Fe Enrichment Research Articles

Strategies and Bottlenecks in Hexaploid Wheat to Mobilize Soil Iron to Grains

Our knowledge of iron (Fe) uptake and mobilization in plants is mainly based on Arabidopsis and rice. Although multiple players of Fe homeostasis have been elucidated, there is a significant gap in our understanding of crop species, such as wheat. It is, therefore, imperative not only to understand the different hurdles for Fe enrichment in tissues but also to address specifically the knowns/unknowns involved in the plausible mechanism of Fe sensing, signaling, transport, and subsequent storage in plants. In the present review, a unique perspective has been described in light of recent knowledge generated in wheat, an economically important crop. The strategies to boost efficient Fe uptake, transcriptional regulation, and long-distance mobilization in grains have been discussed, emphasizing recent biotechnological routes to load Fe in grains. This article also highlights the new elements of physiological and molecular genetics that underpin the mechanistic insight for the identified Fe-related genes and discusses the bottlenecks in unloading the Fe in grains. The information presented here will provide much-needed resources and directions to overcome challenges and design efficient strategies to enhance the Fe density in wheat grains.

Insights into paleoenvironment and chemical weathering as controls on arsenic accumulation in Late Pleistocene to Holocene aquifers

High As groundwater has been reported in aquifers comprising Late Pleistocene and Holocene sediments worldwide, and could be due to the depositional environment and sedimentological processes. To investigate the paleoenvironment and chemical weathering as mechanisms controlling the fate of As, this study characterized the elemental, clay mineral, and Li isotopic compositions of sediments of an As-contaminated aquifer in the Datong Basin, China. Indices for reconstructing chemical weathering conditions, for example, the Chemical Index of Alternation (CIA), indicate overall incipient to intermediate chemical weathering conditions in the Datong Basin during the Late Pleistocene to Holocene. The higher CIA values at depths of ∼20–∼85 m indicate stronger chemical weathering and a shift in climatic regime towards warm and humid conditions in Stage 2 compared to Stage 1 and Stage 3. Under such climatic conditions, intense chemical weathering favors the leaching of silicate-bound Fe and thus the production of various secondary Fe-oxide minerals. Besides, the positive relationship between CIA values and easily reducible Fe oxides further shows the enrichment of more weakly crystalline Fe-oxides during the depositional condition; this finding is also supported by the results of chemical extractions performed on the sediments. Moreover, the good correlations between total organic carbon (TOC) and both Fe/Na and As concentrations suggest the enrichment of As and OM along with Fe enrichment during chemical weathering; this is attributed to the adsorption or co-precipitation of As and OM on Fe minerals. Under warm and humid conditions, intense chemical weathering released a large amount of Fe minerals; As was also released due to stronger weathering of the terrestrial bedrock and sequestered by Fe oxides and organic matter, thus forming complexes involving As, Fe, and OM. FTIR and chemical extraction results confirm the formation of As–Fe-OM complexes during the geological history contributes to As enrichment and accumulation in the late Pleistocene sediments. These findings provide new insights into the interaction between the paleoenvironment and the accumulation of ferric oxides/hydroxides and OM, which serve as controlling mechanisms with respect to As enrichment in Late Pleistocene to Holocene sediments, and thus shed light on the sedimentogenesis of high As aquifers.

Variabilities in autumn cyanobacterial responses to ecosystem external enrichments based on nutrient addition bioassay in Pengxi River, Three Gorges Reservoir, China

Nutrient availability, is a crucial anthropogenic stressor promoting freshwater eutrophication and rapid expansion of harmful algal blooms (HABs), deteriorating water quality and threatening public health worldwide.The estimation of the HABs community responses to diel changes in the nutrients while characterizing the ecosystem growth limiting factors, is key to prudent watershed management. The present study investigated the short-term variabilities in autumn cyanobacterial responses to the external nutrient inputs into the Pengxi River using the nutrient addition bioassay approach. Results reveal phytoplankton community structure dominated by the cyanobacteria: Anabaena and Aphanizomenon spp. (relative abundance = 46.20% equilibrium abundance), followed by the diatoms, out of which Lindayia bodaniica, are preponderant. Nutrient enrichment triggered strong variabilities in dominance and successions among the cyanobacterial group, with maximum dominance (76.34%) exhibited by the Aphanizomenon sp. upon NH4 addition. Fe enrichment led to the succession of cyanobacteria, Leptolyngbya tenuis, which was below the detectable limit in the control, indicating the role of Fe in its proliferation. Studies on nutrient limitation demonstrated P/NH4 co-limited ecosystem, with P as the primary and NH4, a secondary limiting factor. The nitrate preference index (NO3−RPI = 0.991) shows a high preference for NH4 while NO3 constitutes the bulk of the ecosystem TN. Considering the elevated NO3 concentration, we posit that a shift in the phytoplankton community structure from cyanobacteria to diatoms dominated ecosystem, is expected following Fe depletion and a further stretch on the current ecosystem NH4 limitation. The study provides useful and first-ever insights for nutrient reduction in the middle Three Gorges Reservoir (TGR) before the onset of the heavy HABs during spring in the Pengxi River.

