Composition Of Magnetite Research Articles

The Lamandau IOCG deposit, southwestern Kalimantan Island, Indonesia: Evidence for its formation from geochronology, mineralogy, and petrogenesis of igneous host rocks

The Lamandau region of Kalimantan Island, Indonesia is located in Sandaland, in the southern part of the Kuching tectonic belt. A series of Cenozoic epithermal gold deposits and Fe–Cu–Au deposits are located in the Kuching belt. The Lamandau Fe–Cu–Au deposit is hosted by diorite porphyry. In-situ zircon U–Pb dating of the diorite porphyry shows that it formed between 82.1±1.7Ma and 78.7±2.3Ma. Geochemical data indicate a depletion of high field strength elements (HFSE) in the diorite porphyry and related basalt is similar to that of arc-related igneous rocks. The diorite porphyry and basalt were probably derived from typical arc magmas related to continental margin subduction and thus are characterized by light rare earth element (REE) enrichment and HFSE depletion. The sub-chondritic Nb/Ta ratios for the basalt in the Lamandau region indicate that the subducted Pacific slab began partial melting at depths where amphibole was the major residual phase, with some residual rutile. The basalt was derived from a depleted mantle source. The composition of apatite and zircon in the diorite porphyry indicates that the dioritic magma was produced from the subcontinental mantle after it was metasomatized by slab-derived fluids. The magma had a high oxygen fugacity, thus and therefore it was particularly conducive to the precipitation of Cu, Au and other ore-forming elements. The composition of magnetite indicates that it was of volcanic origin. The magnetite has a low REE content, and a high Cu–Au content. The deposit may be classified as an IOCG mineral system. In summary, the ore-related diorite porphyry in the Lamandau region might have formed in an extensional environment during rollback of the subducting western Pacific plate. The convergent velocity between the Philippine Sea and Eurasian plates was at a minimum during the rollback, so that the margin of East Asian began to undergo rifting with associated magmatism.

REEQUILIBRATION PROCESSES IN MAGNETITE FROM IRON SKARN DEPOSITS

Research Article| January 01, 2015 REEQUILIBRATION PROCESSES IN MAGNETITE FROM IRON SKARN DEPOSITS* Hao Hu; Hao Hu 1State Key Laboratory of Geological Processes and Mineral Resources, and Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China Search for other works by this author on: GSW Google Scholar David Lentz; David Lentz 2Department of Earth Sciences, University of New Brunswick, Fredericton, NB E3B 5A3, Canada Search for other works by this author on: GSW Google Scholar Jian-Wei Li; Jian-Wei Li † 1State Key Laboratory of Geological Processes and Mineral Resources, and Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China †Corresponding author: e-mail, jwli@cug.edu.cn Search for other works by this author on: GSW Google Scholar Travis McCarron; Travis McCarron 2Department of Earth Sciences, University of New Brunswick, Fredericton, NB E3B 5A3, Canada Search for other works by this author on: GSW Google Scholar Xing-Fu Zhao; Xing-Fu Zhao 1State Key Laboratory of Geological Processes and Mineral Resources, and Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China Search for other works by this author on: GSW Google Scholar Douglas Hall Douglas Hall 3Microscopy and Microanalytical Facilities, University of New Brunswick, Fredericton, NB E3B 5A3, Canada Search for other works by this author on: GSW Google Scholar Economic Geology (2015) 110 (1): 1–8. https://doi.org/10.2113/econgeo.110.1.1 Article history received: 07 Aug 2014 accepted: 06 Oct 2014 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Hao Hu, David Lentz, Jian-Wei Li, Travis McCarron, Xing-Fu Zhao, Douglas Hall; REEQUILIBRATION PROCESSES IN MAGNETITE FROM IRON SKARN DEPOSITS. Economic Geology 2015;; 110 (1): 1–8. doi: https://doi.org/10.2113/econgeo.110.1.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEconomic Geology Search Advanced Search Abstract Textural and compositional data for magnetite from nine iron skarn deposits in Canada, Romania, and China show that most samples have reequilibrated by dissolution and reprecipitation, oxy-exsolution, and/or recrystallization. The dissolution and reprecipitation processes are most extensive and are present in most magnetite samples examined, whereas the oxy-exsolution occurs only in high-Ti magnetite, forming exsolution lamellae of Fe-Ti-Al oxides. Electron microprobe analysis indicates that the reequilibration processes have significantly modified the minor and trace element compositions of magnetite, notably Si, Mg, Ca, Al, Mn, and Ti, whereas oxy-exsolution is effective in decreasing the Ti content of high-Ti magnetite. Many analyses of magnetite grains from the skarn deposits plot variably in the banded iron formations (BIF), iron oxide–copper-gold (IOCG), or porphyry Cu fields using the Ti + V versus Ca + Al + Mn discrimination diagram. This pattern suggests that trace element data for magnetite that has unusual composition and/or reequilibrated cannot be reliably used as a petrogenetic indicator. Mixing of externally derived saline fluids with Fe-rich magmatic-hydrothermal solutions, an increase in temperature, and local decreasing pressure and fO2 are considered the most important causes for the dissolution and reprecipitation, or recrystallization, of the magnetite; increasing fO2 and decreasing temperature may facilitate oxy-exsolution of Fe-Ti-Al oxides in high-Ti magnetite. Results presented here highlight the importance of detailed textural characterization prior to in situ chemical analysis of magnetite grains so that mineral compositions can be properly evaluated in terms of the genesis and evolution of iron skarn deposits. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Did the massive magnetite “lava flows” of El Laco (Chile) form by magmatic or hydrothermal processes? New constraints from magnetite composition by LA-ICP-MS

