Low Fe Content Research Articles

Effect of Structural Fe Reduction on Water Sorption by Swelling and Non-Swelling Clay Minerals

Ferruginous clay minerals in saturated soils and within hydrocarbon deposits often exist in a reduced state. Upon introduction of dissolved oxygen, or other oxidants, the clay minerals oxidise and changes in mineral surface charge and sorption capacity occur, resulting in changes in hydration as well as flux of intercalated species. Here we examine the sorption of water to the Fe-containing clay minerals nontronite NAu-2 (23 wt% Fe) and illite IMt-2 (7 wt% Fe) as a function of Fe oxidation state and exchangeable cations by means of water vapour volumetry and N2 surface area analysis. The clay minerals were chemically reduced using sodium dithionite. Sorption isotherms of water vapour and nitrogen, controlled relative humidity diffractograms, and chemical analyses were recorded. The results show that, after reduction using sodium dithionite, increased amounts of water vapour and nitrogen were adsorbed to the high Fe content nontronite, despite decreased interlayer separation. Little change was observed for the non-swelling and low Fe content illite. Sodium from the reducing agent was found to exchange with calcium present in the starting clay minerals, and sodium balanced the additional mineral charge generated during reduction. The findings presented in this study deliver improved understanding of sorption at the surface of the reduced clay minerals, which aid constrain the role of clay mineral interfaces in subsurface environments.

Intergranular corrosion behavior of Inconel 625 deposited by CMT/GTAW

The intergranular corrosion (IGC) behavior of Inconel 625 cladding layer deposited by cold metal transfer (CMT) at different positions from the substrate has been studied. Compared with the Gas tungsten arc welding (GTAW) welds, the IGC resistance of the CMT-welds is significantly improved by about 73.7%, which is attributed to the optimized grain boundary structure and lower Fe content in the CMT-welds. Furthermore, as the overlay approaches the X65 substrate, the IGC resistance decreases. This is due to the combined effect of the smaller grain size and high Fe content of the overlay close to the substrate.

Electrochemical Performance Investigation of Sr(Ti1−xFex)O3−δ Fuel Electrodes with Different Fe Contents for Solid Oxide Electrochemical Cells

Sr(Ti1−xFex)O3−δ (STF) is an alternative to Ni-based cermet fuel electrodes for solid oxide electrochemical cells (SOCs) that can provide an improved tolerance to redox cycling, fuel impurities, and hydrocarbon fuels. Sr(Ti0.3Fe0.7)O3−δ electrodes were recently found to exhibit an excellent performance, but lower Fe contents have not been studied. In this work, the electrochemical performance of STF-based fuel electrodes with 0.4 ≤ x ≤ 0.7 are explored in both full cells and symmetric cells at different fuel conditions. The electrode performance in the fuel cell mode (3% H2O humidified hydrogen) became slightly worse as x decreased from 0.7 to 0.5; however, it was much worse at x = 0.4. In the steam electrolysis mode from 50% H2O to 50% H2, the change in the electrode performance showed a similar trend, and a more significant degradation in the performance was found at x = 0.4. The worse electrochemical performance in a high-steam-concentration atmosphere is due to the higher electrode polarization and increased ohmic resistance. These results indicate that STF electrodes with x = 0.5 have a reasonable electrochemical performance for SOC applications.

Preparation of millimeter-scale MIL-53(Fe)@polyethersulfone balls to optimize photo-Fenton process

Fe-MOFs are expected to be the candidates for heterogeneous Fenton catalysts due to their porous channel and high specific surface area feature. However because of their small size they are difficult to recycle, and the low Fe(II) concentration make them low efficiency for H2O2 activation. Herein, we report millimeter-scale polymer anchored porous MIL-53(Fe) composite balls with highly improved Fenton-like performance and easy recycling for the elimination of carbamazepine. It is prepared via MIL-polyethersulfone dope and solvent/water exchange method with organic ligand substitution strategy that affording SO and CO mixed-coordination. The degradation rate constant for MIL-53(Fe)@PES is 4 times that of pure MIL-53(Fe), while the degradation rate constant of photo Fenton is 79 times of dark one. The composite balls can be recovered by simple precipitation process and the removal efficiency of carbamazepine still reach 80% after 5 cycles of regeneration. The mechanism of photo-Fenton degradation of carbamazepine were proposed.

