Magnetite Content Research Articles

A detailed magnetic characterization of combustion products from various metamorphic grade coals

The magnetic properties of combustion products from various metamorphic grade coals including lignite, flame coal, gas coal, fat coal, baking coal and lean coal and anthracite coal, were analyzed. This study was carried out by means of basic magnetic parameters, thermomagnetic and hysteresis measurements. The mass magnetic susceptibility (χ) values ranged from 327 × 10−8 m3/kg to 1722 × 10−8 m3/kg, with an average value of 892 × 10−8 m3/kg, demonstrating a considerable amount of ferrimagnetic minerals in these burned coal samples. The lower χ and SIRM values for the burned lignite were probably due to the lower content of magnetite. A characteristic feature of combustion products was their high values of frequency dependent susceptibility (χfd%), indicating the presence of a large amount of superparamagnetic grains of ferrimagnetic minerals within the combustion products. Thermomagnetic analyses of various combustion products showed the dominant role of magnetite-like phase. Moreover, a significant amount of hematite was also only identified in the combustion product from Flame coal. While the combustion products from Flame coal and Fat coal were characterized by a relatively narrow loop, characteristic of magnetically soft ferrimagnetic minerals, other combustion products including lignite, gas coal, baking coal, lean coal and anthracite coal displayed wasp-waisted loops, indicating the presence of two or more coercivity fractions.

Sulfuric acid pretreatment of oxidized pyrrhotite in flotation desulphurization of magnetite concentrate

The impact of sulfuric acid pretreatment on the surface property of oxidized pyrrhotite (OX-pyrrhotite) and its application in flotation desulphurization of magnetite concentrate were investigated in this study. OX-pyrrhotite using sodium butyl xanthate (BX) collector performed a poor floatability. After sulfuric acid pretreatment, OX-pyrrhotite exposed a new sulphide surface similar to raw pyrrhotite. XPS analysis indicated that the oxidized species such as sulphate were dissolved away from the OX-pyrrhotite surface. This conversion made the natural hydrophobicity and isoelectric point of OX-pyrrhotite proximity to pyrrhotite. Contact angle and zeta potential measurements showed that the sulfuric acid pretreatment increased the adsorption of BX collector and the hydrophobicity of OX-pyrrhotite surface. FTIR and XPS analyses inferred that there existed weak adsorption of BX collector on OX-pyrrhotite surfaces. After sulfuric acid pretreatment, the interaction between BX collector and OX-pyrrhotite surfaces was strengthened, generating dixanthogen species. Therefore, the sulfuric acid pretreatment improved the floatability of OX-pyrrhotite within a wide pH region. When sulfuric acid pretreatment was adopted, the flotation desulfurization could decrease the sulfur content of magnetite concentrate from 4.50% to 0.18%.

Geochemical Anatomy of the Main Magnetitite Layer, Bushveld Complex, South Africa

