Redistribution Of Elements Research Articles

МИКРОЭЛЕМЕНТНЫЙ СОСТАВ ДЕРНОВО-КАРБОНАТНЫХ ПОЧВ СЕВЕРО-ЗАПАДНОГО КАВКАЗА

The aim of the work is to study the peculiarities of the formation of the microelement composition of sod-carbonate soils of the North-West Caucasus. Methods: Determination of the features of the formation of the microelement composition of sod-carbonate soils was carried out in the western part of the Labino-Malkinsky landscape district of forest-steppes and settled meadows. The Kuestov District occupies a band of ridges of the North-western Caucasus, composed of limestones, dolomites and sandstones of the Jurassic (K) and Cretaceous (k) periods. Chemical analysis of the soil was performed by conventional methods. The content of strongly bound compounds Pb, Cu, Zn, and Cd by acid decomposition using 5 M HNO3 was analyzed in the humus horizon of soils. The metal content was determined by the methods of inversion volt-amperometric and atomic absorption analyses. Results: In most cases, the microelement composition of sod-carbonate soils is characterized by the enrichment of Pb, Cu, Cd and depletion of Zn in comparison with the Clark soils. The constant anthropogenic input of pollutants into the soil as a depositing medium directly affects the trace element composition-the soils are intensively enriched with all the elements considered, especially strongly accumulated on CD and PB. In the radial distribution of trace elements between sod-carbonate soils and the soil-forming rock, a high intensity of accumulation of chemical elements in the humus horizon of soils was revealed. The intensity of the redistribution of trace elements in soils is largely determined by the position in the terrain. Within the Cretaceous cuesta, high Cd contents are typical for plakor soils, Cu and Zn-for the soils of the slope of the beam. On the slope of the Jurassic questi higher contents of Pb, Cd and Cu are typical for soils of placorestan cavage array Zn for soils of steep hillside with oak and beech forests. Conclusions: The microelement composition of sod-carbonate soils is a consequence of such soil-forming processes as humification, humus accumulation, leaching, glinting, and loess age, the specifics of which are largely determined by calcium carbonates. The microelement composition of sod-carbonate soils reflects the most significant features of the microelement composition of soil-forming rocks, which are characterized by low Zn content. The possible aerotechnogenic intake of trace elements affects the intensity of the radial accumulation of trace elements in the soil relative to the rocks. The degree of transformation of the microelement composition of anthropogenic disturbed soils depends on the intensity of anthropogenic impact on the soil. The conducted research is important in the aspect of revealing the regularities of the formation of the microelement composition of the soil as a depositing component of the landscape in modern conditions of anthropogenic pressure.

ОСОБЕННОСТИ ПОВЕДЕНИЯ ХИМИЧЕСКИХ ЭЛЕМЕНТОВ В СИСТЕМЕ ВОДА–ПОРОДА РАЙОНА РАЗРАБАТЫВАЕМОГО КАРЬЕРА БУТОВОГО КАМНЯ В ПИТКЯРАНТСКОМ РУДНОМ РАЙОНЕ (КАРЕЛИЯ)