Chromite Composition and Platinum-Group Element Distribution in the Proterozoic Chimalpahad Anorthosite Complex, South India: Implications for Magmatic Processes and Discrimination of Tectonic Setting

Abstract The Proterozoic Chimalpahad Anorthosite Complex (CAC) is a deformed and dismembered complex in South India comprising of anorthosite-leucogabbro-gabbro-ultramafic rocks. It is located in the Nellore-Khammam Schist Belt (NKSB) within the contact zone between the Eastern Dharwar Craton (EDC) and the Eastern Ghats Belt (EGB). The chromitites occur as small dismembered lensoidal bodies within the ultramafic rocks. Presence of micrometric inclusions of iridium-like platinum-group minerals (IPGM), such as laurite (RuS2), erlichmanite (OsS2), irarsite (IrAsS), and Ir-Os-Ru alloys, is reported for the first time in the CAC chromites. The chromite cumulates preserve magmatic character (Cr#: 0.61 to 0.77; Mg#: 0.29 to 0.55), while disseminated chromites and rims of some grains (Cr#: 0.59 to 0.89; Mg#: 0.10 to 0.25) show postmagmatic modifications. The chromites are characterised by higher Cr and Al contents and lower Fe and Ti contents. The mineral chemistry of chromites such as Cr# and Mg# contents of Al2O3 (10.05–20.07 wt.%) and TiO2 (0.1 to 0.25 wt.%) typically suggests that the CAC chromitites and their ultramafic hosts were generated from the S-undersaturated boninite melt in a magmatic arc in suprasubduction tectonic setting. A general negative slope of bulk-rock PGE distribution with upward convex pattern is observed for the CAC chromitites in the chondrite-normalized plot. These geochemical and mineral chemical characters in addition to location of the chromitites and the CAC in the tectonic zone between Eastern Dharwar Craton and Eastern Ghats Mobile Belt point towards ophiolitic affinity of the CAC chromitites. Laurite (RuS2) grains are trapped close to the cores of chromites, whereas erlichmanites (OsS2) are trapped away from the cores. Textural relations indicate primary orthomagmatic nature of laurite and Or-Ir-Ru alloys and their precipitation prior to or concomitant with chromite from an S-undersaturated melt at ~1200–1300°C and log fS2 varying between −2 and −1.3. Ru-Os disulfide and erlichmanite crystallized subsequently with a gradual decrease in temperature in the differentiating ultramafic magma. Precipitation of irarsite and base-metal sulfides can be attributed to local and rapid fluctuations of temperature, fS2, and fAs during the formation of the chromitites due to influx of fresh batch of melts or crystallization in an open magmatic system. The compositional variations of laurite-erlichmanite record heterogeneous physicochemical environment during their crystallization. In addition to zoning, preservation of IPGMs in the CAC chromites points towards fast cooling of the magma possibly associated with rapid exhumation of the chromitites and their ultramafic hosts from the roots of the subcontinental lithospheric mantle (SCLM) towards their final emplacement into the crust. Occurrence of the CAC along a linear extension with the Kondapalli Ultramafic Complex and deformed remnants of ophiolites (Kandra and Kanigiri complexes) along the eastern margin of the Eastern Dharwar Craton (EDC) bordering the Eastern Ghats Belt (EGB) indicates this zone to be a Proterozoic convergent margin.

Soils and spoils: mineralogy and geochemistry of mining and processing wastes from lead and zinc mining at the Gratz Mine, Owen County, Kentucky.