ABSTRACT The mafic layered Bushveld Complex, South Africa, contains numerous examples of monomineralic layers within its succession. The Upper Zone (UZ) contains approximately 24 magnetitite layers, the genesis of which has been extensively debated. The Main Magnetitite Layer (MML) is approximately 2 m thick and is traceable around its edge across >60 000 km2. Its basal contact with underlying anorthosite is planar and sharp, but the top contact grades upward with increasing plagioclase content. Sampling at a vertical spacing of a very few centimetres from seven profiles in the east over many tens of kilometres and one other 300 km to the west reveals concentrations of Cr in magnetite that decrease extremely rapidly upward (typically from >8000 to 1000 ppm within 30–60 cm from the base), punctuated by sharp concentration reversals and rare decreases. Here, we describe an outcrop where the MML splits into three sub-layers, separated by magnetite–plagioclase rocks. Twelve profiles across this zone of splitting have been similarly analysed. Lateral variations in Cr profiles across a few metres are observed at this locality. We offer the suggestion that magnetite formation may have been induced by shock wave nucleation on the bottom of the chamber accounting for the abrupt appearance of magnetitite over such a wide area. Bottom growth of magnetite lowered the density and Cr content of the evolving magma, causing turbulence and convective overturn near the base of the chamber that created inhomogeneities in Cr on various scales, preserved in the ensuing magnetite compositions both vertically and laterally. Intermittent and abrupt (on a scale of 1–2 cm) upward increases in the Cr contents of up to 3000 ppm in magnetite profiles resulted from convective overturn impinging on the floor. The tops of the magnetitite sub-layers grade up into magnetite–plagioclase rocks and continue the upward decrease in Cr content in magnetite, typically at 900 ppm Cr, demonstrating upward continuity of fractionation. In contrast, there are reversals in Cr content between the magnetite–plagioclase rocks and the overlying magnetitite sub-layers that we attribute to convective overturn, with an increase in the Cr content. Two profiles through the MML show abrupt upward discontinuities to lower Cr contents that we attribute to physical erosional events. Anorthosite fragments in magnetitite and magnetitite fragments in anorthosite layers further attest to such processes. The anorthite contents of plagioclase do not change across the MML, suggesting that magma addition was not responsible for the formation of magnetitite layers. Primary topographic variations at the base of the chamber also preclude addition of dense magma for the formation of magnetitite layers. Upward infiltration metasomatism, slightly resetting Cr contents, is limited to <3 cm.

Effect of Magnetite Content and Specificity of Nickel(II) Ions on Electrokinetic Properties of Composites Based on Porous Silica Particles

Effect of Magnetite Content and Specificity of Nickel(II) Ions on Electrokinetic Properties of Composites Based on Porous Silica Particles

Formation of Fe-Ti oxide and Ni-Co sulfide ores by concentric tube flow and hydrous metal-rich melt recharge into the cooling crystal mush: Example from the Hongge intrusion in Panxi region, SW China

The Panxi (ultra-)mafic intrusions are relatively small compared with world-class ore-related (ultra-)mafic intrusions, but they host several super-large Fe-Ti oxide deposits and few small Cu-Ni (PGE) sulfide deposits. The mechanisms that concentrate huge amounts of oxide minerals into these small intrusions and form the distinct oxide and sulfide mineralization remain poorly understood. Here, we investigate the magma dynamics that produced extensive Fe-Ti oxide and coexisting Ni-Co sulfide mineralization in the Hongge intrusion of Panxi region, based on detailed field cross-cutting relations and petrographic observations, bulk-ore/rock geochemistry, and in-situ LA-ICP-MS magnetite trace element analyses. The Fe-Ti oxide ores include magnetite-poor (<60 vol%) disseminated and magnetite-rich (>60 vol%) massive types, with the former further divided into the gabbro-hosted (GH) and (olivine-)pyroxenite-hosted (OPH) subtypes. The GH oxide ores have Cr-poor (median 86.9 ppm) magnetite and abundant apatite interstitial to silicate minerals. In contrast, the OPH and massive oxide ores have Cr-rich (median 13,956 ppm) magnetite that envelops resorbed silicate minerals. Principal component analyses of bulk-ore and magnetite elemental contents reveal genetic links between the OPH and massive oxide ores, but remarkable genetic distinction from the GH oxide ores. Considering the overall lopolith-shape orebody geometry of several branch intrusions, the GH oxide ore formation may have involved spontaneous development of concentric tube flow zones within the cooling crystal mush. However, the lower P but much higher Cr-Cu-Co-Ni contents than the GH oxide ores and the sharp intrusion of massive oxide ores into the OPH oxide ores suggests that the OPH and massive oxide ores were probably formed by upward percolation and later intrusion of hydrous Fe-rich melts from a deep-seated magma reservoir into semi-solidified and fossilized mush, respectively. In addition, sulfide ores occur mainly as irregular/lenticular aggregates in massive oxide ores and are depleted in Cu and platinum group elements (PGEs), indicating early, deep-level sulfide segregation that scavenged the Cu and PGEs from the magmas. Hence, we envisage that the assimilation of S-deficient wall-rocks into basaltic magmas may have induced the early sulfide saturation and retain the majority of Fe for later precipitation as principal oxide and minor PGE-Cu-depleted sulfide ores.

