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Calcium-aluminum-rich inclusions (CAIs) commonly observed in chondritic meteorites are the oldest dated solids formed in the Solar System. Short-lived isotope chronologies (26Al-26Mg, 182Hf-182W) suggest a ∼2 Ma gap between the formation of CAIs and the accretion of the final chondrite parent bodies. One thin section, 3.27 cm2 in size, of an ordinary chondrite NWA 3358 (H3.1) studied contains 52 refractory inclusions (CAIs and amoeboid olivine aggregates (AOAs)) comprising 0.14 % of its area, which is the highest abundance of refractory inclusions among non-carbonaceous chondrites containing on average ∼0.009 area % of CAIs and AOAs. In combination with a low chondrule/matrix ratio of ∼1.5, this makes NWA 3358 a unique ordinary chondrite. The aqueously-formed fayalites (Fa >99) in NWA 3358 have the inferred initial 53Mn/55Mn ratio of (5.56 ± 0.44) × 10−6 which is the highest measured value for secondary minerals in chondrites and corresponds to the formation time of ∼1.0–1.5 Ma after CAIs. Based on the 53Mn-53Cr chronology of fayalite formation and the thermal modeling, we infer that the first-generation of an H chondrite parent body, ∼6–12 km in diameter, accreted within 1.0 Ma after formation of CAIs, filling the gap of ∼2 Ma between CAIs and the earliest chondrite parent bodies. This early accretion provides a possible mechanism of CAIs/AOAs storage in the inner solar nebula and could explain the high amount of refractory inclusions in NWA 3358. A later destruction of these first-generation bodies may also explain the presence of CAIs and chondrules of different ages within later formed chondrite parent bodies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnetite and fayalite were effectively separated by novel combined collector. • AT enhanced the selectivity of flotation and reduced the dosage of collector. • Co-adsorption of AT and PAE on fayalite surface improves its hydrophobicity. • Synergistic mechanism of AT and PAE was revealed from multiple perspectives. As an iron-bearing silicate mineral, fayalite has similar surface properties to magnetite, which makes it challenging to efficiently separate fayalite from magnetite by flotation. In this study, magnetite and fayalite were separated using novel combined collector polyoxyethylene alkyl amine (PAE) and terpinol (AT) through reverse flotation. Combined with a variety of characterization analysis and molecular dynamics (MD) simulation, the synergistic adsorption mechanism of the combined collector on mineral surface was revealed from multiple perspectives. The optimum scheme and pH response range of the combined collector were determined by micro-flotation test. Compared with PAE alone, the difference value of flotation recovery between fayalite and magnetite using combined collector was increased by 10.16%, and the dosage was reduced by 20%. Additionally, an effectively adsorption of combined collector onto fayalite surface to improve its surface hydrophobicity. Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and MD simulations results showed synergistic adsorption was produced onto fayalite surface using combined collector mainly through non-polar interaction, hydrogen bond association and bridge adsorption. Furthermore, the spatial distribution and diffusion behavior of water molecules provide microscopic evidence for the enhancement of surface hydrophobicity of fayalite by combined collector. [ABSTRACT FROM AUTHOR]

The North American Mid-Continent rift (MCR) is a 1.1 Ga aborted rift, which has recently become an area of intense focus for energy resource exploration following the report of H 2 emissions. To document the nature of the producing rocks, we conducted a multi-scale study on preserved drill-core samples from the DR1-A well located in the same area as the H 2 -producing wells in Kansas. We showed that this well reaches an unmapped part of the MRS composed of fayalite-bearing monzo-diorites in which we identified atypical veins of iddingsite, a complex mixing of Fe-rich phyllosilicates. Combining scanning and transmission electron microscopy (SEM and TEM) with scanning transmission X-ray microscopy (STXM) allowed us to differentiate at least two types of sub-micro-meter Fe-rich veins. A central reduced vein cutting the fayalite, other mafic minerals, the plagioclase, and to a lesser extent the alkali feldspar, contains a complex mix of serpentine, chlorite, and mica. Furthermore, a border vein, with a higher degree of Fe-oxidation, is found to be contained only within the fayalite. This external vein mainly contains iron and silicon, together with a few percent of potassium and calcium, and can be divided into two sub-veins composed of Fe3+-rich interstratified chlorite-smectite and Fe3+-rich serpentine in direct contact with the fayalite. Textures and microstructures of these phyllosilicates suggest that they have crystallized from a late magmatic and differentiated fluid, which precipitation produced the central vein together with the exsolution of an H 2 O-enriched fluid phase. This exsolved fluid, chemically far from equilibrium with the fayalite, appears to have induced a deuteric alteration of the fayalite, leading to the crystallization of the external veins enriched in ferric iron. These observations bring new perspectives on the history of formation of iron-rich clay minerals, which may, somehow, be related to H 2 production. • The igneous rock from the Kansas basement is a fayalite-bearing monzo-diorite. • Two generations of iron-rich clay minerals are described within the monzo-diorite. • Reduced‑iron-rich clay minerals are formed by precipitation of a late magmatic fluid. • Oxidized‑iron-rich clay minerals are formed by deuteric alteration of the fayalite. • Late magmatic alteration could be prone to produce hydrogen by iron oxidation. [ABSTRACT FROM AUTHOR]

