Magnetite Research Articles

CHARACTERISTICS OF HEAVY MINERALS IN PEARL RIVER SEDIMENTS AND THEIR IMPLICATIONS FOR PROVENANCE

Heavy minerals in the Pearl River sediments have excellent correlation with their source rocks.Obvious differences in heavy minerals assemblages and their diagnostic minerals have been studied in different branches of the River.The source of the river deposits can be divided into three provinces from west to east on the basis of heavy minerals assemblage types,mineral index(ATi,ZTi,ZTR) values and their correlation.The western province includes the upper reaches of the Xijiang River,where occurs a magnetite-ilmenite-zircon-leucoxene-apatite assemblage characterized by magnetite,ilmenite,apatite and chromite,indicating a provenance dominated by carbonate,with some metamorphic and basic rocks,and scarce ultrabasic and acid rocks.The middle province is located in the lower reaches of the Xijiang River,which is featured by a zircon-ilmenite-magnetite-tourmaline-leucoxene-epidote assemblage,characterized by pyroxene,leucoxene,zircon and epidote,indicating a provenance of clastic rocks and other sedimentary rocks with some metamorphic,basic and acid igneous rocks,as a mixture of local sources and the heavy minerals from upper reaches.The eastern province is the source area of the Dongjiang and Beijiang Rivers dominated by the assemblage of hornblende-tourmaline-magnetite-ilmenite-epidote-garnet characterized by hornblende,tourmaline,garnet,titanite and sillimanite,indicating a provenance of acid rocks with some metamorphic and small amount of sedimentary rocks.The results demonstrate that the characteristics of heavy minerals assemblages are useful tools to trace the provenance evolution of the Pearl River,and of significance in revealing the erosion-transportation-sedimentation pattern in the Pearl River region for source-sink comparison and analysis.

Magnetic Characteristics of Aeolian Sand Sediments in Horqin Sandy Land, Northeastern China, and Its Paleoenvironmental Significance: A preliminary exploration

In the Chinese Loess Plateau,magenetic susceptibility has been widely used as a proxy for the intensity of East Asian summer monsoon.It was generally accepted that pedogenic formation of ultrafine-grained magnetic minerals was the major contributor to the high magenetic susceptibility of the paleosols.However,few works have been done to investigate the mechanisms for the enhancement of magnetic susceptibility in the case of aeolian sand sediments in Horqin Sandy Land,northeastern China.Here detailed environmental magnetism and grain size studies of aeolian sand sediments taken from LHT section,which is located in the northeastern margin of the Horqin Sandy Land,are presented.Results show that the overall magnetic minerals content is low;the main magnetic minerals in the aeolian sand sediments are magnetite,with some haematite and goethite;the main magnetic grain sizes are SSD and SP.χARM/χlf and χARM/SIRM can indicate the relative strength of winter monsoon and summer monsoon.In terms of the whole section,magnetic grain size reflects the intensity of winter monsoon well,but in some strata,it was affected by summer monsson.Pedogenic superparamagnetic particles are the main cause of the magnetic susceptibility enhancement,and single domain particles play a subordinate role in the magnetic susceptibility enhancement during the optimum period of soil development.

Sulfur solubility in fluid-bearing basic silicate melts in dependence on redox conditions

Sulfide–silicate immiscibility (liquation) in silicate melts has a significant influence on the behavior of chalcophile elements in magmatic processes as the main mechanism of the formation of sulfide deposits of nonferrous and precious metals. It is important to know the solubility of sulfur in magmas of different compositions in dependence on the physicochemical parameters in order to reveal the conditions of sul� fide–silicate immiscibility. Among these parameters, the main role belongs to oxygen fugacity f(O2), which varies within a broad range in magmatic systems. The influence of f(O2) on sulfur solubility in model and natural anhydrous sili� cate melts of basaltic composition with O–S fluid at atmospheric pressure is discussed in numerous papers, the results of which are summarized in reviews [2, 3] and demonstrated in Fig. 1. The extreme character of sulfur solubility in dependence on f(O2) with a mini� mal solubility in the area of the quartz–fayalite–mag� netite (QFM) buffer is established. There is a negative dependency under reduced conditions and a positive dependency under the oxidized conditions on f(O2). Sulfur solubility increases with temperature, f(S 2 ), melt basicity, and FeO concentration in the melt. There are limited data on the influence of volatile components (H2O, H2O + CO2) and pressure on sulfur solubility in magmas [4, 5], but the influence of f(O2)

