C), during the rapid cooling process of the silica-rich magma. For single domain, pseudosingle domain and multidomain particles of magnetic minerals, corresponding to different grain sizes, the data points are usually in different areas of the plot. The results show that there is obviously a characteristic difference in the ore grain size and in the grain size distribution for obsidian samples from different regions. 57Fe Mössbauer absorption spectra revealed two distinct kinds of patterns, characterized by contributions from Fe2+ and Fe3+ cations preferentially inside the glassy matrix. The poor resolution of the spectra precludes the application of this method for identification purposes. The Mössbauer parameters of quadrupole splitting, isomer shift and linewidth are compatible with the respective values for Fe2+ and Fe3+ cations in alkali and alkaline-earth silicate glasses.  相似文献   

8.
Rock-magnetic techniques have become a useful tool in environmental issues; in particular, magnetic studies constitute an alternative way to study pollution in different media. The present contribution focuses on magnetic parameters as pollution indicators, especially from their relationship with contents of heavy metals. The work was carried out in two Indian rivers located in Tamil Nadu, southern India. Several sediment samples were collected and studied in the laboratory using magnetic techniques, magnetic susceptibility, anhysteric remanent magnetization, isothermal remanent magnetization, and chemical techniques to determine contents of heavy metals. Magnetic mineralogy indicates the predominance of ferrimagnetic minerals; although magnetite-like minerals are the main magnetic carriers, antiferromagnetic minerals can be present as subordinate carriers. Concentration-dependent magnetic parameters revealed noticeable differences between both rivers, e.g. magnetic susceptibility is four times higher in Cauvery than in Palaru River. Moreover, such increase can be interpreted as “magnetic enhancement” and therefore related to the pollution status. This magnetic enhancement indicated a different pollutant contribution in both rivers, and also, a different spatial distribution along these rivers, where critical (or more polluted) sites were identified. On the other hand, univariate and multivariate statistical analyses—e.g. PCoordA, Multifactorial Analysis of distance, PCA and RDA—were examined, revealing a link between magnetic and chemical variables. Among magnetic parameters, the concentration-dependent magnetic parameters (e.g. magnetic susceptibility) seem to be the most relevant for this study.  相似文献   

9.
Measuring magnetic susceptibility is a method which is used to estimate the amount of magnetic particles in soils, sediments or dusts. Changes in magnetic susceptibility can be due to various reasons: input from different sources of sediments, e.g. from different soils or rocks, atmospheric fallout of anthropogenic dusts containing magnetic particles produced by fossil fuel combustion, steel production or road traffic. In the case of river sediments, input from the catchment is of primary significance. The main aim of this investigation was to test the potential of magnetic susceptibility screening in identifying the effect and significance of anthropogenic activities in an area with complex geological conditions. We investigated the magnetic susceptibility of riverbed sediments of the largest river of the Czech Republic, the Moldau river. Besides that, the magnetic signal of nearby topsoils as well as of outcropping bedrocks in the vicinity of the river was examined. In the upper 300 km of the river, the magnetic enhancement of the river sediments can be linked to anthropogenic activities. Positive correlations were found in the river sediments between the contents of Cu and Zn and magnetic susceptibility, while Fe, Mn and Ni did not show a correlation with magnetic susceptibility. However, the major geogenic magnetic anomaly in the area around the Slapy dam has made it impossible to unambiguously interpret the magnetic signal in terms of anthropogenic impact in the last 80 km downstream.  相似文献   

10.
A magnetic investigation of a loess/paleosol sequences record in Ili area   总被引：1，自引：0，他引：1  
The pedogenic ferrimagnetic minerals have been considered to be the cause of magnetic susceptibility enhancement in loess deposits distributing in the Chinese Loess Plateau and Central Europe, while “wind intensity” mechanism is proposed to be responsible for the magnetic susceptibility enhancement of loess in Alaska and Siberia. However, the magnetic enhancement mechanism is still open for loess in Ili valley, Xinjiang Uygur Autonomous Region, China. To understand this, we conducted a rock magnetic investigation on Axike section that is located in Ili valley. Results show that transitional stage from magnetic (χlf) trough to magnetic (χlf) peak corresponds to soil units. The PSD and MD-grained magnetite dominate the magnetic properties of AXK sequences, and the main factor affecting magnetic properties is the concentration of ferrimagnetic fraction. For the “pedogenesis enhancement” and “wind intensity” model, it seems hard to explain the magnetic susceptibility enhancement in this area. For the concentration of fine-grained magnetite in magnetic mineral shows positive relationship with the intensity of pedogenesis, the magnetic parameters of loess deposit in Ili valley can be used to recover paleoclimatic variations.  相似文献   