Mineralogical and geochemical features of mining and processing wastes collected in Owen County, part of the Central Kentucky Lead-Zinc district, were investigated. The Gratz mine, abandoned in the 1940s, is on a dairy farm. Aside from discerning the nature of mining refuse at the site, the investigation was part of the University of Kentucky College of Pharmacy's mission to explore unusual environments in the search for unique microbiological communities. Four samples of a soil-plus-spoils mix were collected from spoil piles and two samples, the sluice and coarse samples, were closely associated with the site of the ore processing. Optical petrology (polarized reflected-light, oil-immersion optics at a final magnification of 500 ×), X-ray diffraction, X-ray fluorescence, inductively coupled plasma mass spectrometry, field emission scanning electron microscopy (FE-SEM), and high-resolution transmission electron microscope (HR-TEM) with selected area electron diffraction (SAED) and/or microbeam diffraction (MBD), scanning transmission electron microscopy (STEM), and energy-dispersive X-ray spectrometer (EDS) analyses were employed to characterize the samples. Calcite is the main mineral in most samples, followed by near equal amounts of quartz and dolomite. Sphalerite and galena are the principal sulfides and barite is the dominant sulfate. Geochemistry of major elements reflected the mineralogy, whereas trace elements showed different groupings between the minerals. Scandium, Cu, Ga, Ge, Cd, and Sb were found predominantly associated with Zn and Pb and sulfide minerals; Bi, Hf, In, Sn, and Zr with heavy mineral fraction; while the remaining trace elements, including the rare earths, were mostly distributed among other present phases, i.e., oxyhalides, oxides, silicates, and carbonaceous material. The data were used to illustrate the processes and conditions that control the sulfide-mineral oxidation and its potential for the environmental release of associated reaction products. The wastes represent a potential source of environmentally disruptive concentrations of Zn, Pb, and other sulfide-associated elements. The high share of carbonates suggests near-neutral conditions in deposited wastes, restricting sulfide weathering and further limiting the oxidant activity of Fe. The low-Fe content and its predominant presence in highly resistant hematite also constrain sulfide weathering. Consequently, the spoils have a low potential for generation of acidity and release of heavy metal(loid)s in the surrounding environment.

Meteoric freshwater leaching and its significance to reservoir quality in a buried hill of lower-middle Jurassic fluvial sandstones: A case study from the Huanghua Depression, Bohai Bay Basin, China

Within polycyclic sedimentary basins, meteoric freshwater leaching plays an important role in the formation of secondary porosity. Whereas, when superimposed by other late diagenesis processes, it is often difficult to identify its diagenetic indicators. The Jurassic clastic reservoirs in the “Wmy buried hill” of the Huanghua Depression testify from such meteoric freshwater diagenesis. The “buried hill” is named after a village called “Wmy” and nowadays buried deeply into a Paleogene lacustrine sag, which displays like a highland or hill. These reservoir sandstones were studied based on a variety of approaches including 3-D seismic interpretation, core and thin section observations, X-ray fluorescence analysis, Electron Probe Microanalysis and stable isotope analysis, combined with reconstruction of the burial and thermal histories. At last, the evolutionary model of reservoir quality was addressed. Difference of sedimentary fabrics in sand bodies leads to the heterogeneity of pores distribution, making the permeability in coarse-grained and fine-grained sandstones largely different. The meteoric water leaching caused the loss of Fe and Ti, leading to a zonation of core colors with white and red zones. In addition, the dissolution by meteoric water of biotite and volcanic fragments as well as feldspar grains produced large amounts of secondary porosity without formation of diagenetic by-products, which thus points to an open diagenetic system. The calcite cement of meteoric freshwater origin displays relatively low Fe and high Mn content exhibiting a low Fe/Mn ratio. The origin of Mn is probably dissolution of volcanic fragments. The evolutionary process of reservoir quality can be divided into four stages. The second stage is the crucial period for formation of secondary porosity whilst faults derived from the compressional stress during tectonic uplif associate coal-bearing source rocks with Jurassic reservoirs. Moreover, the last stage is the critical period for petroleum and/or gas migration and accumulation because the underlying coal-measures entered the hydrocarbon generation window and overlying Paleogene sealing rocks were intensely compacted. Scale of potential reservoirs in the whole well profile are evaluated by statistical methods, the total thickness of which can reach about 25 m. Reservoirs close to the unconformity surface between the Mesozoic and Cenozoic display more effective porosity than the deeper ones, which should be the target for the subsequent hydrocarbon exploration.

Comparison of Natural and Dyed Fire Opal

Fire opal is much sought after for its flame-like red-orange-yellow body-color. With consumers’ enthusiasm for fire opals, dyed fire opal has gradually entered the jewelry market, which has made an impact on consumer perception and trade. In this work, we present a combined spectroscopic (FTIR, Raman, UV-Vis) investigation and chemical analysis of four natural fire opals from Mexico and Ethiopia and four dyed samples. Ultra-depth microphotographs revealed uniform color distribution in the natural fire opal, while patches of color were observed in the dyed fire opal. The main infrared peak around 1099 cm−1 indicated the hydrophane origin of all the dyed materials. The color of natural fire opals is related to the presence of Fe oxides and hydroxides (hematite, goethite) as confirmed by the Raman spectra, the first derivative of the UV-Vis spectral curves, and the relatively high Fe content by chemical analysis. By contrast, dyeing opals created several Raman peaks produced by external materials, and an extremely low Fe content was detected. The first derivative of the UV-Vis spectral curves can aid in detecting the use of a dyeing treatment in red and yellow opal.