In this study, carbothermal reduction of low grade banded hematite jasper iron ore (Fe~38%) is systematically investigated. The thermodynamic calculations revealed that single phase iron oxide can be reduced to Fe at 700 °C. The thermal pretreatment at 600 °C induced significant random cracks in the underlying matrix. The carbothermal reduction was evaluated using Box Behnken statistical design and was found effective for iron enrichment. Temperature was found as significant factor for optimization of both iron grade and recovery. At a higher temperature, the formation of fayalite and wustite deteriorates the iron grade-recovery. Under optimal conditions (700 °C, 30 min, 9% charcoal, minus 75 μm) a concentrate (FeG–61.2% and FeR–82%) was obtained and can be used for blast furnace feedstock and alternative sponge iron making. Coarser particle size and alternative reductants do not have a significant effect, however, the fused fraction comprising 85%Fe with retained austenite and martensitic iron was obtained. Unlabelled Image • Processing of low grade banded iron ore (Fe~38%) is investigated. • Carbothermal reduction was found successful for iron enrichment. • Optimal concentrate (Fe G –61.2% and Fe R –82%) with hematite and magnetite phases. • Fused mass ̴ 85% Fe with retained austenite-martensitic iron phase was obtained. • Concentrate obtained suitable for sponge iron making and blast furnace feedstock. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The occurrence state of zinc in the copper slag is obtained theoretically. • Zn(II) substitutes for the iron sites in the internal Si O Fe(II) (M2) bond to form Fe 2-x Zn x SiO 4. • Formation mechanism is actually an ion exchange process between Zn(II) and Fe(II). • The priority of the substituting for the iron site in the fayalite structure is proved by MS software calculation. Abstract The interactions between Fe 2 SiO 4 and ZnO play an essential role in the recovery of zinc from copper slag. The dissolution and substitution mechanism of ZnO in fayalite were investigated by using TG-DSC, XRD, PPMS DynaCool, XPS, Mossbauer and SEM-EDS analyses and compared with MS calculation results. The results indicate that the dissolution and substitution are actually processes of the penetrating dissolution of Zn(II) ions that can be divided into three steps: 1) ZnO dissociates into Zn 1-y O and Zn(II) ions; 2) Zn(II) penetrates the gap of the octahedron outer layer to substitute Fe(II) sites in the internal structure of Si O Fe(II) (M2) to form (Fe 2-x , Zn x)SiO 4 ; 3) Fe(II) is forced to migrate to the surface of (Fe 2-x , Zn x)SiO 4 to form (Zn 1-y , Fe(II) y)O. These findings can be derived the occurrence state and distribution of zinc in copper slag theoretically. [ABSTRACT FROM AUTHOR]

The growing problem of typical organic pollution in mines, and the effective utilization of increasing mine industrial wastes have been the most challenging issues in the current global situation. In this study, copper smelting slag (CSS), hydroxylamine (HA) and H 2 O 2 were employed to construct an efficient surface heterogeneous catalyst for the degradation of organic pollutants in mines. Fayalite and its ≡Fe were proved, by multiple methods, to be the crucial ferriferous catalyst in the CSS. HA greatly increased the oxidation effectiveness of the CSS from 53.6% to ∼100% by regulating the Fe2+/Fe3+ circulation within the fayalite lattice. Due to the special structural configuration of iron atoms in fayalite, the surface generation rate of •OH catalyzed by CSS was 101-106 times higher than in other iron-bearing minerals. •OH was demonstrated to be the main active radical species, and as an intermediate, O 2 •- also had a role in the oxidation process. In the presence of low doses of Cr, a synergistic removal of organic pollutants occurred, dominated by the electron transfer. Accordingly, this study proposes both, a new design concept for recycling the industrial solid waste from mines and a new surface catalyst system for the removal of organic pollutants from mining. [Display omitted] • An efficient surface heterogeneous Fenton system was made from CSS, HA and H 2 O 2. • The electron transfer of the lattice iron from fayalite was driving the catalysis. • •OH and O 2 •- were identified to be the active radicals in the CSS/HA/H 2 O 2 system. • CSS catalyst showed environmental friendliness and good reusability. • The mining solid waste was utilized for removal of organic pollutants. [ABSTRACT FROM AUTHOR]

Fayalite (Fe 2 Si0 4 ), the iron end-member of the olivine group, is found in various extraterrestrial environments including the interstellar medium and meteorite. Since the iron rich silicates, i.e. fayalites, are not abundantly found in earth, there has been lack of sufficient experimentation and modeling leading to the unavailability of sufficient experimental data of fayalite for comparative analyses with computations and astrophysical observations. In this work interstellar fayalite dust analogues were synthesized in the laboratory using simple chemical route. Shape and size dispersed interstellar dust analogue models for laboratory synthesized fayalite particles were developed for performing theoretical computations of light scattering parameters (e.g., angular profiles of intensity and degree of linear polarization, geometric and single-scattering albedo, asymmetry parameter and cross-sections of extinction and absorption) using discrete dipole approximation (DDA). In order to demonstrate the validity of our models, phase function and degree of linear polarization were measured using a laboratory based setup and the results were compared with DDA computed theoretical values at three wavelengths 543.5 nm, 594.5 nm and 632.5 nm respectively. [ABSTRACT FROM AUTHOR]

Pyrometallurgical processes for sulfide concentrates produce slag waste materials that contain multiple metals as carry-over impurities. Varied quantities of the metal content can be solubilized from the slag through chemical acid leaching or bioleaching. In this study, copper smelter slags were leached with and without iron- and sulfur-oxidizing bacteria in acid, sulfate-rich solutions and solid phase changes were determined. The samples (10% pulp density) were leached at 28 °C in stirred tanks at pH 2.5 and 3.0. The duration of the experiment was 37 d and the adjusted pH decreased to 2.3 in both sets of experiments. The primary metals of interest in the slag were Cu and Zn, with minor amounts of Ni and Co, and As, Sb, and Pb at trace levels. The metals in the slag were distributed in fayalite, glassy silicates and magnetite phases as well as minor amounts in oxides, metallic Cu and sulfides. Based on the solution analyses, the dissolution yields were 44% and 34% for Cu, 14% and 13% for Zn and Co, and 4.5% and 4.0% for Ni at initial pH values of 2.5 and 3.0, respectively. Fayalite was the most reactive mineral and Cu-sulfides were particularly refractory. The elemental composition of leached residues was matched with solid phase changes and the distribution of metals in the mineral phases. [ABSTRACT FROM AUTHOR]