The El Laco magnetite deposits consist of more than 98 % magnetite but show field textures remarkably similar to mafic lava flows. Therefore, it has long been suggested that they represent a rare example of an effusive Fe oxide liquid. Field and petrographic evidence, however, suggest that the magnetite deposits represent replacement of andesite flows and that the textures are pseudomorphs. We determined the trace element content of magnetite by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) from various settings at El Laco and compared them with magnetite from both igneous and hydrothermal environments. This new technique allows us to place constraints on the conditions under which magnetite in these supposed magnetite “lava flows” formed. The trace element content of magnetite from the massive magnetite samples is different to any known magmatic magnetite, including primary magnetite phenocrysts from the unaltered andesite host rocks at El Laco. Instead, the El Laco magnetite is most similar in composition to hydrothermal magnetite from high-temperature environments (>500 °C), such as iron oxide-copper-gold (IOCG) and porphyry-Cu deposits. The magnetite trace elements from massive magnetite are characterised by (1) depletion in elements considered relatively immobile in hydrothermal fluids (e.g. Ti, Al, Cr, Zr, Hf and Sc); (2) enrichment in elements that are highly incompatible with magmatic magnetite (rare earth elements (REE), Si, Ca, Na and P) and normally present in very low abundance in magmatic magnetite; (3) high Ni/Cr ratios which are typical of magnetite from hydrothermal environments; and (4) oscillatory zoning of Si, Ca, Mg, REE and most high field strength elements, and zoning truncations indicating dissolution, similar to that formed in hydrothermal Fe skarn deposits. In addition, secondary magnetite in altered, brecciated host rock, forming disseminations and veins, has the same composition as magnetite from the massive lenses. Euhedral magnetite lining both open-spaced veins in the brecciated host rock and along the walls of large, hollow chimneys in the massive magnetite lenses also displays oscillatory zoning and most likely formed by fluctuating composition and/or physio-chemical conditions of the fluid. Thus, the chemical fingerprint of magnetite from the supposed El Laco magnetite lava flows supports the hydrothermal model of metasomatic replacement of andesite lava flows, by dissolution and precipitation of magnetite from high-temperature fluids, rather than a magmatic origin from an effusive Fe oxide liquid.

In-situ LA-ICP-MS trace elemental analyses of magnetite: Cu-(Au, Fe) deposits in the Khetri copper belt in Rajasthan Province, NW India

Magnetite is common in many ore deposits and their host rocks, and is useful for petrogenetic studies. In the Khetri copper belt in Rajasthan Province, NW India, there are several Cu-(Au, Fe) deposits associated with extensive Cu±Fe±Au±Ag±Co±REE±U mineralization hosted in phyllites, schists and quartzites of the Paleoproterozoic Delhi Supergroup. Ore bodies of these deposits comprise dominantly disseminated and vein-type Cu-sulfide ores composed of chalcopyrite, pyrite, and pyrrhotite intergrown with minor magnetite. There are also Fe-oxide ores with minor or no Cu-sulfides, which are locally overprinted by the mineral assemblage of the Cu-sulfide ores. In addition to the Fe-oxide and Cu-sulfide ores, the protolith of the Delhi Supergroup includes banded iron formations (BIFs) with original magnetite preserved (i.e. magnetite-quartzites) and their sheared counterparts. In the sheared magnetite-quartzites, their magnetite and quartz are mobilized and redistributed to magnetite and quartz bands. Trace elemental compositions of magnetite from these types of ores/rocks were obtained by LA-ICP-MS. The dataset indicates that different types of magnetite have distinct concentrations of Ti, Al, Mg, Mn, V, Cr, Co, Ni, Zn, Cu, P, Ge and Ga, which are correlated to their forming environments. Magnetite grains in magnetite-quartzites have relatively high Al (800–8000ppm), Ti (150–900ppm) and V (300–600ppm) contents compared to those of BIFs in other regions such as the Yilgarn Craton, Western Australia and Labrador, Canada. The high Al, Ti and V contents can be explained by precipitation of the magnetite from relatively reduced, Al–Ti-rich water possibly involving hotter, seafloor hydrothermal fluids derived from submarine mafic volcanic rocks. Magnetite in sheared magnetite-quartzites is generally irregular and re-crystallized, and has Ni, Mn, Al, Cu and P contents lower than the magnetite from the unsheared counterparts, suggesting that the shearing-related mobilization is able to extract these elements from original magnetite. However, elevated contents of Ti, V, Co, Cr, Ge and Mg of the magnetite in the sheared magnetite-quartzites can be ascribed to involvement of external hydrothermal fluids during the shearing, consistent with occurrence of some hydrothermal minerals in the samples.Compositions of magnetite from the Fe-oxide and Cu-sulfide ores are interpreted to be controlled mainly by fluid compositions and/or oxygen fugacity (fO2). Other potential controlling factors such as temperature, fluid–rock interaction and co-precipitating minerals have very limited impacts. Magnetite in the Cu-sulfide ores has higher V but lower Ni contents than that of the Fe-oxide ores, likely indicating its precipitation from relatively reduced, evolved fluids. However, it is also indicated that the two types of magnetite do not show large distinctions in terms of concentrations of most elements, suggesting that they may have precipitated from a common, evolving fluid. We propose a combination of Ge versus Ti/Al and Cr versus Co/Ni co-variation plots to discriminate different types of magnetite from the Khetri copper belt. Our work agrees well with previous studies that compositions of magnetite can be potentially useful for provenance studies, but also highlights that discrimination schemes would be more meaningful for deposits in a certain region if fluid/water chemistry and specific formation conditions reflected in compositions of magnetite are clearly understood.