Multiple Rodingitization Stages in Alkaline, Tholeiitic, and Calc-Alkaline Basaltic Dikes Intruding Exhumed Serpentinized Tethyan Mantle from Evia Island, Greece

Abstract In Pagondas and Kimi areas, central Evia Island, Greece, variably serpentinized ultramafic rocks of an ophiolitic origin are crosscut by rodingite dikes. Based on their protoliths, these rodingites are distinguished into the following: (i) rodingites of island arc tholeiitic dolerites, (ii) rodingites of Mg-rich tholeiitic gabbros, (iii) rodingites of alkaline basalts, and (iv) rodingites of calc-alkaline basalts. Rodingitization evolved in three successive phases (namely, stages 1, 2, and 3) of increasing metasomatic degree that occurred during the exhumation of the mantle wedge serpentinites. Thermodynamic modeling suggests that stage 1 was developed at ~5 kbar and 450-550°C, whereas at stage 2 and stage 3, gradually decreasing P-T conditions prevailed. Stage 1 affected the protoliths of all rodingite types and was characterized by the crystallization of grossular, diopside, chlorite, and prehnite leading to Ca and LOI enrichments. The observed Si and REE depletions are assigned to the dissolution of primary clinopyroxene and amphibole. Stage 2 mainly affected the rodingites that were derived from alkaline and calc-alkaline basalts, promoting the growth of andradite, vesuvianite, and chlorite at the expense of stage 1 rodingitization mineral phases. At this stage, the marginal zones of rodingite dikes from alkaline and calc-alkaline basalts experienced remarkable Mg and REE enrichments. Stage 3 corresponds to derodingitization and restricted carbonation processes of the previously formed rodingites, which are associated with Fe enrichments. During this stage, significant trace elements including REEs were transferred from the marginal zones to the inner cores of rodingite dikes that were derived from metasomatism of calc-alkaline basalts. Calcite δ18Ο-δ13C isotopic data suggest that carbonation processes were developed at shallow depths below the Tethyan ocean floor, through mixing of seawater and serpentinization-derived fluids. Such multiple stages of rodingitization processes that affected four different lithotypes, as well as the unusual case of alkaline basalts’ rodingitization, would render the Evia rodingites as an important and very rare example of metasomatism.

Skarn formation and Cu[sbnd]Ag mineralization in the McKenzie Gulch area, northern New Brunswick, Canada: Implication for the applications of mineral chemistry in exploration for porphyry copper and skarn deposits

The McKenzie Gulch (MG) copper–silver skarn occurrences are associated with the Middle Devonian intermediate to felsic dyke swarms. Mineralization occurs as veins and stockwork of veinlets, disseminations, patchy, and locally as replacement of calc-silicate skarns in argillaceous limestone. This skarn is interpreted to have developed in three stages: the earliest contact metamorphic stage resulting in hornfels developed from calcareous mudstone and very fine-grained clastic sedimentary rocks (Stage I); this was followed by metasomatic replacement resulting in prograde anhydrous skarn containing grossular-andradite (grandite), diopsidic pyroxene, and wollastonite (Stage II); increasing fluid/rock interaction results in retrograde skarn dominated by epidote, calcite, green amphibole, chlorite, sulfide minerals, titanite, andradite and hedenbergite commonly along veins and veinlets (Stage III). Subordinate sphalerite and pyrite occur in late veins cross-cutting both porphyry dykes, skarns and hornfels zone.Prograde garnets in the study area belong to the grossular-andradite solid solution that ranges from Adr16Gr82 to almost pure andradite - Adr99Gr1, whereas other garnet end-members constitute less than 5% collectively. Pyroxenes form a diopside-hedenbergite solid solution with composition between Di31Hd60 and Di93Hd7, while other pyroxenes constitute less than 10% collectively. These garnets and pyroxenes exhibit chemical zonation patterns generally characterized by a rim of Fe enrichment relative to cores of grains, which may suggest possible change in salinity (or other factor that promotes Fe transport). This means grossular and diopsidic cores are rimmed by more andradite and hedenbergitic compositions for garnet and pyroxene, respectively. In general, there is a tendency for increasing Fe component in both garnet and pyroxene from the prograde to retrograde stages.Epidote formed during the retrograde stage exhibits oscillatory zoning similar to retrograde andradite and indicates Fe enrichment increasing from core to rim. Based on the major element composition, textural and optical characteristics of garnets, we conclude that grandites (Al-rich) formed under low water/rock ratios, in equilibrium with metasomatic fluids whose composition was locally buffered by the host rocks, whereas andradite (Fe-rich) resulted from relatively high water/rock ratios that were in equilibrium with a magmatic-derived fluid. The results of this study indicate that there is a relationship between the composition of pyroxenes and garnets of the skarn alteration facies and the dominant metal of the mineralized skarns. These facies plot in the compositional field of Cu-dominated skarns. As a result, this relationship may be applied in exploration for skarn and porphyry copper mineralization.

