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Opal and calcium carbonate are thought to regulate the biological pump's transfer of organic carbon to the deep ocean. A global sediment trap database exhibits large regional variations in the organic carbon flux associated with opal flux. These variations are well‐explained by upper ocean silicate concentrations, with high opal 'ballasting' in the silicate‐deplete tropical Atlantic Ocean, and low ballasting in the silicate‐rich Southern Ocean. A plausible, testable hypothesis is that opal ballasting varies because diatoms grow thicker frustules where silicate concentrations are higher, carrying less organic carbon per unit opal. The observed pattern does not fully emerge in an advanced ocean biogeochemical model when diatom silicification is represented using a single global parameterization as a function of silicate and iron. Our results suggest a need for improving understanding of currently modeled processes and/or considering additional parameterizations to capture the links between elemental cycles and future biological pump changes. Plain Language Summary: Opal, or hydrated silica, is taken up in the surface ocean by diatoms to construct their protective frustules. Another plankton type, coccolithophores, generate protective platelets from calcium carbonate. These two minerals, and thereby plankton types, play major roles in the global carbon cycle. The 'biological carbon pump' transfers carbon from the upper ocean to the ocean's depths, where it can stay for millenia. This process has influenced past atmospheric carbon dioxide concentrations and could also do so in the future. The transfer of carbon to the deep ocean is partially regulated by the amount of 'ballast' minerals in sinking particles, especially opal and calcium carbonate, which are denser and cause particles to sink faster and/or protect organic carbon from microbial consumption. We show that unlike calcium carbonate, opal's ballasting effect varies a great deal between different regions of the ocean. The variation in opal ballasting is well‐explained by the upper‐ocean concentration of silicate between these regions. This suggests a simple explanation: when silicate concentrations are high, diatoms grow thick frustules which actually results in lower carbon sinking per unit opal. Capturing this ballasting–silicate relationship in carbon cycle models may improve their ability to predict future biogeochemical cycles and climate. Key Points: Opal ballasting varies by more than a factor of six across ocean regions; calcium carbonate ballasting is uniformSilicate concentration predicts opal ballasting which suggests that the latter varies with diatom frustule thicknessThis emergent relationship's absence from a sophisticated biogeochemical model indicates it holds useful information for constraining models [ABSTRACT FROM AUTHOR]

Alkaline iron (Fe) batteries are attractive due to the high abundance, low cost, and multiple valent states of Fe but show limited columbic efficiency and storage capacity when forming electrochemically inert Fe3O4 on discharging and parasitic H2 on charging. Herein, sodium silicate is found to promote Fe(OH)2/FeOOH against Fe(OH)2/Fe3O4 conversions. Electrochemical experiments, operando X‐ray characterization, and atomistic simulations reveal that improved Fe(OH)2/FeOOH conversion originates from (i) strong interaction between sodium silicate and iron oxide and (ii) silicate‐induced strengthening of hydrogen‐bond networks in electrolytes that inhibits water transport. Furthermore, the silicate additive suppresses hydrogen evolution by impairing energetics of water dissociation and hydroxyl de‐sorption on iron surfaces. This new silicate‐assisted redox chemistry mitigates H2 and Fe3O4 formation, improving storage capacity (199 mAh g−1 in half‐cells) and coulombic efficiency (94 % after 400 full‐cell cycles), paving a path to realizing green battery systems built from earth‐abundant materials. [ABSTRACT FROM AUTHOR]

Dissolved Oxygen (DO) plays a key role in reactive processes and microbial dynamics in the critical zone. Recent observations showed that fractures can provide rapid pathways for oxygen penetration in aquifers, triggering unexpected biogeochemical processes. In the shallow subsurface, DO reacts with electron donors, such as Fe2+ coming from mineral dissolution. Yet, little is known about the factors controlling the spatial heterogeneity and distribution of oxygen with depth. Here we present a reduced analytical model describing the coupled evolution of DO and Fe2+ as a function of fluid travel time in silicate catchments. Our model, validated from fully resolved reactive transport simulations, predicts a linear decay of DO with time, followed by a rapid non‐linear increase of Fe2+ concentrations up to a far‐from‐equilibrium steady‐state. The relative effects of geological and hydrological forcings are quantified through a Damköhler number (Da) and a lithological number (Λ). We use this framework to investigate the depth distribution of DO and Fe2+ in two catchments with similar environmental contexts but contrasted hydrochemical properties. We show that hydrochemical differences are explained by small variations in Da but orders of magnitude variations in Λ. Therefore, we demonstrate that the hydrological and geological drivers controlling hydrochemistry in silicate catchments can be discriminated by analyzing jointly the O2 and Fe2+ evolution with depth. These findings provide a new conceptual framework to understand and predict the evolution of DO in modern groundwater, which plays an important role in critical zone processes. Plain Language Summary: Dissolved Oxygen (DO) is involved in important biogeochemical reactions, such as the aerobic respiration of microbes, rock‐weathering or contaminant degradation. The general view is that the deeper subsurface of continents is mostly anoxic. However, recent observations have shown that cracks in rocks can allow oxygen to reach deeper down, thus extending deeper the influence of oxygen in reactions. Here, we present a modeling framework validated with field data to understand and predict the hydrological and geological controls on DO evolution in silicate catchments, shedding new light on its influence on rock‐weathering and microbial life in the continents. Key Points: We derive a reduced analytical model to predict the depth distribution of dissolved O2 and Fe2+ in silicate catchmentsThe theory, validated from a reactive transport model, quantifies the hydrological and geological controls through two dimensionless numbersWe use this framework to analyze and explain the O2/Fe2+ distributions in two sites with contrasted chemical properties [ABSTRACT FROM AUTHOR]