Chondritic planetesimals are among the first planetary bodies that accreted inside and outside water snow line in the protoplanetary disk. CV3 carbonaceous chondrite parent body accreted relatively small amount of water ice, probably near the snow line, and experienced water-assisted metasomatic alteration that resulted in formation of diverse secondary minerals, including fayalite (Fa 80–100 ). Chemical compositions of the CV3 fayalite and its Mn–Cr isotope systematics indicate that it formed at different temperature (10–300 °C) and fluid pressure (3–300 bars) but within a relatively short period of time. Thermal modeling of the CV3 parent body suggests that it accreted ∼3.2–3.3 Ma after CV3 CAIs formation and had a radius of >110–150 km. The inferred formation age of the CV3 parent body is similar to that of the CM2 chondrite parent body that probably accreted beyond the snow line, but appears to have postdated accretion of the CO and ordinary chondrite parent bodies that most likely formed inside the snow line. The inferred differences in the accretion ages of chondrite parent bodies that formed inside and outside snow line are consistent with planetesimal formation by gravitational/streaming instability. [ABSTRACT FROM AUTHOR]

The dissolution behaviors of copper-containing sulfide (Cu 2 S) in fayalite-type slag have been deeply studied through experimental research and theoretical calculations. Results show that there are three phase changes in the process of Cu 2 S dissolution in the fayalite- matrix: (1) the formation of metallic copper particles and ferric iron by a redox reaction; (2) the formation of a matte (Cu 2−x Fe x S) by crystallization; and (3) chemical dissolution to form copper-doped fayalite. The formed Fe(III)-O(BO)-Si increases the content of bridging oxygen in the slag, which slows the migration and growth of metal particles. The dissolved Cu(I) substitutes at the M1 (Fe-O-Fe) site in the fayalite lattice to form the Si-O-Fe(II)-O-Cu(I)-O-Fe(III) structure or substitutes at the M2 (Fe-O-Si) site to form the Si-O-Cu(I)-O-Fe(II)-O-Fe(III) structure to obtain a copper-doped fayalite complex, and the probability is equal for Cu(I) substituting at M1 and M2. Copper-doped fayalite is the main phase causing the chemical loss of copper in the smelting slag, and is difficult to recover by traditional flotation. Through the directional modification of the copper-doped fayalite, making Cu-O-Si bond to transform into Cu-O-S bond that is easy to be leached or Cu-S bond that is easy to be reselected, which can realize the efficient recovery of copper resources from slag. These findings provide theoretical support for improving copper resource recovery in slag or reducing copper loss when producing slag during copper smelting. [Display omitted] • The diffusion rules of Cu(I) in fayalite were proved experimentally and theoretically. • Three reactions of Cu(I) existed in fayalite: redox, ion-exchange and crystallization. • Copper doped fayalite was the main phase causing copper chemical loss in smelting slag. • The substitution mechanism of Fe(II) in Fe 2 SiO 4 by Cu(I) is an ion-exchange process. • The probability was equal for Cu(I) substituting at M1 (Fe-O-Fe) and M2 (Fe-O-Si). [ABSTRACT FROM AUTHOR]

The migration and transformation of hazardous metals in copper smelting slags (CSS) threats the environment. However, the unclear relationship between phases and heavy metals in CSS hinders the development of harmless technology. In this work, we investigated the mineralogical composition of CSS and the corresponding heavy metal distribution, and explored the relationship between mineral phases and bound heavy metals. Fayalite (47.4%) was identified as the main phase in CSS by XRD refinement along with other phases of hedenbergite (38.7%), magnetite (11.0%) and iron (2.9%). Heavy metals mainly distributed in fayalite and less in hedenbergite and other phases. The specific sequential extraction showed fayalite was difficult to extract since 89.7% arsenic, 85.0% lead and 76.9% copper were tightly bound with these minerals. It meant that fayalite had a much stronger binding ability with heavy metals than that of other phases. Fayalite could transform into magnetite during alkali disaggregation resulting in the changing of heavy metal binding from strong to weak. This work is an approximation to break through the bottleneck of phase identification and binding relationship of heavy metals in CSS, and provides novel approaches and theoretical evidence for the CSS and similar smelting slags harmfulness treatment. [Display omitted] [ABSTRACT FROM AUTHOR]

Where ultramafic rocks are exposed to water at temperatures <400°C, they inevitably undergo serpentinization reactions to form serpentine±brucite±talc±magnetite (in addition to minor or trace phase like chlorite, tremolite, secondary diopside, garnet, Ni-Fe sulfides, alloys). In many circumstances, this process releases substantial amounts of hydrogen. Since the compositional controls of the primary lithology on the secondary mineralogy, fluid composition, Fe-distribution, and H2 formation are not well established, we used thermodynamic computations to examine the equilibrium mineral assemblages, mineral compositions and the chemistry of fluids during serpentinization of 21 different ultramafic rock compositions and 10 distinct compositions of olivine between 25°C and 400°C at 50MPa. Our models predict some systematic differences between serpentinization of olivine-dominated lithologies (i.e. peridotite) and of orthopyroxene-dominated lithologies (i.e. pyroxenite). Most notably, it is predicted that serpentinization of peridotite causes the formation of serpentine having elevated Fe+3/(Fe+3 +Fe+2) values, Fe-bearing brucite (at temperatures ≤ca. 320°C), and magnetite (at temperatures >ca. 200°C), while serpentinization of pyroxenite does not produce magnetite, but instead forms Fe-rich serpentine with relative low Fe+3/(Fe+3 +Fe+2) values and Fe-poor talc. The predicted activities of dissolved hydrogen (aH2(aq)), dissolved silica (aSiO2(aq)), as well as the pH vary accordingly. At temperatures ≤ca. 350°C, fluids interacting with peridotite are more reducing, have lower aSiO2(aq) and higher pH than fluids interacting with pyroxenite. A direct correlation between the iron content of olivine, its stability relative to water, temperature and aH2(aq) is apparent from our calculations. In contrast to forsterite-rich olivine, fayalite-rich olivine can be stable to temperatures as low as 180°C in the presence of water. As a consequence, the predicted aH2(aq) for serpentinization of fayalite is maximal at temperatures ≤180°C. [ABSTRACT FROM AUTHOR]