Geochemical focusing and burial of sedimentary iron, manganese, and phosphorus during lake eutrophication

AbstractThe redistributive transport of sedimentary, redox‐sensitive metals such as iron (Fe) and manganese (Mn) along depth gradients in lakes or marine basins, and in particular the concentration of these elements at local depressions, has been described as “geochemical focusing.” However, the impact of variable redox conditions at the sediment–water interface on this process is not entirely understood. In this study, we report that the enrichment and burial of Fe, Mn, and associated phosphorus (P) in dimictic Lake Arendsee, Germany, has been affected by a transition from oligo‐mesotrophic to eutrophic conditions in the first half of the 20th century. Eleven sediment cores (<50 cm long) were obtained from water depths ranging from 38.5 to 49.5 m, and analyzed for their elemental composition. The older, non‐varved section, which was deposited prior ca. 1940 during oligo‐mesotrophic conditions, contains up to 10 times higher Mn and 2.5 times higher Fe contents at the deep sites compared to corresponding intervals at shallower sites. Due to their high Fe content, sediments in this interval also contain up to eight times more P, at least partly owing to vivianite authigenesis. Burial of Mn occurred via Mn‐carbonate authigenesis, possibly as rhodochrosite. Since ca. 1940, calcite and diatom varves have formed under eutrophic conditions, whereas Fe enrichment decreased and finally stopped due to fixation as pyrite in the shallow sites. Our results suggest that redox‐controlled geochemical focusing determines the distribution of Mn and Fe, as well as the occurrence of authigenic minerals such as vivianite and Mn‐carbonate.

A record of low-temperature asteroidal processes of amoeboid olivine aggregates from the Kainsaz CO3.2 chondrite

Amoeboid olivine aggregates (AOAs) from the Kainsaz CO3.2 chondrite were analyzed using transmission electron microscopy in order to gain a more complete understanding of thermal metamorphism on the parent body and the role of fluids during metamorphic heating. The Kainsaz AOAs are dominated by strongly zoned, fine-grained, olivine grains (Fa2-31) with heterogeneous Fe enrichments along the grain boundaries, which are interpreted as the result of Fe2+-Mg2+ interdiffusion with the matrix during thermal metamorphism. However, our diffusion calculations show that such AOA olivine zoning and compositions cannot be produced by a simple diffusional exchange during metamorphic heating, unlike chondrule olivine zoning and compositions. In addition, fine-grained ferroan olivine overgrowths occur heterogeneously in crystallographic continuity with olivines on the AOA exteriors. The overgrowths (Fa33-36) are compositionally distinct from the underlying AOA olivines and are not fully equilibrated with the matrix olivines (Fa∼20-55). The ferroan olivine overgrowths likely formed by precipitation from fluids in an epitaxial relationship with forsteritic olivine on the edges of AOAs. Texturally and compositionally diverse chromite grains are also observed along olivine grain boundaries, in olivine grains, and in pore spaces between olivine grains. They share a similar crystallographic orientation relationship with adjacent olivine, suggestive of their formation by exsolution and/or epitaxial growth. Collectively, these observations provide evidence for the mobilization of Fe, Mg, Si, Cr, and Al in the presence of fluids along olivine grain boundaries and into olivine grains during thermal metamorphism. We conclude that in Kainsaz AOAs, the strong zonation development in individual olivine grains and the formation of ferroan olivine overgrowths and chromite grains were a fluid-driven process that occurred at relatively low temperatures (<500 °C), during the cooling history of the CO3 chondrite parent body, following the peak of thermal metamorphism.

