Bulk Chemical Composition Research Articles

Statistical Evaluation and Hydrogeochemistry of Groundwater from Western Part of Chandrapur District, Maharashtra with Special Emphasis on Human Health Risk Assessment

The groundwater samples were collected from the phreatic aquifers of PG2 watershed of western part Chandrapur district, Maharashtra. The geogenic processes like dissolution of calcium rich minerals are responsible for increase of Ca2+ content in groundwater. In the groundwater samples, HCO - and SO 2- are the prevailing dominant anions. The TDS, TH, Ca2+, Mg2+, Na+, HCO - as well as Cl- ions present in basement rocks have been attributed to the geogenic factor through the factor analysis. K+, SO 2- as well as NO - correspond to fertilizers and soil amendments used by people to enhance crop production, which is regarded as anthropogenic input. The silicate weathering at water-rock interface is the main process of generation of various solutes in groundwater. The multiple regression analysis expresses the TDS as a linear function of the ions and Ca2+, Mg2+, Na+, HCO -, Cl-, SO 2- and NO - contribute significantly to the bulk chemical composition of the groundwater from the study area. The health hazard quotient (HQ) for children (4.94%) and adults (7.95%) denotes the intensity of different health risk vulnerable zones at a specific site. Keywords: Rock-Water Interaction, Silicate Weathering, Statistical Evaluation, Health Risk Assessment, Chandrapur District, Maharashtra

Fluid mobilization of rare earth elements, Th, and U during the terrestrial alteration of H chondrites

AbstractThe chemical effects of terrestrial alteration, with a particular focus on lithophile trace elements, were studied for a set of H chondrites displaying various degrees of weathering from fresh falls to altered finds collected from hot deserts. According to their trace element distributions, a considerable fraction of rare earth elements (REEs), Th, and U resides within cracks observed in weathered meteorite specimens. These cracks appear to accumulate unbound REEs locally accompanied by Th and U relative to the major element abundances, especially P and Si. The deposition of Ce is observed in cracks in the case of most of the weathered samples. Trace element maps visually confirm the accumulation of these elements in such cracks, as previously inferred based on chemical leaching experiments. Because the positive Ce anomalies and unbound REE depositions in cracks occur in all weathered samples studied here while none of such features are observed in less altered samples including falls (except for altered fall sample Nuevo Mercurio), these features are interpreted to have been caused by terrestrial weathering following chemical leaching. However, the overall effects on the bulk chemical composition remain limited as the data for all Antarctic meteorites studied in this work (except for heavily weathered sample A 09516, H6) are in good agreement with published data for unaltered meteorites.

Hydrothermal ferromanganese oxides around a petit-spot volcano on old and cold oceanic crust

Areas of old and cold oceanic plate lack conventional volcanism and have been assumed to be devoid of submarine hydrothermal activity. However, petit-spot volcanoes are common in areas of flexure of such oceanic plates. Here, we report hydrothermal ferromanganese oxides dredged from the vicinity of a petit-spot volcano at 5.7 km water depth in an area of oceanic plate flexure east of the Japan Trench. The bulk chemical, lead isotopic and mineralogical compositions of the samples indicate their formation by low-temperature hydrothermal activity, which can be interpreted as being caused by fluid–rock interactions at <200 °C. We propose that interaction of local marine sediments with volatile-rich petit-spot magmas may produce hydrothermal fluids containing not only iron and manganese but also enough amounts of carbon dioxide and methane to have implications for the global carbon cycle. However, contemporary hydrothermal activities at petit-spot volcanoes have not been confirmed yet.