Актуальность. Изучение особенностей перераспределения химических элементов в системе вода–порода в районах, где ведется активная разработка месторождений полезных ископаемых, актуально ввиду потенциального влияния этих процессов на экологическую обстановку и изменение геохимических условий природной среды. В частности, это важно для выбранного района, который входит в площадь водосбора крупнейшего природного резервуара пресной воды в Европе – Ладожского озера. Целью представленного исследования является изучение выноса химических элементов водой из гранитоидных пород, вскрытых карьером, и их дальнейшего поведения в природных водах и донных отложениях района. Объектом исследования являются природные воды и донные отложения района разрабатываемого карьера бутового камня (Питкярантский рудный район, республика Карелия). Авторы проследили изменения химического состава природных вод и связанных с ними донных отложений по мере движения воды от ее сброса из карьера до впадения в речную сеть. Методы. Анализ химического состава природных вод и донных отложений проведен стандартными методами: потенциометрия, титриметрия, ICP-AES, ICP-MS. Исследования минералов в составе пород карьера бутового камня проведено при помощи LA-ICP-MS, химический состав горных пород изучен методами XRF, ICP-MS и ICP-AES. Физико-химическое моделирование форм нахождения в природных водах и осаждения минералов проведено в программном комплексе HydroGeo. Верификация модели проведена на основе анализа химического состава донных отложений. Результаты. В изученных водных объектах в отдельных точках отмечены превышения ПДК Fe, Mn, Cu, Zn, Mo, V. При удалении от карьера бутового камня снижается величина общей минерализации природных вод и содержание макрокомпонетов, а также Sr, U, V, Mo, Zn, Cd. Концентрация железа, наоборот, увеличивается ввиду роста содержания органического вещества в воде. В донных отложениях пик концентрации многих элементов (Fe, Mn, Co, Cu, Zn, Cs, Ce, La, Y) наблюдается в точке сброса воды из карьера. Максимальное содержание U отмечается чуть ниже по потоку изучаемых вод, что согласуется с данными по составу донных отложений и моделирования, которые указывают на возможность выпадения уранинита из водного раствора в водоеме, сформировавшемся при сбросе воды из карьера бутового камня и истоке ручья, берущего начало в этом водоеме. Роль органического вещества в изученных водах высока для процесса накопления железа в воде за счет образования устойчивого гидроксо-фульватного комплекса железа, а также для редкоземельных элементов за счет образования комплекса с гуминовой кислотой. Анализ распространенности, форм нахождения и осаждения химических элементов позволили заключить, что эксплуатация карьера бутового камня вносит существенный вклад в перераспределение химических элементов в изучаемом районе.

Effect of laser treatment on the characteristics of martensitic transformation in Fe–Ni alloy

The effect of pulsed laser treatment on the structural state and internal stresses of the Fe–Ni alloy has been studied. The influence of the size of austenitic grains, redistribution of chemical elements and internal stresses in the austenitic phase on the characteristics of martensitic transformation in the subsurface layer of the alloy was analyzed. A correlation between the grain size effect of martensitic transformation and the amount of martensitic phase in this layer was established.

Episodic hydrofracturing and large-scale flushing along deep subduction interfaces: Implications for fluid transfer and carbon recycling (Zagros Orogen, southeastern Iran)

We investigate the late Cretaceous blueschist-facies (480 °C-1.8 GPa) segment of the Zagros suture zone, a well-preserved block-in-matrix paleo-subduction channel. We aim to determine the relative chronology, conditions of deformation, and potential fluid sources and processes associated with the widespread occurrence of lawsonite + clinopyroxene + glaucophane veins and aragonite-bearing hydraulic breccias. We use a multi-scale approach methodology to provide new insights into deep fluid flow mechanisms as well as to constrain possible sinks of CO2-bearing fluids in the subducting slab. Petrological analyses suggest that silicate-rich vein systems began precipitating during early burial and evolved with ongoing burial and shearing-related deformation in the blueschist-facies, while most carbonate-rich veins and hydrofractures formed at near-peak P-T conditions. In situ LA-ICP-MS trace element analyses reveal that: (i) individual silicate host-vein pairs have similar REE signatures, reflecting local-scale fluid-mediated element redistribution, (ii) carbonate-bearing veins and metasediments also have similar trace element signatures and (iii) lawsonite in blueschist-hosted veins exhibit REE enrichments along their rims, suggesting an increasing contribution of metasedimentary-derived fluids upon approaching peak P-T. Carbonate OC isotope compositions of the veins and metasedimentary rocks range from +13.6 to +17.9‰ (δ18OVSMOW) and − 1.0 to +3.1‰ (δ13CVPDB), demonstrating metasedimentary-derived fluid sources related to large-scale H2O homogenization with far-traveled mafic- ultramafic-derived fluids. SrNd isotopic ratios in carbonate veins and the adjacent host resemble their host composition indicating that host rock-buffered isotopic homogenization occurred between the infiltrating fluids and the rock matrix, possibly during episodic porous flow. Thermodynamic modeling predicts that decarbonation via fluid-assisted reactions is inefficient at blueschist-facies and that carbon release likely occurs deeper along the subduction interface (i.e., at eclogite-facies). We propose that deeply produced H2O-rich fluids interacted with the carbonate-bearing lithologies along the subduction interface facilitating fluid-mediated decarbonation and further fluid transport as hydraulic pulses (e.g., porosity waves) that traveled at the kilometer-scale parallel to the subduction interface, (i) contributing to the isotopic homogenization herein observed and (ii) triggering episodic hydrofracturing in the lawsonite-blueschist-facies (≈50-60 km depth). Veinsets in exhumed subducted rocks hence provide a unique opportunity to understand fluid-rock interaction processes in the region at which episodic tremor and slow slip events phenomena occur.