The first samples collected by the Mars 2020 mission represent units exposed on the Jezero Crater floor, from the potentially oldest Séítah formation outcrops to the potentially youngest rocks of the heavily cratered Máaz formation. Surface investigations reveal landscape‐to‐microscopic textural, mineralogical, and geochemical evidence for igneous lithologies, some possibly emplaced as lava flows. The samples contain major rock‐forming minerals such as pyroxene, olivine, and feldspar, accessory minerals including oxides and phosphates, and evidence for various degrees of aqueous activity in the form of water‐soluble salt, carbonate, sulfate, iron oxide, and iron silicate minerals. Following sample return, the compositions and ages of these variably altered igneous rocks are expected to reveal the geophysical and geochemical nature of the planet's interior at the time of emplacement, characterize martian magmatism, and place timing constraints on geologic processes, both in Jezero Crater and more widely on Mars. Petrographic observations and geochemical analyses, coupled with geochronology of secondary minerals, can also reveal the timing of aqueous activity as well as constrain the chemical and physical conditions of the environments in which these minerals precipitated, and the nature and composition of organic compounds preserved in association with these phases. Returned samples from these units will help constrain the crater chronology of Mars and the global evolution of the planet's interior, for understanding the processes that formed Jezero Crater floor units, and for constraining the style and duration of aqueous activity in Jezero Crater, past habitability, and cycling of organic elements in Jezero Crater. Plain Language Summary: Here we provide a narrative of sample collection and associated in situ rover observations for the rocks collected by the Perseverance rover to provide a preliminary description of the first samples of the Mars 2020 mission. These rocks collected in Jezero Crater represent the first samples from Mars with a known geologic context, the first collected with the potential to be returned to Earth for laboratory analysis, and the first cores from rock outcrops on another planet. Remote and proximal analyses indicate that all crater floor outcrops investigated are igneous in origin. Laboratory analyses of these rocks will be useful to study the planet's interior at the time of emplacement, characterize martian magmatism, and place timing constraints on geologic processes, both in Jezero Crater and more widely on Mars. All collected rocks have interacted with water and contain secondary geochemical and mineralogical evidence that can be used to understand aqueous environments in the crater and the potential conditions of habitability for ancient life on Mars. Key Points: Nine samples, consisting of four pairs of rock cores and a tube of atmospheric gas, were collected from the floor of Jezero Crater, MarsIn situ observations of crater floor outcrops, used as proxies for the samples, reveal aqueously altered igneous lithologiesPerseverance will leave one sample from each pair at the Three Forks depot and retain a second to be cached with future samples [ABSTRACT FROM AUTHOR]

Iron tailings (ITS), as solid decay absolved afterward beneficiation, are adverse to the environment. ITS to prepare zinc‐containing mesoporous silicate (MAO‐Zn) by a calcination‐crystallization method are used. An admixture of ammonium polyphosphate (APP) and MAO‐Zn can solve the problem of poor flame retardancy in rigid polyurethane foam (RPUF), giving them higher thermal stability and lower heat release. The total heat release rate and smoke factor values exhibited by RPUF‐3 are 24.52 MJ m−2 and 234.29 MW m−2 respectively, a decrease of 38.45% and 29.60% respectively compared to pure RPUF. Lower combustible and toxic gas release intensities are in RPUF‐3. Meanwhile, RPUF‐3 possesses enhanced compactness char residue with higher graphitization degree, endowing RPUF‐3 with excellent fire observed performance. This work demonstrates the potential of ITS in the fire retardancy field. [ABSTRACT FROM AUTHOR]

We report on the mineralogy, petrology, and oxygen isotopic compositions of ferroan olivine–pyroxene‐normative cryptocrystalline chondrules (Fe‐CCs) in CH chondrites and discuss their origin and the origin of other components in the genetically related CH and CB chondrites. There are two kinds of Fe‐CCs: (1) compositionally uniform (Fe/[Fe+Mg] = 0.17–0.34) chondrules with euhedral Fe, Ni‐metal grains and (2) metal‐free chemically zoned (Fe/[Fe+Mg] = 0.05–0.4) chondrules surrounded by ferroan olivine (Fa44−62) rims; the Fe/(Fe+Mg) ratio increases toward the rims. Both types contain low CaO and Al2O3 (<0.04 wt%), but relatively high contents of MnO and Cr2O3 (up to 1 wt%). Compositionally uniform euhedral Fe, Ni‐metal grains are Ni‐rich (9–20 wt%) and have subsolar Co/Ni ratio. There is a positive correlation between iron content in the metal grains and Fe/(Fe+Mg) ratio in silicate portion of their host chondrules. Some Fe‐CCs experienced postcrystallization solid‐state reduction of ferroan silicates to metallic iron. Ferroan cryptocrystalline chondrules and olivine rims have similar oxygen isotopic compositions (interchondrule Δ17O ranges from ~ −2‰ to 2‰), which are slightly 16O‐depleted relative to those of magnesian olivine–pyroxene‐normative cryptocrystalline chondrules (Mg‐CCs; Δ17O ~ −2‰) commonly observed in CBs and CHs. We suggest that the Fe‐CCs and Mg‐CCs formed in the impact plume under different redox conditions (~IW−1 and ~IW−3, respectively), which may have been controlled by heterogeneous distribution of water‐bearing phases (water ice, hydrated materials) in the collided bodies and/or in the disk. We propose the following impact plume scenario for the origin of Fe‐CCs: (1) condensation of ferromagnesian silicate melt around Fe, Ni‐metal melt droplets from a highly oxidized portion of the plume; (2) crystallization of euhedral metal grains from the supercooled ferromagnesian silicate melt followed by its solidification; (3) condensation of ferroan olivine rims around solidified Fe‐CCs; (4) high‐temperature annealing of Fe‐CCs and their rims in the plume accompanied by Fe‐Mg interdiffusion between ferroan olivine rims and their host chondrules. Subsequently, some Fe‐CC experienced solid‐state reduction to various degrees, possibly in the reduced portions of gaseous plume. The impact plume‐produced or reprocessed components in CBs and CHs include Ca,Al‐poor magnesian and ferroan cryptocrystalline chondrules; Ca,Al‐rich skeletal olivine chondrules; isotopically uniform, 26Al‐poor 16O‐depleted (Δ17O ~ −15 to −5‰) igneous CAIs surrounded by igneous forsterite rims; chemically zoned and unzoned Fe,Ni‐metal grains; and metal‐sulfide nodules. These objects are dominant in CBs and abundant in CHs. The CH chondrites also contain other high‐temperature chondritic components, which avoided processing in the plume and most likely predate the plume event: 26Al‐poor and 26Al‐rich, mostly 16O‐rich CAIs (Δ17O ~ −40 to −10‰) surrounded by Wark–Lovering rims, and porphyritic chondrules (magnesian [type I], ferroan [type II], and Al‐rich) showing a range of Δ17O (from ~ −10 to ~ +5‰). Some of these components appear to have been melted in the plume. We conclude that CH and CB chondrites contain multiple generations of chondrules and refractory inclusions formed by different mechanisms at different times and different regions of the protoplanetary disk, consistent with the hypothesis of Wasson and Kallemeyn (1990). [ABSTRACT FROM AUTHOR]