11.
Urban soil samples collected from the city of Xuzhou were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) for Pb and Zn. The samples were also investigated for mineralogy using X-ray diffraction, thermal analyses and scanning electron microscopy (SEM). The identified minerals are mainly composed of quartz and calcite as major minerals. Soil samples contained elevated Zn (2,049 ± 5,439 mg/kg) and Pb (115 ± 58 mg/kg). According to the index of geoaccumulation, the soils of the study area are considered to be moderately to strongly contaminated with respect to Zn, moderately contaminated with respect to Pb. The magnetic measurements indicate that the dominant magnetic components are multidomain grains of ferrimagnetic minerals and that superparamagnetic and stable single-domain ferrimagnetic grains and non-ferrimagnetic minerals are present in small magnetic concentrations in this area. The measured metals correlated positively with the determined magnetic parameters (χ, χ ARM, SIRM and SOFT). This result suggests that simple, rapid, and non-destructive magnetic measurements could provide useful information about Pb and Zn pollution in Xuzhou urban surface soils.  相似文献   

12.
Peatland testate amoebae are widely used to reconstruct paleohydrological/climatic changes, but many species are also known to respond to pollutants. Peatlands around the world have been exposed to anthropogenic and intermittent natural pollution through the late Holocene. This raises the question: can pollution lead to changes in the testate amoeba paleoecological record that could be erroneously interpreted as a climatic change? To address this issue we applied testate amoeba transfer functions to the results of experiments adding pollutants (N, P, S, Pb, O3) to peatlands and similar ecosystems. We found a significant effect in only one case, an experiment in which N and P were added, suggesting that pollution-induced biases are limited. However, we caution researchers to be aware of this possibility when interpreting paleoecological records. Studies characterising the paleoecological response to pollution allow pollution impacts to be tracked and distinguished from climate change.  相似文献   

13.
A total of 115 urban soil samples collected on grid bases from Al-Karak, South Jordan, were investigated for their field and dual-frequency magnetic susceptibility (χ field, χ d) and heavy metal content using Bartington susceptibility meters and ICP-MS. The upper soils have higher magnetic susceptibility values than lower soils, and large particles contain more heavy metals and higher magnetic susceptibility than smaller particles. This might be attributed to the lack of pedogenesis due to arid climate influence. Within the upper soil all heavy metal showed positive significant correlation with upper soil low-frequency χ dlf. This was evident from the distribution maps produced by Surfer 9.0 for χ dlf and heavy metals. The results showed that higher χ dlf is associated with traffic-dominated sites more than other areas. The frequency-dependent susceptibility (χfd %) falls between 2 and 10 %, which indicate the presence of admixture of fine supermagnetic particles. Mildly correlation exists between χfd % and χ dlf, which implies that soils contain anthropogenic multi-domain grains. Selected samples have been analyzed for their mineral constituents; the results indicate the presence of magnetite as the main magnetic mineral. This confirms the anthropogenic source of pollution mainly from the vehicle-related materials. The results indicate the applicability of magnetic susceptibility for pollution detection.  相似文献   

14.
An expressway-side soil profile 22 cm long was sampled from the grassland of the expressway linking Beijing and the Capital International Airport. Magnetic measurements, geochemical and multivariate statistic analyses were performed on the soil samples. The results reveal that the soil profile can be divided into two parts with significant difference in magnetic proxies and heavy metal concentration. The uppermost soil horizon (0–8 cm) represents the pollution-rich layer with higher concentration of ferrimagnetic phases and metallic elements. The values of xare very high with an average of 141.60 × 10−8 m3·kg−1 in the layer. We explain that the anthropogenic dust input from traffic is the predominant cause for strong signals of magnetic phases and heavy metals. Below the profile depth of 8 cm, there is minor pollution in the soil with lower concentration of magnetic minerals and heavy metals compared to the natural background values. χ remains quite stable and relatively low with an average of 49.44 × 10−8 m3·kg−1. S-ratio also generally decreases with depth, and it changes from 0.93 in the 0–8 cm layer to 0.87 below the depth of 8 cm. It indicates that the soil samples are overwhelmingly predominated by ferrimagnetic minerals in the upper part soil, while the contribution of imperfect antiferromagnetic components is stronger in the lower part. Rock magnetic experiments show MD magnetite as the main magnetic carrier both in the upper and lower parts. Themagnetic grain size in the upper part is, however, a bit coarser than that in the lower part. Cluster analysis shows a positive correlation between magnetic properties (χ, ARM, SIRM) and heavy metal pollutants of Pb, Zn, Cu. Fuzzy C-means cluster analysis can clearly help divide the soil profile into two different layers and distinguish their characteristics. It can be concluded that these magnetic concentration-related parameters can be used as proxies for pollution investigation in a fast, sensitive, low-cost and highly efficient approach to screening heavy metal pollution. __________ Translated from Quaternary Sciences, 2007, 27(6): 1113-1120 [译自:第四纪研究]  相似文献   

