Concentration Of Magnetic Minerals Research Articles

New Rock Magnetism and Magnetic Fabrics Studies on the Late Triassic Volcanic Rocks from Qaidam Block, Northern Tibetan Plateau

The Qaidam Block, located at the northern Qinghai–Tibet Plateau, is a pivotal area in unraveling the closure time of the Kunlun Ocean basin which might have recorded the transformation process between the Proto-Tethys and Paleo-Tethys Ocean basins. However, the late Triassic position of the Qaidam Block remains enigmatic, largely due to the scarcity of paleomagnetic data essential for quantitatively determining its paleolatitude. The widespread presence of the Elashan formation, particularly along the southern periphery of the Qaidam block, presents good material for conducting paleomagnetic work. Nevertheless, the primary magnetic carriers preserved within the Elashan formation might be influenced by multiple tectonic thermal events, particularly those associated with collisions between southern blocks and the Qaidam Block. Here we present rock magnetism and magnetic fabrics studies to identify the content and composition of magnetic minerals within the Elashan formation. The rock magnetic and petrologic results show that the magnetic carriers in the samples from the Elashan formation are dominated by magnetite with a small amount of goethite, pyrrhotite, and hematite. The results of Anisotropy in Magnetic Susceptibility indicate that the south of the Longwalangku section might not be obviously influenced by the tectonic events. Our results also provided guidance for future paleomagnetic research, emphasizing the importance of conducting further sampling away from adjacent faults, particularly in the southern Longwalangku area.

Multivariate analysis applied to X-ray fluorescence to assess soil contamination pathways: case studies of mass magnetic susceptibility in soils near abandoned coal and W/Sn mines.

Determining the origin and pathways of contaminants in the natural environment is key to informing any mitigation process. The mass magnetic susceptibility of soils allows a rapid method to measure the concentration of magnetic minerals, derived from anthropogenic activities such as mining or industrial processes, i.e., smelting metals (technogenic origin), or from the local bedrock (of geogenic origin). This is especially effective when combined with rapid geochemical analyses of soils. The use of multivariate analysis (MVA) elucidates complex multiple-component relationships between soil geochemistry and magnetic susceptibility. In the case of soil mining sites, X-ray fluorescence (XRF) spectroscopic data of soils contaminated by mine waste shows statistically significant relationships between magnetic susceptibility and some base metal species (e.g., Fe, Pb, Zn, etc.). Here, we show how qualitative and quantitative MVA methodologies can be used to assess soil contamination pathways using mass magnetic susceptibility and XRF spectra of soils near abandoned coal and W/Sn mines (NW Portugal). Principal component analysis (PCA) showed how the first two primary components (PC-1 + PC-2) explained 94% of the sample variability, grouped them according to their geochemistry and magnetic susceptibility in to geogenic and technogenic groups. Regression analyses showed a strong positive correlation (R2 > 0.95) between soil geochemistry and magnetic properties at the local scale. These parameters provided an insight into the multi-element variables that control magnetic susceptibility and indicated the possibility of efficient assessment of potentially contaminated sites through mass-specific soil magnetism.

Magnetic Response to the Source‐To‐Sink Environmental Changes in the Bay of Bengal Since ∼60 ka

AbstractThe terrestrial magnetic minerals of marine sediments are utilized to track the climatic changes in the source area and the dynamic characteristics of sedimentation processes. However, due to the varied source‐to‐sink environments, the magnetic response to ambient climate cannot be generalized. Here, we conducted systematic environmental magnetic analyses on core CJ04‐50 from the Ninetyeast Ridge and investigated its magnetic response to source‐to‐sink environmental changes. Core CJ04‐50 covers the last 60 Kyr based on accelerator mass spectrometry (AMS) 14C dating and the relative paleointensity (RPI) record. Rare earth element (REE) results suggest that the terrestrial materials are fed by the Ganges‐Brahmaputra (G‐B) and Irrawaddy/Indo‐Burma Ranges. High/low magnetic mineral content corresponds to strong/weak terristrial input during the cold/warm period. This pattern differs from that in the East Asian marginal seas, which have a high magnetic mineral content in warm periods. It might be attributed to the heavier Indian summer monsoon (ISM) precipitation than that of East Asian summer monsoon. Excessive moisture (>1,500 mm/year) would not favor the formation and preservation of magnetic minerals in the source area during interglacials. By contrast, the enhanced physical weathering during glacials results in more magnetic contributions. A significant local magnetite dissolution occurred at the layer of Middle MIS 3, which may be caused by the non‐steady state diagenesis following deposition.

