Solid state technology1.PDF

Sedimentology, 1994

This paper considers the magnetic properties of a range of recent and contemporary sediments from the north eastern part of the Irish Sea. Principal component ordinations of the results show a close link between magnetic property variations and particle size. The magnetic properties of a subset of samples, particles sized by a combination of sieving and pipette analysis, confirm that variations in ferrimagnetic ('magnetite') grain size parallel those in particle size, despite the fact that the magnetic grains in the fine grades have diameters 1-2 orders of magnitude smaller than those of the particle size fraction in which they occur. This is best explained by postulating that the fine magnetic grains occur in the clay fraction but are present in declining concentrations in the coarser grades up to 441 as an artefact of the pipette method. Most samples have a biomodal distribution of magnetic minerals, with a coarse mode associated with heavy minerals in the sands or coarse silts, and a fine mode in the clays. Magnetic susceptibility (x) and saturation isothermal remanent magnetization (SIRM) largely pick out the coarse mode where present; anhysteretic remanent magnetization (ARM) largely picks out the fine mode. The results open up the possibility of normalizing samples from these environments for particle size and, more specifically, clay content, by means of ARM or ARM/x values. The most likely source for the uniform and almost exclusive stable single domain magnetite, which dominates the magnetic properties of the clays, is thought to be bacterial magnetosomes. The measurements as a whole do not appear to hold much promise for discriminating sediment source types.

Geophysical Journal International, 1996

We have applied an integrated procedure for quantitative magnetic mineral extraction, based on the separation method of , to a range of sediment types, to examine the efficiency and representative nature of the extraction process. Carriers of magnetization have been identified by rock magnetic measurements, microscopy and X-ray diffraction. Quantification of the extraction efficiencies is achieved by before-and after-extraction rock magnetic measurements (susceptibility, anhysteretic and isothermal remanences). These magnetic measurements show that our modified extraction method extracts large proportions of the magnetization carriers in a range of sediment types (e.g. over 75 per cent for magnetite-dominated sediments). The extraction efficiency is dependent on the sample magnetic mineralogy and whether the magnetic grains occur as discrete grains or as inclusions within host grains. Susceptibility extraction efficiencies are strongly dependent on whether the susceptibility is of paramagnetic or ferrimagnetic origin. The amount of material recovered in the extract shows some inverse correlation with the density of the sediment suspension used during extraction.

1996

We have applied an integrated procedure for quantitative magnetic mineral extraction, based on the separation method of Petersen, von Dobeneck & Vali (1986), to a range of sediment types, to examine the efficiency and representative nature of the extraction process. Carriers of magnetization have been identified by rock magnetic measurements, microscopy and X-ray diffraction. Quantification of the extraction efficiencies is achieved by before-and after-extraction rock magnetic measurements (susceptibility, anhysteretic and isothermal remanences). These magnetic measurements show that our modified extraction method extracts large proportions of the magnetization carriers in a range of sediment types (e.g. over 75 per cent for magnetite-dominated sediments). The extraction efficiency is dependent on the sample magnetic mineralogy and whether the magnetic grains occur as discrete grains or as inclusions within host grains. Susceptibility extraction efficiencies are strongly dependent on whether the susceptibility is of paramagnetic or ferrimagnetic origin. The amount of material recovered in the extract shows some inverse correlation with the density of the sediment suspension used during extraction. In terms of the mineralogies extracted, we identify a diverse and complex range of mineral assemblages. All sizes of discrete grains of magnetite are extracted (including single-domain and superparamagnetic grains, and chains of bacterial magnetite). Other commonly extracted iron and titanium oxides are haematite and ilmenite. Ferrimagnetic chromites and sulphides were also obtained from some samples. Considerable amounts of quartz and feldspar are extracted, due to the presence of magnetic inclusions within these diamagnetic host grains. In the deep-sea sediments we examined, feldspars constitute a large proportion of the extracts, but are significantly less abundant in other sediments, where quartz is dominant. A wide variety of paramagnetic minerals was identified in the extracts, including pyroxenes, amphiboles, chlorites, micas, Mg-Crspinels, garnets, Ti-oxides, apatites, tourmaline and zircon, many of which contain ferrimagnetic inclusions, possibly less than 0.1 pm in grain size. Dissolution of ultrafine grains of magnetite during pre-extraction carbonate dissolution, as suggested by Sun & Jackson (1994), does not occur in our samples.

Earth and Planetary Science Letters, 2000

The intensity of magnetization in redeposited sediments was measured as a function of salinity and pH of the sediment^water mixture. The intensity was relatively low at high salinity or low pH. Under these conditions, interparticle bonds are enhanced, which lead to the formation of larger flocs. Ferromagnetic minerals (magnetite in our sediment) are incorporated in the flocs consisting mainly of non-magnetic minerals, and orientation along an applied field is resisted by the drag proportional to the third power of the diameter of the floc. Higher intensity is recorded at lower salinity and higher pH, when inter-particle forces are weaker, and floc sizes are smaller. The increase of magnetization as a function of pH stops at a pH of about 5, which is the PZC of the edge of illite (the dominant nonmagnetic mineral in our sediment). Above this pH, both the edge and face of the illite grains are negative, and there is net repulsion, which retards flocculation. The interactions between clay particles therefore have a larger effect on the intensity of magnetization than interactions between magnetite and clay. This suggests that magnetite is always included in a clay-magnetite domain, and this domain is the smallest unit that is reoriented by a magnetic field. ß