EVOLUTION OF INVISIBLE Au IN ARSENIAN PYRITE IN CARLIN-TYPE Au DEPOSITS

Abstract A significant characteristic distinguishing Carlin-type Au deposits from other Au deposits is the abundance of invisible Au in arsenian pyrite. Gold occurs primarily as ionic Au1+ in arsenian pyrite and is unstable during subsequent thermal events. In this study, we used the focused ion beam combined with scanning electron microscope (FIB-SEM) techniques, and a transmission electron microscope (TEM) to examine invisible Au and how it evolved through later geologic events that eventually led to the formation of Au nanoparticles. FIB-SEM techniques were used to prepare site-specific TEM foils from four Carlin-type gold deposits, including Getchell and Cortez Hills, Nevada, USA, and Shuiyindong and Jinfeng, Guizhou Province, China. These samples were analyzed to quantify ore pyrite chemistry and evaluate textures at the nanometer scale. In 17 examined TEM foils, we observed widespread Au-rich domains in high-grade Au arsenian pyrites from the Getchell and Cortez Hills Au deposits and the Jinfeng deposit but only 10 Au-bearing nanoparticles, ~10 to 20 nm in diameter. The Au-rich domains exhibit Au (Sb), (Tl), (Hg), and (Cu) peaks in the energy dispersive X-ray (EDX) spectrum without the presence of recognizable nanoparticles. This confirms that Au is invisible even at a nanometer scale and is most likely present in the crystal structure of arsenian pyrite. Stacking faults and nanometer-sized fluid inclusions were commonly observed in Au-bearing arsenian pyrite from the four deposits, implying rapid crystallization. Moreover, unlike the coarsely crystalline arsenian pyrite from Guizhou Carlin-type Au deposits, arsenian pyrite from Carlin-type deposits in Nevada consists of fine-grained polycrystalline aggregates, further implying rapid crystallization. Additionally, curved dislocations were commonly pinned by solid inclusions, reflecting a former annealing process. Combining nanoscale textures with geologic information previously reported for Carlin-type deposits, invisible ionic Au was initially incorporated into the crystal structure of arsenian pyrite during rapid precipitation. Subsequent post-ore magmatic events in both districts initiated the annealing of the ionic Au-bearing arsenian pyrite, leading to the redistribution of trace elements and formation of Au-bearing nanoparticles in the arsenian pyrite. The presence of predominantly ionically bonded Au in arsenian pyrite confirms that ore fluids were not saturated in Au when Au-bearing arsenian pyrite formed, as previously reported for Carlin-type deposits. Ionic Au that was scavenged from an undersaturated ore fluid and incorporated into the arsenian pyrite crystal structure formed the giant Carlin-type Au deposits.

Microstructure, Tensile and Fatigue Behaviour of Resistance Spot Welded Zinc Coated Dual Phase and Interstitial Free Steel

Galvannealed (hot dip galvanized and annealed) dual phase (DP600) steel and interstitial free (IF) steel are two of the widely used materials in automotive industries owing to their high specific strength, toughness, formability and corrosion resistance. This inevitably requires their joining to form larger components. Resistance spot welding has emerged as the predominant welding technique for joining of sheet metals in automotive industries. There are complexities regarding microstructural variation of the fusion zone and across heat affected zones during spot welding of fundamentally dissimilar steels. This is further aggravated by the prospect of zinc redistribution during the welding process. Current study presents the evolution of microstructure in different zones of welding in IF and DP600 steel. Micro-hardness profiles and electron back scattered diffraction studies were performed. Furthermore, redistribution of elements in different welding zones is studied using electron probe micro analysis. The effect of welding current and time on the nugget size and the strength of the weld during tensile–shear is determined. It was observed that there was an increase in nugget diameter and maximum load bearing capacity of the joint with an increase in heat input, until the occurrence of expulsion. Furthermore, critical nugget diameter for pull-out failure was determined and existing empirical models were verified for the applicability in this case. None of the existing empirical models could predict the critical nugget diameter correctly and thus a new empirical relationship between sheet thickness and critical nugget diameter for zinc coated dissimilar steels has been proposed. Failure behaviour of the spot-welded sheets were studied under tensile–shear configuration under quasi-static and fatigue mode of loading and it showed substantial difference in location of crack initiation and fractographic features. Tensile–shear specimen at optimum welding parameter failed from the base metal of the IF steel side with dimples on the fracture surface, whereas fatigue specimen failed from the heat affected zone of the IF steel side with transgranular striations on the fracture surface.