Complex refractive index and single scattering albedo of Icelandic dust in the shortwave part of the spectrum

Abstract. Icelandic dust can impact the radiative budget in high-latitude regions directly by affecting light absorption and scattering and indirectly by changing the surface albedo after dust deposition. This tends to produce a positive radiative forcing. However, the limited knowledge of the spectral optical properties of Icelandic dust prevents an accurate assessment of these radiative effects. Here, the spectral single scattering albedo (SSA) and the complex refractive index (m=n-ik) of Icelandic dust from five major emission hotspots were retrieved between 370–950 nm using online measurements of size distribution and spectral absorption (βabs) and scattering (βsca) coefficients of particles suspended in a large-scale atmospheric simulation chamber. The SSA(λ) estimated from the measured βabs and βsca increased from 0.90–0.94 at 370 nm to 0.94–0.96 at 950 nm in Icelandic dust from the different hotspots, which falls within the range of mineral dust from northern Africa and eastern Asia. The spectral complex refractive index was retrieved by minimizing the differences between the measured βabs and βsca and those computed using the Mie theory for spherical and internally homogeneous particles, using the size distribution data as input. The real part of the complex refractive index (n(λ)) was found to be 1.60–1.61 in the different samples and be independent of wavelength. The imaginary part (k(λ)) was almost constant with wavelength and was found to be around 0.004 at 370 nm and 0.002–0.003 at 950 nm. The estimated complex refractive index was close to the initial estimates based on the mineralogical composition, also suggesting that the high magnetite content observed in Icelandic dust may contribute to its high absorption capacity in the shortwave part of the spectrum. The k(λ) values retrieved for Icelandic dust are at the upper end of the reported range for low-latitude dust (e.g., from the Sahel). Furthermore, Icelandic dust tends to be more absorbing towards the near-infrared. In Icelandic dust, k(λ) between 660–950 nm was 2–8 times higher than most of the dust samples sourced in northern Africa and eastern Asia. This suggests that Icelandic dust may have a stronger positive direct radiative forcing on climate that has not been accounted for in climate predictions.

Fabrication and properties of high-thermal-storage RTO ceramics using bauxite tailings and red mud

Nowadays, it is critical to find materials and methods that can help reduce the human impact on the environment. Regenerative thermal oxidizers (RTOs) have a wide range of applications owing to their effective energy saving. Among the different RTOs, thermal-storage RTO ceramics have basic heat storage and release capability. The main objective of this work is to study the preparation of thermal-storage RTO ceramics for the treatment of exhaust gas using bauxite tailings and Bayer red mud from Jiaozuo City (Henan Province) with different mass fractions of magnetite as substitutes for the traditional raw materials (quartz and clay). The effect of the magnetite addition on the performance of the thermal-storage RTO ceramics prepared from the bauxite tailings and red mud was investigated. The raw materials were pressed into cylinder shape and then sintered at 950 °C, 1000 °C, 1050 °C, and 1100 °C. The developed materials were analyzed and characterized via X-ray diffraction and scanning electron microscopy, and specific heat capacity tests (differential scanning calorimetry using the sapphire method) were conducted on the thermal-storage RTO ceramics prepared at the optimal sintering temperature (1050 °C). The ceramics exhibit the best overall performance for magnetite content of 25% and sintering temperature of 1050 °C, with compressive strength of 134.96 MPa, volume density of 3.00 g/cm3, and linear shrinkage of 14.68%. The product also has a remarkably low water absorption rate and apparent porosity, water absorption of 0.02%, apparent porosity of 0.06%. Furthermore, the specific heat capacity is sufficiently high to meet the requirements of high-thermal-storage RTO ceramics. This study provides a new, low-cost solution for the preparation of high-thermal-storage RTO ceramics, which is helpful for reducing the exploitation of natural mineral resources.