Alluvial-lacustrine record of Mid- to Late-Holocene moisture variations trend verified by multiple proxies in the middle and lower reaches of the Hutubi River, northwest China

Alluvial-lacustrine deposits are important carriers for studying paleo-hydrological information and the evolution of paleo-environments. In this study, a total of 6 optically stimulated luminescence (OSL) samples from 2 profiles in the lower and middle reaches of the Hutubi River in the North Tianshan Mountains were dated, and a comprehensive analysis was conducted by integrating sedimentary structures, grain sizes, and magnetic susceptibility characteristics to explore the sedimentary environment patterns and regional evolution processes during the Mid to late Holocene. The results revealed the following findings: (1) The OSL signal of quartz samples indicates the predominance of fast components, allowing reliable dating of regional fluvial sediments using the appropriate condition-tested coarse-grained quartz single-aliquot regenerative dose (SAR) protocol within the 90–125 μm range. (2) Analysis of sedimentary structures, grain sizes, and magnetic susceptibility characteristics reveals lithofacies of heterotopic synchronous or homotopic asynchronous in exposed profiles, with predominantly poorly sorted fine and very fine sand. Magnetic susceptibility is primarily controlled by the content of magnetic minerals in the coarse particles, while also being influenced by the combined effects of provenance input and depositional environment, indicating a complex regional sedimentary environment influenced by variable hydrodynamic conditions driven by fluvial processes. (3) Based on OSL dating results and the analysis of various environmental proxy indicators, it is determined that the climatic environment in the Middle and Late-Holocene in the downstream areas of the northern piedmonts of the Tianshan Mountains demonstrates a fluctuating pattern of wet and dry alternations. The sedimentary environment shifted from a stable state in the Mid-Holocene to an unstable state in the Late-Holocene. The intermittent appearance of wet records may be associated with increased river activity caused presumably by the release of high-altitude ice due to rising temperatures and warming conditions.

Chemical and mineralogical characterization to define parameters for comminution, aiming at granulometric adequacy in rock rich in feldspars extracted in Pedra Lavrada-PB

The demand for high purity feldspars with low contaminant content, especially for use in the manufacture of porcelain tiles and white crockery, poses a challenge for processing the ore. Due to the need for very low iron levels, less than 0.15%, operations must be more complex, costly and capable of providing a high purity final product. To this end, it is necessary to employ mineralogical and technological characterization to understand the ore and plan the operations of the processing plant. A sample of rock rich in feldspars collected in an extraction in the municipality of Pedra Lavrada/PB was studied, aiming to identify the chemical composition and release spectrum using XRD and SEM techniques. Aliquots were subjected to preparation, granulometric classification and high-intensity wet magnetic separation steps. The results indicate that the rock has high concentrations of feldspars, quartz and a significant content of magnetite and hornblende. The physical release of magnetic mineral phases occurs below 0.104mm, and fragmentation operations must be designed with this grain size standard in mind. Magnetic separation, with mass recovery of 14.01% in relation to the feed, satisfactorily guaranteed a reduction in the concentration of magnetic minerals in the ore

Early Pleistocene depositional and environmental conditions at Dachangliang, Nihewan Basin, NE China

Early Pleistocene depositional and environmental conditions at Dachangliang, Nihewan Basin, NE China

Origin of magnetic particles in speleothems: A review

Soil erosion poses a significant threat to global socio-economic development and environmental conservation. Particularly, karst regions are grappling with severe erosion issues. Recent researches have shown that the concentration and particles of magnetic minerals in cave stalagmites can reflect past soil erosion. This paper summarizes the sources of magnetic mineral particles in stalagmites and the process of their entry into stalagmites, providing basic information for the study of soil erosion in karst areas. The main carrier of magnetism in stalagmites is magnetite. It is mainly derived from the soil overlying the caves. These magnetic minerals migrate from soils and weathered rocks to cave environments mainly by water infiltration, storm water runoff and flooding.