Effect of Cd diffusion on the electrical properties of the Cu(In,Ga)Se2 thin-film solar cell

Cu(In,Ga)Se2 (CIGSe)-based solar cells are promising candidates for efficient sunlight harvesting. However, their complex composition and microstructure can change under operation conditions, for instance heating from sun light illumination can lead to a degradation in performance. Here, we investigate the thermally-induced degradation processes in a set of CIGSe-based solar cells that were annealed at temperatures between 150 °C and 300 °C. Using correlative atom probe tomography (APT)/transmission electron microscope (TEM), we found that the buffer/absorber interface is not sharp but consists of an interfacial zone (2–6.5 nm wide) where a gradient of constituent elements belonging to the CdS buffer and CIGSe absorber appears. An enhanced short-range Cd in-diffusion inside the CIGSe was observed whenever a low Ga/(Ga + In) ratio (≤ 0.15) occurred at the interface. This might indicate the presence of Ga vacancies as a channeling defect for Cd in-diffusion inside the CIGSe layer leading to a buried p/n-homojunction. We evidence that a considerable amount of Cd is found inside the CIGSe layer at annealing temperatures higher than 150 °C. Further investigations of the elemental redistribution inside the CIGSe layer combined with C–V measurements support the formation of CdCu+ donor like defects deep inside the p-type CIGSe which lead to a strong compensation of the CIGSe layer and hence to strong deterioration of cell efficiency at annealing temperatures higher than 200 °C. Hence, understanding the degradation processes in Cu(In,Ga)Se2 (CIGSe)-based solar cells opens new opportunities for further improvement of the long-term device performance.

The Influence of the Magmatic to Postmagmatic Evolution of the Parent Rock on the Co Deportment in Lateritic Systems: The Example of the Santa Fé Ni-Co Deposit (Brazil)

Abstract The Santa Fé Ni-Co deposit is a major undeveloped lateritic deposit located in the Goiás State of Central Brazil. The deposit comprises two properties that together have indicated resources of 35.7 million tonnes (Mt), grading 1.14% Ni and 0.083% Co, and inferred resources of 104.3 Mt at 1.03% Ni and 0.054% Co. The laterite was derived from Late Cretaceous alkaline ultramafic lithologies that experienced an initial silicification from Eocene to Oligocene, followed by lateritization and partial reworking in Miocene-Pliocene. The deposit is characterized both by oxide- and phyllosilicate-dominated ore zones. In the former, Ni- and Co-bearing hematite and goethite dominate the supergene mineralogical assemblage, while ore-bearing Mn oxyhydroxides occur as minor components. In the phyllosilicate-dominated horizons the major Ni-carrying phase is chlorite. Multivariate statistical analyses (factor analysis and principal components analysis) conducted on the drill core assay database (bulk-rock chemical analyses) showed that significant differences exist between Ni and Co distributions. The Ni distribution is not controlled by any clear geochemical correlation. This is because the highest Ni concentrations have been measured in the ferruginous and in the ochre saprolite zones, where Ni-bearing minerals (chlorite and goethite) are mostly associated with reworked material and only in a limited way, with zones affected by in situ ferrugination. Cobalt has an atypical statistical distribution at Santa Fé if compared with other laterites, correlated not only with Mn but also with Cr in the majority of the laterite facies. From microchemical analyses on several potential Co-bearing minerals, it was found that the Co-Cr association is related to elevated Co contents in residual spinels, representing unweathered phases of the original parent rock now included in the laterite. This element distribution is atypical for Ni-Co laterite deposits, where Co is normally associated with Mn in supergene oxyhydroxides. In the case of the Santa Fé laterite, the Co concentration in spinels is likely related to magmatic and postmagmatic processes that affected the original parent rock before lateritization, specifically (1) orthomagmatic enrichment of Co in chromite, due to its high affinity to spinels in alkaline melts, and (2) trace elements (i.e., Co, Mn, Ni, and Zn) redistribution during the hydrothermal alteration of chromite into ferritchromite. The Santa Fé deposit represents a good example of how the prelateritic evolution of a parent rock strongly affects the efficiency of Co mobilization and enrichment during supergene alteration. Based on the interpretation of metallurgical test work, a fraction of total Co between 20 and 50% is locked in spinels.