15.
长江与黄河河口沉积物磁性特征对比的初步研究   总被引：11，自引：1，他引：10  
根据2001年8月和9月分别采自黄河与长江河口沉积物样品的磁性测量和粒度分析,探讨长江和黄河河口沉积物的磁性特征及其差异。长江河口沉积物中亚铁磁性物质的含量高于黄河口,但长江口与黄河口沉积物中都是亚铁磁性矿物主导了样品磁性特征,亚铁磁性矿物晶粒都以假单畴-多畴为主。相比黄河口沉积物,长江口沉积物不完整反铁磁性物质对磁性特征的的贡献较小。长江与黄河河口的这种磁性特征主要反映了不同的沉积物来源的控制影响。此外,无论是长江口还是黄河口沉积物,磁性参数χARM、χfd%与沉积物细粒级组分存在显著的相关性,表明这两个参数作为粒度的代用指标具有普遍性。  相似文献   

16.
Rock‐magnetic measurements of two sediment cores from the Madeira Abyssal Plain (MAP), north Atlantic, are used to investigate post‐depositional changes in the concentration, grain size and composition of magnetic minerals in the sediments that have occurred within organic‐rich turbidite horizons. The changes are associated with an initial stage of suboxic (reductive) diagenesis, following depletion of porewater O2, and a later stage of oxidative diagenesis associated with the slow descent of an oxidation front through the sediment, as a result of diffusion of O2 from the overlying sea water. The turbidites are of late Quaternary age (δ18O stages 1–3) and derive both from different sites on the NW African continental margin, and from the flanks of the Canary Islands. Thus, the turbidites are variable compositionally, especially in terms of carbonate, detrital magnetic mineral and organic carbon content. Diagenetic changes in these sediments have been identified using solid‐phase geochemical data (U, Mn, Corg and CaCO3) reported previously in more than one study. Rock‐magnetic parameters of the sediments, when expressed on a carbonate‐free basis, reveal that significant depletion of detrital ferrimagnetic iron (Fe2+/Fe3+) oxide grains has occurred within organic‐rich turbidites during redoxomorphic diagenesis. Normalized quotients of magnetic parameters also show that reductive diagenesis is a ferrimagnetic grain size‐selective process, but it has a minimal effect on the canted‐antiferromagnetic Fe3+ oxides in the sediment. Such components, if present, therefore become relatively enriched in magnetic assemblages as the ferrimagnetic grains are dissolved progressively, and bulk magnetic concentration is thus depleted. There is clear evidence in both cores for the existence of ultrafine ferrimagnetic grains at depth within the suboxic zone of the organic‐rich turbidites, beneath both active and fossil oxidation fronts. These grains are most probably associated with populations of live magnetotactic bacteria, which commonly inhabit such organic‐rich horizons and play a part in the chain of bacterially mediated reactions normally associated with suboxic diagenesis. These results show that simple and rapid rock‐magnetic techniques can be used to characterize early diagenetic processes involving iron phases in deep‐sea sediments, at least as effectively as more laborious, time‐consuming and sample‐destructive geochemical measurements.  相似文献   