Superparamagnetic Magnetite Nanoparticles Synthesized by Thermal Decomposition of Polyols and Their Properties

The magnetite nanoparticles were synthesized by thermal decomposition of iron(Ⅲ) acetylacetonate(Fe(acac)3) in methoxy polyethylene glycol(MPEG),which was used as solvent,reducing agent,and modifying agent in this reaction.The morphologies and phase compositions of the nanoparticles were determined by transmission electron microscopy and X-ray diffraction,respectively.The modification of the nanoparticles was characterized using Fourier transform infrared spectroscopy.Magnetic properties were measured using superconducting quantum interference device(SQUID).The zeta potential of the nanoparticles was determined.The results indicate that the magnetite nanoparticles obtained in this way have a much uniform size and monodispersion.The diameter is about(10.1±1.6) nm.The nanoparticles show superparamagnetic behavior at 300 K with saturation magnetization of 45 A·m2/kg.The FTIR spectroscopic results prove the existence of —COO-covalently attached to the surface of the magnetite nanoparticles,and the zeta potential results show that the nanoparticles have negative surface about-25 mV.Compared with the magnetite nanoparticles synthesized in triethylene glycol(TREG),the nanoparticles synthesized in MPEG show a longer dispersion time in deionized water(for more than 60 days),due to the steric and electrostatic interactions between the nanoparticles.

Acute Phase Pulmonary Responses to a Single Intratracheal Spray Instillation of Magnetite (Fe<sub>3</sub>O<sub>4</sub>) Nanoparticles in Fischer 344 Rats

Iron nanomaterials are of considerable interest for application to nanotechnology-related fields including environmental catalysis, biomedical imaging, drug delivery and hyperthermia, because of their superparamagnetic characteristics and high catalytic abilities. However, information about potential risks of iron nanomaterials is limited. The present study assessed pulmonary responses to a single intratracheal spray instillation of triiron tetraoxide nanoparticles (magnetite) in rats. Ten-week-old male and female Fischer 344 rats (n=5/group) were exposed to a single intratracheal spray instillation of 0 (vehicle), 5.0, 15.0 or 45.0 mg/kg body weight (BW) of magnetite. After 14 days, the rats were sacrificed, and biological consequences were investigated. The lung weights of the 15.0 and 45.0 mg/kg BW male and female groups were significantly higher than those of the control groups. The lungs of treated rats showed enlargement and black patches originating from the color of magnetite. The typical histopathological changes in the lungs of the treated rats included infiltration of macrophages phagocytosing magnetite, inflammatory cell infiltration, granuloma formation and an increase of goblet cells in the bronchial epithelium. The results clearly show that instilled magnetite causes foreign body inflammatory and granulating lesions in the lung. These pulmonary responses occur in a dose-dependent manner in association with the increase in lung weight.

Characteristics of ferro fluid

This paper focuses on the synthesis and characterization of ferro fluid (smart fluid). The colloidal mixtures of magnetite in carrier fluid were made by different chemical processes. The characteristics like particle size, turbidity, density, viscosity, and damping were studied. The average particle size after repeated filtering measured to 12 nm. The turbidity variation was found to be almost negligible. The damping coefficient varied from 0.2418 Ns/m to 0.8348Ns/m in the magnetic field. The effect of magnetic field on viscosity was studied on in house made viscometer and calibrated with the existing Redwood viscometer. It was possible to change the viscosity with the change in magnetic field. Such smart fluid could be used in a semi active shock absorber of a vehicle for better performance.