Although the seismic properties of polycrystalline olivine have been the subject of systematic and comprehensive study at seismic frequencies, the role of orthopyroxene as the major secondary phase in the shallow parts of the Earth's upper mantle has so far received little attention. Accordingly, we have newly prepared three synthetic melt‐free polycrystalline specimens containing different proportions of olivine (Ol, Fo90) and orthopyroxene (Px, En90) by hot pressing precursor powders produced with the solution‐gelation method at 1,200°C and 300 MPa. The resulting specimens (of Ol95Px5, Ol70Px30, and Ol5Px95 phase proportions) were mechanically tested by torsional forced‐oscillation from 1,300 or 1,200–400°C during staged cooling under a confining pressure of 200 MPa. Within the observational window (1–1,000 s), the shear modulus and dissipation vary monotonically with period and temperature for each of the tested specimens. There is no evidence of the superimposed high‐temperature dissipation peak reported by Sundberg and Cooper (2010, https://doi.org/10.1080/14786431003746656) for an Ol60Px40 specimen derived from natural precursor material and containing ∼1.5% melt. The forced‐oscillation data for each specimen are well‐described by a model based on an extended Burgers‐type creep function. The findings suggest that an olivine‐based model for high‐temperature viscoelasticity in upper mantle olivine requires only modest adjustment of the unrelaxed shear modulus to accommodate the role of orthopyroxene. Plain Language Summary: Olivine is the most abundant mineral phase in the Earth's upper mantle, and accordingly seismic wave speeds and attenuation within polycrystalline olivine have been studied systematically in laboratory. However, orthopyroxene, the second major phase in the upper mantle, has received less attention. In this study, we applied oscillating torque at the periods of seismic waves to synthetic olivine‐orthopyroxene samples with different phase proportions at temperatures ranging from 1,300 or 1,200°C down to 400°C. We found that, regardless of the difference in phase proportions, the strain‐energy dissipation in each of the three samples increases smoothly with increasing period and temperature, accompanied by systematic relaxation of the rigidity or shear modulus. In particular, the behavior of the sample containing 30% orthopyroxene is essentially indistinguishable from that of the sample with 95% olivine and 5% orthopyroxene. We therefore conclude that variation only of the (high‐frequency) unrelaxed modulus is needed to accommodate the role of orthopyroxene in olivine‐based seismological models. Key Points: Viscoelastic behavior of olivine‐orthopyroxene mixtures is relatively insensitive to variation of orthopyroxene concentrationAn olivine‐based viscoelasticity model requires adjustment only of the unrelaxed shear modulus to accommodate the role of ≤30% orthopyroxeneA dissipation peak and enhanced dispersion observed in a previous study of an olivine‐orthopyroxene specimen are now plausibly attributed to melt squirt [ABSTRACT FROM AUTHOR]

Chemical gardens, which are self‐organizing, abiotic, inorganic precipitates in far‐from‐equilibrium systems, are of interest for prebiotic chemistry/origin of life research and, under certain reaction systems, can be considered hydrothermal vent analogs. While the presence of different additives to chemical gardens, including phosphate and amino acids, have been explored, the reactivity of organic molecules in chemical garden systems is not well understood. Here we explored the reactivity of two metabolically important alpha‐keto acids (pyruvic acid and glyoxylic acid) and ammonia in the presence of iron‐silicate chemical gardens. While reactivity was not observed in the case of pyruvic acid, we found that glyoxylic acid formed alpha‐hydroxy acids and amino acids. We found that the observed organic reactivity can be attributed to the silicate in the exterior solution as opposed to the solid iron‐containing chemical garden structure. These results have implications for the reactivity of hydrothermal vent chimneys and their surrounding environments in iron‐ and silica‐rich systems. [ABSTRACT FROM AUTHOR]

Whether Earth's core is a significant repository of noble gases is an open question because their partitioning between liquid metal and silicate melt during core formation is poorly known. Here we calculated the He and Ar partition coefficients (D) between liquid Fe and MgSiO3 melt from 20 to 135 GPa at 5,000 K using ab initio molecular dynamics combined with thermodynamic integration. Our simulations show that DHe does not change significantly with pressure, while DAr increases strongly with increasing pressure. Furthermore, we found that the metal/silicate partitioning behaviors of He and Ar are controlled by their atomic size and the charge density properties of the host compositions. These results indicate that Earth's core is a plausible reservoir for 3He and could possibly account for the high 3He/4He ratios in the OIBs that associated with deep‐rooted plumes, but the core is unlikely to be a significant source for 36Ar. Plain Language Summary: The deep Earth source of primordial noble gases that are emitted at volcanoes is currently in active debate. Previous studies have mainly focused on the silicate mantle, but the metallic core is also a potential noble gas reservoir. In this work, by calculating the metal/silicate partition coefficients of He and Ar under conditions corresponding to core formation, we found that the concentration of He dissolved into Earth's core is much higher than that of Ar. Therefore, Earth's core could serve as a source for 3He degassing throughout geological time, but not as a source for 36Ar. Key Points: DHe is insensitive to pressure from 20 to 135 GPa, while DAr is positively dependent on pressureThe pressure dependences of DHe and DAr are controlled by the atomic size of the noble gas and the charge density of the host phaseEarth's core is a plausible source of 3He in the OIBs associated with plumes, but is unlikely to be a significant source of 36Ar [ABSTRACT FROM AUTHOR]

Reaction‐induced fracturing occurs when fluid‐rock interactions lead to the growth of a mineral phase that produces a volume increase, which perturbs the stress field and can cause fracturing in the surrounding rock. This process may occur with a positive feedback loop because, as more fractures are formed, more water can infiltrate the pore space, enhancing the kinetics of reaction. Yoshida et al. (2020, https://doi.org/10.1029/2020JB020268) have studied and modeled reaction‐induced fracturing in oceanic rocks collected during the Oman Drilling Project. These rocks have been intensively hydrated by a process called serpentinization, which has profound geodynamic implications. The authors couple detailed microstructural observations and numerical modeling of reaction‐induced fracturing that incorporates permeability evolution. Building on the outcomes of their study, I discuss here the current knowledge of the reaction‐induced fracturing process, in which chemical forces control rock fracture in various geological environments. Based on recent experimental results and molecular dynamics simulations, I discuss the conditions under which reaction‐induced fracturing may either self‐amplify or slow down and even stop. Plain Language Summary: In the oceanic crust, rocks may interact with oceanic fluids and become hydrated, producing a new class of minerals called serpentine. These minerals have a larger specific volume (+50%) and smaller density (−25%) than the original rock. Two main hypothesis have been proposed to explain how this volume and mass difference may be accommodated: (1) either the transport of dissolved elements by intense fluid circulation removes significant mass from the original rock and thus keeps a constant volume, or (2) the volume of the initial rock increases by the opening of fractures that accommodate the volume increase of the new minerals. Rocks collected during the Oman Drilling Project have recorded microstructures that demonstrate that this second hypothesis better matches the observations. Both detailed observations of oceanic rocks and mechano‐chemical numerical simulations demonstrate that as mineral transformation occurs, the generated stresses are high enough to fracture the surrounding rock, and accommodate volume expansion. This mechanism, called reaction‐induced fracturing, involves an intricate coupling between chemical and mechanical forces that could self‐amplify or self‐stop the overall rock transformation process. Key Points: Couplings between chemical and mechanical forces may lead to rock fracturing, with important geodynamic consequencesThis process is called reaction‐induced fracturing and involves positive and negative feedback loopsSerpentinization of the Oman ophiolite rocks is controlled by reaction‐induced fracturing [ABSTRACT FROM AUTHOR]