Molecular dynamics study on the strengthening mechanisms of Cr–Fe–Co–Ni high-entropy alloys based on the generalized stacking fault energy

The correlation between the generalized stacking fault energy and the strengthening mechanisms of Cr–Fe–Co–Ni high-entropy alloys during uniaxial tensile deformation is investigated using molecular dynamics simulations. An increase in the Cr and Fe content decreases the generalized stacking fault energy, while an opposite trend is observed for the content of Co and Ni. A linear correlation is identified between the unstable stacking fault energy and the yield stress. Alloys with a lower Fe content and higher Co and Ni contents show a higher unstable stacking fault energy, and hence higher yield stress. A high density of Lomer–Cottrell locks or deformation twins leads to higher flow stress. The deformation twins play a more important role in enhancing the flow stress as compared to sessile dislocations. Additionally, high unstable stacking fault energy is required to stabilize the defects formed and contribute to increasing flow stress. For a low unstable stacking fault energy, the plastic deformation progresses at lower stress and a bidirectional defect transformation is observed. The results agree with recent experiments and serve as guidelines for how the composition can be used to enhance the yield strength and the efficiency of strengthening mechanisms in Cr–Fe–Co–Ni high-entropy alloys.

Effects of vacuum annealing on the phase constituents and mechanical properties of the AlxCrFeMn2-xNi multiprincipal component alloys

The development of high-performance Co-free multiprincipal component alloys (MPCAs) is of great significance in recent years. In the present work, eight arc-melted Co-free AlxCrFeMn2-xNi alloys were prepared and then vacuum annealed at 800 or 1000 °C for 5–10 days. Their phase constituents, microstructures and mechanical properties were investigated. The second-order L21-Ni2MnAl phase with low Cr and Fe content was confirmed and had similar contribution to the alloy hardness as B2 phase. When x ≥ 1, the as-cast AlxCrFeMn2-xNi alloys are composed of BCC + B2 phase and have an elastic modulus of ∼228 GPa. Their mechanical properties slightly change after annealing, although the phase grains are coarsened after 1000 °C annealing and small amount of FCC phase precipitated after 800 °C annealing. When x = 0.1–0.75, the BCC phase transforms into the σ phase after 800 °C annealing, which leads to greatly increased hardness and reduced ductility. The decomposition temperature of the σ phase decreased with Al content, from 1036.9 °C to 912.0 °C. Compared to the AlxCo2-xCrFeNi alloys, the similar phase constituent and similar hardness can be obtained by replacing Co with Mn. Therefore, Co-free Al–Cr–Fe–Mn–Ni MPCAs have great application prospects.

Matrix effects and improved calibration procedures for SIMS titanite U[sbnd]Pb dating

Titanite is a U-bearing accessory mineral that can serve as a geochronometer. Compared with zircon, titanite is more likely to contain multi-stage fluid-induced growth. Thus, individual titanite grains may yield complex UPb ages that reveal the entire geological history of the rock. Secondary ion mass spectrometry (SIMS), which has high sensitivity and spatial resolution, is a good choice for UPb titanite analyses. A titanite UPb standard named YQ82 was developed with 206Pb/238U age of 1837.6 ± 1.0 Ma (2 standard error (SE), n = 4) and 207Pb/206Pb age of 1845. 0 ± 1.1 Ma (2SE, n = 4), as determined herein using isotope dilution isotope ratio mass spectrometry (ID-IRMS). However, UPb dating of YQ82 via SIMS yielded a bias of up to 14% compared to the ID-IRMS value, indicating a matrix effect. To correct for this matrix effect, six UPb titanite dating reference materials (RMs) were analyzed. Based on the correlations between the age biases and the Fe contents of the six RMs, a calibration protocol was established using the index of the Fe content (FeO+/IP, intensity of primary beam) and a power-law relationship between the calibrated Pb+/U+ and UO+/U+. Using this calibration protocol, the UPb ages decreased the age bias from approximately ±14% to ±1.4%. To test the protocol, a titanite sample (BMB108) with a low Fe content (Fe2O3, 0.4 wt%) was calibrated using MKED1 (Fe2O3, 1.5 wt%) as the RM. Without the calibration, the apparent SIMS 206Pb/238U age was 10% younger than the thermal ionization mass spectrometry (TIMS) 206Pb/238U age (1890 ± 4 Ma). Using the calibration method, the apparent SIMS UPb age was 1898 ± 14 Ma (2SE, n = 19), which is consistent with the TIMS age. This study shows that a considerable matrix effect related to Fe content is present in the SIMS titanite UPb dating results. The calibration protocol developed herein improved the SIMS titanite UPb dating accuracy, yielding a more accurate thermal history of the samples.