Intra‐Seasonal Variability in Sediment Provenance and Transport Processes in the Brahmaputra Basin

AbstractSediment composition in modern fluvial settings is commonly assessed regarding spatial but rarely temporal variability, potentially leading to a bias of unknown extent. Here, we present the grain‐size distribution, bulk chemical and mineralogical composition of a time‐series set of 36 suspended sediment samples from the Brahmaputra river, as well as clay and heavy mineral analysis of selected samples. Sampling covers the June–November 2021 period, which included two major flooding events. We show that the two flooding events are characterized by contrasting grain size, with the first event characterized by a grain‐size minimum and the second by a grain‐size maximum. Although grain sizes of the first flood and the period after the second are similar, their compositions differ significantly, highlighted by a factor‐two decrease of biotite largely compensated by an increase in quartz. By contrast, the content of garnet, clinopyroxene, sillimanite, and rutile increased compared to epidote and amphibole during the second flood event. By relating the results to spatio‐temporal rainfall and discharge patterns and basin morphology, we conclude that the first flooding primarily mobilized hydraulically pre‐sorted sediments from the exposed sandbars of the floodplains, while those sandbars are already submerged during the second flooding in a single‐channel system, resulting in higher sediment contributions from highland tributaries draining igneous and high‐grade metamorphic rocks. Such temporal variations pose constraints on the interpretation of compositional differences between individual samples regarding sediment provenance and dispersal and should be considered in studies of modern drainage basins as well as ancient sediment routing systems.

A Workflow for Uncertainty Assessment in Elemental Analysis of Archaeological Ceramics: A Case Study of Neolithic Coarse Pottery from Eastern Siberia

In this study, the assessment of uncertainties introduced at different stages of the elemental analysis of archaeological ceramics has been described using the example of the Neolithic pottery sherds from Popovsky Lug (eastern Siberia). To evaluate the uncertainty introduced by sampling due to ceramic heterogeneity, three original sherds were cut into small subsamples. Powdered subsamples (250–350 mg) were analyzed using wavelength-dispersive X-ray fluorescence and inductively coupled plasma mass spectrometry methods, and the variations between analytical results for independent subsamples were compared with the variations introduced during the analytical process (measurement and sample preparation). It was shown that 250–350 mg of ceramic is sufficient to obtain good reproducibility (2–15%) between separate subsamples for most major and trace elements, even for the heterogeneous Neolithic ceramics included in this study. The differing behavior of concentration variations in some elements was explained by measuring the ceramic cross-sections by scanning electron microscopy and micro-X-ray fluorescence spectrometry, as well as by the theoretic modeling of the sampling error. The described workflow can be useful in finding uncertainties in elemental analysis results, which may affect the interpretation of bulk chemical composition in ceramic provenance studies.

Electrochemical Deposition of Polypyrrole in the Presence of Silanes as Adhesion Promoters.

Polypyrrole adhesion to indium-tin oxide electrodes was improved by adding pre-hydrolyzed alkoxysilanes to the electrodeposition media. The pyrrole oxidation and film growth rates were studied by potentiostatic polymerization in acidic media. The morphology and thickness of the films were studied by contact profilometry and surface-scanning electron microscopy. The bulk and surface semiquantitative chemical composition was studied by Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy. Finally, the adhesion was studied by scotch-tape adhesion test, where both alkoxysilanes showed a significant improvement in adhesion. We proposed a hypothesis for the improvement in adhesion, that involves the formation of siloxane material as well as in situ surface modification of the transparent metal oxide electrode.

Grain size and mineralogical constraints on leaching in the bottom ashes from municipal solid waste incineration: a comparison of five plants in northern Italy