Evidence of hydrothermal fluid circulation driving elemental mass redistribution in an active fault zone

Important fault zone processes can be discerned from the characterization of fracture damage and chemical transformations associated with active seismic sources. To characterize the 2010 M7.2 El Mayor-Cucapah rupture zone, continuous samples of fault core and 23 samples of damaged rock were collected perpendicular to strike of the Borrego fault. Samples were analyzed for clay mineralogy, bulk geochemistry, and bulk and grain density from which porosities and volumetric strains were derived. Prior to the Borrego fault forming, the tonalitic protolith, containing chlorite, epidote, and titanite, was subjected to temperatures of ∼330–340 °C during deuteric alteration. Rocks within the damage zone are partially pulverized and contain abundant cataclastic seams. Porosity and volumetric strain peak in zones 1.5 m–10.5 m from the core. Within these zones, losses in Ca and P mass, increases in Mg and Na mass, along with the conservation of Fe and Si mass are consistent with oxidizing acidic conditions at < 200 °C. Gains in LOI are attributed to increases in clay content. The above data support a model of Mg- and Na-rich oxidizing fluid circulation within the damage zone of the Borrego fault.

Interfacial La Diffusion in the CeO2/LaFeO3 Hybrid for Enhanced Oxygen Evolution Activity.

The electrochemical oxygen evolution reaction (OER) is of great significance for energy conversion and storage. The hybrid strategy is attracting increasing interest for the development of highly active OER electrocatalysts. Regarding the activity enhancement mechanism, electron coupling between two phases in hybrids has been widely reported, but the interfacial elemental redistribution is rarely investigated. Herein, we developed a CeO2/LaFeO3 hybrid electrocatalyst for enhanced OER activity. Interestingly, a selective interfacial La diffusion from LaFeO3 to CeO2 was demonstrated by the electron energy loss spectra and elemental mapping. This redistribution of cations triggers the change of the chemical environment of interface elements for charge compensation because of the electroneutrality principle, which results in increased oxygen vacancies and high-valent Fe species that promote the OER electrocatalysis. This mechanism might be extended to other hybrid systems and inspire the design of more efficient electrocatalysts.

A Mineralogical Investigation on Volatilization of Impurity Elements from Cu-Rich Polymetallic Concentrates During Roasting in Inert Atmosphere

Four different Cu-rich polymetallic concentrates are tested for volatilization of Sb and As during laboratory-scale roasting. The experiments are performed between 200 °C and 700 °C, at intervals of 100 °C and in an inert atmosphere. Sb volatilization is much less (maximum approximately 45 pct) than As volatilization (maximum approximately 95 pct) in these conditions at 700 °C. As volatilization is however limited from the concentrate having As mainly in a tetrahedrite solid solution ((Cu,Ag,Fe,Zn)12(Sb,As)4S13). Sb and As retained in the roasted calcine are found in the low-melting liquid phase, formed at approximately 500 °C. This melt phase gets enlarged and enriched in Sb with an increase in temperature. However, there is noticeable As volatilization from this melt phase with the temperature approaching 700 °C. Furthermore, there is an early and relatively high Sb volatilization from the concentrate having Sb substantially as gudmundite. Micron-scale elemental redistribution in gudmundite in the 350 °C roasted calcine confirms its transformation at this temperature. Other Sb minerals did not undergo any detectable transformation at this temperature, suggesting that the significant Sb volatilization starting between 300 °C and 400 °C was primarily from gudmundite. This benign attribute of gudmundite featured in this work in the context of roasting should also be relevant from the geometallurgical perspective during concentrate production, where concentrates bearing Sb are considered substandard for further Cu extraction irrespective of the Sb mineralogy.