Hydrothermal Method to Synthesize Nanomagnetite by Water Extract of Averrhoa bilimbi : Effect of Time and Reactor Size

Nanomagnetite was synthesized using water extract of bilimbi (Averrhoa bilimbi). The high citric acid content has the potential as a reducing agent in the synthesis of magnetite using the hydrothermal method. The synthesis was conducted using different sizes of hydrothermal reactors, 50, 150, and 1700 mL. The results showed that a reactor with a volume of 150 mL and a synthesis time of 12 h was the best condition for synthesis. The results obtained from X-ray diffraction analysis showed that in the best conditions, the crystallinity level was 74.4%, the ratio of product to volume was 3.7×10–2 g/mL, the Fe content in magnetite was 22.0%, the Fe content in the remaining liquid was 0.02%, the Fe ratio was 96.9%, and the ammonium content in the solution was 1.24% w/v. The best conditions were 150 mL reactor and 12 hours synthesis.

Low-Temperature Treatment of Boehmitic Bauxite Using the Bayer Reductive Method with the Formation of High-Iron Magnetite Concentrate.

The Bayer process is the main method of alumina production worldwide. The use of low-quality bauxites for alumina production results in the formation of a significant amount of technogenic waste-bauxite residue (BR). The Bayer reductive method is one possible way to eliminate BR stockpiling, but it requires high-pressure leaching at temperatures higher than 220 °C. In this research, the possibility of boehmitic bauxite atmospheric pressure leaching at both the first and second stages or high-pressure leaching at the second stage with the simultaneous reduction of hematite to magnetite was investigated. Bauxite and solid residue after NaOH leaching were characterized using XRD, SEM-EDS, and Mössbauer spectroscopy methods. The first stage of leaching under atmospheric pressure with the addition of Fe(II) species in a strong alkali solution (330-400 g L-1 Na2O) resulted in a partial reduction of the iron minerals and an extraction of more than 60% of Si and 5-25% of Al (depending on caustic modulus of solution) after 1 h. The obtained desilicated bauxite was subjected to atmospheric leaching at 120 °C in a strong alkali solution (350 g L-1) or high-pressure leaching at 160-220 °C using the Bayer process mother liquor in order to obtain a concentrate with a magnetite content higher than 83 wt. %.

Cretaceous to Palaeogene boundary events and palaeoenvironmental responses across pelagic sequences of the Žilina core section, Slovakia: Rock magnetic, biotic, and geochemical characterization

The Žilina-Hradisko borehole in Slovakia intersects a succession from the Cretaceous Hradisko formation to the Paleocene Hričovské Podhradie formation. In this paper, we mainly focus on the Cretaceous–Palaeogene (K–Pg) boundary interval, which is marked by an abrupt change in planktonic biota and magnetic properties. Micropalaeontological findings suggest a rapid change from a stable, oxygen-rich, oligotrophic environment during the Maastrichtian to an unstable, cooler environment with reduced oxygenation and evidence of biotic stress in the lowermost Danian strata. An abrupt change in the magnetite concentration in the same interval indicates increased detrital input and probably biogenic (soft) magnetite production. Evidence recorded in borehole with enhanced Hg input into the Maastrichtian Ocean suggests that the Deccan eruptions mostly occurred prior to the K–Pg boundary, whereas no volcanic Hg input was detected at the K–Pg boundary itself. Double peaks in multiple magnetic properties mark the Danian hyperthermal Dan-C2 event, which was characterised by a series of environmental changes, including enhanced terrigenous input, oxygen deficit, increased nutrient supply, high benthic productivity, and Parasubbotina acme. Prior to the Latest Danian event, foraminiferal assemblages were significantly affected by dissolution and oxygen depletion, followed by warming, water column stratification, and diversification of calcareous plankton groups. An increase in detrital input and nutrient export drove the productivity of deep-dwelling subbotinids and globanomalinids and were correlated with the mid-Paleocene biotic event (MPBE). The seafloor biota associated with the MPBE implies oxygen deficiency and the prevalence of benthic infauna. The Selandian–Thanetian strata markedly differ from planktonic foraminifera of older formations, with their rich content of large, diversified, and heavily calcified morozovellid and igorinid foraminifera, revealing the existence of water column stratification with surface-water productivity and meso- to oligotrophic conditions. The microfauna of ornate morozovellids and benthic biota from the lowermost formation implies the onset of environmental stress and CaCO3 dissolution during the Paleocene-Eocene Thermal Maximum (PETM).