Introduction: Bottom ashes (BA) from municipal solid waste incinerators (MSWIs) are currently classified by the European Waste Catalogue as industrial non-hazardous waste. To promote their reuse, identification and characterization of the heavy metal-bearing phases (both glass and minerals), as well as their weathering behavior, must be addressed for what concern the chemical composition, mineralogical phases, and in high concentrations and pollutants’ mobility. An important point to be noted is whether the results from a given plant can be generalized.Materials and methods: In this work, BA from five waste-to-energy (WtE) plants in northern Italy were sorted based on different grain sizes. The area showed similar MSW production, collected from a culturally homogeneous area, and similar collection management. For each grain size, a mineralogical, chemical, and physical characterization was carried out using XRF, XRD, TGA, and the leaching test.Results and discussion: We found that for major elements, the average chemical composition of the incinerators is similar, with some differences in minor elements. Ferrara (FE) and Forlì-Cesena (FC) BA show portlandite, higher ettringite, and less amorphous than the Torino (TO), Parma (PR), and Piacenza (PC) BA. This affects the pH, the release, and toxicity of the leachates. In FE and FC ashes, ettringite is insoluble, and we not only have low sulfate but also Ni and Ba beyond reglementary limits, suggesting that Ni and Ba are present as hydroxides with portlandite, which are soluble. In TO, PR, and PC, Cr and sulfates are beyond limits, suggesting that Cr comes from dissolution in ettringite. Cu and Cl are always beyond limits; the dissolution of chlorides accounts for only 30%–35% of the global Cl leachate. We observe that in the assessment of the potential toxicity of the ashes, mineralogy has a higher effect than the bulk chemical composition. Grain size sorting, although useful together with other techniques, is not by itself able to comply with the PTE risk level.Conclusion: The findings contribute to the development of efficient treatment strategies for BA, highlighting the need for a more thorough investigation to understand composition and properties and to find innovative ways to reuse, promoting the circular economy and sustainable waste management practices.

Towards understanding the TiO2 doping at the surface and bulk

AbstractAnatase titanium dioxide is a common photocatalyst with limited application scope due to its wide band gap energy. Valence and conduction band doping have long been used to narrow TiO2 band gap energy. The effectiveness of the process is highly dependent on the procedure adopted, and its underlying mechanism remains largely unknown. Importantly, optical changes caused by bulk doping are not always represented at the surface where the catalysis occurs. Therefore, methodologies sensitive to bulk and surface modifications are key for a holistic understanding of the doping mechanism and its effect on photocatalysis quantum yield. Herein, it is proposed the use of X‐ray absorption spectroscopy (XAS) with different probing depths to elucidate the chemical composition of bulk and surface. Soft XAS was employed to determine the chemical state of typical dopants (N and Cu) in TiO2 thin films. The XAS measurements at N K‐edge and Cu L2,3‐edge were performed in surface and bulk‐sensitive detection modes, providing direct insight into the surface‐bulk effects caused by the dopants. In the case of copper doping in the TiO2 conduction band, the data show the formation of Cu2+ in the bulk states. In contrast, the surface states are dominated by Cu+ components resulting from surface termination geometries. Moreover, X‐ray absorption spectra confirmed that the substitutional mechanism is the dominant process in Cu doping. The nitrogen doping was found to be interstitial, causing minor changes to the band structure but affecting the photoluminescence. The proposed methodology closes the gap in knowledge between materials design and photocatalytic performance by establishing atoms' disposition in bulk that affects electronic properties and on the surface that impacts the catalytic cycle.

Corrosion Resistance of 309L Stainless Steel Claddings on Carbon Steel Produced with Wire-Fed Directed Energy Deposition

Additive manufacturing (AM) tools are capable of applying overlay austenitic stainless steel (SS) claddings to carbon steel components. The benefits of this approach over arc welding include a smaller heat-affected zone, residual stress reduction, and material savings. In particular, wire-directed energy deposition is a suitable technique because of its low material cost and high rate of production compared to other AM methods. However, metallurgical variations in composition, phase fraction, and microsegregation can potentially influence the corrosion behavior of such claddings. In this work, 309L SS is clad on carbon steel substrates and electrochemical methods are used to measure their general and pitting corrosion resistance in simulated marine environments (3.5 wt% NaCl solutions). Two-layer claddings are fabricated with four laser powers to understand the effects of bulk chemical composition, austenite/δ-ferrite phase fractions, and individual phase compositions on corrosion behavior. The two-layer claddings are compared to a single-layer cladding, wrought 304 SS, and the carbon steel substrate for a comprehensive assessment of corrosion performance. The two-layer claddings are remarkably resistant to general corrosion in the 3.5 wt% NaCl environment because of their high Cr content (21.6 wt% to 23.3 wt% Cr). The single-layer cladding exhibits localized corrosion at unmixed Fe-rich peninsulas that originate at the dissimilar metal boundary and protrude into the first cladding layer. All two-layer claddings possess higher pitting corrosion resistance than wrought 304 SS, demonstrating their effectiveness as a corrosion-resistant barrier. The pitting corrosion resistance is superior for claddings made with lower laser powers, due to low dilution and greater δ-ferrite contents.