HEAVY MINERAL DISTRIBUTION AND MAGNETIC CHARACTERISTICS OF SURFACE SEDIMENTS IN THE NORTH BRANCH OF THE CHANGJIANG RIVER

Based on data from the surface sediments obtained from the north branch of the Changjiang River,this paper deals with the distribution of heavy minerals,the spatial variations of sediment magnetic properties and their controlling factors.Results indicate that hornblende and epidote dominate in heavy minerals in the research area,followed by mica and magnetite,but mineral assemblages vary in different sedimentary dynamic zones.The mica-stable mineral assemblage mainly occurs in sandspits and tidal sands,where,under strong hydrodynamic conditions,coarse sediments prevail and magnetic parameters,such as Xarm、Xfd%、Xarm/Xl and Xarm/SIRM are relatively low.The assemblage of hornblende-magnetite-carbonate is mainly distributed in river channels and tidal inlets,where hydrodynamic condition is relatively low and fine sediments,such as clayey silt,dominate,and as the result,magnetic parameters of Xarm、Xfd%、Xarm/Xl and Xarm/SIRM are quite high.Data suggest that the sediments in the north branch of the Changjiang River are mainly from the Changjiang River drainage.The distribution of heavy minerals and magnetic parameters are controlled by hydrodynamics,sediment types,source rocks and sediment transportation.

Effect of microwave heating on magnetic separation: Kesikkpr magnetite deposits in Ankara, Central Turkey

In this study, the effect of microwave heating on magnetic separation of the iron ore of magnetite from Kesikkopru (Bala-Ankara, Central Turkey) was investigated. The investigation was based on understanding the enrichment factor differences of magnetic separation and microwave+magnetic separation methods. Only five fractions of magnetite ore display high level of enrichment by using magnetic separation. The optimum results (98.11% enrichment, 63.14% grade for iron) were captured on 150 x 106 µm grain sizes and 0.8 Tesla magnetic field intensity. On the other hand, optimum results (96.99% enrichment, 67.81% grade for iron, 180 watt energy consumption) were hold on three different grain size of ore by using microwave+magnetic separation method. On this method, to get high enrichments, the ore has to be pre-treated for 5 to 7 min on microwave heating. It has been realized that the grade of iron were increased by 3 to 5% for microwave+magnetic when compared to sole magnetic separation. Key words: Magnetite, microwave heating, magnetic separation, Kesikkopru, Turkey.

The Influences of Water Vapor/Hydrogen Ratio, Gas-Flow Rate and Antimony on the Surface Oxidation of Trip Steels

In the current paper, we are reporting the results from an investigation of the surface and sub-surface oxidation of a TRIP steel containing 2 wt.% Mn and 0.5 wt.% Al with and without 0.03 wt.% Sb. The oxidizing conditions in the gas were successively varied in terms of the linear gas flow-rate and dew-point, from conditions were gas-phase mass transport limited conditions prevailed, to those were solid state processes became the rate determining conditions. It was found, that at sufficient low oxidizing conditions (defined as flow-rate/dew-point), the metal surfaces were clear of any external oxides, and as the oxidizing conditions were increased, Mn- and Si- oxide nodules formed along with magnetite. As the oxidizing conditions were increased further, a dense magnetite layer was present. The limits of the various regions were experimentally quantified and a proposed hypothesis for their occurrences is presented. No obvious effect of Sb was noted in this micro-structural research of the oxides that results from the various conditions investigated in this study.