Abstract: Phase equilibria of α, β, and γ (Mg,Fe)2SiO4 are important to understanding the mineralogy of the Earth’s upper mantle. Using the first principles approach, we studied thermodynamic properties and phase stability fields of Fe2SiO4. We show that the correct phase transition sequence in Fe2SiO4 (α→γ) can be obtained with the DFT+self-consistent Hubbard U method, while standard DFT methods (LSDA and σ-GGA) as well as the DFT+constant U method fail the task. The vibrational virtual crystal approximation was used to derive the phonon density of state of the Fe2SiO4 polymorphs. High-pressure thermodynamic properties of Fe2SiO4 are then derived with the aid of the quasi-harmonic approximation. They are in very good agreement with experiments. The phase diagram of the (Mg,Fe)2SiO4 system is calculated under the assumption of ideal mixing within α, β, and γ solid solutions. The model permits the investigation of the temperature and pressure effects on the phase boundaries. The widths of the divariant α–β and β-γ loops are barely sensitive to temperature between 1473 and 1873K. This study shows the promise of applying the DFT+self-consistent Hubbard U method to study phase equilibria of iron-bearing Earth minerals. [Copyright &y& Elsevier]

Abstract: Glass-ceramics based on blast-furnace slag (56.78wt%) were prepared by mixing quartz sand, dolomite, limestone, clay as other batch constituents. The nucleating agents Cr2O3, LiF, CaF2 and TiO2 were added to the batches to study their effects on the crystallization, phase assemblages, and microstructure. Glass-ceramics were obtained by single and double heat-treatment schedules and examined by DTA, XRD and polarizing microscope. The presence of Cr2O3, TiO2, CaF2 and LiF was found to enhance the crystallizability of the glass. Cr2O3 and TiO2 are much better than LiF and CaF2 in promoting homogeneous nucleation and the formation of extremely fine-grained microstructure of aluminous pyroxene and magnetite. [Copyright &y& Elsevier]

Abstract: The phase transformation of a silica-rich iron ore during planetary milling has been studied. A mixture of silica-rich low grade iron ore and iron powder (4.75wt.%) was subjected to high energy ball milling and the resulting products were characterized at various milling times. The major constituents of the silica-rich iron ore are hematite (54.2%) and quartz (44.6%). Upon milling, these phases have undergone phase transformation to form fayalite (Fe2SiO4) as the major phase along with unreacted quartz as the minor phase. X-ray and Mössbauer spectroscopy studies confirmed the formation of fayalite phase. It was observed that the optimal constitution of the product, in which fayalite is the major phase, could be attained within 15h of milling. [Copyright &y& Elsevier]

Abstract: Dissolution of fayalite has been monitored in a small size batch reactor at a constant pressure of 30MPa and temperatures of 50, 65, 80 and 100°C, either in dilute HCl or in acetate buffered solutions. The technique, based on in situ X-ray absorption spectroscopy measurements, allowed simultaneous measurements of aqueous iron concentration and speciation as a function of time under high pressure and high temperature conditions. Far from equilibrium, dissolution rate normalised to geometric surface area (R net) can be described in dilute HCl solutions by:with log(k 0)=0.17±0.63 (k 0 being expressed in molcm−2 s−1); E a =45,100±4200Jmol−1; n =0.74±0.15, so that R net is expressed in molcm−2 s−1. These results are found to be consistent with some previous fayalite dissolution studies. In acetate buffered solutions, the dissolution rate was found to be enhanced and positively correlated with the activity of acetate. Whereas speciation of Fe2+ in HCl solutions is dominated by hexahydrated octahedral species, the combination of ab initio XANES calculations, measurement of X-ray absorption spectra, and thermodynamic modelling allowed us to determine that aqueous Fe2+ was complexed octahedrally with two acetate ligands, each bonded to iron through one oxygen atom, the corresponding formula being Fe(CH3COO)2·4H2O. Supposing that surface complexes resemble the major complex species in solution, this solvation by acetate ions would explain the observed enhancement of the dissolution rate, because of the nucleophilic attack of acetate ligands at the silicate surface. [Copyright &y& Elsevier]

Abstract: We have calculated the high-pressure properties of fayalite, including band structure, magnetism, equation-of-state and elastic properties using density functional theory within the generalized gradient approximation (GGA) and using the GGA +U method. We show for the first time that the addition of an on-site Hubbard repulsion term to the GGA leads to improved agreement between calculated and experimental values of structural and elastic properties, as well as electronic band gap, particularly at high pressure. High-pressure elastic instability, originating in the vanishing of the elastic constant c 44 and previously predicted on the basis of extrapolated experimental data, is found with the GGA +U method. Experimental measurements of the elastic constants agree better with the GGA +U method, than with the GGA, which calls for a reassessment of the structural and elastic properties of iron-bearing minerals calculated using standard density functional theory, which have hitherto been used to interpret the structure and dynamics of the mantle. The improvement can be related to the better description of magnetic structure: without the Hubbard U the magnetic moments on the iron ions decrease with pressure, whereas when it is included they remain almost constant, at least, up to the highest pressure studied. This also leads to better predictions of equation-of-state. Our calculated partial density-of-states indicate that the lowest energy excitation across the electronic band gap lies within the d-orbital manifold, and we argue that this is not observed at ambient pressure because the signal in the optical spectrum is too weak, accounting for apparent discrepancies with reported experimental values. Upon compression the nature of the gap changes due to the broadening of the 3d manifold, and this likely renders the fundamental gap observable in optical spectroscopy at high pressure, accounting for the better agreement between theory and experiment above 20GPa. We associate the changes in the character of the bands with a change in the crystal structure. [Copyright &y& Elsevier]