Evaluating the performance of enriched finite elements for Hertzian contact problem

Solution of contact problems in the field of mechanics is often very challenging, as it is hard to predict the contact forces and stresses due to non-constant boundary conditions. It is observed that when standard finite elements of linear order are used to represent the contact boundary, it is difficult to capture the contact forces within the contact region accurately. To improve this situation, different techniques usually are adopted. One such technique is using highly refined mesh at the contact zone. But it increases the computational time. Thus, it is more efficient to adopt the enrichment strategies for the contact elements lying within the contact region. Such elements are also referred to as the enriched contact finite elements. To the best of the authors' knowledge, the effects of contact enrichment with various interpolation orders on the solution accuracy of contact problems have not been exploited completely and hence is the scope for the present work. The current contribution evaluates the performance of enriched finite elements in solving the Hertz contact problem. The enrichment strategy is based on the introduction of extra degrees of freedom for the contact elements in the slave surface. The contact surface is locally enriched to represent the surface more accurately than the bulk. Thus, the improved computational contact formulation helps to correctly approximate the contact forces while keeping the total degrees of freedom low. In this work, the penalty method enforces contact constraints, and material behaviour follows the Neo-Hookean hyperelastic material model. A benchmark problem on the Hertzian contact is considered to demonstrate the FE enrichment technique. The numerical results exhibit the better performance of the FE enrichment over the mesh refinement for the solution accuracy. This work also shows that the higher-order finite elements after enrichment outperform the linear order finite elements in the contact region.

Dynamic atmospheres and winds of cool luminous giants

Context. The winds observed around asymptotic giant branch (AGB) stars are generally attributed to radiation pressure on dust formed in the extended dynamical atmospheres of these long-period variables. The composition of wind-driving grains is affected by a feedback between their optical properties and the resulting heating due to stellar radiation. Aims. We explore the gradual Fe enrichment of wind-driving silicate grains in M-type AGB stars to derive typical values for Fe/Mg and to test the effects on wind properties and synthetic spectra. Methods. We present new radiation-hydrodynamical DARWIN models that allow for the growth of silicate grains with a variable Fe/Mg ratio and predict mass-loss rates, wind velocities, and grain properties. Synthetic spectra and other observables are computed a posteriori with the COMA code. Results. The self-regulating feedback between grain composition and radiative heating, in combination with quickly falling densities in the stellar wind, leads to low values of Fe/Mg, typically a few percent. Nevertheless, the new models show distinct silicate features around 10 and 18 microns. Fe enrichment affects visual and near-IR photometry moderately, and the new DARWIN models agree well with observations in (J − K) versus (V − K) and Spitzer color–color diagrams. The enrichment of the silicate dust with Fe is a secondary process, taking place in the stellar wind on the surface of large Fe-free grains that have initiated the outflow. Therefore, the mass-loss rates are basically unaffected, while the wind velocities tend to be slightly higher than in corresponding models with Fe-free silicate dust. Conclusions. The gradual Fe enrichment of silicate grains in the inner wind region should produce signatures observable in mid-IR spectro-interferometrical measurements. Mass-loss rates derived from existing DARWIN models, based on Fe-free silicates, can be applied to stellar evolution models since the mass-loss rates are not significantly affected by the inclusion of Fe in the silicate grains.

Lattice Strain of Zn-Mn Mixed Ferrite Nanocrystals in a Core-Shell Morpho-Chemical Structure

In this work, the crystalline structure, chemical composition, size, and morphology of core@shell nanoparticles based on Zn-Mn ferrite nanocrystals were investigated. These materials have been proposed as promising candidates for multifunctional applications in biomedicine, catalysis, environmental remediation, among others. Those properties were probed by using several experimental techniques such as Synchrotron X-Ray Diffraction, Energy-Dispersive X-ray Spectroscopy, Transmission Electron Microscopy and Selected Area Electron Diffraction. Results show that all synthesized nanoparticles present a single crystalline spinel phase without the appearance of undesirable byproducts. The nanoparticles present a non-stoichiometric Zn-Mn ferrite core, due to a Fe enrichment and a Zn loss with respect to the synthesis medium. The surface treatment of the nanoparticles induces a greater iron enrichment, which occurs at the nanoparticles surface without changing the crystalline structure. Finally, modifications in lattice parameters and strain suggest a contribution of the Mn2+ cations, mainly related to their easy oxidation in the synthesis route, which increases the structural vacancies of Mn-richer ferrites.