Study of Conditions for Improving Chemical and Structural Homogeneity of Ferritic Class Hot-Rolled Steels

Redistribution of carbon and other elements, and formation of the structure, composition, and properties of low-carbon Nb, Nb–Ti, Nb–V, Nb–V–Mo and Ti–Mo microalloyed steels during hot rolling is studied using metal of five laboratory melts. It is established that by selecting the temperature for the beginning of rolling in the finishing group of stands according to steel composition (microalloying system) it is possible to achieve a significant improvement in the homogeneity of the composition, structure, and set of rolled product properties. Therefore, it is demonstrated by experiment that chemical and structural heterogeneity of metal formed in the billet casting stage may be largely eliminated during hot rolling on the basis of controlling carbide (carbonitride) precipitate formation.

Особенности проявления контактового метаморфизма руд Ново-Учалинского месторождения на Южном Урале

The article presents the impact of contact metamorphism on the ores of the large Novo-Uchaly Cu-Zn massive sulfide deposit (South Urals) as well as structural features of the contact zone and change in mineral composition of the ore and dikes. The study of contact metamorphism is also of practical interest because the ores are enriched in precious metals and rare elements in the local contact areas. The author together with geologists from the Uchaly Mining and Processing Plant carried out a geological and mineralogical mapping of the deposit (underground mine). The analytical studies were based on using optical and scanning electron microscopes. The results of detailed geological mapping are as follows: the thick gabbro-diorite dike is alterated by chloritization, hematitization and silicification, and contains quartz-carbonate-sulfide veinlets. The exocontact zones are usually thin, with thickness less than 10 cm, rarely reach 2 m. The signs of the contact metamorphism of the ores: cataclasis, recrystallization of sulfides; the appearance of the increased amount of rare minerals (magnetite, fahlore, galena); violation of the geochemical zoning caused by local redistribution of chemical elements. These factors characterize the ore transformation by the processes — local contact metamorphism and the subsequent hydrothermal mineralization caused by the remobilization of the ore substance.

ГЕОДИНАМІКА

Purpose. Our research main purpose is to demonstrate the use of entropy maximization method for calculating the geochemical system composition, which consist of solid and gaseous organic substances. Changing the geodynamic situation is the driving force of elements redistribution between compounds in such systems. According to thermodynamic apparatus the main factors influencing this redistribution are pressure, temperature and the initial number of elements. Methods. Gibbs energy minimizing, maximizing the entropy, independent chemical reactions constants, Lagrange's method of undetermined multipliers, Newton–Raphson iterative method. It is well known that the fossilized organic matter, which is mainly represented by many types of kerogen, is an irregular polymer with structure, which cannot be described definitely. To calculate the equilibrium in the kerogen/gas system and obtain reliable results, it is necessary to apply a new model, without using the model structures of kerogen. We have proposed and described in detail a method of applying the Jaynes' formalism and maximizing entropy method to calculate the change in the composition of the kerogen/gas system with geodynamic regimes changing. Software in the Excel macros form and a compiled dynamic library, written in Visual Basic language, was created for calculations. Results. To verify the reliability of the proposed method and algorithm, we calculated the composition of the geochemical system, consisting of type II kerogen, methane to pentane hydrocarbons (including isomers), carbon dioxide, water and hydrogen sulfide. The calculation result is the molar fractions of hydrocarbon components and additive groups that make up kerogen, for different depths of the earth's crust. The calculations were performed for three heat fluxes: 40, 75 and 100 mW/m2, lithostatic pressure taken in account. Scientific novelty. It is established that the geodynamic situation changing in a complex way affects the distribution of elements between gases and kerogen in a closed thermodynamic system; modeling the kerogen/gas system behavior by method of entropy maximization provides results that do not contradict to study the structure of type II kerogen at different stages of maturity; the character of changes in the concentrations of hydrocarbon gases in equilibrium with type II kerogen indicates the inconsistency of the "oil window" hypothesis with the postulates of equilibrium thermodynamics. Practical significance. The entropy maximization method can be successfully used to calculate the composition of various geochemical systems consisting of organic compounds. The method is suitable for determining chemical composition of the irregular polymers, such as kerogen, bitumen, humic, in equilibrium with organic and inorganic gases and liquids.