Effect of TiO2‐content on Reduction of Iron Ore Agglomerates

The effect of titanium oxide on iron ore agglomerates is studied by the use of test sinter, test pellets and synthetic briquettes under laboratory conditions. Titanium favours secondary hematite rather than magnetite, which is the main phase in the sinter of Rautaruukki's Raahe plant. Additionally, the effects of sinter RDI and pellet LTD on the blast furnace process are evaluated using the test results of basket trials in LKAB's Experimental Blast Furnace. The effect of titanium in synthetic hematite is studied as hematite is reduced to magnetite in the RDI test. This occurrence causes deterioration in burden permeability. Synthetic titanium-bearing iron oxides under controlled conditions are investigated at the University of Oulu. The effect of TiO2, in solid solution in magnetite, on the magnetite to hematite oxidation is studied separately in order to simulate the final stage of the sintering process. In other experiments, hematite samples doped with various contents of TiO2 are studied using thermogravimetry under a controlled gas atmosphere (CO/CO2/H2/N2). The TiO2 content of hematite has a clear effect on reduction degradation. Also increasing content of TiO2 in solid solution in magnetite radically accelerates the oxidation rate. In the pilot tests, TiO2 content has a similar negative effect on the reduction strength of both sinter and pellets

Preparation of Mono-, Di- and Hemicalcium Ferrite Phases via Melt for Reduction Kinetics Investigations

Iron ore concentrates that are used in the iron production are usually agglomerated into sinter or pellets in order to improve their properties in the blast furnace. The main minerals in the magnetite base sinters are hematite, magnetite and Si and Al containing calcium ferrites of which the latter can exist as either monocalcium ferrite, dicalcium ferrite or hemicalcium ferrite depending on the conditions and on the material's iron/calcium-ratio. In order to study the reduction behaviour of the sinter in the iron production, samples of monocalcium ferrite, dicalcium ferrite and hemicalcium ferrite were prepared by melting different proportions of pure calcium and iron oxides. After melting the samples were cast and cooled. Samples of hemicalcium ferrite were also heated at a certain temperature before the actual reduction experiments in order to ensure the wanted phase composition of the samples. The mineral compositions of the samples were verified using scanning electron microscopy (SEM-EDS) as well as X-ray diffraction (XRD). The verification showed that it was possible to produce the samples of calcium ferrites via melting. The conditions needed to reduce the calcium ferrites were estimated with thermodynamic calculations.

Influence of Magnesia on Iron Ore Sinter Properties and Productivity – Use of Dolomite and Dunite

For production of fluxed sinter the use of dolomite and other MgO bearing materials has increased in the recent past. Flux materials influence the microstructure and chemical properties of the resultant sinter. Improvement in raw material quality and use of alternative raw materials play an important role for improving the sinter quality and overall economics of iron and steel making. The physical and metallurgical properties of sinter mainly depend on the mineralogy of the sinter. Dolomite is composed of calcium magnesium carbonate and dunite consists of magnesium silicate. In the present work laboratory sintering experiments have been carried out with different MgO level (1.40 to 2.60 mass%) to know the influence of MgO on the mineralogy, productivity, physical and metallurgical properties of sinter prepared by using dolomite and dunite. Microstructural examinations of the produced sinter revealed that dunite sinter is bounded with higher amounts of hematite and less calcium ferrites when compared to dolomite sinter. Hematite and calcium ferrite phases decreased whereas magnetite phase increased with increase of magnetite content in sinter using both dolomite and dunite. From the test results it was found that dunite sinter showed better metallurgical properties whereas dolomite sinter showed better physical properties.

Influence of Alumina on Iron Ore Sinter Properties and Productivity in the Conventional and Selective Granulation Sintering Process

Iron ore sinter constitutes a major proportion of blast furnace burden. Hence, its quality and consistency have a significant impact on blast furnace performance. Iron ore fines are the main source for sinter, and the chemical composition of the iron ore fines, together with the thermal conditions that blends are subjected to, plays an important role in forming the primary melt during the sintering process and accordingly determines the sinter structure and quality. Therefore, considerable importance has been placed on the chemical composition and consistency of iron ore fines, particularly in terms of alumina content. Due to depletion of high grade iron ore resources, alumina content in the iron ore fines is expected to increase gradually. Ore with higher alumina content is usually expected to be detrimental in forming the sinter matrix, if sintered alone, due to the low reactivity of alumina bearing minerals and the high viscosity of primary melts. The selective granulation process is a new sintering process for high alumina iron ore fines, and can eliminate the adverse effects of ‘hard to sinter’ or ‘unsuitable – for ironmaking’ ores. In the present work laboratory sintering experiments have been carried out with iron ore fines of different alumina level (2.00 to 5.46 mass-%) to know the influence of alumina on mineralogy, productivity, physical and metallurgical properties of sinter prepared by the conventional and the selective granulation process. With increasing alumina content in sinter of both the conventional and selective granulation process, the fractions of hematite and of silico-ferrites of calcium and alumina (SFCA) as well as the pore phase increased whereas the magnetite and silicate phases decreased. With increase in alumina content sinter productivity and tumbler index (T.I.) decreased, and metallurgical properties like sinter RDI and reducibility improved. However, sinter of the selective granulation process showed better results compared to the conventional process.