Obtention of magnetite nanoparticles via the hydrothermal method and effect of synthesis parameters

Magnetic nanoparticles (MNPs) have been widely studied for their properties and applications in the fields of electronics and medicine. Hydrothermal synthesis, in which the reaction parameters are extremely important because they influence the product characteristics, properties, and final applications, is an existing method for producing nanomaterials. Therefore, in this study, hydrothermal syntheses were performed to obtain nanomagnetite by varying the temperature, reaction time, and molar ratio, and their influences on the product particle size were analyzed using statistical analysis. The products were characterized in terms of composition and purity.Tthe purest samples were obtained at a reaction temperature of 214 ℃ and the longest reaction time of 6 h, with 96 % purity for the tests with a higher magnetite content. All syntheses produced products with particles on the nanometer scale. The purest magnetite samples exhibited an average hydrodynamic diameter of 220 nm and ferromagnetic behavior. Statistical analysis revealed that the reaction time was the only statistically significant parameter influencing magnetite particle size, with smaller sizes at longer reaction times. The cytotoxicity of MNPs was evaluated in non-tumor cells (NIH3T3 and RAW 264.7). Human erythrocytes did not exert any cytotoxic effects on non-tumor cells, indicating that MNPs are promising drug delivery systems.

New Insight into Magnetic Enhanced Methane Production from Oily Sludge via Mesophilic Anaerobic Degradation Processes

Anaerobic digestion is a promising technology for treating and disposing of oily sludge, but the presence of oil in the sludge reduces methane production and sludge volume reduction. To overcome this limitation, this study creatively reports the use of magnetite to enhance methane production in oily sludge mesophilic anaerobic digestion and elucidates the underlying mechanism. Results show that the addition of magnetite increases methane production, with a 5% magnetite content leading to a 1.42-fold increase in cumulative methane output compared to the blank. Mechanistically, magnetite accelerates the release of organic matter, promotes oil degradation, increases volatile fatty acids (VFA) accumulation, and reduces the proportion of propionate. Additionally, magnetite alleviates pH decreases and increases the release of ammonia nitrogen and phosphate, resulting in effective sludge reduction, with volatile suspended solids (VSS) reduction ranging from 26.9% to 32.6%, higher than that of the blank. Moreover, magnetite accelerates electron transfer and increased the relative abundance of microorganisms associated with methane production, with the relative abundance of Methanosarcina increasing to 37.6~38.5% due to the presence of magnetite. This study provides a theoretical framework for effectively utilizing oily sludge through the application of magnetite.

Effect of magnetite on physical, tribological and magnetic characteristics of kenaf fibre

The demand for organic fibres with remarkable mechanical, magnetic and physical properties is rising. As a result, the current study investigated the impact of magnetite reinforcement on kenaf fibre. The test samples were prepared by using the hand lay-up process with the addition of magnetite in the range 10–40 wt%. The test results showed that samples with a 30% magnetite content had the best mechanical, physical and tribological characteristics. They showed water absorption of 0 g, average wear of 112 μm and an average frictional force of 1.1 N. The magnetic absorption values of samples with 30 and 40 wt% magnetite were −0.0003 78 to 0.0003 8623 and −0.0002 6021 8 to 0.0002 5781 4 emu/g, respectively.