Material property models for polyethylene-based conductive blends suitable for PEM fuel cell bipolar plates

Electrical and thermal conductivity models from Mamunya et al. and Kerner’s equation for elastic and flexural modulus have been applied to experimental data to assess model accuracies. Experimental data were gained from a previous study where polyethylene and carbon black, graphite and magnetite composites produced by injection and compression moulding were tested. The electrical conductivity modelling gave accurate fits to the data, though available data were limited and the thermal conductivity modelling produced good fits with R2 values greater than 0.93. The electrical and thermal model exponents were tuned for best fit and used to compare the modelling results with the literature and gain information about conduction mechanisms such as tunnelling and links, nodes and blobs and variations in local filler concentrations. A modified Kerner’s equation to effectively allow for filler type and variations in composite processing was used to improve upon the original equation which modelled modulus behaviour based on the pure matrix. The new equation proved to be a better predictor of elastic modulus than flexural modulus.

In-situ LA-ICP-MS trace elemental analyses of magnetite: Fe–Ti–(V) oxide-bearing mafic–ultramafic layered intrusions of the Emeishan Large Igneous Province, SW China

The Taihe, Baima, Hongge, Panzhihua and Anyi intrusions of the Emeishan Large Igneous Province (ELIP), SW China, contain large magmatic Fe–Ti–(V) oxide ore deposits. Magnetites from these intrusions have extensive trellis or sandwich exsolution lamellae of ilmenite and spinel. Regular electron microprobe analyses are insufficient to obtain the primary compositions of such magnetites. Instead, laser ablation ICP-MS uses large spot sizes (~40μm) and can produce reliable data for magnetites with exsolution lamellae. Although magnetites from these deposits have variable trace element contents, they have similar multi-element variation patterns. Primary controls of trace element variations of magnetite in these deposits include crystallography in terms of the affinity of the ionic radius and the overall charge balance, oxygen fugacity, magma composition and coexisting minerals. Early deposition of chromite or Cr-magnetite can greatly deplete magmas in Cr and thus Cr-poor magnetite crystallized from such magmas. Co-crystallizing minerals, olivine, pyroxenes, plagioclase and apatite, have little influence on trace element contents of magnetite because elements compatible in magnetite are incompatible in these silicate and phosphate minerals. Low contents and bi-modal distribution of the highly compatible trace elements such as V and Cr in magnetite from Fe–Ti oxide ores of the ELIP suggest that magnetite may not form from fractional crystallization, but from relatively homogeneous Fe-rich melts. QUILF equilibrium modeling further indicates that the parental magmas of the Panzhihua and Baima intrusions had high oxygen fugacities and thus crystallized massive and/or net-textured Fe–Ti oxide ores at the bottom of the intrusive bodies. Magnetite of the Taihe, Hongge and Anyi intrusions, on the other hand, crystallized under relatively low oxygen fugacities and, therefore, formed net-textured and/or disseminated Fe–Ti oxides after a lengthy period of silicate fractionation. Plots of Ge vs. Ga+Co can be used as a discrimination diagram to differentiate magnetite of Fe–Ti–(V) oxide-bearing layered intrusions in the ELIP from that of massif anorthosites and magmatic Cu–Ni sulfide deposits. Variable amounts of trace elements of magmatic magnetites from Fe–Ti–(P) oxide ores of the Damiao anorthosite massif (North China) and from Cu–Ni sulfide deposits of Sudbury (Canada) and Huangshandong (northwest China) demonstrate the primary control of magma compositions on major and trace element contents of magnetite.