Titanite U-Pb dating and geochemical constraints on the Paleozoic magmatic-metamorphic events and Nb-Ta mineralization in the Yushishan deposit, South Qilian, NW China

Titanite, as one significant petrogenetic tracer, occurs in the ore-bearing alkaline unit (syenite and aegirine-augite syenite dikes) and in the barren calc-alkaline unit (monzodiorite) and metamorphosed strata (called as leptynite) in the recently found large Yushishan Nb-Ta deposit from South Qilian, NW China. Most titanite grains in the alkaline unit display obvious shape-preferred orientation and zonation, coexisting with allanite, zircon and alkali feldspar. Some titanite grains from the alkaline unit have been partially or completely altered into fine-grained euxenite and/or Nb-rich rutile, but retained their original crystal shapes. Although some titanite grains in the igneous rocks show obvious core-rim textures, both of them yield almost the same U-Pb ages. Combined with U-Pb dating of zircon from these different rock units, the complex magmatic-metamorphic events in the Yushishan district can be subdivided into two different periods: the first one occurring in the Neoproterozoic (ca. 834–790 Ma, zircon U-Pb ages) that are related to the regional volcanism and metamorphic activities and the formation of leptynite during the metamorphism, while the second one occurring in the early Paleozoic (ca. 490–470 Ma, titanite and zircon U-Pb ages) that are related to the formation of granitic intrusions and subsequent metamorphic process and Nb-Ta mineralization. Geochemically, titanite from these igneous rocks is consistent with the typical features of igneous titanite, such as high Fe and REE contents, and negative Eu anomalies. The zoned titanite in both alkaline (mainly syenite) and calc-alkaline units uniformly displays a core-to-rim decreasing trend for the Fe, REE, Nb and Ta contents and Th/U ratios, corresponding to a secular variation from the magmatic to metamorphic evolution. Titanite from the leptynite is interpreted to be of metamorphic origin, with low Fe and REE contents, weakly positively sloping REE patterns, along with positive Eu anomalies. It is suggested that the titanite can be used as an indicator of metal fertility and ore potential for the host rocks/fluids. The high Nb and Ta features in titanite from the alkaline unit suggest a genetic relationship between the alkaline granitic magmatism and Nb-Ta mineralization in the Yushishan deposit. In addition, the high and variable Nb and Ta contents in titanite from the leptynites reveal an inherited signature of the metamorphic fluids. Considering the absence of titanite in the ore-bearing leptynites, we speculate that titanites with high and variable Nb and Ta contents of titanite in the barren leptynites have the potential to provide abundant metals for the precipitation of Nb-Ta-bearing minerals to form economic orebodies.

The Influence of Pickling Treatment Parameters on the Surface State and Pre-Passivation Behavior of Super 13Cr Martensitic Stainless Steel