Size and Composition Control of Magnetic Nanoparticles

Magnetite nanoparticles are a type of magnetic nanoparticle (MNP) that are inexpensive to make and can be formed in different shapes and sizes. MNPs can be used in DNA/RNA purification, drug delivery, and other biomedical applications. The commonly employed solvothermal route to make these MNPs gives the most uniform products with the smallest size distribution, but there is a need to identify easily controlled changes to reaction parameters that can reliably tune the size and composition of the MNPs made by this method. In this work we report simple and reliable methods whereby adjusting the total water content and basic salt concentration affords size and composition control, respectively. We employ synchrotron X-ray absorption measurements to prove our method offers monotonic control over MNP composition from maghemite-rich (γ-Fe2O3) to the more magnetic magnetite (Fe3O4). This demonstrates a simple, general method to produce particles with high magnetite concentration and the desired size.

Heavy concrete shielding properties for carbon therapy

As medical facilities are usually built at urban areas, special concrete aggregates and evaluation methods are needed to optimize the design of concrete walls by balancing density, thickness, material composition, cost, and other factors. Carbon treatment rooms require a high radiation shielding requirement, as the neutron yield from carbon therapy is much higher than the neutron yield of protons. In this case study, the maximum carbon energy is 430 MeV/u and the maximum current is 0.27 nA from a hybrid particle therapy system. Hospital or facility construction should consider this requirement to design a special heavy concrete. In this work, magnetite is adopted as the major aggregate. Density is determined mainly by the major aggregate content of magnetite, and a heavy concrete test block was constructed for structural tests. The compressive strength is 35.7 MPa. The density ranges from 3.65 g/cm3 to 4.14 g/cm3, and the iron mass content ranges from 53.78% to 60.38% from the 12 cored sample measurements. It was found that there is a linear relationship between density and iron content, and mixing impurities should be the major reason leading to the nonuniform element and density distribution. The effect of this nonuniformity on radiation shielding properties for a carbon treatment room is investigated by three groups of Monte Carlo simulations. Higher density dominates to reduce shielding thickness. However, a higher content of high-Z elements will weaken the shielding strength, especially at a lower dose rate threshold and vice versa. The weakened side effect of a high iron content on the shielding property is obvious at 2.5 μSv/h. Therefore, we should not blindly pursue high Z content in engineering. If the thickness is constrained to 2 m, then the density can be reduced to 3.3 g/cm3, which will save cost by reducing the magnetite composition with 50.44% iron content. If a higher density of 3.9 g/cm3 with 57.65% iron content is selected for construction, then the thickness of the wall can be reduced to 174.2 cm, which will save space for equipment installation.

Origin of ironstones of the Udokan Cu deposit (Siberia, Russia): A key study using SEM and LA-ICP-MS

Iron is an important element involved in the formation of sedimentary-hosted copper deposits. Its accumulation in sedimentary basins and subsequent redistribution ultimately affect the position of copper mineralization. The Udokan copperstone deposit contains considerable Fe reserves as magnetite and hematite. The Fe oxides form disseminated and layered aggregates in both Cu-bearing horizons and host metasandstones. The layered aggregates of Fe oxides contain detrital (zircon, chromite and apatite) and authigenic (a Th silicate) components. The ironstones bear chemical features both of clastic and chemical sediments. The enrichment of ironstones in Cr, Zr and Hf is due to the presence of relics of detrital chromite and zircon. The presence of rare earth elements (REEs), U, and Th in composition of ironstones is a result of chemical precipitation/sorption.According to the LA-ICP-MS data, Al, Mg, and V are the most significant trace elements of magnetite, whereas Ti and V are hosted in hematite. The extremely high Ti, Cr and Cu contents of magnetite are associated with inclusions of minerals of these elements. In hematite, the high Ti contents are due to inclusions of rutile or titanite. The correlations between the trace elements in Fe oxides reflect the mineral assemblages characteristic of two stages of sediment transformation: (i) earlier diagenetic with the formation of a hematite-rutile assemblage and early Cu sulphides and Th and REE mineralization and (ii) later metamorphic, which is related to the formation of magnetite metacrysts and recrystallization of Cu sulphides.The Fe-rich sediments formed at a river–sea geochemical barrier as a result both of sedimentation of clastic Fe oxides and flocculation of dissolved iron. The maturation of gel and lithification of sediments were accompanied by desorption of metals that accumulated in the ferruginous sediments. Some of them formed the authigenic phases (like Th), while others were isomorphically incorporated in other authigenic minerals (e.g., Nb, Ta and Sn in rutile).