The Content of Magnetic Material in Black Sand of Yeh Gangga Beach

Yeh Gangga Beach is one of the black sand beaches in the Tabanan district. The abundant black sand on this beach stretches along the shoreline with varying grain sizes. This black sand characterizes the specific surface composition as iron sand deposits with high magnetic mineral content. The very high need and use of magnetic minerals in various fields prompt a study of the magnetic mineral content in the black sand of Yeh Gangga beach.The magnetic material content was determined by the extraction method which was expressed in terms of mass fraction. The grain size distribution was determined by the sieve method using a sieve shaker consisting of six mesh numbers, namely 30, 100, 170, 200, 270, and 325.The density of magnetic materials was determined by the principle of mass and volume ratio. The magnetic susceptibility was tested by using a Bartington MS2B susceptibility meter. Meanwhile, the characterization of the elements and their oxides used non-magnetic methods, namely the X-Ray Fluorescence test.The research results show that the magnetic material fraction of Yeh Gangga black sand reach 84.84% with 58.39% of the grains having sizes in the range 150r ≥90 μm. The magnetic susceptibility value is 28.26 10-6 m3/kg with an Fe element content of 85.15% w. The hematite (Fe2O3) content reaches 81.69%. This magnetic material has a density of 1914.43 kg/m3.

Glacial‐Interglacial Circulation and Climatic Changes in the South Indian Ocean (Kerguelen Plateau Region) Recorded by Detrital and Biogenic Magnetic Minerals

AbstractThe Southern Ocean (SO) plays a fundamental role in global climate due to the presence of the intense eastward‐flowing Antarctic Circumpolar Current (ACC), one of the most important ocean current systems. The configuration of the frontal systems of the ACC is controlled by the orbital‐ and millennial‐scale variations of the Southern Hemisphere westerly winds (SHWW) and the SO upwelling. However, the reconstruction of paleoclimate and paleocurrent in the SO remains controversial possibly because of the complex interpretation of paleo‐proxies and the regional variations. Here, we present results from rock magnetic measurements and electron microscopic analyses on marine core MD11‐3353 over the past 150 Kyr, which is located in the Polar Front Zone, west of the Kerguelen Plateau. Our data sets indicate that magnetic mineral assemblages in the core are dominated by detrital magnetic minerals mixed with biogenic magnetic minerals (i.e., magnetofossils formed by magnetotactic bacteria) during the interglacial periods. Changes in the detrital magnetic mineral content indicate a strong modulation of the ACC intensity and the SHWW stress at the orbital scale over the last climatic cycle with an enhanced activity during the glacial periods. The increase in magnetofossils content during the interglacial periods indicates an enhanced nutrient supply from the SO upwelling resulting from the southward migration of the Antarctic Polar Front. Our results suggest that the variations of concentration and assemblage of magnetic minerals can be used as faithful proxies for reconstructing ocean circulation and upwelling changes in the South Indian Ocean over the past 150 Kyr.

Environmental magnetic characterization for the Pialli Level and the Cretaceous Oceanic Red Bed 7 (late Albian, Poggio le Guaine core, central Italy)

The mid-Cretaceous is known as the most extreme greenhouse period in the last 150 Myr and was punctuated by repeated environmental perturbations. The mid-Cretaceous was also characterized by the emplacement of major Large Igneous Provinces and the deposition of organic-rich layers known as Oceanic Anoxic Events. Here, we present a high-resolution environmental magnetic and stable isotopic records of the western Tethyan pelagic interval in the Poggio le Guaine (PLG, Italy) core, deposited during the late Albian. Environmental magnetic data are here applied to detect redox and paleoproductivity variations across the OAE 1d and CORB 7 events. Combing the magnetic data and geochemical data from carbon (δ13C) and oxygen (δ18O) isotopic records, we document changes in the paleoenvironmental conditions across the Pialli Level and CORB 7 events in the Tethyan realm. The magnetic properties of the 10-m-thick pelagic marine sediments of the PLG core record the onset between upper part of Cretaceous Oceanic Red Bed 7 (CORB 7) and the Pialli Level that is a part of the Oceanic Anoxic Event (OAE) 1d. An increase in the magnetic mineral concentrations with hematite and goethite as the main magnetic carrier characterizes the upper CORB 7 sediments. Variations in “hard” isothermal remanent magnetization and the S-ratio during the upper CORB 7 are interpreted as changes in aeolian dust input into the Umbria-Marche Basin. During the interval between the upper part of CORB 7 and OAE 1d (Pialli Level), the magnetic mineral concentration decreases, and the magnetic mineralogy changes from hematite to magnetite, suggesting a change in the oceanic system. This change might be associated to an increase in orbital forcing capable of modulating the monsoon activity at the onset of the Pialli Level. First-order reversal curves for all samples from the PLG core are similar and indicate a dominance of detrital magnetite. The absence of magnetically non-interacting single domain biogenic particles suggests that an increase in primary productivity was not significant or variation of the anoxic-oxic boundary could have also occurred. Finally, our records show cyclic alterations that reflect changes in the terrigenous input that was triggered by a period of enhanced orbital forcing paced by monsoonal systems.