The effect of pressure on grain‐growth kinetics of olivine was investigated up to 10 GPa at 1773 K under relatively water‐poor conditions. The results are interpreted using a relation dn−d0n=k0texp(−(Ek∗+PVk∗)/RT) to obtain the activation volume Vk∗ = 5.0 ± 1.1 cm3/mol for n = 2 or Vk∗ = 5.2 ± 1.1 cm3/mol for n = 3. The small activation volume means that grain‐growth kinetics in pure olivine aggregates is fast even in the dry deep upper mantle, implying that grain‐size is controlled by the pinning by other phases or by dynamic recrystallization except for the early stage after the phase transformation from wadsleyite in upwelling materials. The present results are applied to seismic wave attenuation that is likely controlled by grain‐boundary processes. The inferred peak in attenuation just below the oceanic lithosphere‐asthenosphere boundary from the NoMelt array is difficult to be explained by the pressure effects assuming the absorption band behavior because such a model requires a much larger activation volume than determined in this work and it also fails to explain high attenuation in the deep asthenosphere. This suggests that either melt accumulation or other processes such as elastically accommodated grain‐boundary sliding (EAGBS) is responsible for the peak in attenuation. The present results are also applied to EAGBS. We suggest that the deep upper mantle is likely to be relaxed by EAGBS, which implies that the shear velocity of the deep upper mantle can be several percent smaller than that inferred from single crystal elasticity. Plain Language Summary: Processes involving grain‐boundaries play an important role in Earth's interior. They include seismic wave attenuation and resultant reduction in seismic wave velocities. These properties are controlled by thermally activated processes, and hence they are expected to be sensitive to pressure. However, direct experimental studies in seismic attenuation are difficult under high‐pressure conditions. In this study, we performed experiments of grain‐growth in olivine (the dominant mineral of the Earth's upper mantle) at various pressures and applied the experimental data to discuss how the propagation of seismic waves in the Earth's mantle is affected by grain boundary‐related processes. Key Points: The activation volume of grain‐growth in olivine aggregates was experimentally determinedA small pressure effect was observed, indicating that grain‐growth is fast even in the deep upper mantle unless pinning is effectiveThe anelasticity in the deep upper mantle is evaluated under the assumption that it has a similar activation volume as grain‐growth [ABSTRACT FROM AUTHOR]

Alteration of mantle peridotite in the Samail ophiolite forms secondary minerals, mainly serpentine and Mg‐rich carbonates. Magnesium accounts for ∼25 – 30% of peridotite mass and its mobility can be used to trace this alteration. We report the first set of Mg isotope measurements from peridotites and their alteration products in Oman. Partially serpentinized peridotites have Mg isotope ratios that are indistinguishable from estimates for the average mantle and bulk silicate earth (δ26Mg = −0.25 ± 0.04‰). However, more extensively altered peridotite samples show large shifts in Mg isotopic composition. The range of δ26Mg values for our suite of alteration products from the mantle section is ∼4.5‰ (from −3.39‰ to 1.19‰), or >60% of the total range of terrestrial variability in δ26Mg values. Serpentine veins are typically enriched in 26Mg (max δ26Mg value = 0.96‰) whereas Mg‐carbonate veins are associated with low 26Mg/24Mg ratios (magnesite δ26Mg = −3.3‰, dolomite δ26Mg = −1.91‰). Our preferred explanation for the range in δ26Mg values involves coprecipitation of serpentine and carbonates at water‐to‐rock ratios >103. The coincidence of alteration products characterized by δ26Mg values that are both lower and higher than bulk silicate Earth and the finite 14C ages of the carbonates suggest that both serpentinization and carbonation are ongoing in Oman. Rates of calcite precipitation in travertines inferred from Δ26Mgcal‐fl suggest that travertine formation in Oman sequesters a total of 106–107 kg CO2/yr, consistent with previous estimates. Key Points: The range of δ26Mg from samples of the mantle section in the Oman ophiolite is ∼4.5‰, or >60% of the total range of terrestrial variabilityThe range in δ26Mg values involves coprecipitation of serpentine and carbonates at high water‐to‐rock ratiosSerpentinization and carbonation are ongoing in the mantle section of the Oman ophiolite [ABSTRACT FROM AUTHOR]

Lithium iron silicate (LFS) attracts a lot of attention due to its 330 mAh g−1 theoretical capacity (2 Li+ per formula unit). However, inherently it exhibits poor Li‐ion intercalation kinetics, interfacial reactivity, and complex phase transitions resulting in lower than one Li+ capacity and poor retention. In this work, a core–shell architecture is devised largely overcoming these obstacles. At first, the nanostructure of Pmn21 LFS is annealed via mechanochemical processing enabling the activation of Li‐ion diffusion. Subsequently, the LFS nanocrystals are coated via in situ poly(3,4‐ethylenedioxythiophene) (PEDOT) polymerization involving partial chemical de‐lithiation/re‐lithiation, the latter catalyzed with FeCl3. As a result of the devised mechanochemical/interphasial engineering of the LFS@PEDOT nanocrystals, their Li‐ion storage capacity is augmented to > 1 Li, namely 200 mAh g−1 after 50 cycles or 1.2 Li+ units—the highest capacity reported for the Pmn21 LFS cathode. A key attribute of the new PEDOT coating technique is the generation of a Fe3+‐rich subsurface layer that contributes to structure stabilization via accelerated phase transition to inverse Pmn21 phase, in addition to rendering the nanocrystals electronically conductive and protected against reaction with electrolyte. Such core–shell engineered nanocrystals provide a powerful paradigm in developing viable high energy density cathodes for next‐generation Li‐ion batteries. [ABSTRACT FROM AUTHOR]