Meteorite from Astomulyo Village, Central Lampung, Indonesia: Investigation of its chemical properties

In early 2021, a rare extraterrestrial object passed at high speed, followed by a powerful boom, with a bright flare crossing the atmosphere and falling in Astomulyo Village, Punggur, Central Lampung, Indonesia. This object has been scientifically determining as a meteorite. Toward the spot where we first found it, we presented this object named Astomulyo meteorite. This research investigated its chemical properties using an X-ray fluorescence (XRF) analyzer. As the result, the major composition of this meteorite is Si (28.3-27.1%), Fe (22.1-19.8%), Mg (17.3-15.2%), Al (2.9-2.4%), Ca (1.7-1.9%), and S (1.0-0.97%). Its minor elements are Mn, Ni, Cr, P, and some trace elements such as Co, Ti, Sb, Sn, V, Cd, Zn. This meteorite suggested classifying as the H-Chondrites group. Fe, Ni, Al, and Ti enrichment occur on the meteorite’s surface. It is probably related to this meteorite origin and continuously processes until it falls to the Earth’s surface.

Experimental study on Fe solubility in vapor-rich hydrothermal fluids at 400–500 °C, 215–510 bar: Implication for Fe mobility in seafloor vent systems

In seafloor hydrothermal systems, vent fluids usually contain elevated dissolved iron (Fe) that is significantly enriched relative to deep ocean seawater. It is commonly thought that Fe is preferentially transported in dense Cl-rich fluids due to the formation of aqueous Fe-Cl complexes. However, Fe enrichment in vapor-rich low-density fluids with low Cl concentrations (<550 mmol/kg) underscores the efficacy of the low-Cl vapor-rich phase to transport Fe in both subaerial and submarine hydrothermal systems. Currently, transport of Fe in low-density vapor-rich fluids is poorly understood due to the lack of high temperature–pressure (T-P) solubility experiments and requisite thermodynamic data. Here, we report new data of Fe solubility from experiments conducted at 400–500 °C, 215–510 bar, targeting fluids with low-density (∼0.1–0.35 g/cm3). The experiments were performed in the KCl-H2O system with hematite-magnetite and K-feldspar-muscovite-quartz as mineral buffering assemblages. Our results show that Fe solubility positively correlates with density and fluid chlorinity, which are affected by temperature and pressure. The equilibrium constants (log Khm) for Fe-buffering reaction Fe3O4(s) + 2HCl(aq) = Fe2O3(s) + FeCl2(aq) + H2O were determined. The new data and the data calculated using Helgeson-Kirkham-Flowers (HKF) equation of state were fit into a density model to extrapolate log Khm for hematite-magnetite Fe buffering reaction over a wide T-P range. The density models for magnetite dissolution reaction and pyrite-pyrrhotite equilibrium were also fit based on HKF to allow redox constraints. We show that calculated Fe solubility are in good agreement with measured values in vapor-rich fluids formed via phase separation in mineral buffered and basalt alteration experiments at elevated T-P. The density model was further applied to model Fe transport in fluids at the Brandon hydrothermal field at East Pacific Rise (EPR) 21°S, with T-P constrained by Si-Cl geothermobarometer. The calculations suggest that the reported Fe concentrations of vent fluids at Brandon reflect phase separation occurring at depth in the seafloor, with T-P up to 450 °C, 400 bar, and redox conditions buffered by pyrite-pyrrhotite-magnetite equilibrium.

Micro-analytical study of the distribution of iron phases in ferromanganese nodules

The differentiation of Fe and Mn within the nodules and its relation to the fabric is a well-known phenomenon. However, the relationship of this differentiation to the nodules mineralogy was not studied yet. This study aimed to fill this gap through the micro-mineralogical and geochemical investigation of nodules from soils with different hydromorphic conditions by electron probe microanalysis and micro-X-Ray diffractometry.Different conditions of hydromorphism resulted in the same nodule types and their similar vertical distribution in soils. In soils with shallow groundwater table, nodules exhibited more developed fabric, and crystalline hydrous Fe oxides (goethite) prevailed in them. Contrarily, nodules showed smaller size, lower Fe enrichment, and a higher frequency of non-crystalline hydrous Fe oxides in soils with regular flooding and stagnant surface water. The difference could be related to the lower intensity of water oscillation and the shorter redox periods in the latter soils. The formation of the nodules’ fabric may have been followed by the slow crystallization of Fe-oxyhydroxides when favorable redox oscillation conditions occur allowing subsequent recrystallization. The association of hydrous Fe oxides to clay minerals may have also affected the crystallization process within the nodules.Although the observation of assumed differentiation of hydrous Fe oxides failed within the nodules, soils with different conditions of hydromorphism could be characterized by different Fe-oxyhydroxide mineralogy, at least in the progression of their crystallization process.