As a pre-treatment process in the pre-passivation of stainless steel, pickling treatment has a significant effect on the formation of the pre-passivation film. Thus, the surface composition and defects of Super 13Cr martensitic stainless steel (Super 13Cr) were evaluated under different pickling parameters to further improve the corrosion resistance of the pre-passivation film. The samples were prepared using the acid immersion method and by changing the immersion duration and the acid concentration. The inclusion and chemical composition on the Super 13Cr surface were characterized via a scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). The pickling treatment contributes little to the morphology, dimension, and other characteristic parameters of the inclusions. With the increasing duration and acidification concentration, the Cr content on the surface of Super 13Cr increases initially and then decreases. By contrast, the Fe content decreases initially and then increases. The pickling parameters corresponding to the lowest Fe content and the highest Cr content are identical, i.e., the exposure duration is 50 s and the acid concentration is 48 g/L. The pickling treatment in this case could be divided into two stages: outer film dissolution and inner film dissolution. The pickling parameters basically contribute little to the defects of martensitic stainless steel but can significantly affect the surface Cr and Fe content. Retaining the Cr-enriched inner layer could improve the content of Cr in the pre-passivation film and then improve the corrosion resistance of the film. Thus, compared with the original sample with native film, the corrosion resistance of the sample with a Cr-enriched inner layer improved by a factor of about 40.

Impact of Zn substitution on Fe(II)-induced ferrihydrite transformation pathways

Iron oxide minerals are ubiquitous in soils, sediments, and aquatic systems and influence the fate and availability of trace metals. Ferrihydrite is a common iron oxide of nanoparticulate size and poor crystallinity, serving as a thermodynamically unstable precursor to more crystalline phases. While aging induces such phase transformations, these are accelerated by the presence of dissolved Fe(II). However, the impact of trace metals on Fe(II)-catalyzed ferrihydrite phase transformations at ambient temperatures and the associated effects on trace metal speciation has seen limited study. In the present work, phase transformations of ferrihydrite that contains the trace metal zinc in its structure were investigated during aging at ambient temperature in the presence of two different Fe(II) concentrations at pH 7. X-ray diffraction reveals that low Fe(II) concentration (0.2 mM) generates hematite plus minor lepidocrocite, whereas high Fe(II) concentration (1.0 mM) produces a magnetite-lepidocrocite mixture. In both cases, a substantial fraction of ferrihydrite remains after 12 days. In contrast, zinc-free ferrihydrite forms primarily lepidocrocite and goethite in the presence of 0.2 mM Fe(II), with minor hematite and a trace of ferrihydrite remaining. For 1.0 mM Fe(II), magnetite, goethite, and lepidocrocite form when zinc is absent, leaving no residual ferrihydrite. Transformations of zinc-ferrihydrite produce a transient release of zinc to solution, but this is nearly quantitatively removed into the mineral products after 1 h. Extended X-ray absorption fine structure spectroscopy suggests that zinc partitions into the newly formed phases, with a shift from tetrahedral to a mixture of tetrahedral and octahedral coordination in the 0.2 mM Fe(II) system and taking on a spinel-like local structure in the 1.0 mM Fe(II) reaction products. This work indicates that substituting elements in ferrihydrite may play a key role in promoting the formation of hematite in low temperature systems, such as soils or sediments. In addition, the retention of zinc in the products of ferrihydrite phase transformation shows that trace metal micronutrients and contaminants may not be mobilized under circumneutral conditions despite the formation of more crystalline iron oxides. Furthermore, mass balance requires that the abundance and isotopic composition of iron oxide-associated zinc, and possibly other trace metals, in the rock record may be retained during diagenetic phase transformations of ferrihydrite if catalyzed by dissolved Fe(II).

Geochemical and Geochronological Constraints on a Granitoid Containing the Largest Indosinian Tungsten (W) Deposit in South China (SC): Petrogenesis and Implications