Interaction Between Mineralization and Rock Magnetization: New Constraints From a Silurian‐Lower Devonian Volcanogenic Massive Sulfide (VMS) Deposit

AbstractThe unclear relationship between mineralization, hydrothermal alteration, and rock magnetization in volcanogenic massive sulfide (VMS) deposits limits us from fully understanding the magnetic anomalies and remagnetization process in this type of deposit. We address the issue by conducting systemic paleomagnetic, rock magnetic, petrographic, and X‐Ray diffraction studies in the Dapingzhang VMS deposit on the northwestern Indochina Block. Magnetite is the dominant magnetic carrier of hydrothermally altered surrounding rocks and orebody. Magnetite consumption and secondary magnetite formation occurred at different stages and types of hydrothermal alteration. The overall decrease in magnetite concentration from chloritization via silicification to mineralization implies that the magnetite was mostly consumed during hydrothermal alterations. Secondary single domain magnetite, which can carry a remagnetization direction, is proposed to be formed during illitization via the smectite‐to‐illite transformation. Secondary superparamagnetic magnetite, which was most likely formed during the late stage of chloritization, is unable to carry the stable characteristic remanent magnetization. The site‐mean direction of high‐temperature and high‐coercivity components is Dg/Ig = 324.5°/43.1°, and kg = 35.1, with α95 = 6.8° before tilt correction, and Ds/Is = 316.2°/37.6°, and ks = 16.4, with α95 = 10.1° after tilt correction, with a negative fold test. However, plate reconstruction is limited by the uncertainty of the tilting process following mineralization and the possibility of remagnetization during burial alteration. Therefore, this study provides a mechanism for rock magnetic variation and remagnetization during VMS mineralization.

Magneto-mineralogical characteristics of mafite-ultramafites of the Middle Bug River area and Holovaniv suture zone of the Ukrainian Shield (overview)