Effect of enzymatic treatment on Eucalyptus globulus vessels passivation

Hardwood vessel elements generate problems in industrial uncoated wood-free printing paper operation, causing vessel picking and ink refusal. These problems are mitigated using mechanical refining at the cost of paper quality. Vessel enzymatic passivation, altering its adhesion to the fiber network and reducing its hydrophobicity is a way of improving paper quality. The object of this paper is to study how the enzymatic treatment by xylanase and by an enzymatic cocktail containing cellulases and laccases affect elemental chlorine free bleached Eucalyptus globulus vessel and fiber porosities, bulk, and surface chemical compositions. Thermoporosimetry revealed the vessel structure to be more porous, surface analysis showed its lower O/C ratio and bulk chemistry analysis its higher hemicellulose content. Enzymes had different effects on porosity, bulk and surface composition of fibers and vessels, affecting vessel adhesion and hydrophobicity. Vessel picking count decreased 76% for papers containing vessels treated with xylanase and 94% for the papers with vessels treated with the enzymatic cocktail. Fiber sheet samples had lower water contact angle (54.1º) than vessels rich sheets (63.7º), that reduced with xylanase (62.1º) and cocktail (58.4º). It is proposed that differences in vessel and fiber porosity structures affect the enzymatic attacks, eventually causing vessel passivation.

Atmospheric nanoparticles hygroscopic growth measurement by a combined surface plasmon resonance microscope and hygroscopic tandem differential mobility analyzer

Abstract. The hygroscopic growth of atmospheric aerosols plays an important role in regional radiation, cloud formation, and hence climate. Aerosol hygroscopic growth is often characterized by hygroscopic tandem differential mobility analyzers (HTDMAs), and Xie et al. (2020) recently demonstrated that hygroscopic growth measurements of a single particle are possible using a surface plasmon resonance microscope-azimuthal rotation illumination (SPRM-ARI). The hygroscopic properties of ambient aerosols are not uniform and often exhibit large relative humidity (RH) and size variabilities due to different chemical compositions and mixing states. To better understand the contribution of different aerosol components and establish a link between the apparent hygroscopic properties of single particles and bulk aerosols, we conduct combined hygroscopic growth measurements using a SPRM-ARI and an HTDMA as a case study to prove the concept (experimental information: 100–200 nm, during noontime on 28 September 2021 and 22 March 2022 in Hefei, China). According to the distinct hygroscopic growth behavior from single-particle probing using a SPRM-ARI, the individual particles can be classified into three categories defined as non-hygroscopic (NH), less hygroscopic (LH), and more hygroscopic (MH). The mean growth factor (GF) of the three categories can be utilized to reproduce the GF distribution obtained from the HTDMA measurement. The chemical compositions of individual particles from the three categories are identified to be organic carbon (OC), soot (mainly elemental carbon), fly ash, and secondary aerosols (mainly OC and sulfate), using scanning electron microscopy (SEM) with an energy-dispersive spectrometer (EDS). The coupled SPRM–HTDMA measurement suggests a size-dependent variation of aerosol chemical components, i.e., an increase of OC fraction with increasing particle sizes, which agrees reasonably well with the chemical compositions from collected aerosol samples. This likely links the hygroscopic properties of individual particles to their bulk hygroscopic growth and chemical composition.