Is biomagnetic leaf monitoring still an effective method for monitoring the heavy metal pollution of atmospheric particulate matter in clean cities?

The development of a reasonable method for predicting heavy metals (HMs) pollution in atmospheric particulate matter (PM) remains challenging. This paper presents an elution-filtration method to collect PM from the surface of Osmanthus fragrans in a very clean area (Guiyang, China). The aim is to evaluate the effectiveness of biomagnetic leaf monitoring as a simple and rapid method for assessing HMs pollution in clean cities. For this purpose, we determined the magnetic parameters and concentrations of selected HMs in PM samples to investigate their relationships. The results showed that the magnetic minerals in PM samples were mainly low coercivity ferrimagnetic minerals, with a small amount of high coercivity minerals. The types of magnetic minerals were generally single, and the magnetic domain state was pseudo-single domain (PSD). There was a significant correlation between magnetic parameters and the heavy metal (HM) concentrations in PM. Low-field magnetic susceptibility (χ) could be used as an ideal proxy for determining anthropogenic HM pollution. Traffic emissions were the main atmospheric pollution source in urban Guiyang. Due to the incomplete traffic network and large traffic flow, traffic congestion (TC) often occurred at road intersections in the northwest and southwest corners of the city, resulting in the highest concentration of magnetic minerals and the most severe PM pollution. To mitigate atmospheric PM pollution and protect public health, it is strongly recommended that municipal authorities prioritize urban planning and traffic management to address TC. Measures should be implemented urgently to alleviate stop-and-go traffic.

Preparation and Characterization of Fe2O3 from Iron Sand of the Coastal Sea of Cidaun Beach-South Cianjur (Indonesia) using the Co-precipitation Method

The synthesis and characterization of Fe2O3 from Iron Sand of the coastal sea of Cidaun Beach - South Cianjur using the coprecipitation method has been carried out. The purpose of this research was to identify the crystal structure, magnetic mineral content, and magnetic properties of iron sands. The characterizations used in this research are X-Ray Diffraction (XRD), Scanning Electron Microscope-Energy Dispersive X-Ray (SEM-EDX) and Vibrating Sample Magnetometer (VSM). Based on the XRD results, it shows that the iron sand sample produces multi-phases, namely hematite (????-Fe2O3), maghemite (????-Fe2O3) and ilmenite (FeTiO3). SEM-EDX results indicate that the iron sand samples have an average particle size of 12.396 ????m. VSM results indicate that the iron sand sample is soft magnetic (ferrimagnetic) with saturation, remanence and coercivity values of 47 emu/g, 1.53 emu/g and 102.97 Oe, respectively.

Analysis of The Susceptibility Value Dry Ink (Toner) From Raw Material Iron Sand Pasie Nan Tigo Beach and Rice Husk Biomass

