Magnetic Grain Size Research Articles

Temperature- and frequency-dependent magnetic susceptibility on archaeological ceramics of the Tlatilca culture (Mexico City): A pilot study towards an archaeointensity approach

Temperature-dependent susceptibility curves are commonly used in archaeointensity studies to identify changes in the magnetic mineralogy of archaeological ceramics. In this pilot study, we investigated the low- and high-temperature thermomagnetic behavior and frequency-dependent susceptibility of eight ceramics from a Tlatilca culture archaeological site in Mexico City, after heating them at five different temperatures (from 120 to 440 °C). Our objective is to establish a correlation between the thermomagnetic behavior and the parameters that determine the magnetic grain-size and magnetic domain in similar style of ceramics from different occupations of the site. Our findings show that superparamagnetic grains (SP) degrade with increasing reheating temperature in ceramics, and we conclude that this behavior is related to details in artifact processing, such as the use of pastillage to represent headdresses, and an important aspect to consider when working with samples for archaeointensity procedures.

Magnetic characterization and iron oxide transformations in Technosols developed from thermal power station ash

Fly and bottom ash originating in thermal power stations (TPSs) are industrial wastes containing magnetic minerals, primarily Fe-bearing phases, which are formed during coal combustion. Ash deposited on disposal sites becomes the parent material for technogenic soils (Technosols), in which the transformations of Fe-bearing magnetic minerals accompany the soil-forming processes. This study presents the application of magnetic methods together with mineralogical techniques for the determination of the magnetic properties and mineral composition of (1) fresh (unweathered) fly and bottom ash resulting from bituminous coal and lignite combustion, and (2) two Technosols developed on dry ash disposal site and former ash settling pond. Magnetite with a mean coercivity (B1/2) of 36–47 mT and hematite (B1/2 of 200–900 mT) were found to be the major magnetic minerals of fresh fly and bottom ash. The size of magnetic grains of ash ranged from 1 to 20 µm, which corresponds to the typical pseudo-single-domain grains. The heterogeneity of the parent material (i.e. TPS ash) along the soil profiles significantly affected the magnetic parameters and composition of magnetic minerals. In the soil developed from bituminous coal ash, the magnetic susceptibility ranged from 771 to 2538 × 10-8 m3 kg−1, whereas in the soil developed from lignite ash it was 622–7657 × 10-8 m3 kg−1. The most abundant Fe oxides in Technosols were (i) magnetite with (ii) a few percent of hematite admixture (both minerals mainly inherited from fresh ash and partly neoformed), and (iii) low-coercivity maghemite (B1/2 ~ 15–20 mT) which most likely formed by the surface oxidation of fine magnetite grains inherited from the parent material. Magnetic methods were found to be a valuable research technique in the case of TPS ash-derived Technosols, for the identification of Fe-bearing magnetic minerals that are hardly recognizable by mineralogical methods, and for tracking the transformations of magnetic minerals resulting from soil-forming processes.

Environmental Magnetic Properties of Lateritic Soils from Southwestern India

Soil formation is influenced mainly by lithology, climate, organic matter, vegetation, topography, and time. Soil-forming processes have been well studied in temperate regions. However, there is little data on such processes in the tropics. In this work, we have studied the environmental magnetic properties of lateritic soils developed on gneiss and charnockite. We sampled surficial soils from different environmental settings (urban, agricultural, pristine, and gleyed) to determine the processes involved in their formation. A range of environmental magnetic parameters and inter-parametric ratios were investigated to determine the magnetic concentration, grain-size and mineralogy of the soil samples. Redness rating (RR) index was also calculated to estimate the reddening of tropical soils and to examine its relationship with magnetic properties. The pristine soils exhibit the highest average value for χlf and a higher value of χfd%, indicating a greater amount of ultra-fine magnetic minerals. The gleyed and agricultural soils are weakly magnetic, probably be due to waterlogging, and are characterized by a coarser magnetic grain size. A high proportion of “soft” ferrimagnetic minerals like magnetite and titanomagnetite is present in the samples (average S-ratio ~ 0.90). Hematite content is the highest in unburnt soils and the least in gleyed soils (unburnt > burnt > pristine > urban > agricultural > gleyed). The high concentration of hematite in these soils could be due to transformation of maghemite, resulting from low-temperature oxidation of magnetite. We documented a distinction between the magnetic properties of burnt and unburnt soil types as fire can significantly enhance the magnetic values of unburnt soils. The concentration of hematite (indicated by HIRM) and redness rating (RR) index are fairly well correlated for all the sample types with the exception of urban (r = 0.51; p = 0.11; n = 11) and unburnt soils (r = 0.60; p = 0.28; n = 5), which show a strong correlation. Therefore, RR index can be effectively used as an indicator of reddening of tropical soils due to pedogenesis. This study demonstrates that environmental magnetism can aid in differentiating the diverse environments of soils even though they developed on a similar rock type and under similar climatic conditions.