Journal of Earth System Science, 2008

Three sediment cores in a north-south transect (3 • N to 13 • S) from different sediment types of the Central Indian Ocean Basin (CIOB) are studied to understand the possible relationship between magnetic susceptibility (χ) and Al, Fe, Ti and Mn concentrations. The calcareous ooze core exhibit lowest χ (12.32 × 10 −7 m 3 kg −1 ), Al (2.84%), Fe (1.63%) and Ti (0.14%), terrigenous clay core with moderate χ (29.93 × 10 −7 m 3 kg −1 ) but highest Al (6.84%), Fe (5.20%) and Ti (0.44%), and siliceous ooze core with highest χ (38.06 × 10 −7 m 3 kg −1 ) but moderate Al (4.49%), Fe (2.80%) and Ti (0.19%) contents. The distribution of χ and detrital proxy elements (Al, Fe, and Ti) are identical in both calcareous and siliceous ooze. Interestingly, in terrigenous core, the behaviour of χ is identical to only Ti content but not with Al and Fe suggesting possibility of Al and Fe having a non-detrital source.

Journal of Geophysical Research, 1994

The magnetic properties of low field susceptibility (Z), frequency dependent susceptibility (Zfd), and susceptibility of anhysteretic remanent magnetisation (Z^RM) are used to define sets of natural soil and sediment samples within which, by the criteria of King et al. (1982) and Maher (1988), the modal ferrimagnetic grain diameter is less than-0.07-0.1 gm. Within this sample set, two distinct groups with low and high values, respectively, for the quotients Z•M/Z and Za,•/zfd are defined. The first group includes sediment samples from sites where published studies propose a detrital origin for the fine-grained ferrimagnetic content. Where catchment samples are available for comparison, they fall within the same envelope, as do clays from palaeosol samples within Chinese loess. This envelope of low quotient values also overlaps with the values for the fine grained synthetic magnetite samples within Maher's (1988) New MT series. The high quotient envelope of values includes sediments from the Adriatic Sea and clays from saltmarsh and shallow water marine sediments in NW Britain. In these cases, no catchment source is postulated for the fine-grained magnetite. The size range of magnetite in this set appears to be almost exclusively stable single domain (SSD), and a bacterial origin seems likely. Sample sets from estuarine environments between river inflow sites and the open sea show intermediate values which, in the case of the Potomac, are ordered by distance down river. Although at this stage, magnetic measurements alone cannot discriminate between bacterial and fine-grained detrital ferrimagnets in sediments, they hold out some promise of doing so provided the distinctions proposed here can be substantiated by transmission electron microscopy.

Boreas, 2008

Roy 19850901: The use of magnetic measurements to invcstigate the mineralogy of Icelandic lake sediments and to study catchment processes. Borem, vol. 14. pp. 203-215.

Reviews of Geophysics, 1977

This paper surveys 40 years of research on the processes by which a sediment acquires a detrital remanent magnetization (DRM). These processes can be divided into two types: depositional processes, which arise from interactions between the magnetic carriers and the substrate at the sediment/water interface, and postdepositional processes, which arise from the mobility of magnetic carriers within fluidfilled voids in the sediment. Depositional DRM is well understood theoretically and experimentally, but its applicability to natural sediments may be quite limited. Postdepositional DRM, which has not been studied in sufficient detail, may well be the dominant process by which sediments acquire a magnetization. The nature and composition of both the magnetic carriers and the matrix as well as the pore water content of the sediment influence the balance between depositional and postdepositional DRM. The identification of the method of magnetization in a given sedimentary environment, such as glacial lakes, the deep sea, or lakes and marginal seas, can be a difficult problem. Since postdepositional DRM accurately records the ambient geomagnetic field, whereas depositional DRM does not, such an identification is necessary in order to use the detrital reinanent magnetism of sediments in studies of the fine scale behavior of the geomagnetic field, the paleomagnetic correlation between sedimentary environments, and the possible relation between paleomagnetic parameters and paleoclimatic indicators. CONTENTS

Developments in Paleoenvironmental Research, 2002

Iran J Sci Technol Trans Sci, 2020

The measurement of magnetic susceptibility is a simple and rapid method that provides a reliable idea of the degree of heavy metal contamination in sediments. In the present work, the concentration of heavy metals such as Mg, K, Ca, Ni, As Ba, V, Cr, Mn, Co, Zn, La, Pb, Ti, Al and Fe was determined by EDXRF technique in sediments collected from Poombuhar to Karaikal of Tamilnadu coast. The results show that aluminum (Al) is the most abundant metal in the sediments. In order to identify the source of metals in sediments, the magnetic susceptibility measurements were carried at both low (0.465 kHz) and high (4.65 kHz) frequencies using MS2B dual-frequency susceptibility meter and statistical methods such as correlations, factor and cluster analysis were applied between the heavy metals and magnetic parameters in sediments. These results show that high magnetic susceptibility value was found in locations Ammantherumedu-I, Ammantherumedu- II, Karaikal-II, and Karaikal-III in the study area. Finally, for better understanding of worldwide researchers, the spatial distribution of magnetic susceptibility in sediments is studied by contour maps.