Abstract: We have performed petrographic characterization, 53Mn–53Cr age determination and thermodynamic stability evaluations of fayalite in Vigarano meteorite that belongs to the reduced subgroup of CV3 chondrites. Vigarano is a breccia consisting of clasts which are separate chondrules surrounded by olivine-rich fine-grained materials. Four out of twenty three explored clasts contain fayalites that represent materials of the Bali-like oxidized subgroup of CV3 chondrites. The fayalites (Fa>80) with grain sizes typically <20 µm occurs in veins that extend from chondrules into the fine-grained materials. The fayalite commonly coexists with troilite and/or magnetite. The fayalite-bearing veins terminate at the boundaries of clasts. No evidence of strong impact enough to make melt veins is found in materials adjacent to the veins. These observations suggest that the fayalite-bearing veins in the Bali-like clasts formed through aqueous alteration in an asteroid prior to fragmentation and re-accretion to the Vigarano parent body. In saponite-rich fine-grained materials, we also found troilite–magnetite veins, which are similar to the fayalite-bearing veins in morphology. Morphological evidences and thermochemical equilibrium calculations suggest that fayalite replaced magnetite, and that replacement occurred at temperatures <200 °C and low water/rock mass ratios from 0.07 to 0.18, which represent aqueous to metamorphic transition. Fayalite grains typically show iron-magnesium zoning (fayalite content decreases towards the grain edges). Based on equilibrium models, this zoning may have occurred at increasing temperature. The observed initial ratio of (53Mn/55Mn)0 =(2.3±0.5)×10−6 suggests that fayalite formed ~5 Ma before the timing when the Mn–Cr system was closed in angrite NWA 4801 and has an absolute age of ~4563±1 Ma. The age of fayalite is identical within errors to that in Mokoia and Kaba CV3 chondrites, which belong to the Bali-like oxidized subgroup. The identical age implies that aqueous alteration occurred at the same time in parent asteroids of Bali-like subgroup materials. These fayalite-bearing materials may have been derived from a single CV3 asteroid or from separate CV3 asteroids where aqueous alteration simultaneously occurred. [Copyright &y& Elsevier]

Abstract: Discarded slags have potential adverse environmental impact and valuable metal contents. High pressure oxidative acid leaching (HPOXAL) was employed to clean a slow-cooled copper–nickel flash smelter slag containing about 1% Cu and 1% Ni and selectively leach the contained base metal values. Characterization of the slag and leach residues was carried out using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and particle size analysis (PSA). It was found that the copper–nickel smelter slag was composed of major crystalline fayalite and minor amorphous silica phases with trace amounts of magnetite and entrapped matte, existing as uneven and finely dispersed particles, which are responsible for the loss of base metals. Most of the copper in the slag appeared as sulfide, while most of the nickel existed in the oxide form with a minor portion as sulfide. Cobalt and zinc phases were rarely detected because of their low content. During high pressure oxidative acid leaching, temperature and acidity were the key variables controlling the leaching of the base metals and iron. At 250 °C and 20% acid addition, >99% Ni, Co and Cu could be extracted into solution together with 94% Zn and <2.2% Fe. Iron and silicon were transformed into crystalline hematite and amorphous silica in the residue. By adjusting the acidity to control the rate of fayalite dissolution and the growth of precipitates, flower-like hematite particles associated with amorphous silica were produced. An excellent slurry filtration rate of 0.36 m3·m−2·h−1 was obtained. [Copyright &y& Elsevier]

The present study investigates the effect of Si on the oxide morphology and picklability of automotive steels. It was observed that in steels containing high levels of Si, Si exists as a non-stoichiometric fayalite (Fe2.44Si0.55O4) phase, and such a phase is not easily picklable. It was also noted that as the amount of Si increases, the pickling kinetics becomes slower. Hence the amount of Si should be kept low for automotive and other applications where a surface finish is required. [Copyright &y& Elsevier]

Abstract: Within the Panxi rift of the Permian Emeishan large igneous province (ELIP), SW China, a 20 km2 quartz-bearing fayalite syenitic pluton intrudes the 260 Ma Baima igneous complex (BIC). The fayalite syenite is dated using SHRIMP zircon U–Pb techniques at 252±2.5 Ma. The Panxi fayalite syenite is mainly composed of alkali feldspar, ferroan augite, fayalite, quartz and Fe–Ti oxides and contains 61.8–63.7 wt.% SiO2, 5.0–7.3 wt.% Fe2O3 t and 9.9–12.1 wt.% total alkalis, belonging to an A-type variety of ferroan alkalic metaluminous granitoids. The fayalite syenite displays positive Eu anomalies (Eu/Eu⁎ =0.9–8.9) and is enriched in LREE [(La/Yb) N =6.6–11.5]. The ɛNd values and (87Sr/86Sr)initial ratios of the fayalite syenite range from +1.3 to +1.9 and from 0.7035 to 0.7068, respectively. The fayalite syenite and the BIC had the same mantle source; however the 8 myr age gap between them suggests the fayalite syenite formed by remelting of underplated mafic magmas injected into the crust during ELIP magmatism. The ages of the fayalite syenite and BIC are coincident with two Permian mass extinction events and suggest that ELIP may have influenced both. [Copyright &y& Elsevier]