Understanding room-temperature magnetic properties of anthropogenic ashes from municipal solid waste incineration to assess potential impacts and resources

Environmental magnetic studies are widely used to trace sources of anthropogenic pollution and have revealed promising applications to the urban waste management system. Here, a collection of solid samples from Municipal Solid Waste Incinerators (MSWI) were studied to probe the capability of geochemical and magnetic data integration as a tool for assessing mineralogy, grain-size, and metal enrichment. A data set of room-temperature magnetic parameters was compared with chemical data by X-ray fluorescence and electron microscopy observations. The aim was to validate or reject methods for urban mining purposes, testing and exploiting the correlations that magnetic properties typically experience with iron and heavy metals, as well as their relation to magnetic grain-sizes (from mm-scale down below 30 nm). We noted that the room-temperature magnetic data of MSWI ashes, used to assess grain-size according to the magnetic domain states, is complicated by the clumping of tiny and large grains displaying similar magnetic properties, so it needs to be supported by optical methods or more advanced magnetic techniques. On the other hand, the integration between magnetic and geochemical data, constrained by the analyses of the magnetic/diamagnetic extracts, helped in assessing magnetic mineral assemblages and potential metal enrichment.

High-Efficient Adaptive Modulation for PWM-Based Multi-Level Perpendicular Magnetic Recording on Insufficient Resolution Channel

In this paper, we propose a high-efficient constrained adaptive 5-binary to 4-ternary (5B4T)-modulation in pulsewidth modulation (PWM)-based ternary perpendicular magnetic recording (PMR). The high-efficient modulation is required to obtain higher user-bit density (UBD) gain in low-resolution channel, in which transition interval and magnetic-grain size are equivalent on media. In our proposed constrained adaptive 5B4T-modulation, one mapping-set is adaptively selected from the prepared two different mapping-sets to satisfy a specific constraint of ternary signal in modulation block-by-block. For the signal detection in the proposed modulation, we provide a practical solution which is a blind-detection method on likelihood vector. The likelihood vector is re-calculated as joint-metric using the likelihood values of adjacent modulation blocks. By using the vector of joint-metric, a likelihood vector is further generated to decode non-binary low-density parity-check (NB-LDPC) codes. Our simulation results demonstrate that the proposed adaptive 5B4T-modulated PWM-based ternary-PMR, combined with NB-LDPC codes over GF(32), shows a significant robustness in ultra-low-resolution channel, which occurs magnetization-missing frequently.

Domain structure of volcanics’ ferromagnetic grains: A case study of the Saatly ultradeep well, Azerbaijan

Various magnetic properties of magnetic minerals show strong grain-size depen-dence. This dependency occurs because these parameters are influenced by the magnetic grain-size (domain state) of the samples. Natural rocks often contain a mixture of different magnetic minerals with different grain-size (domain states). Thus determination of the domain state is important. The Saatly ultradeep well’s volcanics were used as a research material. In the depth intervals of 3540—8126 m the volcanics had been revealed by the borehole. According to data of the petrographic and microprobe analysis the volcanogenics of the ultradeep borehole is conditionally divided into a two parts: 1) the upper part (an interval of depths of 3540—5500 m); 2) the bottom part (an interval of depths of 5500—8126 m). In the upper part of section according to microprobe analysis of volcanogenic rocks ore grains are presented by two generations: 1) large grain of titanomagnetites (Ti-poor), homogeneous or with a decay structures; 2) small-sized usually well faced grain of practically stoichiometric magnetite. So, homogeneous small-sized grains or fragments of decay large grains (which are strongly changed chemically) can have properties of single-domain particles. Here the ferromagnetic grains (especially in the depth interval 3540—5000 m) are often noted as a pseudo-single domain. In the bottom part of the section the presence of multidomain grains of the Ti-poor titano-magnetite is noted. And since depths of 7000 m the oxidized magnetite is also observed. The pseudo-single-domain grains are fixed much less than in the upper section. And, since a depth mark of 7300 m and deeper, they are absent wholly. In the result of rese-arch it turned out that the ferromagnetic is presented by basically multidomain grains. It should be noted that Lauri—Fuller’s Criterion is not applicable at identification of a domain structure of the complex ensemble of the ferromagnetic grains.