Geochemical record of the subsurface redox gradient in marine red beds: A case study from the Devonian Prague Basin, Czechia

AbstractMarine red beds are usually interpreted as indicating water column oligotrophy, good bottom‐water oxygenation and redox conditions. Lower Devonian successions of the Prague Basin, Czechia, exhibit a distinct centimetre to metre‐scale alternation of layers of marine red beds, grey carbonates, marls and black shales. In order to understand why the redox potential fluctuated so rapidly, reflectance spectroscopy, microscopy, elemental geochemistry data and stable isotopes of Mo have been analysed in this paper. Whilst the grey and black facies only contain goethite, the marine red beds are enriched with synsedimentary and early diagenetic, submicronic hematite, which is present in micrite, skeletal interiors, microstromatolites and oncoids. It was formed by microbially mediated precipitation, the replacement of detrital Fe phyllosilicates, and/or by the oxidation of microbially precipitated Fe‐bearing aluminosilicate precursors. The marine red beds are frequently enriched in Fe, depleted in U, V, Mo and Cu, and show negative δ98Mo values indicating oxic conditions. Peloidal micrite, microbial coatings and cements with the marine red beds exhibit positive (up to 9) Ce/Ce* anomalies. The non‐red facies show opposite patterns. This geochemical variability is probably related to Mn oxyhydroxide cycling and organic matter remineralization along the sediment subsurface redox gradient, particularly by reactions between pore water and various elemental pools. These patterns, combined with the centimetre‐scale colour alternation of the sediments, may reflect redox zonation that has been preserved beneath the ancient seafloor. Four zones are recognized: (i) the oxic zone of Fe‐oxide precipitation (marine red beds); suboxic zones of (ii) Fe enrichment, and (iii) U‐Mo enrichment; and (iv) suboxic–anoxic zone of Cu, V (± Mo) enrichment. The presented model of a marine red bed origin from redox reactions in the sediment subsurface contradicts models of the formation of marine red beds through iron enrichment from Fe2+ supersaturated ocean waters following periods of ocean anoxia.

The São Francisco cratonic root beneath the Neoproterozoic Brasilia belt (Brazil): Petrophysical data from kimberlite xenoliths

Petrostructural analysis of 31 mantle xenoliths from three kimberlitic pipes intruding the Neoproterozoic Brasilia belt close to the southwestern margin of the São Francisco craton (SFC) reveals microstructures and compositions similar to those observed in cratonic roots worldwide. (1) The spinel-peridotites sampling the upper section of the lithospheric mantle have dominantly refractory modal and mineral compositions, whereas garnet-peridotites sampling the deep lithospheric mantle have more fertile compositions, consistent with those observed in cratonic roots worldwide. (2) The spinel-peridotites present a variation in microstructure from coarse-granular to coarse-porphyroclastic, but similar olivine crystallographic preferred orientations (CPO). (3) The garnet-peridotites have fine-porphyroclastic microstructures. (4) Many coarse-porphyroclastic spinel-peridotites display Fe-enrichment in olivine and pyroxenes, often associated with Ti-enrichment in pyroxenes or spinel and occurrence of modal phlogopite. (5) Equilibrium temperatures and pressures of garnet-peridotites are consistent with a cratonic geotherm, but equilibrium conditions of spinel-peridotites require a warmer geotherm. We interpret these observations as indicating that the xenoliths sample the SFC mantle root, which extends beneath the Brasilia belt, but was modified by reactive transport of the magmas forming the Alto Parnaiba Igneous Province (APIP) between 120 and 90 Ma. The APIP magmatism resulted in heterogeneous modal metasomatism, Fe enrichment, development of coarse-porphyroclastic microstructures in spinel peridotites and fine-porphyroclastic microstructures in garnet-peridotites, and moderate heating of the cratonic mantle root. These changes may produce a decrease in seismic velocities explaining the local weak negative anomaly observed in the lithospheric mantle beneath the APIP, which contrasts with the positive velocity anomalies characterizing the SFC mantle root in P-wave tomography models. However, reactive magma transport did not erase the olivine CPO. Comparison of the average seismic properties of the xenoliths with seismological data implies dominantly subhorizontal fossil flow directions and a non-negligible contribution of the cratonic root to teleseismic S-waves splitting.