Abstract: The ice-covered Öræfajökull stratovolcano is composed mostly of subglacial pillow lava and hyaloclastite tuff, ranging from basalt to rhyolite. A large devastating plinian eruption in 1362 AD produced 10 km3 (2 km3 DRE) rhyolitic ash and pumice from a vent within the summit caldera, with fallout mainly towards ESE. The ejected rhyolite magma with 0.5–1% crystals of oligoclase, fayalite, hedenbergite, ilmenite and magnetite was remarkably homogenous throughout the eruption. A 1.8 m thick tephra section on the SE flank of the volcano has 14 recognizable units. The tephra is dominated by fine-grained vesicular glass with bubble wall thickness of 1–5 μm. The high and even vesiculation of the glass indicates fast magma ascent and explains the extreme mechanical fragmentation within the eruptive column. The grain-size distribution indicates time-variable intensity of the plinian eruption with three evenly spaced phases of maximum fragmentation. An initial vent-clearing explosion produced phreatomagmatic debris with up to 35% lithic fragments. The low abundance (<3%) of lithic fragments during the subsequent eruption indicates that the conduit and vent remained stable. The tephra fallout deposit is characterized by upwards increasing pumice dimensions and occasional bomb-like pumice blocks, indicating less mechanical fragmentation during contraction and lowering of the plinian column. A conservative estimate of 20–40 km3 for the total volume of the magma reservoir is based on the erupted volume of highly differentiated and homogeneous rhyolite. The 365-year period between 1362 and a minor benmoreitic eruption in 1727, and the absence of currently detectable magma reservoirs in the crust below Öræfajökull show that differentiated crustal magma chambers feeding large plinian eruptions can be established and disappear on a 100–500 year timescale. [Copyright &y& Elsevier]

Abstract: An oxidative pressure acid leaching process was investigated for the extraction of Ni/Co/Cu/Zn metal values from base metal smelter slags. The process is applicable to smelting furnace dump slags, as well as to mid-stream converter slags. In addition to the economical advantages, extracting the base metal values from the dump slags produces an environmentally benign residue. To produce high level of extraction for the metal values, it is necessary to have the slag in crystalline structure. This, in turn, requires cooling the molten smelter slags sufficiently slowly during solidification. It was shown that if the same slags are quenched in water thereby producing an amorphous structure, the resulting metal extractions are substantially lower. The role of oxygen in the leaching reactions was also tested. The presence of oxygen is necessary for successful leaching of the metal values. After fine grinding, the slags were subjected to pressure acid leaching at 250 °C with an oxygen overpressure of 520 kPa. Sulfuric acid at a typical 0.3 acid to slag ratio was employed. Extractions higher than 90% of each of the nickel, cobalt, copper and zinc were achieved. Operating at 250 °C ensures that the concentration of Fe and Al impurity metals in leached solution remains very low. It was finally found that for high concentrations of divalent metals (Ni+Co+Cu+Mg) in the slag, a much higher quantity of sulfuric acid than the stoichiometric value is required. The latter is due to the drop of hydrogen ion concentration due to bisulphate formation. [Copyright &y& Elsevier]

Abstract: We measured (U–Th)/He ages of fayalite and hedenbergite phenocrysts with britholite and chevkinite inclusions from the ∼1.6 Ma Otowi (Lower) Member of the Bandelier Tuff, Jemez Volcanic Field. U and Th, the major parent nuclides of radiogenic 4He, are concentrated in britholite and chevkinite inclusions and are essentially absent from the host grains. We analyzed 36 fayalite (21 non-abraded+15 abraded) and 13 hedenbergite (7 non-abraded+6 abraded) phenocrysts, and applied alpha-ejection corrections assuming uniform intracrystalline distributions of inclusions and parent nuclides in the phenocrysts. A subset of phenocrysts was subjected to abrasion to remove the alpha-ejection affected regions. The alpha-ejection correction factors (F T ) of the non-abraded samples range between 0.90 and 0.96, whereas those of the abraded samples are virtually unity. The fayalite and hedenbergite crystals yield mean ages of 1.60±0.10 Ma (S.D.) and 1.69±0.13 Ma, respectively. The overall mean age of 1.62±0.11 Ma (S.D.) is indistinguishable from previously published 40Ar/39Ar ages of 1.61±0.01 Ma (1σ). Our results suggest that other inclusion-bearing volcanic phenocrysts and their host units may be dateable by the (U–Th)/He method. [Copyright &y& Elsevier]

The electronic structure and magnetism in fayalites M2SiO4 (M=Fe and Co) have been studied by density functional theory within the generalized gradient approximation with the on-site Coulomb energy taken into account (GGA+U). Stable insulating antiferromagnetic solutions are obtained. It is found that the gap opening in these fayalites results mainly from strong on-site Coulomb interactions of the magnetic atoms. In the band structures, the conduction bands originate mainly from the M(3d) orbitals of M2SiO4. The top of valence bands consists of the Fe (3d) orbitals in Fe2SiO4, and of the Co(3d)–O(2p) hybridization in Co2SiO4. All calculated orbital magnetic moments are very small. [Copyright &y& Elsevier]

An experimental technique for in situ stress and strain measurements at high pressure and temperature using synchrotron X-rays has been developed at the X17B beamline of the National Synchrotron Light Source. The strain is measured by correlating sample-length marks in recorded X-ray radiographs. The stress is measured by simultaneously collecting energy-dispersive X-ray diffraction patterns of the sample in two perpendicular diffraction planes. Differential stress in the sample is derived from the different lattice strains along the different orientations relative to principal stress direction. Example measurements are conducted to study rheological properties of fayalite. Accuracy of the measurement is about 10–100 MPa for stress and about 10-4 for strain. [Copyright &y& Elsevier]