Structural and Magnetic Characteristics of Nanogranular Co–Al2O3 Single- and Multilayer Films Formed by the Solid-State Synthesis

The results of structural and magnetic investigations of nanogranular Co–Al2O3 films formed from Co3O4/Al thin-film layered structures upon vacuum annealing are reported. The Co3O4/Al films have been obtained by sequential reactive magnetron sputtering of a metallic cobalt target in a medium consisting of the Ar + O2 gas mixture and magnetron sputtering of an aluminum target in the pure argon atmosphere. It is shown that such a technique makes it possible to obtain nanogranular Co–Al2O3 single- and multilayer thin films with a well-controlled size of magnetic grains and their distribution over the film thickness.

Bridging atomistic magnetism and coercivity in Nd-Fe-B magnets

Coercivity in rare-earth permanent magnets depends on the size and shape of magnetic grains. Recent experimental studies have revealed that, however, atomic scale structures around the grain-boundaries of magnets also play a crucial role to determine their coercivity. In this paper, we construct an effective spin model for the Nd2Fe14B structure based on first-principles calculations to describe atomistic magnetization dynamics of the magnetic grains, incorporating the information of the electronic states of the system. We find that the Nd ions located on the surfaces of the grains may have planar magnetic anisotropy, and that they can cause coercivity reduction.

Структурные и магнитные характеристики однослойных и многослойных наногранулированных пленок Co-Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-, полученных методом твердофазного синтеза

AbstractThe results of structural and magnetic investigations of nanogranular Co–Al_2O_3 films formed from Co_3O_4/Al thin-film layered structures upon vacuum annealing are reported. The Co_3O_4/Al films have been obtained by sequential reactive magnetron sputtering of a metallic cobalt target in a medium consisting of the Ar + O_2 gas mixture and magnetron sputtering of an aluminum target in the pure argon atmosphere. It is shown that such a technique makes it possible to obtain nanogranular Co–Al_2O_3 single- and multilayer thin films with a well-controlled size of magnetic grains and their distribution over the film thickness.

A whole rock absolute paleointensity determination of dacites from the Duffer Formation (ca. 3.467 Ga) of the Pilbara Craton, Australia: An impossible task?

We have conducted a whole-rock type magnetic and absolute paleointensity determination of the red dacite of the Duffer Formation from the Pilbara Craton, Australia. The age of the dated rock unit is 3467±5Ma (95% confidence). Vector analyses results of the step-wise alternating field demagnetization (NRM up to 100mT) and thermal demagnetization (from NRM up to 650°C) yield three components of magnetization. Curie point determinations indicate three characteristic temperatures, one at 150–200°C, a second one at ∼450°C and a third one at ∼580°C. Magnetic grain-size experiments were performed on small specimens with a variable field translation balance (VFTB). The coercivity of remanence (Hcr) suggests that the NRM is carried by low-coercivity grains that are associated with a magnetite fraction as is shown by the high-temperature component with blocking temperatures above 450°C and up to at least 580°C. The ratios of the hysteresis parameters plotted as a modified Day diagram show that most grain sizes are scattered within the Single Domain (SD) and the Superparamagnetic and Single Domain SP-SD domain ranges. In addition to the rock magnetic experiments we have performed absolute paleointensity experiments on the samples using the modified Thellier-Coe double heating method to determine the paleointensities. Partial-TRM (p-TRM) checks were performed systematically to document magnetomineralogical changes during heating. The temperature was incremented by steps of 50°C between room temperature and 590°C. The paleointensity determinations were obtained from the slope of Arai diagrams. Our paleointensity results indicate that the paleofield obtained was ∼6.4±0.68 (N=11) micro-Teslas with a Virtual Dipole Moment (VDM) of 1.51±0.81×1022Am2, from a medium-to high-temperature component ranging from 300 to 590°C that has been interpreted to be the oldest magnetization yet recorded in paleomagnetic studies of the Duffer Formation. The absolute paleointensity is relatively low and we interpret this low-paleofield bias a result of a thermochemical remanent magnetization (TCRM) process that indicates a possible underestimate of the paleofield by a factor of four for the red dacite of the Duffer Fm.