BACKGROUND: The aim of this work was to develop a cheap and easy method for the synthesis of porous iron oxide/iron silicate composite materials in the form of spheres to replace their corresponding counterparts in powder form. Macrospheres with diameters in the range 1.2–1.3 mm were prepared by the spray‐gelling technique using the multi‐templating method. Iron nitrate and tetraethyl orthosilicate were used as iron and silica sources respectively. Chitosan played a dual role (pore‐ and shape‐generating agent), while other inexpensive and easily accessible biomaterials including yeast and gelatin were used as pore generators. By this technique can be obtained metallosilicates or metal oxides/metallosilicates containing high amounts of metal incorporated within the silica framework. RESULTS: The iron oxide/iron silicate composite beads were characterized by nitrogen sorption, scanning electron microscopy (SEM), energy‐dispersive X‐ray (EDX), Fourier transform infrared (FTIR), Raman, X‐ray diffraction (XRD), diffuse reflectance (DR) ultraviolet (UV)–visible and X‐ray photoelectron spectroscopy (XPS) analyses. Wide angle XRD indicated the presence of iron oxides on the surface of sample. XPS, FTIR, Raman and UV–visible analyses showed that the samples contained both intra‐framework as well as extra‐framework iron species. SEM images indicated that the macrospheres were endowed with large pores. The iron oxide/iron silicate beads exhibited good catalytic activity in the hydroxylation reaction of phenol with hydrogen peroxide. CONCLUSION: This synthesis method allowed the obtaining of spherical shaped particles with large pores which exhibited good mechanical, thermal and chemical stability. Owing to their size, hardness and shape, these materials can be easily handled, recovered and reused. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The thermodynamic properties of iron silicate liquids at high pressures and temperatures are poorly constrained, even though they are important for understanding the thermal and chemical evolution of a magma ocean. Here we report the results of the P‐V‐T equation of state, thermodynamic properties, and spin transition of iron in FeSiO3 liquid at 2500–6000 K and pressure conditions spanning the entire mantle using first‐principles molecular dynamics simulations. Our calculations predict that FeSiO3 liquid undergoes a linear high‐to‐low spin transition over a broad pressure interval (>296 GPa), and the spin state of iron in FeSiO3 liquid is mainly the high‐spin state near the conditions of the core‐mantle boundary. Our results of FeSiO3 liquid adiabats show that iron content has little effect on the adiabatic temperature profile of liquid (Mg,Fe)SiO3 in a magma ocean. Plain Language Summary: A magma ocean is likely to have existed in the early history of Earth due to terrestrial planet accretion and the Moon‐forming giant impact. The thermodynamic properties of silicate liquids have significant effects on the evolution of the magma ocean which are closely related to compositions and structures of the modern mantle. However, thermodynamic properties of iron silicate liquid are poorly constrained, and the concentration of iron silicate liquid was likely higher than that today in an early magma ocean. In this study, we report the thermodynamic properties and spin transition of iron in FeSiO3 liquid using first‐principles molecular dynamics simulations. Our calculations show that the FeSiO3 liquid undergoes a linear transition from a high‐spin to low‐spin state over a broad pressure interval. Surprisingly, the addition of iron has little effect on the temperature structure of a magma ocean. Our results provide new insight into the evolution of the magma ocean. Key Points: The P‐V‐T equation of state of FeSiO3 liquid at deep‐mantle conditions is investigatedIron in FeSiO3 liquid undergoes a linear transition from a high‐spin to low‐spin state over a broad pressure interval (>296 GPa)Iron content has little effect on the adiabatic temperature profile of liquid (Mg,Fe)SiO3 in a magma ocean [ABSTRACT FROM AUTHOR]

Abstract: The molecular structures of CaO–FeOx–SiO2 slags and their inorganic polymer counterparts were determined using neutron and X‐ray scattering with subsequent pair distribution function (PDF) analysis. The slags were synthesized with approximate molar compositions: 0.17CaO–0.83FeO–SiO2 and 0.33CaO–0.67FeO–SiO2 (referred to as low‐Ca and high‐Ca, respectively). The PDF data on the slags reasserted the predominantly glassy nature of this iron‐rich industrial byproduct. The dominant metal‐metal correlation was Fe–Si (3.20‐3.25 Å), with smaller contributions from Fe–Ca (3.45‐3.50 Å) and Fe–Fe (2.95‐3.00 Å). After inorganic polymer synthesis, a rise in the amount of Fe3+ was observed via the shift of the Fe–O bond length to shorter distances. This shortening of the Fe–O distance in the binder is also evidenced by the apparent rise of the Fe–Fe correlation at 2.95‐3.00 Å, although this feature may also suggest a potential aggregation of FeOx clusters. In general, the atomic arrangements of the reaction product was shown to be very similar to the precursor structure and the dominance of the Fe–Si correlation suggests the participation of Fe in the silicate network. The binder was shown to be glassy, as no distinct atom‐atom correlations were observed beyond 8 Å. [ABSTRACT FROM AUTHOR]

The operating pressure has a significant influence in the performance of a fuel cell, as it influences the output voltage via activation, ohmic, and mass transport losses. In this work, experiments with a 50 cm2 polymer electrolyte membrane (PEM) fuel cell with serpentine flow field have been carried out to investigate the effects of the operating pressure on the cell performance, with a particular analysis of the liquid water distribution within the cell. A comprehensive matrix of anode and cathode pressures was analyzed, varying the anode and cathode pressure from 1.25 to 2.00 bar (abs). Neutron imaging was used to determine the liquid water distributions within the cell for each operating condition and to assess the effect of the different operating pressures. Cell voltage was also monitored during the experiments and included in the analysis. A certain accumulation of liquid water was found in the cathode channels, were the overall liquid water accumulation was found to be more significant for higher pressures. This dependence on the operating pressure was more pronounced for lower current densities, and it was more significant for cathode pressure than for anode pressure. [ABSTRACT FROM AUTHOR]

Abstract: We investigated several olivine‐bearing, medium‐grained, ophitic to subophitic eucritic clasts from three different Antarctic howardites. Based on grain size (0.5–2 mm), these clasts could represent intrusive igneous units. Based on mineral composition (pyroxene and plagioclase), they are similar to basaltic eucrites. Elemental concentrations of the major silicates and bulk mg#, however, range from those known for basaltic eucrites to those found in cumulate eucrites. Recognizable cumulus phases are absent. Conservatively speaking, the clasts examined may simply classify as relatively coarse‐grained unequilibrated basaltic eucrites. Alternatively, at least one of the clasts showing intermediate grain size and a relatively primitive chemical composition (mg# 50) may sample a rock type that could be genetically placed between the basaltic and cumulate eucrite lines of origin. A minor, yet genetically meaningful common feature of the clasts studied is the occurrence of fayalitic olivine. Two distinct categories exist. They are (1) fine veinlets exclusively percolating through pyroxene and (2) more substantial (up to 100 μm wide) veins and/or interstitial deposits. Only the fine veinlets also contain variable amounts of anorthite, ilmenite, and troilite. Although both types of olivine are ferroan, textural aspects suggest distinct paths of generation. The fine veinlets are best explained by decomposition of relatively FeO‐rich, heterogeneous, and locally metastable pyroxene, caused in situ by impact heating and subsequent fast cooling. The wider, often very ragged‐looking monomineralic olivine fillings, on the other hand, may represent the iron‐enriched portion of a highly fractionated magma. [ABSTRACT FROM AUTHOR]