The Younger Granites of Nigeria, emplaced in the basement complex 213–141 Ma ago, occur in the form of ring complexes. About 50 complexes are known with the town of Jos approximately in the center of the area. Apart from biotite granite (main rock type) granites and porphyries occur that contain olivine, pyroxene, amphibole, and mica. Granites and porphyries of five ring complexes were investigated in this study. These are the Jos-Bukuru, Shere, Ganawuri, Rop, and Ririwei complexes.Among the granitic minerals (feldspar and quartz) mafic clots were observed being mainly rounded to oval in shape (300 μm to 3 mm) often showing reaction rims and corroded outlines. These clots contain extremely iron-rich minerals: Olivine, exclusively found in the granites, is represented by nearly pure fayalite; Ca–Fe pyroxene, restricted to rocks (granites and porphyries) of the Shere complex, consist of hedenbergite and iron-rich augite; calcic amphiboles (occurring in all complexes) have Mg/(Fe2+ + Mg)-ratios mainly below 0.2 and vary from hastingsite via ferro-edenite to ferro-hornblende and ferro-actinolite; and mica (not observed in the Rop complex) consist nearly of the annite endmember.With decreasing temperature (lying in the range 850–600 °C) the following mineral succession was found: fayalite, Ca–Fe pyroxene, calcic amphibole, and annite. These minerals were directly formed from the melt. Due to cooling and resulting disequilibrium conditions, the primary minerals became unstable and were replaced by a variety of minerals of sub-solidus origin and a temperature lower than 600 °C. Fayalite decomposes into grunerite + magnetite or alters into ferro-saponite; pyroxene is rarely replaced by calcic amphibole and often by an unidentified water-rich mineral; calcic amphibole may be replaced by titanite and ilvaite or decomposes into grunerite, chlorite and stilpnomelane; and annite into chlorite (iron-rich chamosite or delessite).Different in composition are pyroxene and amphibole of the albite-rich granite of the Ririwei complex where fayalite and annite do not occur. Pyroxene is dominated by the aegirine endmember and amphibole is arfvedsonite. The formation of these minerals is attributed to sodic metasomatism and higher oxygen fugacity conditions than observed in the other rocks. [Copyright &y& Elsevier]

Shock-wave equations of state (EOS) of initially solid (300 K) and molten (1573 K) fayalite (Fe2SiO4, Fa) are measured over the pressure ranges of 23–212 and 5–47 GPa, respectively. The 300 K data indicates that Fa undergoes a phase change from the low-pressure olivine structure (Lpp) over the 35–55 GPa range. In agreement with earlier analyses of Rockport fayalite shock data and diamond cell recovery experiments, the high pressure phase (Hpp) data are consistent with an oxide (2FeO+SiO2, stishovite) mixture. A fit to the Hpp Hugoniot data in the shock velocity (uS)–particle velocity (uP) plane yields: uS=4.07 (0.22) km/s + 1.43 (0.06)uP. Here, the initial density, ρ0 is 4.375 (0.027) Mg/m3.The 1573 K data yields: uS=2.63 (0.02) km/s + 1.59 (0.01)uP. Initial density calculated from temperature data is 3.750 (0.018) Mg/m3 and K0S=25.9±0.4 GPa, and K0S′=5.36±0.04 GPa. The bulk modulus, K0S, compares favorably with Agee’s result [Geophys. Res. Lett. 19 (1992a) 1169], 24.4 GPa, but the pressure derivative is much less than the K0T′=10.1 GPa previously reported.Molten Fa compression data >40 GPa are closely fit with an ideal mixture of oxides, SiO2 (stishovite) + 2FeO (Lpp), in support of the hypothesis of Rigden et al. [J. Geophys. Res. 94 (1989) 9508].A model molten basalt incorporating previous molten anorthite (An)–diopside (Di) eutectic and the present molten Fa (EOS) data implies that a zone of basic silicate liquid, could be neutrally buoyant at a depth of ∼250–400 km, upon partial melting of a peridotite mantle as discussed by Rigden et al. [Science 226 (1984) 1071]. This conclusion is based on comparison of the density of the model basalt: (An0.36Di0.64)0.85Fa0.15, with Dziewonski and Anderson’s Preliminary Reference Earth model [Phys. Earth Planet. Inter. 25 (1981) 297]. [Copyright &y& Elsevier]