The Crvenka loess-paleosol sequence (Vojvodina, Northern Serbia)- a record of continuous domination of the Late Pleistocene grasslands

In this study we present a comparison of two independent paleo-environmental evidences: novel n-alkane biomarkers and traditional land snails assemblages, associated with widely used proxy records such as the low field magnetic susceptibility, grain size and various isotopic and geochemical indices. These paleo-environmental proxy records provide evidence for the continued predominance of the different grassland vegetation types during the entire Late Pleistocene. The results presented in this study highlight the spatial differences in the environmental conditions during the Late Pleistocene across the European loess belt. Contrary to other European loess provinces characterized by high diversity of the Late Pleistocene environments (ranging from tundra-like to deciduous forest habitats), our investigations indicate a continued dominance of grassland-dominated ecosystems in the southeastern Carpathian Basin. This uninterrupted presence of Late Pleistocene grassland zone in the southeastern part of the Carpathian Basin may have played an important role in the preservation of exceptional biodiversity of the Balkan region, as well as in the migration of anatomically modern humans into Europe

Magnetic and chemical parameters of andic soils and their relation to selected pedogenesis factors

In the case of andic soils − developed on volcanic rocks − permanently humid conditions are essential for andosolisation processes. Although volcanic rocks are usually rich in highly magnetic iron oxides, knowledge about these minerals in andic soils with respect to the soil development is missing. The aim of this contribution is to investigate the relationship between magnetic and basic chemical properties of soils developed on volcanic basement and parameters related to the pedogenesis factors. The studied sites are located on basaltic lava flows in the eastern part of the French Massif Central. Investigated pedons with alu-andic, sil-andic, and vitric properties were pedologically described and analysed by a set of magnetic and soil-chemical methods. Magnetic parameters include low-field volume-specific and mass-specific magnetic susceptibility, frequency-dependent magnetic susceptibility, remanent properties (including S-ratio) and coercivities. Chemical parameters included the pHH2O, soil organic matter, total cation exchange capacity, base saturation, and content of Fe and Al extracted in dithionite-citrate, acid-ammonium oxalate, and pyrophosphate solutions. Micro-morphology of Andosols and parent material was observed by scanning electron microscopy, completed with energy dispersive spectrometry. The pedogenesis factors are represented by parent-rock age, annual precipitation, and soil thickness. Our findings suggest that (1) precipitation is the most important pedogenesis factor with a strong relationship to the relative magnetic grain-size, concentration of ferrimagnetic minerals, aluminium dissolved in pyrophosphate and acid-ammonium oxalate, and content of organic matter; (2) parent-material age shows a well-pronounced relationship with magnetic grain-size parameters represented by the frequency-dependent susceptibility and ratio of saturation remanent to saturation induced magnetisation (Mrs/Ms), selective dissolution parameters, and pHH2O; (3) thickness of soil profile shows a link to Mrs/Ms, pHH2O, and content of organic matter.

Magnetic properties of tektites and other related impact glasses

We present a comprehensive overview of the magnetic properties of the four known tektite fields and related fully melted impact glasses (Aouelloul, Belize, Darwin, Libyan desert and Wabar glasses, irghizites, and atacamaites), namely magnetic susceptibility and hysteresis properties as well as properties dependent on magnetic grain-size. Tektites appear to be characterized by pure Fe2+ paramagnetism, with ferromagnetic traces below 1 ppm. The different tektite fields yield mostly non-overlapping narrow susceptibility ranges. Belize and Darwin glasses share similar characteristics. On the other hand the other studied glasses have wider susceptibility ranges, with median close to paramagnetism (Fe2+ and Fe3+) but with a high-susceptibility population bearing variable amounts of magnetite. This signs a fundamental difference between tektites (plus Belize and Darwin glasses) and other studied glasses in terms of oxygen fugacity and heterogeneity during formation, thus bringing new light to the formation processes of these materials. It also appears that selecting the most magnetic glass samples allows to find impactor-rich material, opening new perspectives to identify the type of impactor responsible for the glass generation.