The competition engaged in manufacture of the dry ink industry (toner) is increasing, with many types of dry ink (toner) emerging from various brands. This makes each brand compete to try to create quality dry ink. However, this is not easy, because raw material for making dry ink is expensive and stickiness of dry ink on the paper can change if the material is modified. The dry ink in this study was made by modifying the raw materials using natural mineral magnetic (Fe3O4) from the iron sand of Pasie Nan Tigo beach, activated carbon from rice husks biomass, and organic polymer Acacia Senegal. Taking into account the mixture of three raw materials in made of dry ink (toner) will affect the characteristics of dry ink (toner), one of the characteristics affected is the large content of magnetic minerals (Fe3O4) in it, it is necessary to test the value of susceptibility in dry ink (toner) to see the amount of magnetic minerals that are still present in the dry ink after mixing. The tool used for testing magnetic susceptibility values here is Bartington Magnetic Susceptibility MS2B. The purpose of this study is to produce quality dry ink with good dry ink paste power (toner) with based the characteristics of the susceptibility value of the dryink (toner). This research method uses extraction and coprecipitation methods and emulsion polymerization methods to increase the strength of the stickiness dry ink (toner) on paper. The results of characterization obtained by range 11924.60 x 10−8m3/kg until 27916.97 x 10−8m3/kg.

Magnetic Mineral Consistency Analysis the main ingredients of cement and Rowmix materials with Magnetic Susceptibility Method using Bartington Magnetic Susceptibility Type B (MS2B)

Cement has hydraulic properties (mixed with water) will form a bond and harden. Cement-making materials consist of the main ingredients (Limestone, Iron Sand, Silica, and Clay) which are the ingredients in the manufacture of Rowmix in the Rowmill. In the main ingredient there is a magnetic mineral content for the manufacture of Component Compoun. To see changes in magnetic minerals from the cement manufacturing process, it is necessary to analyze the consistency of the material until the initial manufacture. The purpose of this study was to determine the consistency of the magnetic mineral as the main ingredient of cement in the Rowmix manufacturing process. The research method used is rock magnetism using a Bartington Susceptibility Meter Type B (MS2B) which can measure based on mass and volume with 2 different frequencies, namely Low Frequency and High Frequency. This measurement uses 6 different samples, namely the main ingredients of cement (Limestone, Irond Sand, Silica, Clay) and Rowmix materials (Rowmix 1 (RX1) and Rowmix 2 (RX2). From these measurements, the susceptibility values obtained from the main ingredients including Limestone approx. 23.7 x 10−8 m3/kg - 46.6 x 10−8 m3/kg, Irond Sand ranged from 470 x 10−8 m3/kg - 1791.1 x 10−8 m3/kg, Clay ranged from 852.7 x 10−8 m3/kg - 986.4 x 10−8 m3/kg, Silica ranges from 148.2 x 10−8 m3/kg - 166.9 x 10−8 m3/kg, while in Rowmill I process (Rx1) around 133, 4 x 10−8 m3/kg - 180.3 x 10−8 m3/kg, Rowmill 2 (Rx2) 133.4 x 10−8 m3/kg - 244.2 x 10−8 m3/kg, Magnetic susceptibility values in the main material range from 1532 x 10−8 m3/kg up to 2838,6 x 10−8 m3/kg, while the value of Rowmix 1 (RX1) and Rowmill 2 (Rx2) is lower than the magnetic susceptibility value of the main ingredient.

Holocene evolution of the Banni Plain at the north‐east margin of the Arabian Sea: Constraints from a ca 50 m long sediment core

AbstractHolocene evolutionary history of the Banni Plain in the Great Rann of the Kachchh Basin is reconstructed from a subsurface sediment core of ca 50 m. Detailed data on textural and lithofacies variations, grain‐size analysis, environmental magnetism and accelerator mass spectrometry 14C dates on seven samples were generated on the sediment core retrieved from the Banni Plain near Berada. A high‐resolution record extending back to 10 ka has been reconstructed from the top ca 40 m of the core section comprising shallow marine sediments. The core is divisible into five depositional units. The basal part is a fluvial depositional unit followed upward by estuarine, sub‐tidal, intertidal and supra‐tidal environments. The sediment accumulation rate is highest in the sub‐tidal to intertidal facies (1.9 cm year−1) and decreases towards the supra‐tidal facies to 0.09 cm year−1. Environmental magnetic analysis, χlf coupled with the S‐ratio, indicates high magnetic mineral concentrations during the Early Holocene, suggesting a wet period accompanied by high monsoon precipitation. This is followed by the onset of semi‐arid conditions in the Great Rann of the Kachchh Basin as indicated by the low values of the χlf and S‐ratios. A westward and northward shift in the shoreline towards the deeper part of the basin is suggested during the Late Holocene, which is coupled with aridity and reduced monsoonal conditions. The change in depositional pattern from the retrogradational deposit of fluvial (Unit 1) to estuarine sediment (Unit 2), progressing to sub‐tidal (Unit 3), is attributed to sea‐level transgression followed by regressive intertidal (Unit 4) to supra‐tidal deposition (Unit 5), culminating in complete withdrawal of the sea, aided by tectonic uplift, during the Late Holocene. The results reveal that the sediment accumulation rates and depositional environments changed over time in response to changes in sea level from minima to maxima and then eventually to the present level.