17.
钢铁厂附近树木年轮的磁学性质及其环境意义   总被引：11，自引：8，他引：3       下载免费PDF全文
通过磁学手段以树木年轮为研究对象,通过多参数磁学研究探讨钢铁厂周围环境污染的历史.研究表明:钢铁厂附近树木年轮样品中磁性矿物为准单畴(其中颗粒偏向于多畴)的磁铁矿,磁性矿物形状各异,粒径大小不一;样品中磁铁矿的含量随年份的不同差异很大;通过树木不同方向上磁性参数尤其是饱和等温剩磁(SIRM)值的差异以及扫描电镜(SEM)和X射线能谱(EDX)分析,发现树木木质部中的磁性颗粒来自于树皮,即大气中颗粒被树皮和树叶表面吸附后,在树木的生长季节通过树皮进入形成层的木质部细胞,然后通过木质化作用被固定在当年生长的树木木质部木材中;另外,朝向钢铁厂方向的树干年轮钻芯样品SIRM值与对应年份钢铁厂年生产量之间高度相关,磁性颗粒在年轮之间不存在横向迁移,树干年轮钻芯的磁性参数(SIRM和部分磁滞参数)可指示该区大气环境污染的历史;污染树木钻芯样品的SIRM随时间的变化曲线说明该研究区大气污染日益严重.  相似文献   

18.
Detailed magnetic and geochemical measurements were performed on urban roadside soils collected from Lishui city, China, to establish a possible link between the enhanced concentration of traffic-related magnetic particles and heavy metals. Relatively higher magnetic susceptibility (mean: 124.1 × 10−8 m3 kg−1) and concentrations of metals (Cd, Cu, Pb and Zn) were observed for roadside soils. Concentration-dependent magnetic parameters (χ and SIRM) are highly significantly positively correlated to the concentration of metals (Ca, Cr, Ni, Cu, Zn, Cd, Pb, Fe, and V), but not significantly correlated with As, Mn, Co, Mg, and K. The principal component analysis showed that χ and SIRM significantly correspond to elements Ca, Cd, Cu, Pb, and Zn. The χ and SIRM also have significant linear correlation with integrated pollution index, indicating that χ and SIRM can be used as effective proxy indicators for the pollution of heavy metals. Magnetite in the pseudo-single-domain/multidomain (PSD/MD) grain size was identified as the dominant magnetic carrier by temperature-dependent measurements of saturation magnetization (Ms–T curve), XRD and hysteresis loops. Field emission scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS) analysis of the magnetic particles revealed the presence of large traffic-related angular-subangular, blocky, and spherical iron oxide particles. These iron oxide particles are typical for particles produced by traffic-related anthropogenic activities. It is concluded that vehicle emissions may be the major source of elevated heavy metals and magnetic particles in roadside soils. The results proved the applicability of magnetic method in detecting roadside pollution derived from vehicle emissions.  相似文献   

19.
In this study, environmental magnetic, heavy metal and statistical analyses were conducted on 21 surface sediments collected from Chennai coast, India, to examine the feasibility of heavy metal pollution using magnetic susceptibility. The Chennai coastal sediment samples are dominated by ferrimagnetic minerals corresponding to magnetite-like minerals. The percentage of frequency dependent magnetic susceptibility reflects the presence of super-paramagnetic/single domain magnetic minerals in Chennai harbour, Cooum and Adayar rivers sediments. High pollution load index in sample E1, E2, CH7, C11, C12 and A16 is mainly due to anthropogenic activities such as, harbour activities, Cooum and Adayar rivers input and industrial effluent. Factor analysis shows that the magnetic concentration dependent parameters (χ, χ ARM and SIRM) covary with the heavy metal concentrations, suggesting that the input of magnetic minerals and heavy metals in Chennai coastal sediments are derived from the same anthropogenic sources. Strong correlation obtained between pollution load index (PLI) and concentration dependent parameters (χ, χ ARM and SIRM) for the polluted samples with magnetic susceptibility excess of 50×10 − 8 m3kg − 1. Significant correlations between heavy metals and magnetic susceptibility point out the potential of magnetic screening/monitoring for simple and rapid proxy indicator of heavy metal pollution in marine sediments.  相似文献   

20.
Records from magnetic signals in Buenos Aires loess–paleosol sequences have been published, but their relationship with environmental changes has been difficult to establish. Studies on the superparamagnetic (SP) population in present soils can help to understand these processes. Samples from present soils (Argiudolls) and a paleosol from the Buenos Aires Province (Argentina) were analyzed using low and room temperature magnetic measurements. They show that it is possible to support the hypothesis of a lognormal distribution of superparamagnetic particles, the median diameter near 15 nm. The presence of detritic pseudosingledomain (PSD) titanomagnetite, with low titanium content ranging between TM 28 and TM40, has been established. The linear correlation of SP content with ferrimagnetic susceptibility and with magnetization suggests that ferrimagnetic minerals drive the SP generation. Finally, it can be concluded that SP magnetic grains, in the Pampean plain, are generated by an inorganic process in adequate environmental pH and Eh of the soils.  相似文献   

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