Beneficiation Studies on Recovery of Secondary Sources of Iron from Ferrigenous Alluvial Sands

Beneficiation studies were carried out on iron bearing alluvial sand to recover iron values for pelletisation. The studies include detailed mineralogical characterization, physical and chemical characteristics, beneficiation studies including grinding, magnetic and high tension separation. The results of these investigations indicate that the samples contain 50.2% Fe and 8.2% SiO2 on average. The mineralogical studies reveal that the sand contains dominantly heavy minerals with small amount of quartz. The heavy minerals are magnetite and ilmenite with small quantities of amphibole and pyroxene group minerals. Detailed beneficiation studies carried out by various techniques indicated that the iron content can be upgraded by simple low intensity wet magnetic separation after grinding the sample to below 210 microns. A product with 62.7% Fe can be obtained at 65.5% yield. The product obtained can be used for pelletisation by blending with suitable high grade iron concentrate.

The investigation of the low magnetic iron ores by EPR and their component FeO by DFT

The results of low magnetic ores investigations by EPR in X-band and their component FeO by DFT are presented in article. The laws in change of the absorption area, values of the g-factor and the intensities in samples depending on concentration FeO are found out. The presence at samples of the paramagnetic ions of the chromium and the manganese brings the features in laws of the absorption. The electronic configuration, equilibrium distance, total energy for FeO has been received in calculations using Hartree–Fock, Becke88 exchange potentials, Lee–Yang–Parr (LYP) correlation potential and combination potential B3-LYP.

The first find of grothite in gold ore deposits

1083 Grothite, representing an Aland Frich titanite variety that is described by the theoretical formula (Ca,REE)(Ti,Al,Fe)SiO4(O,OH,F) (1), is a relatively rare mineral, which was previously unknown in ores from noble metal deposits. Titanites with high concen� trations of Al (up to 14 wt %) and F (up to 2.5 wt %) are characteristic of eclogites, dolomites, and marbles of Austria (2, 3). Tinbearing minerals of the titanite- malayaite series (described by the theoretical formula CaSnO(SiO 4 )) are widespread in tin ore skarn deposits of the world, Russia included (4). Compositionally peculiar fluoraluminous titanite with respective Al2O3 and F contents ranging from 9.0 to 13.5 and from 3 to 5 wt %, which may be attributed to grothite, was estab� lished in metamorphosed carbonaceous-siliceous sediments of the cherty formation in the SikhoteAlin mountainous system (Primor'e region) (5). Grothite was first established in noblemetal objects during the mineralogical study of ores from the Berizitovoe gold-polymetallic deposit of the Verkhnii Amur region. The deposit is located in the northeast� ern flank of the Amur goldore province (6) in acti� vated structures of the southeastern North Asia Craton at its junction with surrounding structures of the Tuku� ringra-Dzhagda Terrane of the Mongol-Okhotsk orogenic belt (7). The ore body of this deposit is repre� sented by the nearmeridional zone of metasomatic rocks with sulfide mineralization localized in the mas� sif of Paleoproterozoic porphyric granodiorites. The zone consists of two steep funnelshaped bodies joined near the surface and pinching out downward (Fig. 1). In plan, the zone is characterized by a complex lentic� ular shape and dips at angles of 70°-75° in the south� western direction. It is 950 m long at the surface and from 10-15 to 110 m thick. Metasomatites of the deposit are represented by quartz-muscovite rocks with impregnated almand� ine-spessartine garnet and tourmaline. Accessory minerals with variable concentrations are orthoclase, chlorite, biotite, anorthite, zinc spinel (ferruginous gahnite), sphene, zircon, epidote, allanite (orthite), prehnite, fluorapatite, fluorite, and graphite. Polymetallic mineralization widespread in the metasomatic zone of the deposit occurs in the form of complex stringers and nests. The main ore minerals are sphalerite, galenite, pyrite, pyrrhotite, and magne� tite. Ores of the deposit are of the dominant zinc com� position with subordinate admixture of lead.