Abstract: Banded iron formations (BIFs) represent chemical precipitation from Earth's early oceans and therefore contain insights into ancient marine biogeochemistry. However, BIFs have undergone multiple episodes of alteration, making it difficult to assess the primary mineral assemblage. Nanoscale mineral inclusions from 2.5 billion year old BIFs and ferruginous cherts provide new evidence that iron silicates were primary minerals deposited from the Neoarchean ocean, contrasting sharply with current models for BIF inception. Here we used multiscale imaging and spectroscopic techniques to characterize the best preserved examples of these inclusions. Our integrated results demonstrate that these early minerals were low‐Fe(III) greenalite. We present potential pathways in which low‐Fe(III) greenalite could have formed through changes in saturation state and/or iron oxidation and reduction. Future constraints for ancient ocean chemistry and early life's activities should include low‐Fe(III) greenalite as a primary mineral in the Neoarchean ocean. [ABSTRACT FROM AUTHOR]

We have studied the gamma/X-ray interaction parameters such as mass attenuation coefficient, mean free path (λ), half value layer, 10th value layer, energy-absorption buildup factors, and variation of electrical conductivity with the energy of gamma/X-ray between 1 keV and 100 GeV for Kondo insulators such as FeSi, Ce3Bi4Pt3, SmB6, YbB12, CeNiSn, CeRhSb, CeRuSn, and CeFeP. The variation of photon interaction parameters with incident energy of gamma/X-ray is graphically represented. We have also identified the X-ray absorption edges for the Kondo insulators. This identified X-ray absorption edges are useful in the characterizing of Kondo insulators such as FeSi, Ce3Bi4Pt3, SmB6, YbB12, CeNiSn, CeRhSb, CeRuSn, and CeFeP. Hence, these data are also useful in the material science. This type of data for Kondo insulators is not available in literature. Hence, this work is first of its kind, and it is useful in various fields of nuclear physics. [ABSTRACT FROM AUTHOR]

We reconstruct the 3-D microstructure of centimetre-sized olivine crystals in rocks from the Almirez ultramafic massif (SE Spain) using combined X-ray micro computed tomography ( [ABSTRACT FROM AUTHOR]

From a mineralogical point of view the La Unión ore field (SE Spain) can be regarded as an oddity as some of its hydrothermal, stratabound type deposits display an extremely unusual paragenesis comprising magnetite ± greenalite ± minnesotaite ± siderite and galena ± sphalerite (IOSC - LZS). Recent mineralogical studies have shown that this paragenesis is also present at the neighboring Mazarrón ore field. These ore fields share a similar geologic setting, involving metamorphic and sedimentary rocks (Paleozoic s.l. to Permian) hosting late Miocene high-K calc-alkaline volcanic and subvolcanic rocks. The latter have andesitic to dacitic composition, and triggered hydrothermal activity and ore deposition. This study discusses the detailed mineral chemistry of magnetite samples from Mazarrón and La Unión and provides some hints for the origin of the IOSC - LZS paragenesis. We performed electron microprobe (EPMA) analyses in magnetite samples from La Unión and Mazarrón to determine the contents of minor and trace elements (Zn, Ni, Mn, Cr, V, K, Ca, Ti, Al, Si, Mg). Given that some results fell below the detection limit for the EPMA instrumental conditions we used robust regression on order statistics (robust ROS), with the NADA package in R to deal with these data sets. The Ca + Al + Mn contents in magnetites from San Cristóbal and Emilia are equivalent to the mean contents of those of IOCG, Kiruna, BIF, Cu porphyry, skarn, VMS, hydrothermal and clastic Pb-Zn deposits, but they are low in Ti + V and Ni + Cr. The principal components analysis indicates that Zn, Ni, Cr, V, K, Ca, Ti, and Mg are roughly collinear, therefore correlated, being also independent from Fe. Besides, the function discriminant analysis of data shows that the magnetites from Emilia and San Cristóbal cluster in differentiated groups, thus probably reflecting some differences related to the distance to the magmatic source that triggered the hydrothermal system: proximal in the case of San Cristóbal and distal in Emilia. [ABSTRACT FROM AUTHOR]

Anthophyllite is an amphibole form of asbestos historically used in only a limited number of products. No published resource currently exists that offers a complete overview of anthophyllite toxicity or of its effects on exposed human populations. We performed a review focusing on how anthophyllite toxicity was understood over time by conducting a comprehensive search of publicly available documents that discussed the use, mining, properties, toxicity, exposure and potential health effects of anthophyllite. Over 200 documents were identified; 114 contained relevant and useful information which we present chronologically in this assessment. Our analysis confirms that anthophyllite toxicity has not been well studied compared to other asbestos types. We found that toxicology studies in animals from the 1970s onward have indicated that, at sufficient doses, anthophyllite can cause asbestosis, lung cancer and mesothelioma. Studies of Finnish anthophyllite miners, conducted in the 1970s, found an increased incidence of asbestosis and lung cancer, but not mesothelioma. Not until the mid-1990s was an epidemiological link with mesothelioma in humans observed. Its presence in talc has been of recent significance in relation to potential asbestos exposure through the use of talc-containing products. Characterizing the health risks of anthophyllite is difficult, and distinguishing between its asbestiform and non-asbestiform mineral form is essential from both a toxicological and regulatory perspective. Anthophyllite toxicity has generally been assumed to be similar to other amphiboles from a regulatory standpoint, but some notable exceptions exist. In order to reach a more clear understanding of anthophyllite toxicity, significant additional study is needed. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Perfluoropentane (PFP) gas-filled biodegradable iron-doped silica nanoshells have been demonstrated as long-lived ultrasound contrast agents. Nanoshells are synthesized by a sol-gel process with tetramethyl orthosilicate (TMOS) and iron ethoxide. Substituting a fraction of the TMOS with R-substituted-trialkoxysilanes produces ultrathin nanoshells with varying shell thicknesses and morphologies composed of fused nanoflakes. The ultrathin nanoshells have continuous ultrasound Doppler imaging lifetimes exceeding 3 h, are twice as bright using contrast-specific imaging, and have decreased pressure thresholds compared to control nanoshells synthesized with just TMOS. Transmission electron microscopy shows that the R-group-substituted trialkoxysilanes can reduce the mechanically critical nanoshell layer to 1.4 nm. These ultrathin nanoshells have the mechanical behavior of weakly linked nanoflakes but the chemical stability of silica. The synthesis can be adapted for general fabrication of 3D nanostructures composed of nanoflakes, which have thicknesses from 1.4 to 3.8 nm and diameters from 2 to 23 nm. [ABSTRACT FROM AUTHOR]