Favourable IOCG and polymetallic environs in Marwar - Khetri, NW Indian Shield imprints from aerogeophysical data analysis

The analysis of aeromagnetic data reveals two significant broad oval-shaped aeromagnetic anomalies oriented in the NE-SW direction, west of Laxmangarh and east of Fatehpur. These significant anomalies identified beneath sand-alluvium-covered areas of Rajasthan's Marwar region are of a low dominance nature. These magnetic signatures are associated with gravity gradients in the regional Bouguer gravity map. Magnetic anomalies and subsurface modeling revealed that the remanence source had a high magnetic susceptibility. The ground gravity profiles across the Laxmangarh anomaly show a high gravity variation of 5 mGal/km. The integration of geochemical distribution patterns, spectrometric elemental concentrations, different ratios, and composite image maps has brought out alteration/shear zones that are favourable for mineralization. The results of selective 2D-profiles, plate modeling, and 3D-inversion modeling of these anomalies reveal that the depth of the causative source varies from 300 to 1000 m. The higher-order magnetic susceptibilities, geochemical dispersion pattern, and spectrometric ratio maps and composite images distinguished hydrothermal alteration zones characterised by potassium enrichment. The results indicate the possibility of concealed source rocks with high magnetic mineral content (magnetite, maghemite, titanomaghemite, pyrrhotite, and franklinite?) and a relatively high density. The geophysical signatures observed around Fatehpur and Laxmangarh, with high magnetic contrast, low dominance, and remanence coupled with high gravity values, as well as hydrothermal alteration zones, appear to have striking similarities with the geophysical and geochemical scenarios of some of Australia's Iron Oxide Copper-Gold (IOCG) prospects in the Gawler, Arunta, Tennant, and Mount Isa regions. Therefore, these anomalous areas may be explored for the possibilities of an IOCG or polymetallic type of mineral.

Rock Magnetic and Mineralogical Properties of Lateritic Soil Profiles Developed on Two Different Parent Rocks in Northern Kerala, South-Western India

The rock magnetic and mineralogical properties of two lateritic soil profiles developed on two different parent rocks (khondalite and granite) in northern Kerala, south-western India were investigated to better understand pedogenic processes under tropical climate. Field investigations reveal the presence of various horizons in the lateritic profiles, such as saprolite, mottled zone, pebble horizon and top soil. The particle size, rock magnetic, Vibrating Sample Magnetometer (VSM), Scanning Electron Microscopy (SEM)-Energy-Dispersive X-ray Spectrometer (EDS) and X-Ray Diffraction (XRD) analyses were performed on samples collected from different horizons of the two profiles. Magnetic susceptibility (χlf) values of the lateritic profiles vary from 9.97 to 1717.04 x 10-8 m3 kg-1, with the granitic profile exhibiting overall higher values. The percentage frequency-dependent susceptibility (χ %) ranges between 0 % and 13.9 %. The XRD data reveal the presence of kaolinite, gibbsite (except for top soil layer) and quartz along with magnetic minerals like magnetite, hematite and goethite. The upper horizons (top-soil and pebble horizon) exhibit high values for concentration dependent magnetic parameters like χlf and χfd%, whereas, the lower horizons (saprock, saprolite, pallid zone horizons) exhibit low values. The tropical soils in the region have undergone a higher degree of pedogenesis with increased magnetic mineral concentration compared to temperate soils. The magnetic enhancement in the topsoil may be due to the neoformation of ultra fine-grained SP magnetite/maghemite (with minor anti-ferro magnetic component), aided by sufficient Fe supply, alternate wetting and drying cycles, dehydration, oxidation and redox conditions. Keywords: Lateritic Soils; Soil Magnetism; XRD; SEM; Magnetic Enhancement; Pedogenesis; Southern India