Mafites and ultramafites manifest in the magnetic field as significant magnetic anomalies due to the high content of magnetite, titanomagnetite and iron-magnesium silicates. Studying the mineralogy and magnetic properties of Archean rocks formed deep in the lower crust and uplifted to the surface allows to understanding the sources of magnetic anomalies. Such rocks are known in the Ukrainian shield, in particular in the Middle Bug River region and in the Holovaniv suture zone (HSZ). We consider mafic-ultramafic assemblages of the rocks of this region, their mineral composition and magnetic characteristics, manifestations in the magnetic field, and the distribution of magnetic minerals. Several mafic-ultramafic associations of different ages, composed of effusive, sedimentary-effusive and intrusive formations, are recognized for the area the Pobuzkiy ore mining region. Most of them were transformed intensively by metamorphism of granulite (to eclogite) facies and by intense tectonic and diaphoretic processes. The main volcanics and volcanogenic-sedimentary rocks belong to the Tivriv stratum of the Paleoarchean Dniester-Bug and Neoarchaean Bug series. Mantle rocks were the protolith of the Tivriv stratum, which are similar in composition to oceanic basalts. The Pavliv stratum is considered as a part of the Dniester-Bug series. It is composed mainly of two-pyroxene crystal schists (sometimes amphibolized, often with significant magnetite content (up to 10 %)), magnetite-orthopyroxene crystal schists, and bodies of ferruginous quartzites. Both series contain gneiss complexes, as well as bodies of basite-hyperbasites. Mafic rocks are mainly represented by hornblende-pyroxene crystal schists and amphibolites. Ultramafite and mafit-ultramafite intrusive bodies were mapped in the central and northern parts of the HSZ where they are presented by rocks of the hyperbasite and gabbro-peridotite formations. The Holovaniv block of the HSZ is spatially coincident with the Holovaniv gravitational maximum and magnetic anomalies, which are probably caused by the rooting of mafit-ultramafits from the upper mantle along deep fault zones. Magnetic sources with increased magnetization were identified within the district of Haivoron. They are associated with pyroxene schists, gneisses, coarse-grained pyroxene schists, and ferruginous quartzites. The high values of magnetic parameters of the rocks of the Haivoron-Zavallya region are explained by the presence of eulysites and magnetite-hypersthene crystal schists. Within the area of occurence of charnockite-enderbite rocks, the magnetic field with increased intensity and a large-mosaic structure is observed. Differentiation of the magnetic properties of the rocks of the upper part of the Earth’s crust, the shape and low power of the sources indicate their possible primary magmatic formation in the form of massifs and dykes with further metamorphic transformations. Magnetite is the main magnetic mineral of mafite-ultramafites according to thermomagnetic analysis and ore microscopy. Several generations of magnetite are observed. Early generations (reliably magmatic) are present in the dark-colored minerals as point inclusions and emulsion discharges along fissures (disintegration structures of solid solutions). The increase of the amount of magnetite in all types of rocks is associated with superimposed secondary transformations. Redistribution of iron occurs in the recrystallization zones with the formation of clusters of secondary coarse-grained magnetite. According to the hypothesis, the magnetite of ferruginous quartzites has metamorphic origin, while the origin of the magnetite of iron-carbonate and iron-siliceous formations is a controversial issue. It depends on the determination of the genesis of the original substance.

Microwave heating characteristics and energy utilisation efficiency of the double-layer magnetite cement concrete (DLMCC)

ABSTRACT In order to save and improve the utilisation of magnetite meanwhile rise the road microwave deicing efficiency, double-layer cement concrete specimens with different magnetite contents were designed. The heating efficiency and heat distribution of the surface and heat conduction process and electromagnetic loss of internal of the double-layer magnetite cement concrete (DLMCC) were studied. In addition, the relative absorptivity based on energy conservation was used to evaluate the energy utilisation efficiency. The results show that the double-layer structure could save 80% of magnetite and make utilisation of magnetite reach 93.39%. The surface temperature rise rate of DLMCC was improved greatly while was obtained through a low surface temperature/magnetite ratio. The optimum heat distribution of DLMCC was in the range of −2.24°C to 1.66°C of surface temperature. The influence regions of internal heat on the surface temperature were constant. The maximum electromagnetic loss of DLMCC within 10 mm of the surface was 27.43%, and the maximum energy utilisation efficiency of DLMCC increased by 14.35%.

Influence of Synthesis Parameters on the Magnetic, Thermal, and Morphological Properties of Poly(Glycidyl Methacrylate‐co‐Divinylbenzene)/Magnetite

AbstractIn this work, polymeric microspheres based on glycidyl methacrylate and divinylbenzene with magnetic properties are synthesized by the suspension polymerization technique. To obtain magnetic properties, magnetite particles modified by oleic acid are synthesized in the laboratory. The effects of stirring speed, concentration of magnetite added, and concentration of stabilizer on the particles’ properties are studied. The magnetic microspheres are characterized according their morphology, magnetite incorporation, and magnetic and thermal properties. The incorporation of iron particles is mainly affected by stirring speed during synthesis and the amount of added magnetic material. The saturation magnetization of the microspheres is affected by the content of incorporated magnetic material. The modification with oleic acid is important for incorporation of the magnetic material in the copolymer matrix. Polymeric particles with superparamagnetic behavior are obtained with spherical morphology and saturation magnetization of 7.11 (emu g−1) when employing a monomer molar ratio of 50/50, 1% poly(vinyl alcohol), 20% magnetite particles modified by oleic acid, and stirring speed of 500 rpm.