Hydrothermal alteration in Eshtehard volcanoes, Iran: Constraints from trace elements redistribution and stable isotope geochemistry

We use the mineralogy, trace element compositions and elemental mass balance of volcanic materials collected from propylitic, potassic and phyllic alteration facies in the Eshtehard area of Iran to document the nature and effects of hydrothermal alteration. Incompatible element abundances in hydrothermally–altered samples show transformations that include: (i) depletion of alkalis and alkaline earth elements (i.e., Ba, Sr), (ii) variable behavior of first series transition elements (depletion in Cr, Co and Ni; enrichment in Zn and Cu), and (iii) depletion of HREE, Hf and Th relative to U and LREE. In detail, potassic (associated with a major addition of Cu) and phyllic zones are characterized by enrichment of SiO2 and MgO whereas propylitization depleted SiO2 and MnO, enriched MgO and Fe2O3, and increased LOI. Whole rock geochemistry along hydrothermal facies revealed consistent negative Ce and Eu anomalies, indicating that reducing conditions persisted during hydrothermal processes. Substantial changes in isovalent elements ratios (i.e., K/Ba, K/Rb, Y/Ho, Sr/Eu, Zr/Hf and Eu/Eu*) along the facies illustrate non–charge and radius control behavior are construed as lanthanide tetrad–effect phenomena. The co–occurrence of zigzag patterns (i.e., M and W–shapes) is evidence for partial or incomplete tetrad effect reaction between REE3+ and F-and Cl-rich fluids in hydrothermal systems. Low T4 tetrad–effect values overall suggest rock–fluid interaction involving rather low temperature hydrothermal solutions. Mass (ΔM) and volume (ΔV) were slightly depleted in the propylitic (−3.80% and −5.66%) potassic (−3.48% and −5.66%), and phyllic (−2.52% and −2.91%) zones with isocon slopes of 1.06, 1.06 and 1.03, respectively. We envisage a secondary phenomenon in open system conditions which accompanied fluid–rock interaction as the plausible cause of slight REE tetrad effect observed in the hydrothermally altered samples. Fluid inclusions studies yield homogenization temperatures of 275–596 °C and salinity ranging from 34 to 39 wt% NaCl equivalent suggesting boiling during mineralization in the Eshtehard area. The calculated δ18O and δD of the fluids range between 5.3 and 7.1 and −75 to −62 per mil, respectively. On this basis, we suggest that the ore-forming fluids had a magmatic source and underwent boiling and/or exchange with hydrous minerals.

The evolution of compositional and microstructural heterogeneities in a TaMo0.5ZrTi1.5Al0.1Si0.2 high entropy alloy

We report the chemical segregation and the phase decomposition as well as the microstructural response upon plastic deformation in a TaMo0.5ZrTi1.5Al0.1Si0.2 (at.%) refractory high entropy alloy (RHEA) by combining the thermodynamic calculation and the multiple experimental characterization techniques down to near-atomic scales. The alloy's compositional and microstructural heterogeneities under different processing conditions, including casting, annealing and room/high temperature compression, are emphasized. Results show that casting creates the original compositional heterogeneity with evident dendritic microstructures. The dendrite consists of a single body-centered-cubic (BCC) phase enriched with Ta and Mo. The interdendritic region is delineated by Zr, Ti, Al and Si, with the formation of rod-like BCC/silicide eutectics. After annealing at 1300 °C for 48 h, both dendritic and interdendritic BCC phases experience evident phase decomposition and elemental redistribution. This leads to the increase of compressive strength at room temperature to ~2050 MPa, which is ~300 MPa higher compared to that of the as-cast material. Strain softening of the annealed alloy occurs when subjected to compression at 1000 °C, which is associated with the formation of a heterogeneous necklace microstructure composed of dynamically recrystallized grains