Generalized Partial Response Equalization and Data-Dependent Noise Predictive Signal Detection Over Media Models for TDMR

Two-dimensional magnetic recording (2-D TDMR) is an emerging technology that aims to achieve areal densities as high as 10 Tb/in2 using sophisticated 2-D signal-processing algorithms. High areal densities are achieved by reducing the size of a bit to the order of the size of magnetic grains, resulting in severe 2-D intersymbol interference (ISI). Jitter noise due to irregular grain positions on the magnetic medium is more pronounced at these areal densities. Therefore, a viable read-channel architecture for TDMR requires 2-D signal-detection algorithms that can mitigate 2-D ISI and combat noise comprising jitter and electronic components. Partial response maximum likelihood (PRML) detection scheme allows controlled ISI as seen by the detector. With the controlled and reduced span of 2-D ISI, the PRML scheme overcomes practical difficulties such as Nyquist rate signaling required for full response 2-D equalization. As in the case of 1-D magnetic recording, jitter noise can be handled using a data-dependent noise-prediction (DDNP) filter bank within a 2-D signal-detection engine. The contributions of this paper are threefold: 1) we empirically study the jitter noise characteristics in TDMR as a function of grain density using a Voronoi-based granular media model; 2) we develop a 2-D DDNP algorithm to handle the media noise seen in TDMR; and 3) we also develop techniques to design 2-D separable and nonseparable targets for generalized partial response equalization for TDMR. This can be used along with a 2-D signal-detection algorithm. The DDNP algorithm is observed to give a 2.5 dB gain in SNR over uncoded data compared with the noise predictive maximum likelihood detection for the same choice of channel model parameters to achieve a channel bit density of 1.3 Tb/in2 with media grain center-to-center distance of 10 nm. The DDNP algorithm is observed to give $\sim$ 10% gain in areal density near 5 grains/bit. The proposed signal-processing framework can broadly scale to various TDMR realizations and areal density points.

An interval fuzzy model for magnetic biomonitoring using the specie Tillandsia recurvata L

Studies of magnetic monitoring for assessing air pollution have been proposed as alternative and complimentary of chemical methods. Such magnetic studies provide measurements at low cost and relative promptness. In this work, we present and apply a methodology to build an interval fuzzy model, which calculates the Tomlinson pollution load index (PLI). The input variables for the model are magnetic parameters relative to magnetic concentration, grain size and mineralogy. The model aims to two purposes, on one hand, to calculate the values of PLI only using magnetic variables and, on the other hand, to analyze the relationship between magnetic and chemical variables. The studied dataset was obtained from measurements of the biomonitor Tillandsia recurvata L. in a Mexican urban area (Santiago de Querétaro). The best model was selected from a total of about half a million possible models using a fitness measure (RIF). The model yields a satisfactory approximation of the PLI data and it was concluded that PLI increases with relation to: an increase in concentration of magnetic materials, an additional contribution to the magnetic signal of paramagnetic materials, and an increase in size of magnetic grains.

Magnetic mineralogy of a weathered tropical basalt, Hainan Island, South China

Numerous studies have shown that mineral magnetic properties are sensitive indicators of weathering and soil formation (pedogenesis). However, the formation pathways and subsequent alteration mechanisms of specific weathering products are poorly constrained. We report a detailed magnetic investigation through a basalt profile that has been weathered under tropical conditions in South China. The rock magnetic analyses show that hot and humid conditions led to the neoformation of fine-grained magnetite and promoted mineral transformations in the form of maghemitization and hematization. Thus, although the basaltic parent material is rich in titanomagnetite, the final products of the weathering process are maghemite and hematite. Magnetic grain-size varies through the profile, with a combination of pseudo-single domain and single-domain particles at the base, with fining to single-domain in the middle and a mixture of superparamagnetic and single-domain particles in the uppermost profile. Importantly, the magnetic mineral assemblage through the profile is influenced by the mobilization and migration of iron through the sequence. This process is illustrated by concentration-dependent magnetic parameters, which reach maxima at the assembly depth of major and trace elements and minima at the oxic front where Fe content is its lowest.