• Geochemically, Lan / Ybn ratios (7.95 and 9.07) indicate greater LREE enrichment than HREE. • Spectral ID of Raman of ignimbrites determines anorthoclase, fayalite, hematite, and bitovnite. The different colors may be from high Th, U and Fe-Ti oxide minerals. • The fayalite which rarely seen in ignimbrites is determined in Bitlis ignimbrite. • In formation of ignimbrites were effective devitrification, cooling and gravitational differentiation. The mineralogy, trace and minor element geochemistry and different color changes of Bitlisignimbirite (eastern Turkey) were measured with Neutron Activation Analysis and Confocal Raman spectrometr methods. From these analyzes, were determined three levels as lower, middle and upper according to texture, color, welded degree, component and chemical differences in Bitlis ignimbrites in study area. The most distinguishing feature observed in black, red and grey color ignimbirite levels are partially mineralogical compositions, fiamme geometry and appearance of different colors. The mineralogical compositions of all levels are plagioclase, feldspar, augite, fayalite, biotite, sanidine, hematite and Fe-Ti oxide (titanomite, ilmenite) minerals. The matrix consists of quartz, anorthoclase, Fe-Ti oxide and sanidine. In addition, the matrix rarely contains glassy and dispersed mineral microliths, apart from intermediate levels of iron oxide/hydroxides. The intermediate levels have higher Fe-Ti oxide composition than others. The hydrous minerals in all ignimbrite levels have been partially replaced by devitrification minerals. The fayalite, which rarely seen in ignimbrites is determined by Raman spectroscopy method in Bitlis ignimbrite. The Raman spectra of different colored ignimbirites obtained using Confocal Raman spectroscopy showed different spectra between 869 and 3062 cm−1 for the grey, black, and reddish colored ignimbirites. In spectral ID are determined anorthoclase, fayalite, hematite, bitovnite minerals. The REEs patterns of ignimbrites normalized to chondrite are similar each other. All of them show a decrease from high LREE to HREE. The LREE enrichment and La n /Yb n ratios (7.95–9.07) in ignimbrites is the sign of the liquid-rich calalkaline magmatic source. The cerium anomaly shows the decrease in solubility accompanying the oxidation of Ce (+3) to Ce (+4). The different color levels of ignimbrites can be summarized as cooling, iron oxide/iron hydroxides ratios (high in middle level), volatile elements (U,Th,Cl) (low in middle levell), devitrification of volcanic glass and chemical reactions. [ABSTRACT FROM AUTHOR]

• Glycolipids have the potential to leach metals from low grade secondary materials. • Acidic sophorolipids selectively leach copper sulfide species/metallic copper from fayalite (27%) and CuS tailings (53%) • CuS and Cu(0) extraction from the fayalite occurs through acidification and oxidation mechanisms. With the global demand for economically important metals increasing, compounded by the depletion of readily accessible ores, secondary resources and low-grade ores are being targeted to meet growing demands. Novel technologies developed within biobased industries, such as microbial biosurfactants, could be implemented to improve the sustainability of traditional hydrometallurgy techniques. This study investigates newly developed microbial biosurfactants (acidic- and bolaform glycolipids) for the leaching of metals (particularly Cu and Zn) from a suite of mine tailings, metallurgical sludges and automotive shredder residues. Generally, acidic sophorolipids were the most performant, and optimal Cu leaching was observed from a fayalite slag (27%) and a copper sulfide mine tailing (53%). Further investigation of the leached fayalite material showed that leaching was occurring from small metallic Cu droplets in this material via a corrosion-based mechanism, and/or from Cu-Pb sulfides, selective against the dominant Fe-silicate matrix. This study highlights that acidic sophorolipid microbial biosurfactants have the potential to leach Cu and Zn from low-grade secondary materials. It also provides important fundamental insights into biosurfactant-metal and mineral interactions that are currently unexplored. Together, the convergence of leaching and mining industries with bio-industries can improve material recovery and will positively impact the bio- and circular economies and the environment. [ABSTRACT FROM AUTHOR]

• Viscosity of Fe 2 SiO 4 liquid is lower than that of Mg 2 SiO 4 liquid. • Iron content has little effect on the adiabat of (Mg,Fe) 2 SiO 4 liquid in a magma ocean. • The upper bound of the potential temperature for crystallization is 3250 K. • The viscosity of an early magma ocean may be several mPa s. The initial cooling stage and crystallization of a magma ocean were significantly affected by the thermodynamics and viscosity of iron silicate liquid. Here, we use first-principles molecular dynamics based on density functional theory plus the Hubbard U method to study the structures, thermodynamics and viscosities of Fe 2 SiO 4 liquid at 3000–6000 K under pressure conditions spanning the entire mantle. Our calculations show that the compressibility of Fe 2 SiO 4 liquid is weakened at pressures above 50 GPa. The densification of Fe 2 SiO 4 liquid under compression is mainly manifested by a decrease in the distance among Si–O polyhedra and an increase in the cation-anion coordination number. We find that the viscosity of the Fe 2 SiO 4 liquid has a positive pressure dependence, and the effect of pressure on viscosity decreases with increasing temperature. The predicted behaviour of viscosity coefficients of the Fe 2 SiO 4 liquid at different P-T conditions can be described well as: η (P , T) = exp[ − 7.89 + 0.0042 P − 0.0000632 P 2 + (3800 + 61.6 P + 0.18 P 2) / (T − 1000) ]. Compared to Mg 2 SiO 4 liquid, the viscosity of Fe 2 SiO 4 liquid is lower under the pressure of the lower mantle along isotherms. We calculate the adiabat of the Fe 2 SiO 4 liquid in a magma ocean, and the results show that the iron content has little effect on the adiabats of (Mg,Fe) 2 SiO 4 liquid in the magma ocean. Combining our calculated thermodynamic properties and viscosities with those of previous studies, the physical properties of an early magma ocean were constrained. The upper bound of the potential temperature for magma ocean crystallization is 3250 K. We constructed the range of the viscosity profile of a magma ocean and found that the lower viscosity of iron-rich silicate liquid would maintain the viscosity of an early magma ocean in the range of several mPa s. As the magma ocean starts to crystallize, the lower bound of the viscosity at the surface and the core-mantle boundary are 0.0020 Pa s and 0.0068 Pa s, respectively. The weakening of the viscosity of the iron silicate liquids would have a significant impact on the evolution of the magma ocean. [ABSTRACT FROM AUTHOR]

The oxide subscale formed on the decarburization annealing of 3% Si–Fe was investigated using microscopy and spectroscopy techniques. It was found that the morphology as well as the molecular structure of the subscale are affected by temperature and dew point. The results suggest that there is an optimum level of internal oxidation and an optimum fayalite/silica ratio in the subscale to achieve a oriented grain silicon steel having a continuous and smooth ceramic film and low core loss. [Copyright &y& Elsevier]