Oxygen isotope and chemical compositions of magnetite and olivine in the anomalous CK3 Watson 002 and ungrouped Asuka‐881595 carbonaceous chondrites: Effects of parent body metamorphism

AbstractWe report in situ O isotope and chemical compositions of magnetite and olivine in chondrules of the carbonaceous chondrites Watson‐002 (anomalous CK3) and Asuka (A)‐881595 (ungrouped C3). Magnetite in Watson‐002 occurs as inclusion‐free subhedral grains and rounded inclusion‐bearing porous grains replacing Fe,Ni‐metal. In A‐881595, magnetite is almost entirely inclusion‐free and coexists with Ni‐rich sulfide and less abundant Ni‐poor metal. Oxygen isotope compositions of chondrule olivine in both meteorites plot along carbonaceous chondrite anhydrous mineral (CCAM) line with a slope of approximately 1 and show a range of Δ17O values (from approximately −3 to −6‰). One chondrule from each sample was found to contain O isotopically heterogeneous olivine, probably relict grains. Oxygen isotope compositions of magnetite in A‐881595 plot along a mass‐dependent fractionation line with a slope of 0.5 and show a range of Δ17O values from −2.4‰ to −1.1‰. Oxygen isotope compositions of magnetite in Watson‐002 cluster near the CCAM line and a Δ17O value of −4.0‰ to −2.9‰. These observations indicate that magnetite and chondrule olivine are in O isotope disequilibrium, and, therefore, not cogenetic. We infer that magnetite in CK chondrites formed by the oxidation of pre‐existing metal grains by an aqueous fluid during parent body alteration, in agreement with previous studies. The differences in Δ17O values of magnetite between Watson‐002 and A‐881595 can be attributed to their different thermal histories: the former experienced a higher degree of thermal metamorphism that led to the O isotope exchange between magnetite and adjacent silicates.

The morphology and degradation behavior of electrospun poly(3‐hydroxybutyrate)/Magnetite and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)/Magnetite composites

ABSTRACTElectrospinning of biodegradable poly(3‐hydroxybutyrate) (PHB)/magnetite and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV)/magnetite composites in 2,2,2‐trifluoroethanol (TFE) and chloroform are investigated to develop nonwoven nanofibrous structure. Ultrafine PHB/magnetite fibers are obtained and the resulting fiber diameters are in the range of 690–710 nm and 8.0–8.4 µm for the polymer dissolved in TFE and chloroform. The surface of PHB composites fiber fabricated in chloroform contains porous structures, which are not observed for the sample of PHB composites fiber dissolved in TFE. The fiber diameters for PHBV5/magnetite composites are in the range of 500–540 nm and 2.3–2.5 µm, depending on the use of TFE and chloroform. The average diameters of PHBV5/magnetite composite fibers are smaller than those of PHB/magnetite composites fiber. All electrospun PHB/magnetite and composite fibers are superparamagnetic. The degradation behaviors of PHB/magnetite and PHBV5/magnetite composite fibers were investigated using Caldimonas manganoxidans. For the fabricated composite fibers, it is found that the degradation rate increased with the increasing loading of magnetite nanoparticles. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41070.

Thermodynamic behaviors of magnetic-fluid in a thin channel with magnetic field and aspect ratio

The objective of this study is to numerically investigate the thermodynamic behaviors of a magnetic fluid with nano-sized magnetic particles in a thin channel. The numerical model developed using the FEM (finite element method) technique with mesh sensitivity analysis was validated with existing data and thermodynamic characteristics such as isotherms, streamlines and Nusselt numbers of the magnetic fluid were analyzed with variations of the composition of magnetite, the aspect ratio, the magnetic field intensity and the inclination angle of the channel. The numerical analysis showed the increase in the magnetic volume force in the thin channel with increasing magnetic field intensity and magnetic fluid viscosity. Under all magnetic field intensities, the mean Nusselt numbers of the magnetic fluid in the thin channel at the inclination angle of 45° were on average 77.9% higher than those at the inclination angle of 15° due to the increased convective heat transfer in the thin channel.

Mineralogical and microfabric characteristics of magnetite in the Wuyang Precambrian BIFs, southern North China Craton: Implications for genesis and depositional processes of the associated BIFs

Precambrian Banded Iron Formations (BIFs) are widely distributed in the North China Craton (NCC). Among them, the Wuyang BIFs located in the southern margin of NCC occur in the Late Archaean Tieshanmiao Formation and can be subdivided in two different sub-types: (i) quartz–magnetite BIFs (QMB), consisting of magnetite, fine-microcrystalline quartz and minor calcite and (ii) pyroxene–magnetite BIFs (PMB), composed of pyroxene, fine-microcrystalline quartz and subordinate feldspars. Both sub-types display apparent discrepancies in terms of petrography and mineral composition.As shown in Electron BackScattered Diffraction (EBSD) images and micrographs, magnetite grains from the QMB range in size from tens up to hundreds of μm, whereas magnetite crystals from the PMB can be up to a few tens of μm across. The X-ray diffraction (XRD) structural data indicate that magnetite from both BIF sub-types is equiaxed (cubic) and was generated by sedimentary metamorphic processes. The cell parameters of magnetite in the QMB are a=b=c=8.396Å and Z=8, which deviate slightly from these of magnetite in the PMB: a=b=c=8.394Å and Z=8. The analytical results of Raman spectroscopy analysis revealed micro-structural signatures of both magnetite (Raman shifts near 552cm−1 and 673cm−1) and hematite (Raman shifts near 227cm−1, 295cm−1 and 413cm−1). In magnetite from both QMB and PMB, the crystallinity degree is similar for magnetite micro-structures but varies significantly for hematite micro-structures. Oxygen fugacity (fO2) conditions fluctuated during the recrystallization of magnetite in the QMB, whereas no evident variation of fO2 occurred during the formation of magnetite in the PMB. Analytical results of laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS) show that the Si, Al and Mg abundances are higher in magnetite from the QMB, whereas the Ti and Mn contents are more elevated in magnetite from the PMB. Magnetite composition also denotes that both BIF sub-types are sedimentary-metamorphic origin, whereas the deposition of PMB was also affected by volcanic activities. Overall data indicate that the differences in the depositional environment of each BIF sub-type are due to the involvement of volcanic eruption processes in the genesis of the PMB. Thus, this paper indicated that the QMB was deposited by chemical deposition at the long-term interval of volcanic eruptions, and the PMB were the product of chemical deposition affected by the volcanic eruption.