Chuankou tungsten (W) ore field, with an estimated WO3 reserve exceeding 300,000 tonnes, is so far the largest Indosinian (Triassic) granite-related W ore field in South China. However, the precise emplacement ages, sources of granitoids, and their relationship with W mineralization are still not well understood. In this research, four main magmatic stages (G-1 to G-4) have been identified in the Chuankou ore field, including G-1 (phase I, biotite monzogranite), G-2 (phase II, two-mica monzogranite), G-3 (phase III, fine-grained granite), and G-4 (phase IV, granite porphyry). LA-ICP-MS U-Pb dating of zircon grains from granitoids of the Chuankou W ore field yields emplacement ages of 230.8 ± 1.6 Ma, 222.1 ± 0.56 Ma, 203.1 ± 1.6 Ma, and 135.5 ± 2.4 Ma, respectively. Granitoids from the Chuankou ore field contain a large amount of peraluminous minerals such as biotite, musvite, garnet and tourmaline. Geochemically, the granitoids have high Si and Al (A/CNK > 1.1) content but low alkali, Fe, Mg, Mn, and Ca content. Moreover, there is enrichment of Rb, Zr, Hf, Th, and U, but depletions of Ba, Sr, P, and Ti. The granitoids have especially low Zr + Nb + Ce + Y and high Rb/Ba ratios, further indicating a highly fractionated S-type granite affinity with a significant crystal fractionation process in regard to K-feldspar, plagioclase, biotite, Ti-bearing minerals (except rutile), zircon, apatite, allanite, and monazite. Whole-rock εNd(t) and TDM2 values are −10.77 and 2090 Ma for G-1, −9.09 to −7.47 and 1764–1684 Ma for G-2, −10.07 to −6.53 and 1669–1471 Ma for G-3, respectively, indicating that the Chuankou granitoids were derived from two episodes of partial melting of the Paleoproterozoic to Mesoproterozoic metamorphic basement. Trace elements within the zircons and whole-rock geochemistry yielded evidence of the close relationship between W mineralization and G-1 and G-2 granitoids of the Chuankou ore field. The batholith of the Chuankou ore field was formed 20–10 Ma later than the peak age of the collisions orogeny and formed in a post-collisional setting.

Effect of Ca2+ on the Microstructure, Morphology and Magnetic Properties of La-Co Substituted M-Type Strontium Ferrite at Low Fe Content

Effect of Ca2+ on the Microstructure, Morphology and Magnetic Properties of La-Co Substituted M-Type Strontium Ferrite at Low Fe Content

Olovem bohatá oxidační zóna polymetalické mineralizace na lokalitě Kvasetice u Havlíčkova Brodu: distribuce minerálních asociací s pyromorfitem a arzenáty

Supergene mineral assemblages rich in Pb, As and P occur on the dumps after the historical mining of the base-metal deposit in Kvasetice (Havlíčkův Brod ore district, Bohemian-Moravian Highlands, Czech Republic). The primary hydrothermal assemblage of pyrite > sphalerite > arsenopyrite > galena >> boulangerite hosted in the quartz veins is partly different from other similar localities in this area, which belong to the typical k-pol ores with iron-rich sphalerite, pyrrhotite, pyrite, arsenopyrite and chalcopyrite. Kvasetice locality is characterized by a relatively higher stability of pyrite and sphalerite with a relatively low Fe content (< 0.12 apfu of Fe) compared to arsenopyrite and galena in supergene conditions, as well as a total deficit of Cu, Ca and partly S. In the supergene mineral association rich in Pb-P-Fe-As, two main assemblages can be distinguished. Supergene assemblage I contains common microscopic anglesite replacing galena and two sub-groups of arsenates with sulphide relics in small quartz veins: (a) in close association with the relic arsenopyrite are pharmacosiderite and hydroniumpharmacosiderite, both relatively Pb-rich (≤ 0.18 apfu of Pb), accompanied by a rare scorodite. (b) More abundant assemblage of segnitite >> beudan­tite > mimetite >> carminite and coronadite without a direct association with sulphides. Other phases with a non-stoichiometric Fe/As ratio (HFA) are only locally found. A sporadic greenockite is the only detected decomposition product of sphalerite. The Pb-Fe3+ sulfates (minerals of the jarosite subgroup), gypsum, and Ca-, Zn-, Sb- and Cu-supergene minerals are missing. Supergene assemblage II is mainly represented by pyromorphite (mostly with As below detection limit, but locally with ≤ 0.44 apfu), rarely by mimetite and only locally also by cerussite. They overgrow thin crusts of mainly Fe-oxyhydroxides covering the altered granite matrix or line thin druse quartz veinlets. The supergene mineral assemblages from Kvasetice differ not only from other localities in the ore district studied, but also from other localities of supergene mineralization in the Bohemian-Moravian Highlands. They are the product of weathering in the shallow supergene zone, however, they could also have been arised by subrecent weathering of materials deposited on the dumps during the 13-16th century.