Thermodynamic determination of condensation behavior for the precursory elements of radioxenon following an underground nuclear explosion

The measurement of radioactive xenon isotopes (radioxenon) in the atmosphere is a tool used to detect underground nuclear explosions, provided that some radioxenon escaped containment and that fractionation leading to the alteration of the relative proportions of these isotopes, is accounted for. After the explosion, volatilization followed by melting of the surrounding rocks produces a magma where the more refractory radioactive species get dissolved while the more volatile ones contribute to the gas phase that might escape. Indium, tin, antimony, tellurium and iodine are the main fission products involved in the decay chains leading to radioxenon. In this study, condensation as a function of temperature for these precursors of radioxenon were determined using thermodynamic calculations for systems with complex chemical composition corresponding to major environments of known underground nuclear explosions and for a range of pressure values representative of the cavity evolution. Our results illustrate a large difference between the relevant condensation temperatures for the radioxenon precursors and the tabulated boiling temperatures of the pure compounds often used as indicators of their volatility. For some precursory elements such as tin, the often-considered Heaviside function represents an oversimplification of the concept of condensation temperature, as condensation occurs over a temperature range as large as 2000 K. This results from the speciation of the elements in the gas phase mainly driven by the formation of oxides. Condensation also strongly depends on pressure while it moderately depends on the bulk chemical composition of the system. This study shows the importance and complexity of the condensation process following underground nuclear explosions. It also shows how thermodynamic computations allow the prediction of the quantity and the relative proportions of radioactive xenon isotopes in the gas phase in the presence of magma, before their potential emission to the atmosphere. Better detection, discrimination and understanding of underground nuclear explosions should arise by taking into account the fractionation resulting from the condensation of the radionuclides producing radioxenon in nuclear cavities.

Impact of Catholyte Lewis Acidity at the Molten Salt–NaSICON Interface in Low-Temperature Molten Sodium Batteries

Low-temperature molten sodium batteries comprising molten sodium anodes, a NaSICON solid-state separator, and molten halide salt catholytes offer promise as low-cost, earth-abundant energy storage technologies. The emergence of a specific, high-voltage, sodium iodide (NaI)-based catholyte chemistry has prompted the evaluation of chemical and electrochemical properties of the molten salts, particularly at critical interfaces with high-performance NaSICON separators. Herein, batteries operated at 110 °C with NaI-AlCl3-based catholytes of differing Lewis acidities were evaluated. Batteries with >50 mol % AlCl3 (acidic catholytes) experienced a linear decline in energy efficiency during cycling, whereas batteries with >50 mol % NaI (basic catholytes) maintained >95% energy efficiency for 50 cycles (>80 days) at 2.5 mA cm–2. A three-electrode cell was developed, enabling identification of the NaSICON–catholyte interface as the source of increased battery impedance. Complementary physical and chemical characterization of the NaSICON exposed to acidic and basic catholytes showed no changes in crystallinity, bulk morphology, or bulk chemical composition, but surface sensitive X-ray photoelectron spectroscopy (XPS), however, revealed subtle changes in local NaSICON surface chemistry. In addition, Raman spectroscopy indicated that stably performing basic catholytes lack the dimer species Al2Cl6I– present in acidic catholytes. Select thermodynamic and formal charge assessments suggest that preferential interactions between these acidic dimeric species and the NaSICON surface may be responsible for the observed increases in electrochemical impedance and degraded battery performance. These results indicate that maintaining a Lewis basic catholyte avoids such potentially deleterious interactions, enabling efficient and stable battery cycling.