Magnetite composition in Ni-Cu-PGE deposits worldwide: application to mineral exploration

The concentration of trace elements in magnetite is determined primarily by the geological environment at the time of its formation, which makes magnetite a useful indicator mineral in the exploration of ore deposits. Magnetite is a common accessory mineral in magmatic Ni–Cu–Platinum-Group Element (PGE) sulfide deposits forming primary grains in massive sulfide ore and/or secondary grains during alteration of sulfide ore and host rock. We report magnetite composition from massive and disseminated sulfide samples (n=94), representative of 13 major Ni–Cu–PGE deposits, worldwide, and from a range of geological environments and formation ages (Archean to Permo–Triassic). The samples are divided into 6 different types according to the composition of the parental host magma: (1) komatiite, (2) ferropicrite, (3) picrite–tholeiite, (4) anorthosite–troctolite, (5) flood basalt and (6) impact melt. The minor and trace element composition of magnetite was measured by electron probe micro-analysis and a subset of samples (n=61) by laser ablation-inductively coupled plasma-mass spectrometry.The composition of all primary magnetite, crystallized from an immiscible sulfide liquid, plots on a trend in Ti vs. Cr and V vs. Cr. However, primary magnetite trace element content is controlled by element partitioning during sulfide liquid differentiation, from early-forming Fe-rich monosulfide solid solution (MSS) to Cu-rich intermediate solid solution (ISS). The concentration of most lithophile elements (Cr, Ti, V, Al, Sc, Nb, Ga, Ta, Hf and Zr) is highest in the early-forming magnetite, which crystallized with Fe-rich MSS. The fractionated Cu-rich liquid was depleted in lithophile elements so that late-forming magnetite, which crystallized with the Cu-rich ISS, has a low concentration of these elements. Compatible chalcophile elements partitioning into magnetite depends largely on the co-crystallizing sulfide mineral. Elements such as Ni partition preferentially in Fe-rich sulfide minerals (pyrrhotite or pentlandite) such that coprecipitated magnetite is depleted in chalcophile elements compatible with the sulfides. In contrast, magnetite co-crystallized with Cu-rich ISS is enriched in Ni because Ni is not compatible with the co-crystallizing Cu sulfides. Magnetite composition is also dependent on parental magma composition. Magnetite in massive sulfides from ultramafic parental magmas is most similar in compositions to primitive magnetite from Fe-rich sulfides in fractionated intermediate to mafic hosted orebodies.Two types of secondary magnetite are distinguished from the komatiite-hosted Thompson Ni-deposit (Manitoba, Canada): (1) magnetite formed by replacement of pyrrhotite and (2) magnetite formed during the serpentinization of the ultramafic host rocks. Secondary magnetite is depleted in most trace elements (Ni, Mn, V, Ti, V, Al, Cr), with the exception of Si and Mg, which are enriched.To be useful as a tool for mineral exploration, primary and secondary magnetite should not have the same minor and trace element composition. Primary magnetite from all 13 major Ni–Cu deposits plot in the field for Ni–Cu sulfide deposits in the Ni+Cr vs. Si+Mg discrimination diagram. Secondary magnetite plot outside of the field for Ni–Cu deposits. Therefore using this diagram, we can discriminate between primary and secondary magnetite using the low Ni+Cr content of secondary magnetite. Magnetite is resistant to surficial weathering and destruction during mechanical transport, such that it is a useful indicator mineral in exploration that can be used to detect eroded Ni–Cu–PGE deposits in surficial sediments.

Sorptive Uptake Studies of an Aryl-Arsenical with Iron Oxide Composites on an Activated Carbon Support.

Sorption uptake kinetics and equilibrium studies for 4-hydroxy-3-nitrobenzene arsonic acid (roxarsone) was evaluated with synthetic magnetite (Mag-P), commercial magnetite (Mag-C), magnetite 10%, 19%, and 32% composite material (CM-10, -19, -32) that contains granular activated carbon (GAC), and synthetic goethite at pH 7.00 in water at 21 °C for 24 h. GAC showed the highest sorptive removal of roxarsone and the relative uptake for each sorbent material with roxarsone are listed in descending order as follows: GAC (471 mg/g) > goethite (418 mg/g) > CM-10 (377 mg/g) CM-19 (254 mg/g) > CM-32 (227 mg/g) > Mag-P (132 mg/g) > Mag-C (29.5 mg/g). The As (V) moiety of roxarsone is adsorbed onto the surface of the iron oxide/oxyhydrate and is inferred as inner-sphere surface complexes; monodentate-mononuclear, bidentate-mononuclear, and bidentate-binuclear depending on the protolytic speciation of roxarsone. The phenyl ring of roxarsone provides the primary driving force for the sorptive interaction with the graphene surface of GAC and its composites. Thus, magnetite composites are proposed as multi-purpose adsorbents for the co-removal of inorganic and organic arsenicals due to the presence of graphenic and iron oxide active adsorption sites.