Understanding the reaction mechanism of olivine compounds as electrode materials for lithium lithium-ion batteries have has received much attention recently. The question whether olivine LiFePO4 undergoes two-phase or non-nonequilibrium single-phase reaction during electrochemical processes has taken center stage in the understanding of the faster reaction kinetics observed in this material. Here, the lithiation/delithiation mechanism of Mg Mg-substituted LiFePO4 using high high-resolution X-ray diffraction(XRD), transmission electron microscopy(TEM), and electrochemical measurements is reported. Ex situ partially (de)lithiated olivine- LiMg0.2Fe0.8PO4 show the existence of stable equilibrium intermediate phases as characterized by the presence of more than two phases and broadness of diffraction peaks. Electron energy loss spectroscopy profiles across individual nanoparticles further confirm uniform lithiation with a constant Fe-L3 energy measured across each nanoparticle, suggestive of solid solution behavior in individual particles. In addition, a continuous shift in the diffraction peak position is observed even in the 'two-phase' region in the ex situ electrochemical (de)lithiated electrodes. [ABSTRACT FROM AUTHOR]

Understanding the reaction mechanism of olivine compounds as electrode materials for lithium lithium-ion batteries have has received much attention recently. The question whether olivine LiFePO4 undergoes two-phase or non-nonequilibrium single-phase reaction during electrochemical processes has taken center stage in the understanding of the faster reaction kinetics observed in this material. Here, the lithiation/delithiation mechanism of Mg Mg-substituted LiFePO4 using high high-resolution X-ray diffraction(XRD), transmission electron microscopy(TEM), and electrochemical measurements is reported. Ex situ partially (de)lithiated olivine- LiMg0.2Fe0.8PO4 show the existence of stable equilibrium intermediate phases as characterized by the presence of more than two phases and broadness of diffraction peaks. Electron energy loss spectroscopy profiles across individual nanoparticles further confirm uniform lithiation with a constant Fe-L3 energy measured across each nanoparticle, suggestive of solid solution behavior in individual particles. In addition, a continuous shift in the diffraction peak position is observed even in the 'two-phase' region in the ex situ electrochemical (de)lithiated electrodes. [ABSTRACT FROM AUTHOR]

Introduction: Silicate inclusions in primitive achondrite winonaites and IAB iron meteorites record a complex history of heating, brecciation, fragmentation, and metamorphism. Stony winonaite and IAB irons are thought to come from the same parent asteroid because of their similar silicate mineralogy, mineral chemistry, and oxygen isotopic composition [1]. While both meteorite groups exhibit geochemical trends consistent with differentiation and partial melting, there are questions about whether the compositions of IAB silicate inclusions reflect precursor chondrites or parent body processes. The most common model of parent body evolution is that the winonaite-IAB parent asteroid underwent incomplete differentiation followed by catastrophic impact breakup and reassembly [2]. Application of thermometers sensitive to different temperature intervals and characterization of apatite volatile chemistry that reflects different melt sources and/or melting events place constraints on these processes. To understand the origin and evolution of winonaite-IAB iron parent bodies, we applied traditional two-pyroxene [3] and Ca-in-olivine thermometry [4] along with recently developed REE-in-two pyroxene [5] and Mg- and REE-inplagioclase-clinopyroxene [6] thermometers that rely on relatively slow diffusive exchange of REEs between mineral pairs to constrain peak or near-peak temperatures. These methods have helped constrain the thermal histories of ordinary chondrites and other primitive achondrites including acapulcoites and lodranites, suggesting early fragmentation and reassembly in at least four meteorite parent bodies [7,8]. Peak temperatures of IABs are scattered but consistent with thermal metamorphism, and perhaps mechanical phase mixing, before and/or during fragmentation. Winonaites record more self-consistent thermal histories and also record fast cooling rates consistent with fragmentation. Samples and Methods: We studied six winonaites (Graves Nunataks (GRA) 12510, Queen Alexandra Range (QUE) 94535, Northwest Africa (NWA) 4024, NWA 6448, NWA 725), and three IAB irons with silicate inclusions (Grosvenor Mountains (GRO) 06050, Larkman Nunatak (LAR) 06876, and Maslyanino). Texture and modal mineralogy were explored using X-ray elemental maps using an SX100 electron microprobe at Brown University. Major and minor element compositions of cpx, opx, plg, and ol were measured using an SX100 electron microprobe at University of Tennessee. Silicate trace element compositions including REEs and Y were measured by LA-ICP-MS at University of Texas and Brown University. Apatite major and minor element compositions including F and Cl were measured using the JEOL 8530 field emission electron microprobe at NASA JSC. The apatite X-site hosts F, Cl, and OH as essential structural constituents so OH was calculated as the missing component (MC = 1 - F - Cl) or if F + Cl > 1, then F = 1 - Cl because F can be overestimated by electron microprobe analysis in high F apatite. Results and discussion: Cpx REEs(+Y) are typically above detection limit and exhibit a negative Eu anomaly. Opx light-REEs and plg heavy REEs(+Y) are typically below detection limits, but light REEs (in plg) and heavy REEs (in opx) exhibit smooth and systematic chondrite normalized patterns, suggesting the data are good quality. REE patterns are roughly consistent among meteorites except for IABs. This REE variability indicative of disequilibrium partitioning translates into high peak temperature variability suggesting an exogenic origin for some silicate inclusions and thermal metamorphism before and/or during fragmentation and reassembly in IABs. Where cooling rates could be determined, the fast rates at high temperature of ~900-1000 °C (0.5-2 °C/year) are orders of magnitude more rapid than lower temperature metallographic rates [9] and those anticipated for parent bodies with onion shell configurations (3-7 x 10-5 °C/year) [7]. This thermal history is consistent with reassembly after early fragmentation. Apatite in winonaite and IAB iron meteorites exhibit high intersample variability in X-site composition that range from 13-61% Cl and 29-87% F (winonaites: NWA 6448 with Cl61F29MC10 and QUE 94535 with Cl37F63; IABs: LAR 06876 with Cl61F29MC10, Maslyanino with Cl32F53MC15, and GRO 06050 with Cl13F87). The most Cl-rich apatite in NWA 6448 and LAR 06876 are similar to apatite compositions in some H, L, and LL ordinary chondrites [10], but apatite in the other samples are more F-rich and plot outside the chondritic range. The more F-rich compositions of apatite are consistent with the expected apatite X-site evolution of apatite that remains in the residue after partial melting, as F is much more compatible in apatite than OH and Cl [11]. Future work will explore any corrolations between apatite X-site composition and other indicators of partial melt extraction from primitive achondrites. [ABSTRACT FROM AUTHOR]