Bulk and surface chemical compositions and microstructure properties of CaF2:Y3+ material

The structural and chemical compositions of Y3+ ion-doped CaF2 were investigated as a possible lanthanide hosting material. A series of CaF2 nanomaterials doped with various concentrations of Y3+ ions under the chelating agent ethylene diamine tetraacetic acid (EDTA) were synthesized using the hydrothermal method. The x-ray diffraction results demonstrated that a mixture of cubic CaF2 and [CaY]F2 phases gradually formed with an increasing Y3+ ion concentration. A single [CaY]F2 cubic phase was formed when EDTA was added as the chelating agent. Scanning electron microscopy results demonstrated that the particle size and the morphology of the material depended on the Y3+ concentration and that EDTA (0.5 g) produced a spherical morphology. The surface and bulk chemical compositions were determined using a combined system of soft x-ray photoemission spectroscopy (XPS) (Al-Kα 1486.7 eV) and hard x-ray photoemission spectroscopy (HAXPES) (Cr-Kα 5414.7 eV). The relative changes in the chemical composition of the surface and subsurface/bulk were investigated. The combined XPS-HAXPES analysis demonstrated that the surface impurities in the accessible peaks (Ca 2p, Y 3d, and F 1s) completely diminished in the subsurface region. However, XPS-HAXPES analysis confirmed that the composition of the [CaY]F2 nanomaterial on the surface differs from that in the subsurface region.

Lateral variations in the Hosen 8‐2 vein in the Hishikari deposit, Japan: Implications for high Au‐grade zone

AbstractLateral sampling of each blasting interval (~ 2.6 m) along a 79 m strike length was conducted for the Hosen 8‐2 vein on the −5 ML (mining level, meters relative to sea level) of the Main ore zone in the Hishikari epithermal Au deposit, Kagoshima, Japan. The horizontal variation of mineral textures, bulk chemical compositions, and fluid inclusion temperatures and apparent salinity of ore fluids were determined. The major gangue minerals of the quartz veins studied include quartz and adularia with minor amounts of calcite and smectite. The major ore minerals include electrum, galena, and sphalerite with minor pyrite, petzite, and hessite. Electrum commonly occurs in a discrete band with microcrystalline quartz, granular adularia, and smectite. The electrum‐bearing band is followed by tabular adularia, and finally by granular or comb quartz. Mineral textures that indicate high degrees of supersaturation with respect to amorphous silica (presently quartz with microcrystalline/mosaic and feathery textures) and adularia (with tabular, rhombic, and granular textures) were common throughout the vein strike. Bulk chemical analyses indicate that Au grade is positively correlated with Ag, Bi, Pb, and Te contents. A bonanza zone with Au grades up to 10,800 ppm occurs in the central part of the Hosen 8‐2 vein on the −5 ML, and is associated with high adularia content, calculated as adularia / (quartz + adularia). The wide lateral variation in the geochemical composition contrasts with the consistent association of electrum with microcrystalline quartz, granular adularia, and smectite throughout the Hosen 8‐2 vein on the −5 ML. Fluid inclusion microthermometry of primary and pseudosecondary inclusions in quartz and adularia yielded histogram modes of homogenization temperature between 160 and 240°C; the most frequent mode is 200–210°C, with most data within ±10°C from this value. The maximum ice‐melting temperature of most samples excluding late comb quartz is −1.5°C, which is equivalent to an apparent salinity of 2.6 wt% NaCl eq. The wide variation in ice‐melting temperatures and apparent salinities (up to 5.2 wt% NaCl eq.) may be due to dissolved CO2 in the fluids, while the sharp decrease in apparent salinity with temperature decrease indicates CO2 loss due to fluid boiling during vein formation. The intimate association of electrum with microcrystalline quartz that recrystallized from amorphous silica indicate sharp boiling and vapor loss as the primary mechanism of Au deposition in the Hosen 8‐2 vein.