Formulation Design Facilitates Magnetic Nanoparticle Delivery to Diseased Cells and Tissues

Magnetic nanoparticles (MNPs) accumulate at disease sites with the aid of magnetic fields; biodegradable MNPs can be designed to facilitate drug delivery, influence disease diagnostics, facilitate tissue regeneration and permit protein purification. Because of their limited toxicity, MNPs are widely used in theranostics, simultaneously facilitating diagnostics and therapeutics. To realize therapeutic end points, iron oxide nanoparticle cores (5-30 nm) are encapsulated in a biocompatible polymer shell with drug cargos. Although limited, the toxic potential of MNPs parallels magnetite composition, along with shape, size and surface chemistry. Clearance is hastened by the reticuloendothelial system. To surmount translational barriers, the crystal structure, particle surface and magnetic properties of MNPs need to be optimized. With this in mind, we provide a comprehensive evaluation of advancements in MNP synthesis, functionalization and design, with an eye towards bench-to-bedside translation.

Trace Element Geochemistry of Magnetite from the Fe(‐Cu) Deposits in the Hami Region, Eastern Tianshan Orogenic Belt, NW China

AbstractLaser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) was used to determine the trace element concentrations of magnetite from the Heifengshan, Shuangfengshan, and Shaquanzi Fe(–Cu) deposits in the Eastern Tianshan Orogenic Belt. The magnetite from these deposits typically contains detectable Mg, Al, Ti, V, Cr, Mn, Co, Ni, Zn and Ga. The trace element contents in magnetite generally vary less than one order of magnitude. The subtle variations of trace element concentrations within a magnetite grain and between the magnetite grains in the same sample probably indicate local inhomogeneity of ore–forming fluids. The variations of Co in magnetite between samples are probably due to the mineral proportion of magnetite and pyrite. Factor analysis has discriminated three types of magnetite: Ni–Mn‐V–Ti (Factor 1), Mg–Ai–Zn (Factor 2), and Ga–Co (Factor 3) magnetite. Magnetite from the Heifengshan and Shuangfengshan Fe deposits has similar normalized trace element spider patterns and cannot be discriminated according to these factors. However, magnetite from the Shaquanzi Fe–Cu deposit has affinity to Factor 2 with lower Mg and Al but higher Zn concentrations, indicating that the ore–forming fluids responsible for the Fe–Cu deposit are different from those for Fe deposits. Chemical composition of magnetite indicates that magnetite from these Fe(–Cu) deposits was formed by hydrothermal processes rather than magmatic differentiation. The formation of these Fe(–Cu) deposits may be related to felsic magmatism.

Platinum-group element geochemistry of the Zhuqing Fe-Ti-V oxide ore-bearing mafic intrusions in western Yangtze Block, SW China: control of platinum-group elements by magnetite

Platinum-group element (PGE) geochemistry combined with elemental geochemistry and magnetite compositions are reported for the Mesoproterozoic Zhuqing Fe–Ti–V oxide ore-bearing mafic intrusions in the western Yangtze Block, SW China. All the Zhuqing gabbros display extremely low concentrations of chalcophile elements and PGEs. The oxide-rich gabbros contain relatively higher contents of Cr, Ni, Ir, Ru, Rh, and lower contents of Pt and Pd than the oxide-poor gabbros. The abundances of whole-rock concentrations of Ni, Ir, Ru, and Rh correlate well with V contents in the Zhuqing gabbros, implying that the distributions of these elements are controlled by magnetite. The fractionation between Ir–Ru–Rh and Pt–Pd in the Zhuqing gabbros is mainly attributed to fractional crystallization of chromite and magnetite, whereas Ru anomalies are mainly due to variable degrees of compatibility of PGE in magnetite. The order of relative incompatibility of PGEs is calculated to be Pd < Pt < Rh < Ir < Ru. The very low PGE contents and Cu/Zr ratios and high Cu/Pd ratios suggest initially S-saturated magma parents that were highly depleted in PGE, which mainly formed due to low degrees of partial melting leaving sulfides concentrating PGEs behind in the mantle. Moreover, the low MgO, Ni, Ir and Ru contents and high Cu/Ni and Pd/Ir ratios for the gabbros suggest a highly evolved parental magma. Fe–Ti oxides fractionally crystallized from the highly evolved magma and subsequently settled in the lower sections of the magma chamber, where they concentrated and formed Fe–Ti–V oxide ore layers at the base of the lower and upper cycles. Multiple episodes of magma replenishment in the magma chamber may have been involved in the formation of the Zhuqing intrusions.