Banded iron formation ( BIF) of the Gorumahisani-Sulaipat-Badampahar ( GSB) belt in Singhbhum Craton, India, consists predominantly of magnetite. This BIF is intruded by a magnetite dyke. The magnetite dyke is massive and compact with minor sulphide minerals while the host banded magnetite ore, a component of the BIF, shows thin lamination. The magnetite ore of the dyke is fine to medium grained and exhibits interlocking texture with sharp grain boundaries, which is different from the banded magnetite that is medium to coarse grained and show irregular martitised and goethitised grain boundaries. Relics of Fe- Ca- Mn- Mg-carbonate and iron silicates (grunerite and cummingtonite) are observed in the banded magnetite. The intrusive magnetite is distinctly different in minor, trace and REE geochemistry from the banded magnetite. The banded magnetite contains higher amounts of Si, Al, Mn, Ca, Mg, Sc, Ga, Nb, Zr, Hf, Co, Rb and Cu. In contrast, the massive magnetite is enriched in Cr, Zn, V, Ni, Sr, Pb, Y, Ta, Cs and U with higher abundance of HREE. In the chondrite normalized plot, the massive magnetite shows a slight positive Eu anomaly while the banded ore does not show any Eu anomaly. Field disposition, morphology, mineralogy and chemistry show that the intrusive magnetite dyke is of igneous origin, while magnetite in BIF formed from a carbonate protolith through the process of sedimentation. [ABSTRACT FROM AUTHOR]

Iron centres incorporated in silicate frameworks or located in their pores have been shown to possess unique catalytic properties. As compared to aluminosilicates this area of zeolite chemistry is much younger and in the first part of this review the findings made so far are summarised. Molecular model compounds may help to understand the formation, corrosion and reactivity of such materials or to even develop new ones. Hence, the subsequent parts deal with molecular iron siloxides, the number of which is still quite limited, and their behaviour also in relation to the iron-modified zeolites is outlined. At first, compounds based on an incompletely condensed cubic silsequioxane are discussed, before iron(III) complexes of more basic siloxide ligands with varying steric demands are described. Finally, recent developments based on branched polydentate siloxides are presented. [ABSTRACT FROM AUTHOR]

Hot springs at Gongxiaoshe and Zhuyuan (maximum temperatures of 73 to 84°C, respectively) are characterized by deposits formed of calcite, aragonite, non-crystalline Si-Mg-Fe deposits, and minor amounts of barite and gypsum. The deposits at Gongxiaoshe are formed largely of alternating calcite and aragonite laminae, whereas those at Zhuyuan are formed largely of calcite. The calcite is in the form of: (i) pseudodendrites that grew as sub-crystals stacked upon each other; and (ii) unattached euhedral and incompletely formed dodecahedral and rhombohedral crystals. Amorphous Ca CO3, formed of nanoparticles <1 μm long, is common in some of the Zhuyuan deposits, but minor in the Gongxiaoshe deposits. The morphologically diverse arrays of aragonite crystals that lie parallel to bedding were not nucleated on a growth surface. Many substrates in these deposits are covered with reticulate coatings that are formed largely of Si and Mg with minor Fe and micro-granular coatings that are formed largely of Si and Fe. Biofilms, with their extracellular polymeric substances, and microbes are common at both springs. The compositionally and crystallographically diverse precipitates at these two springs are attributed to a biologically influenced model with precipitation taking place in micro-domains that developed in the extracellular polymeric substances. According to this model, precipitation varied at the micron-scale influenced by the elemental concentrations that developed in the hydrogel of extracellular polymeric substances. Critically, the very low preservation potential of the extracellular polymeric substance and its formative microbes means that the precipitates will rapidly lose evidence of their biotic origin. The compositional diversity of the precipitates, the crystallographic diversity of the calcite and aragonite with numerous incompletely formed crystals, and local concentrations of Si, Mg and Fe may, however, serve as proxies of that biologically influenced precipitation. [ABSTRACT FROM AUTHOR]

Zircon in five samples of variably comminuted, melted, and hydrothermally altered orthogneiss from the Maniitsoq structure of southern West Greenland yield a weighted mean 207Pb/206Pb age of 3000.9 ± 1.9 Ma (ion probe data, n = 37). The age data constitute a rare example of pervasive and nearly complete isotopic resetting of zircon during a regional hydrothermal event. Many zircon grains are homogeneous or display weak flame-like patterns in backscattered electron images. Other grains show complex internal textures, where homogeneous, high-U fronts commonly cut across relict igneous-type oscillatory zonation. Inclusions of quartz, plagioclase, mica, and other Al ± Na ± Ca ± Fe-bearing silicates are very common. In two samples, selective replacement of zircon with baddeleyite occurs along concentric zones with relict igneous zonation, and as specks a few microns large within recrystallized, high-U areas. We interpret the 3000.9 ± 1.9 Ma date as the minimum age of the recently proposed impact structure at Maniitsoq. The great geographical extent and intensity of the hydrothermal event suggest massive invasion of water into the currently exposed crust, implying that the age of the hydrothermal alteration would closely approximate the age of the proposed impact at Maniitsoq. At the western margin of the Taserssuaq tonalite complex, which postdates the Maniitsoq event, a 207Pb/206Pb mean age of 2994.6 ± 3.4 Ma obtained from zircon has mostly retained igneous-type oscillatory zonation. A subsequent thermal event at approximately 2975 Ma is recorded in several samples by zircon with baddeleyite replacement textures. [ABSTRACT FROM AUTHOR]

Silicate Nanocrystals: PEDOT Encapsulated and Mechanochemically Engineered Silicate Nanocrystals for High Energy Density Cathodes (Adv. Keywords: interfacial engineering; Li-ion batteries; lithium iron silicate; mechanochemistry; PEDOT; surface modification EN interfacial engineering Li-ion batteries lithium iron silicate mechanochemistry PEDOT surface modification 1 1 1 07/13/20 20200709 NES 200709 In article number 2000226 Majid Rasool, George P. Demopoulos, and co-workers report the fabrication of a robust core-shell lithium iron silicate (Li SB 2 sb FeSiO SB 4 sb , LFS) cathode architecture, where nanocrystal's core is prepared via mechanochemical annealing and shell via PEDOT polymerization. Interfacial engineering, Li-ion batteries, lithium iron silicate, mechanochemistry, PEDOT, surface modification. [Extracted from the article]