The high-grade Fe skarn deposit of Jinling, North China Craton: Insights into hydrothermal iron mineralization

Skarn-type Fe deposits constitute a major source of iron in the world, and 57% of the high-grade iron ores in China are hosted by skarn deposits. Most researchers agree that skarn-type Fe deposits are genetically linked with the associated magmas and precipitate from hydrothermal fluids, however, whether these ore-forming fluids are mainly derived from magmas or some other external sources is controversial. Besides, the detailed process of iron concentration in the high-grade ores in skarn Fe deposits has not been well constrained. To better understand these issues, we investigated the petrological, mineral chemical, geochronological, fluid inclusion and oxygen isotope characteristics of the Jinling Fe deposit, which is a typical high-grade skarn-type Fe deposit in the North China Craton. Zircon grains in these skarns were demonstrated to result from completely modification of magmatic zircons by the later hydrothermal fluids and they yield a weighted mean 206Pb/238U age of 126.7 ± 2.0 Ma (2σ) constraining the timing of the skarn iron formation, which is consistent with that of the ore-hosting Jinling complex. The similarity in chondrite-normalized REE patterns of the zircons in skarns and magmatic zircons suggests that the ore-forming hydrothermal fluids might mainly be derived from magmas. Additionally, the oxygen isotopes of the hydrothermal fluids in various stages as estimated based on δ18O values of representative hydrothermal minerals show relatively constant values during the evolution of hydrothermal system, suggesting that there was no significant involvement of external fluids. Three types of fluid inclusions, namely, high-salinity Type 1 with daughter minerals (homogenizing into liquid phase, with salinity of 42–71 wt% NaCl equivalent), vapor-rich Type 2 (homogenizing into vapor, with salinity ≤23 wt% NaCl equivalent), and relatively low-salinity Type 3 (homogenizing into liquid, with salinity ≤23 wt% NaCl equivalent) were identified in the various skarn minerals (garnet, clinopyroxene, epidote, and anhydrite). Among these, only Type 3 fluid inclusions occur in the clinopyroxene within the dominant massive ores, implying that the relatively low-salinity fluids were the predominant ore-forming hydrothermal fluids from which the magnetite ores precipitated. The high-salinity Type 1 fluids which might have resulted from phase separation (or boiling) of the primary magmatic hydrothermal fluids due to pressure drop, were believed to be responsible for the Fe-rich rims of zoned clinopyroxenes (with Fe-poor cores) in the thin magnetite-clinopyroxene interbedding layers between skarns and the massive magnetite orebodies. Thus, this zoned texture also implies an Fe re-enrichment event after formation of magnetite ores. The process of multiple Fe enrichment may significantly contribute to the formation of high-grade skarn-type Fe deposits.

Iron supplementation in anemic Zanzibari toddlers is associated with greater loss in erythrocyte iron isotope enrichment

Heavy parasitic loads increase the risk of iron (Fe) deficiency anemia, which remains prevalent globally. Where parasites are common, understanding the influence of parasitic infections on Fe incorporation and erythropoiesis in toddlers is especially important. The aim of this study was to identify the impacts of malarial and helminth infections on red blood cell (RBC) Fe incorporation and subsequent changes in RBC Fe isotope enrichment for 84 days postdosing in toddlers at high risk for parasitic infections. Fe incorporation was measured in a group of Zanzibari toddlers (n=71; 16-25 months) using a stable Fe isotopic method. At study entry, an oral stable Fe isotope was administered. Blood was collected 14 (D14) and 84 (D84) days postdosing for the assessment of Fe status indicators and RBC isotopic enrichment. Blood and stool samples were collected and screened for malaria and helminth parasites. Factors associated with changes in RBC Fe isotope enrichment were identified using regression models. Toddlers who had larger weight-for-age z-scores, lower total body Fe, and helminth infections (n=26) exhibited higher RBC Fe incorporation. RBC Fe isotope enrichment decreased from D14 to D84 by -2.75 percentage points (P<0.0001; n=66). Greater loss in RBC Fe isotope enrichment from D14 to D84 was observed in those who received Fe supplementation, those with either helminths or both malarial and helminth infections, and in those with greater RBC Fe incorporation on D14. Toddlers who received Fe supplementation exhibited significantly greater losses of RBC Fe isotope enrichment over time. We speculate this greater loss of RBC Fe enrichment is indicative of increased erythropoiesis due to the provision of Fe among anemic or helminth-infected toddlers.