Dissolution–reprecipitation process of magnetite from the Chengchao iron deposit: Insights into ore genesis and implication for in-situ chemical analysis of magnetite

Magnetite formed in different environments commonly has distinct assemblages and concentrations of trace elements that can potentially be used as a genetic indicator of this mineral and associated ore deposits. In this paper, we present textural and compositional data of magnetite from the Chengchao iron deposit, Daye district, China to provide a better understanding in the formation mechanism and genesis of the deposit and shed light on analytical protocols for in-situ chemical analysis of hydrothermal magnetite. Magnetite grains from the ore-related granitoid pluton, mineralized endoskarn, magnetite-dominated exoskarn, and vein-type iron ores hosted in marine carbonate intruded by the pluton were examined using scanning electron microscopy and analyzed for major and trace elements using electron microprobe. Back-scattered electron images reveal that primary magnetite from the mineralized skarns and vein-type ores were all partly reequilibrated with late-stage hydrothermal fluids, forming secondary magnetite domains that are featured by abundant porosity and have sharp contact with the primary magnetite. These textures are interpreted as resulting from a dissolution–reprecipitation process of magnetite, which, however, are mostly obscure under optically.Primary magnetite grains from the mineralized endoskarn and vein-type ores contain high SiO2 (0.92–3.21wt.%), Al2O3 (0.51–2.83wt.%), and low MgO (0.15–0.67wt.%), whereas varieties from the exoskarn ores have high MgO (2.76–3.07wt.%) and low SiO2 (0.03–0.23wt.%) and Al2O3 (0.54–1.05wt.%). This compositional contrast indicates that trace-element geochemical composition of magnetite is largely controlled by the compositions of magmatic fluids and host rocks of the ores that have reacted with the fluids. Compared to its precursor mineral, secondary magnetite is significantly depleted in most trace elements, with SiO2 deceasing from 1.87 to 0.47wt.% (on average) and Al2O3 from 0.89 to 0.08wt.% in mineralized endoskarn and vein type ores, and MgO from 2.87 to 0.60wt.% in exoskarn ores. On the contrary, average content of iron is notably increased from 69.2wt.% to 71.9wt.% in the secondary magnetite grains. The results suggest that the dissolution–reprecipitation process has been important in significantly removing trace elements from early-stage magnetite to form high-grade, high-quality iron ores in hydrothermal environments. The textural and compositional data confirm that the Chengchao iron deposit is of hydrothermal origin, rather than being crystallized from immiscible iron oxide melts as previously suggested. This study also highlights the importance of textural characterization using various imaging techniques before in-situ chemical analysis of magnetite, as is the case for texturally complicated UTh-bearing accessory minerals that have been widely used for UPb geochronology study.

Lithostratigraphic analysis and geochemistry of a vitric spatter-bearing ignimbrite: the Quaternary Adeje Formation, Cañadas volcano, Tenerife

The 1.5-Ma Adeje Formation in SW Tenerife contains an ignimbrite sheet with remarkable textural and chemical complexity. A basal Plinian pumice-fall layer is overlain by a partly welded compound ignimbrite in which phonolitic pumice lapilli and dense obsidian spatter rags with irregular, fluidal-shaped margins are supported in a poorly sorted tuff matrix. The lower ignimbrite flow-unit contains accretionary lapilli in its upper part, overlain by an ash-pellet-bearing fallout layer from a co-ignimbrite plume. The upper ignimbrite flow-unit comprises a locally welded massive lapilli-tuff that grades up into lithic breccia containing juvenile obsidian blocks and both cognate and vent-derived lithic blocks. Geochemically, the Adeje Formation shows two distinct juvenile populations that relate to crystal-poor and crystal-rich magma types. Crystal-rich juvenile clasts contain multiple compositions of ilmenite and magnetite, and crystal aggregates of bytownite (An79–86). The varied assemblage of juvenile clasts reflects an eruptive style that may have involved rapid changes in magma chamber pressure associated with caldera collapse, and possibly the disruption of a lava lake. The Adeje eruption started with a Plinian explosive phase that rained ash and pumice lapilli across SW Tenerife; followed by pyroclastic fountaining feeding density currents with explosive ejecta of juvenile glassy material producing the coarse, spatter-bearing ignimbrite facies. A short pause between pyroclastic density currents is recorded by the co-ignimbrite ash and pellet-fall bed. The climactic phase of the eruption probably involved caldera subsidence as recorded by a widespread massive heterolithic breccia.