Element redistributions during early stages of oxidation in a Ni38Cr22Fe20Mn10Co10 multi-principal element alloy

Element redistributions after initial oxidation of a Ni38Cr22Fe20Mn10Co10 (at.%) multi-principle element alloy at 120 °C and 300 °C is captured via in situ atom probe tomography. All cations contribute to the oxide in both conditions, consisting of a Cr-rich inner oxide and a Fe, Mn, Co and Ni-rich outer oxide. At lower temperature, Ni tends to be trapped at the outer/inner oxide interface, while Ni enriches at the oxide/metal interface at higher temperature in tandem with Cr metal depletion. These observations confirm oxidation of complex alloys involves the formation of metastable, multi-layered oxide films, with a distinct tendency for solute trapping.

Analysis of Wear Resistance of Borided Steel C45.

The wear resistance of diffusion coatings in conditions of specific pressures of 3, 7 and 10 MPa was studied. The boride coatings were prepared by means of diffusion methods using C45 steel as the substrate material. Research on the microstructure and redistribution of chemical elements on wear surface of a borided layer was carried out. It was found that the boride coatings should be used under a specific pressure of 7 MPa. It was found that the wear of friction couple coating of steel C45 under specific pressure of 3 MPa proceeds according to the oxidation wear mechanism, while under specific pressures of 7 and 10 MPa the abrasive wear prevails. The wear-induced segregation of atoms in coatings was studied using secondary mass-spectroscopy method (SIMS). Increased C, O, and B concentrations were noticed at the wear surface on depth from 50 to 2000 Å. The secondary wear-induced structure formation on the wear surface resulted in high wear resistance of diffusion borided coatings.

Impact of Flooding and Urbanisation on the Content of Heavy Metals in the Water and Bottom Sediments of the Amur River

The impact of floods on the migration activity of elements coming from urbanized territories to the Amur river was assessed. The influence of large cities on pollution of water and floodplain ecosystems is revealed. The content of heavy metals in water, bottom sediments, and small watercourses draining urban areas is characterized. The processes of sediment accumulation in the floodplain, their influence on the redistribution of elements and geochemical transformations in the soil space of floodplain soils are studied. Conditions for the accumulation of heavy metals in soils are described, their concentration levels and migration activity are determined. The role of organic matter in swamps and silts on water pollution and bottom sediments of the Amur river is shown. It was found that the main mass transfer of soluble substances and pollutants dispersed fractions of nailc is carried out by water flow during floods.

Elemental redistribution and precipitation reactions of 9Cr1.5Mo1CoB(FB2) steel during tempering

The effect of tempering temperature on the precipitation reactions and elemental redistribution in 9Cr1.5Mo1CoB(FB2) steel has been studied using scanning electron microscope(SEM), transmission electron microscope(TEM), secondary ion mass spectrometry(Tof-SIMS) and atom probe technique (APT). The results show that water-cooling from normalization at 1100 °C produced lathy martensite. During tempering at 500 °C, only C and B atoms were segregated, and formed needle-like Fe3(C, B); After tempering at 600 °C, the segregation of Cr, Mo and Mn showed noticeable difference, forming Cr + Mn + Mo + C + B and Mo + Cr + C + B clusters. Consequently, (Cr,Mo)2(C,B), Cr-rich M7(C,B)3 and Cr-rich M23(C,B)6 were observed in sample tempered at 600 °C. And both (Cr,Mo)2(C,B) and M7(C,B)3 particles were entirely replaced by Cr-rich M23(C,B)6 by enhancing the tempering temperature to 700 °C. Therefore, the evolution of carbides in FB2 steel during tempering at 500 °C–700 °C can be summarised as follows: Fe3(C,B) → (Cr,Mo)2(C,B) + Cr-rich M7(C,B)3 → Cr-rich M23(C,B)6. Besides, the Mo element in (V,Nb,Mo)(N,C) particles was gradually replaced by V and Nb with the increase of temperature from 600 °C to 700 °C. While Si and Co were rejected to the interfaces of carbides/matrix during tempering, forming a flux of Si and Co. Then, this flux may suppress carbides coarsening by retarding the diffusion of Cr, Mo and Mn from the matrix into carbides.