Aegirine-Bearing Clinopyroxenes in Granulites from Xenoliths of the Udachnaya Kimberlite Pipe, Siberian Craton: Comparison of the Results of Mössbauer Spectroscopy and Electron Micropobe Analysis

The aegirine end-member (NaFe3+Si2O6) in clinopyroxenes resulted from incorporation of Fe3+ into the mineral structure effects the accuracy of reconstruction of the P-T conditions in the high-grade metamorphic rocks and also allows evaluation the redox conditions of their formation. As a rule, the content of this end-member in clinopyroxenes is evaluated based on the crystal chemical recalculations of microprobe analyses. However, in some publications on eclogites, the results of recalculations of clinopyroxenes were compared with the data of Mössbauer spectroscopy. Significant difference was revealed between the measured and calculated Fe3+/ΣFe ratios, that can significantly affect the results of geothermometry. This paper presents the results of the Mössbauer spectroscopy measurements of clinopyroxene fractions separated from three samples of garnet-clinopyroxene granulites from the Udachnaya kimberlite pipe. The ratios Fe3+/ΣFe = 0.22–0.26 measured in clinopyroxenes correspond to 6–10 mol. % aegirine. These estimates are in good agreement with the values obtained for clinopyroxenes from the same samples by the recalculation of microprobe analyzes using the charge balance method. Following to this conclusion, we believe that crystal chemical recalculations of microprobe analyzes of clinopyroxenes from non-eclogitic rocks make it possible to correctly estimate the Fe3+ content in them. Similar recalculation of microprobe analyzes of clinopyroxenes from crustal xenoliths from other localities, as well as from ferrobasalts of the continental flood basalts provinces, ferrodolerite dikes, and gabbroid xenoliths (similar in bulk chemical composition to many lower-middle-crustal xenoliths) revealed significant amounts of previously unaccounted aegirine in them (up to 13 and 4–9 mol. %, respectively), that unleashes the potential for the reconstruction of redox conditions in many rocks.

Petrographic Characteristic and Geochemical features of Basement Rocks in Ikogosi, Southwestern Nigeria.

This study investigates and reports petrographic characteristics, geochemical features and the processes of formation of rocks in Ikogosi, southwestern Nigeria. Eighteen (18) rock samples (six quartzite, six migmatite gneiss and six schists) were collected and subjected to optical study. Ten (10) representative samples (six quartzite, three schist and one migmatite gneiss) were evaluated for major elements composition using Energy Dispersive X-Ray Fluorescence (ED-XRF). Petrographic evaluation revealed quartz, feldspar, muscovite, biotite, hornblende, pyroxene and opaque are dominant mineral constituents in quartzite and schist while migmatite gneiss contains the same set of minerals but without opaque constituents. Quartz forms a dominant constituent in quartzite and migmatite gneiss but as subordinate mineral in the schist. The feldspars are mainly plagioclase with albite twinning, associated microcline has characteristic crosshatched twinning. Chemical investigation reveals the rock units are generally siliceous. Three oxides (SiO2, Al2O3 and Fe2O3) constitute 85–90% of the bulk chemical composition of the rocks. SiO2 constituent as applied in rock classification indicates the quartzite is unequivocally felsic, migmatite is intermediate while the schist is mafic to ultramafic. K2O versus SiO2 variation plot revealed that the quartzite and schist are tholeiitic while the migmatite gneiss is shoshonitic. TiO2 versus SiO2 variation diagram depicts igneous antecedent.

The Role of Magma Mixing in the Petrogenesis of Eocene Ultrapotassic Lavas, Western Yunnan, SW China