Mineral magnetic properties of surface soils from the Broknes and Grovnes Peninsula, Larsemann Hills, East Antarctica

This study presents the mineral magnetic, particle size, and organic content data of surface soils from Larsemann Hills, East Antarctica. The analysis of isothermal remanent magnetization and the high specific magnetic susceptibility values –mean (±S.D.) values of 117.7 (±175.0) × 10−8m3kg−1 for Broknes Peninsula and of 330.9 (±217.4) × 10−8m3kg−1 for Grovnes Peninsula– indicate high concentrations of low-coercivity magnetic minerals. The magnetic minerals are coarse-grained in the multidomain and pseudo-single domain range, and the significant correlation between some magnetic parameters suggests the dominant control of multidomain grains. The remanent acquisition coercivity H1/2 shows mean (±S.D.) values of 38.2 (±4.9) for Broknes and 38.3 (±3.7) mT for Grovnes soils suggesting magnetite dominance. The soils lie in the sand and loamy sand textural classes, and the concentration of organic matter is very low. Values of percentage frequency-dependent susceptibility indicate insignificant proportions of superparamagnetic grains, and therefore no significant evidence for pedogenic magnetic minerals was observed in these soils. The magnetic signal of Larsemann Hills soils was primarily terrigenous with no contributions from bacterial magnetite, authigenic greigite and anthropogenic magnetic minerals.

Impact of temperature increase on the formation of magnetic minerals in shales. The example of Tournemire, France

Remagnetization is a pervasive mechanism affecting all kinds of rocks. Sedimentary rocks are particularly prone to such a mechanism because they can experience a wide range of physical and biogeochemical processes which can lead to partial or total loss of the original paleomagnetic record. Temperature increase is one of key factors affecting the rock magnetic properties in sedimentary rocks. Laboratory experiments on shales in the literature have shown that the magnetic mineralogy changed with temperature as low as 50 °C, and that new magnetic phase(s) are formed. The latter was identified to be mostly iron oxides (e.g., magnetite) and iron sulfides (e.g., pyrrhotite). In this study similar to what previously conducted on samples from the Paris Basin, a laboratory heating experiment is conducted on shale samples from the Tournemire tunnel (SE France) in a temperature range of 50 to 130 °C. This aims to simulate a new exposition of the samples to temperature and to identify the changes in magnetic phases, especially on FeIII-bearing minerals, with temperature. The remanence of the analyzed samples increases stepwise, suggesting an increasing concentration of magnetic minerals above their blocking volume with increasing temperature. Magnetite is the main magnetic carrier present and formed in the heated samples, with possibly pyrrhotite forming at high temperature. A conceptual model of magnetic mineralogy changes with temperature is presented and compared to previous results on claystones from the Paris Basin. The experimental observations support that the paleomagnetic record in sedimentary rocks affected by a later temperature increase during burial should be interpreted carefully. Indeed, remagnetization will likely occur when magnetic minerals record a secondary remanence either growing above their blocking volume or when exposed again to a temperature higher than the maximum burial temperature formerly experienced by the samples.

Analysis of Magnetic Material Abundance in Black Sand

The analysis of the magnetic material abundance on the black sand of Nyanyi beach revealed magnetic material content, grain size, density, magnetic mineral content, and magnetic susceptibility value.The results of this study can be used for black sand development inTabanan district. The black sand magnetic material was determined by the extraction method. Mineral content was tested by using XRF equipment, and the magnetic properties of black sand were determined by using a Bartingtons MS2 Magnetic Susceptibility Meter and a Vibrating Sample Magnetometer. The data were analyzed descriptively quantitatively. The results show thatNyanyi beach sand physically has a characteristic dark gray color, tends to be black, and shiny with a weight fraction of magnetic material reaching 95.52%.The density of the magnetic material is 2072.6 with varying grain sizes of 53 600 .The average value of magnetic susceptibility is 27.212x 10-with Fe2O3magnetic mineral content of 86.68% and the element of Fe is 89.41%.The values of saturation magnetization, remanance magnetization, and coervicity reach37.74; 4.64; 103.93 Oe.