Magnetic properties and particle-size analysis of dust-storm samples collected in Lanzhou and Sydney

Measurements of magnetic properties and particle size were carried out for dust-storm samples collected from Sydney (Australia) on 23 September 2009 and from Lanzhou (China) on April 2010. The results show that the magnetic mineral content of the Lanzhou sample is much higher than that of the Sydney sample. Magnetite, maghemite and possibly hematite occur in the Lanzhou sample. In addition to these minerals, there is also goethite in the Sydney sample. The magnetic grainsize of the Sydney sample is finer than that of the Lanzhou sample. These magnetic property differences are probably related to the source materials and anthropogenic particles. As to particle-size distribution, the Sydney sample shows a wide and flat curve with four peaks, while the Lanzhou sample displays a narrow curve with three peaks. The multi-peak particle-size distribution curves for the dust-storm samples indicate that there are multiple dust sources. Furthermore, a comparison of particle size between the Lanzhou storm sample and Jiuzhoutai loess/paleosol samples was also carried out. The results show that an increase in the 1–10 µm component and decrease in the 10–20 µm component of the loess/paleosol samples are mainly caused by pedogenic process (i.e. physical and chemical weathering of unstable minerals), while the increase in the 0.02–1 µm component is principally attributed to the formation of new minerals and the weathering of unstable minerals. The similarity of particle-size distribution curves between dust-storm and loess/paleosol samples implies that modern storm events are a good analogue for eolian processes operating in the Quaternary Period when loess/paleosol layers formed.

Quantitative relationships between magnetic enhancement of modern soils and climatic variables over the Chinese Loess Plateau

Environmental magnetism has been widely employed to reconstruct past climate changes on the Chinese Loess Plateau (CLP), and several climofunctions based on the magnetic properties of loess have been developed. However, systematic investigation of the quantitative relationship between topsoil magnetic enhancement and modern climate remains uncommon. In this study, we obtained surface soil samples from 257 sites over the CLP and adjacent regions. From this set, we used 180 samples from sites unaffected by potential contamination to investigate the relationship between the commonly measured magnetic properties of magnetic susceptibility and magnetic remanence and modern climatic variables. The spatial distribution of the results demonstrates a strong NW–SE gradient of the magnetic enhancement of surface soils. The results of more detailed magnetic parameters indicate that pedogenic viscous superparamagnetic and stable single-domain particles are mainly responsible for the magnetic enhancement of the soils in the studied region; and that the magnetic grain-size distribution of the ferrimagnetic components of pedogenic origin remains almost constant, independent of pedogenic intensity. The uniform mechanism of magnetic enhancement, mainly linked with the concentration of the pedogenic components rather than with variations in magnetic grain-size, decreases the level of ambiguity in climate reconstructions based on magnetic measurements of Chinese loess. Statistical analyses, including correlation, Principal Component Analysis (PCA) and multiple regression analysis, suggest that annual rainfall rather than temperature exerts the dominant effect on soil magnetic enhancement. Finally, we used the results to develop several transfer functions to reconstruct mean annual precipitation (MAP). Transfer functions based on frequency-dependent susceptibility (χfd) and anhysteretic remanent magnetization (χARM) provide the most reliable estimates of MAP. This study significantly improves the understanding of the relationship between soil magnetic properties and climate.

Marine magnetic signature of the Last Glacial Maximum and last deglaciation from the Southern Hemisphere mid-latitudes

An environmental magnetic record is presented from piston core TAN0712-23, collected on the southern flank of Challenger Plateau at a water depth of 2817 m. Magnetic grain-size and concentration variations during the Last Glacial Maximum (LGM) are interpreted to reflect variations in terrestrial influx corresponding to glacial advance and stagnation events on millennial time-scales. The LGM signal between 25 and 23 ka demonstrates an antiphase relationship with Northern Hemisphere records implying that the bipolar seesaw was active during that period. The number and timing of features in TAN0712-23 suggest that LGM millennial scale climate fluctuations are strongly realized in the mid-latitudes, possibly due to amplification by regional forcing mechanisms. The onset of the deglacial magnetic signal, defined by a low concentration of magnetic minerals, is constrained at 18.6 cal ka BP by the radiocarbon age model and corresponds to southward migration of the Southern Hemisphere westerly wind system and Subtropical Front.

Magnetic studies and elemental analysis of river sediments: a case study from the Ponnaiyar River (Southeastern India)

Fil: Chaparro, Marcos Adrian Eduardo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas; Argentina