Ash deposition mechanism of shoe manufacturing waste combustion in a full-scale CFB boiler

China is the largest shoe production country and the disposal of large amounts of shoe manufacturing waste (SMW) has become a rising problem. Incineration is regarded as a promising route for the utilization of SMW, since there exist considerable amounts of carbonaceous compounds in SMW. However, there are still some challenges for SMW incineration plant, such as corrosion, ash deposition, and pollution issues. This work investigated the ash deposition behavior in a full-scale SMW CFB boiler with 576 t/d treatment capability. Results suggest that submicron particles and uncooled inorganic vapors are the deposit precursors during initial deposition stage, and they are normally rich in alkali chlorides. Therefore, inner ash deposit layer contains a high concentration of alkali chlorides, even though alkali content in original fuel is negligible. The alkali chlorides in initial deposits can further aggravate tube surface corrosion and cause Fe enrichment in the initial layer. In contrast with inner layer deposits, the outer deposit layer shows relatively uniform characteristics and is mainly composed of Ca-rich minerals since raw ash in SMW is dominated by CaO. Overall, the ash deposition rate in SMW combustion is fairly high compared to other solid waste and biomass, and the deposition propensity increases when the flue gas temperature increases. The ash deposits are observed to have high compressive strength and hard to be removed through soot-blowing during operation. This work sheds the light on the ash deposition behavior of SMW during circulating fluidized bed combustion, which facilitates the design and optimization of industrial boilers.

Manganese Benefits Heat-Stressed Corals at the Cellular Level

The intensity and frequency of coral bleaching events have increased worldwide especially due to thermal stress and seawater pollution. Although it has been observed that metal concentration in seawater can affect the coral’s ability to adopt cellular defensive mechanisms to counteract bleaching, more investigations are needed to better understand the role of metals in coral physiology. In this study, we analyzed the individual and combined effects of prolonged heat stress and manganese (Mn) and iron (Fe) enrichments at the cellular level on the coralStylophora pistillata. Thermal stress caused an up-regulation in the expression of the host Heat shock proteins (Hsps) 60 and 70, which showed a parallel pattern of modulation in all treatments, as well as an increase of lipid peroxidation (LPO) in the holobiont. Fe enrichment did not induce any change in Hsp expression or in the oxidative status of the corals both at the ambient temperature of 26°C or at increased temperature, suggesting that Fe didn’t seem to play a role in mitigating the cellular damages and the coral bleaching. Mn or MnFe enrichment at 26°C seemed to increase the oxidative stress in zooxanthellae, since high LPO and glutathione reductase (GR) levels were recorded, but it did not cause any effect on polyp Hsp expression, probably due to the antioxidant action of GR. With the temperature increase, Mn enrichments prevented any increase in Hsp levels and caused a significant decrease of LPO and GR activity, strengthening a previous hypothesis suggesting that Mn could mitigate the negative cellular effects produced by the thermal stress.

Subcellular dynamics studies of iron reveal how tissue-specific distribution patterns are established in developing wheat grains.

Understanding the mechanisms of iron trafficking in plants is key to enhancing the nutritional quality of crops. Because it is difficult to image iron in transit, we currently have an incomplete picture of the route(s) of iron translocation in developing seeds and how the tissue-specific distribution is established. We have used a novel approach, combining iron-57 (57 Fe) isotope labelling and nanoscale secondary ion mass spectrometry (NanoSIMS), to visualize iron translocation between tissues and within cells in immature wheat grain, Triticum aestivum. This enabled us to track the main route of iron transport from maternal tissues to the embryo through the different cell types. Further evidence for this route was provided by genetically diverting iron into storage vacuoles, with confirmation provided by histological staining and transmission electron microscopy energy dispersive X-ray spectroscopy (TEM-EDS). Almost all iron in both control and transgenic grains was found in intracellular bodies, indicating symplastic rather than apoplastic transport. Furthermore, a new type of iron body, highly enriched in 57 Fe, was observed in aleurone cells and may represent iron being delivered to phytate globoids. Correlation of the 57 Fe enrichment profiles obtained by NanoSIMS with tissue-specific gene expression provides an updated model of iron homeostasis in cereal grains with relevance for future biofortification strategies.