Study on the pH-sensitive secondary structure of gamma-PGA embedded with magnetite nanoparticles

The conformational transition of poly gamma-glutamic acid (gamma-PGA) embedded with magnetite nanoparticles under various pH conditions was investigated by Fourier transform infrared spectroscopy (FTIR). The secondary structure content was determined through the analysis of amide I bands of Fourier deconvolution spectra, secondary derivative spectra and the Gaussian curve fitting of the original infrared spectra. The results showed that the conformation of the gamma-PGA was affected by solution pH. The total contents of beta-sheet and beta-turn were higher than 65%, while alpha-helix and random coil were low. The content of beta-turn increased with increasing pH, while the beta-sheet decreased. Additionally, the zeta potential results showed that the pH-sensitive secondary structure of gamma-PGA had influence on the stability of suspension of magnetic gamma-PGA nanospheres. The minimum value of zeta potential (-35. 4 mV) was obtained at pH 10.2.

DYNAMIC MONITORING OF MINING AREA EXPANSION BASED ON MULTITEMPORAL REMOTE SENSING IMAGES

Mining activity is responsible for the deterioration of the vegetation environment,and the variation of vegetation environment reflects the information of mining area expansion.With the Panzhihua vanadium-titanium magnetite ore deposit area as a study case,the authors extracted the mining area expansion information by using the SARVI difference model and then used the supervised cassification method.The results of the two performances were superimposed upon each other and analyzed under the condition of ArcView 9.1 so as to obtain the dynamic information of mining area expansion.A comparison was made with the manual interpretation classification result of seasoned expert in 2005,and it is shown that the precision can reach 95.3%.The experimental results show that this method is very simple and effective in the extraction of the mining area expanding information,and is also very important both in theory and in practice.This method proves to be very promising in dynamic inspection of mining area.

Cytotoxicity study of rock wool by cell magnetometric evaluation

The cytotoxicity of rock wool (RW), an asbestos substitute, was evaluated by cell magnetometry. Alveolar macrophages were isolated from male Fisher rats. Following addition of triiron tetraoxide (Fe 3O 4) to macrophages, RW was added. Then, the remnant magnetic field strength was measured for 20 min after magnetization by an external field. Relaxation, an indicator of decay of cytotoxicity, was observed by cell magnetometry immediately postmagnetization in the group to which RW was added. In general, materials phagocytosed by macrophages are ingested into phagosomes and digested while migrating. This migration of phagosomes occurs by polymerization and depolymerization of the cytoskeleton. As a result of evaluation, relaxation was not delayed by addition of RW, since RW caused no effect on the cytoskeleton. It was suggested that RW has no cytotoxicity as evaluated by cell magnetometry.

Interactions of Magnetic Domains in Grain Boundaries and Cores of Nanopolycrystalline Magnetite

J. Santoyo-Salazar*, M. A. Castellanos-Roman, B. Gomez-Looh, D. Ihiawakrim, C. Lefevre, G. Pourroy. 1 Institut de Physique et Chimie des Materiaux de Strasbourg, UMR CNRS-ULP-ECPM 7504, 23, rue du Loess, BP 43, 67034 Strasbourg cedex 2, France. 2 Facultad de Quimica, Departamento de Quimica Analitica, Universidad Nacional Autonoma de Mexico, Mexico D.F., 04510, Mexico. 3 Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, AP 70-360, Mexico D.F. 04510, Mexico.