Re–Os isotopic ages of pyrite and chemical composition of magnetite from the Cihai magmatic–hydrothermal Fe deposit, NW China

The Eastern Tianshan Orogenic Belt of the Central Asian Orogenic Belt and the Beishan terrane of the Tarim Block, NW China, host numerous Fe deposits. The Cihai Fe deposit (>90 Mt at 45.6 % Fe) in the Beishan terrane is diabase-hosted and consists of the Cihai, Cinan, and Cixi ore clusters. Ore minerals are dominantly magnetite, pyrite, and pyrrhotite, with minor chalcopyrite, galena, and sphalerite. Gangue minerals include pyroxene, garnet, hornblende and minor plagioclase, biotite, chlorite, epidotite, quartz, and calcite. Pyrite from the Cihai and Cixi ore clusters has similar Re–Os isotope compositions, with ∼14 to 62 ppb Re and ≤10 ppt common Os. Pyrrhotite has ∼5 to 39 ppb Re and ∼0.6 ppb common Os. Pyrite has a mean Re–Os model age of 262.3 ± 5.6 Ma (n = 13), in agreement with the isochron regression of 187Os vs. 187Re. The Re–Os age (∼262 Ma) for the Cihai Fe deposit is within uncertainty in agreement with a previously reported Rb–Sr age (268 ± 25 Ma) of the hosting diabase, indicating a genetic relationship between magmatism and mineralization. Magnetite from the Cihai deposit has Mg, Al, Ti, V, Cr, Co, Ni, Mn, Zn, Ga, and Sn more elevated than that of typical skarn deposits, but both V and Ti contents lower than that of magmatic Fe–Ti–V deposits. Magnetite from these two ore clusters at Cihai has slightly different trace element concentrations. Magnetite from the Cihai ore cluster has relatively constant trace element compositions. Some magnetite grains from the Cixi ore cluster have higher V, Ti, and Cr than those from the Cihai ore cluster. The compositional variations of magnetite between the ore clusters are possibly due to different formation temperatures. Combined with regional tectonic evolution of the Beishan terrane, the Re–Os age of pyrite and the composition of magnetite indicate that the Cihai Fe deposit may have derived from magmatic–hydrothermal fluids related to mafic magmatism, probably in an extensional rift environment.

Magnetite: Synthesis and Characterization

Magnetite nanopowder is a nanostructured magnetic material which is of great importance due to its electric and magnetic properties at room temperature. There are quite enough methods to produce magnetite. In the present work, four samples of magnetite powder were produced, the first three with the alkaline precipitation method from aqueous solution of mixed Fe (II)/Fe (III) salts, without any surfactants and the last one with the micro emulsion method. The prepared powders have been characterized using transmission electron microscopy, Raman and FT-IR spectroscopy and x-ray diffraction in order the structure and the morphology of magnetite to be examined. The produced magnetite powders have a size range of 10-12±2nm and the chemical composition of magnetite.

Texture, Microstructure and Geochemistry of Magnetite from the Banduhurang Uranium Mine, Singhbhum Shear Zone, India – Implications for Physico-chemical Evolution of Magnetite Mineralization

Abstract The Singhbhum Shear Zone in eastern India is one of the largest repositories of uranium and copper in India. Besides uranium and copper, apatite-magnetite mineralization is widespread in this shear zone. This study aims at deciphering the physico-chemical evolution of magnetite mineralization in relation to progressive shearing integrating field relations, micro-textures, structures and compositions of magnetite in the Banduhurang uranium mine. Apatite-magnetite ores occur as discrete patches, tongues, and veins in the strongly deformed, fine grained quartz-chlorite schist. Textures and microstructures of magnetite indicate at least three stages of magnetite formation. Coarse-grained magnetite (magnetite-1) with long, rotational, and complex strain fringes, defined by fibrous and elongate quartz, is assigned to a stage of pre-/early-shearing magnetite formation. Medium grained magnetite (magnetite-2), characterized by single non-rotational strain fringe equivalent to the youngest fringe of magnetite-1, grew likely at the mid-/late-stage of shearing. Fine grained magnetite (magnetite-3) is generally devoid of any pressure shadow. This indicates even a much later stage of formation of this magnetite, presumably towards the closing stage of shearing. Some of the magnetite-1 grains are optically heterogeneous with a dark, pitted Cr-Ti-bearing core overgrown by lighter, fresh rim locally containing pyrite, chalcopyrite, and chlorite inclusions. The cores are also locally characterized by high Al and Si content. Homogeneous magnetite-1 is optically and compositionally similar to the overgrowth of heterogeneous magnetite-1. This homogeneous magnetite-1 that grew as separate phase is contemporaneous with the overgrowth on pitted core of heterogeneous magnetite-1. Magnetite-2 is compositionally very similar to homogeneous magnetite-1, but is devoid of sulfide inclusion. Magnetite-3 is generally devoid of any silicate or sulfide inclusion and is most pure with least concentrations of trace/minor elements. The high Al and Si content in some magnetite can be explained by coupled substitution that involves substitution of Si4+ for Fe3+ in the tetrahedral sites and Fe2+ for Fe3+ in the octahedral sites, with a simple substitution of Al3+ for Fe3+ in the octahedral sites. The mode of occurrences of apatite-magnetite ores indicates a predominantly hydrothermal origin of most magnetite. However, the Cr-Ti-bearing magnetite-1 cores and inferred mafic nature of the original protolith indicates that some magnetite was inherited from the original igneous rock. We propose that the pre-/early-shearing hydrothermal event of magnetite formation was associated with sulfide mineralization and alteration of existing magmatic magnetite. The second stage of magnetite formation at the mid-/late-stage of shearing was not associated with sulfide formation. Finally, fine-grained compositionally pure magnetite formed at the closing stage of shearing likely due to metamorphism of Fe-rich protolith.