Chemical and short‐wave infrared characteristics of white mica associated with the Gajah Tidur porphyry copper system at the deep Grasberg Cu—Au—(Mo) deposit, Indonesia

AbstractThe Grasberg Cu—Au—(Mo) deposit comprises the shallower Main Grasberg porphyry Cu—Au and the deeper Gajah Tidur (GT) porphyry Cu—Mo—(Au) systems. The GT porphyry preserves various types of white mica whose geochemical variations provide insights into the white mica‐dominated alteration of porphyry systems. The white mica assemblages within the GT porphyry system comprise: (1) muscovite‐anhydrite‐chlorite (MAC), (2) muscovite‐chlorite‐anhydrite (MCA), and (3) muscovite‐quartz ± pyrophyllite (MQP). These assemblages display zonation from central and deep parts of the system to its shallower and peripheral parts. The MAC alteration white micas are characterized by high Na, Fe, Ti, and V concentrations, and with short‐wave infrared Al—OH absorption wavelengths of 2203–2208 nm. The MCA white micas have higher Mg content than the other two GT white mica assemblages but similar Al—OH absorption wavelengths to the MAC white micas. The MQP alteration white micas have low Na, Fe, Mg, and Ti, but relatively high Si, Al, and F, and Al—OH absorption wavelengths are largely shorter than 2202 nm. We interpret that the high Fe and Ti content of the MAC white micas is due to inheritance of these elements from mafic minerals they replaced. The higher Fe content of these white micas explain their longer wavelength Al—OH absorption positions relative to the MQP white micas. In contrast, lower Fe content and shorter Al—OH wavelengths of the MQP white micas are caused by their higher Si and Al content, which reduces iron occupancy in the white mica crystal structure. White micas in this assemblage formed at lower temperature and probable lower pH condition that may have led to a replacement of Fe by Al. The short‐wave infrared Al—OH position of white mica together with the associated hydrothermal assemblage can be used as a proximitor for porphyry Cu hydrothermal centres. White mica associated with chlorite, anhydrite, and chalcopyrite, which commonly occur overprinting or adjacent to the potassic alteration center, are characterized by Al—OH absorption positions at 2200–2215 nm. By contrast, white mica associated with quartz‐pyrite are characterized by Al—OH wavelengths shorter than 2202 nm. In the distal part of porphyry Cu system, white micas may be associated with chlorite and have Al—OH absorption positions longer than 2204 nm.

Restricted diffusion preparation of fully-exposed Fe single-atom catalyst on carbon nanospheres for efficient oxygen reduction reaction

Single-atom catalysts (SAC) stabilized by nitrogen in carbon support are promising candidates for oxygen reduction reaction (ORR). However, conventional preparation methods usually lead to encapsulation of metallic centers in matrix and thus the utilization efficiency (UE) is underexploited. Herein, we report a novel strategy to prepare an Fe-SAC with all Fe atoms anchored on the surface of carbon nanospheres, which exhibited an extraordinary UE of 80% for ORR. This efficiency was achieved by coating polydopamine spheres with silica, followed by the pyrolysis of their blend with FeCl3. During thermal treatment, Fe migrates across the silica shell by atomic exchange with silicon, which inhibits the aggregation of Fe and allows Fe atoms to anchor on the surface. As such, it showed excellent ORR activity at a low Fe content. Zn-air batteries assembled using this catalyst showed a peak power density of 113 mW cm−2 and specific capacity of 710 mAh gZn−1.

Effect of Extra-Framework Fe Species in Pt/Fe/ZSM-23 Catalysts on Hydroisomerization Performance of n-Hexadecane

Pt/xFe/ZSM-23 catalysts with various Fe contents were prepared to explore the influence of extra-framework Fe (EF-Fe) on the n-hexadecane (n-C16) hydroisomerization performance. UV–vis and 57Fe Mössbauer spectroscopic results suggest that the Fe species composition was significantly different under various Fe contents, with (HO–Fe(III)–O–Fe(III)–OH) and [Fe(OH)2]+ as the main Fe species at low Fe content (<1.98 wt %), whereas the Fe2O3 clusters/particles as the dominant ones at high Fe content (>1.98 wt %). Moreover, the concentration of Brønsted acid sites and Pt dispersion could be controlled by tailoring the Fe content. Correspondingly, the hydroisomerization performance of n-C16 over Pt/xFe/ZSM-23 catalysts was dramatically changed with various Fe contents. The Pt/1.98Fe/ZSM-23 catalyst with 1.98 wt % EF-Fe content exhibited considerably excellent hydroisomerization performance, and both n-C16 conversion and selectivity to iso-hexadecane (i-C16) could reach over 80 wt % when the reaction temperature was 310 °C.