AbstractMagma mixing is a widespread magmagenic process. However, its significance in the formation of ultrapotassic magmas has been largely overlooked so far as they are commonly thought to originate directly from the mantle and ascend rapidly through the crust. The Hezhong ultrapotassic lavas in Western Yunnan (SW China) are (basaltic) trachy-andesitic in composition. These rocks display porphyritic textures with olivine, clinopyroxene (Cpx), spinel, and phlogopite occurring as both phenocryst and glomerocryst. Disequilibrium textures and complex zonation of crystals are commonly observed. Specifically, based on the textural and compositional characteristics, olivines can be classified into three different populations: two populations are characterized by highly to moderately magnesian olivines with normal chemical core-rim zonation (Fo~94–86 to Fo~89–79 and Fo~91–89 to Fo~86–84, respectively). The third population lacks obvious crystal zonation, but individual crystals exhibit some compositional variety at lower Fo contents (Fo83–76). Similarly, four populations of Cpx and two populations of spinel phenocrysts are recognized in terms of texture and composition. Notably, Cpx with reverse zoning contains a ‘green-core’ surrounded by a colourless mantle and rim. Hence, based on the variations of mineral assemblage, types of inclusions, and chemical compositions, all phenocryst/glomerocryst minerals can be divided into three groups. Mineral Group I (MG I) consists of high Fo cores of olivine, cores of the zoned spinel, and phlogopite. MG II only includes the green cores of reversed zoned Cpx (green-core Cpx), and MG III is composed of micro phenocrysts without obvious zoning and rims of large phenocrysts. Comparing these mineral groups with relevant minerals occurring in typical temporally and spatially associated igneous rocks, we suggest that the MG I and II could have been derived from magmas with compositions resembling an olivine lamproite and a trachyte, respectively. The overall bulk-rock geochemical and isotopic features of Hezhong lavas also agree with a mixing process between these two endmembers. Hence, we infer that mixing between these two magmas played a key role in the petrogenesis of the ultrapotassic Hezhong lavas and that the MG III crystallized from the mixed magmas. Our study highlights the complex formation of ultrapotassic magmas inferring that caution must be taken when using bulk chemical magma compositions are to deduce source signatures.

Elemental composition and thickness determination of thin films by electron probe microanalysis

Electron probe microanalysis (EPMA) applies to solid samples of homogenous (bulk) chemical composition and can usually not be applied to structures which are inhomogeneous in the micrometer range such as thin film systems down to a few nm. However, in combination with the established thin film software Stratagem, the thickness as well as the elemental composition of thin films on a substrate can be determined. This has been recently successfully demonstrated for Fe‐Ni on Si and Si‐Ge on Al2O3 thin film systems. For both systems five samples of different elemental composition and a reference were produced and characterised by inductively coupled plasma mass spectrometry (ICP‐MS), Rutherford backscattering (RBS), and transmission electron microscopy (TEM) as reference values. Last year, a new and open‐source thin film evaluation programme called BadgerFilm has been released. It can also be used to determine thin film composition and thickness from intensity ratios of the unknown sample and standards (k‐ratios). In this contribution, we re‐evaluated the data acquired for the Fe‐Ni and Si‐Ge systems using the BadgerFilm software package and compared the obtained elemental compositions and thickness values with the results of the Stratagem software and the reference methods. The conclusion is that the BadgerFilm software shows good agreement with the elemental composition and thickness calculated by Stratagem (mostly &lt;2% for both composition and thickness) and with the reference values for two representative thin film systems (&lt;1%–2% for composition and &lt;10%–20% for thickness).

The Role Played by the Bulk Hygroscopicity on the Prediction of the Cloud Condensation Nuclei Concentration Inside the Urban Aerosol Plume in Manaus, Brazil: From Measurements to Modeled Results

This work use observed and modeled data to trace a basic model that describes how the bulk chemical composition can be used to determine the aerosol size-dependency of hygroscopicity inside the urban aerosol pollution plume from Manaus, Brazil. The procedure is then used to predict the Cloud Condensation Nuclei (CCN) concentration (NCCN) from the Aerosol Size Distribution (ASD). The work briefly described hourly averaged data of ASD, Black Carbon size distribution (BCSD), Black Carbon mass concentration (BC), NCCN, and aerosol size hygroscopicity (κ) observed about 70 km downwind of the City of Manaus, inside the amazon rain forest, during 60 days of 2014, in the course of the rainy season. It uses a description of aerosol chemical composition obtained previously in the city of São Paulo, Brazil, as starting point to formulate a model that describes how particles in the pollution plume act as CCN as a function of their sizes and bulk chemical composition. A parameterization based on a polynomial fitting is proposed to determine BCSD from the BC. The measured and parameterized BCSD agree very well with more than 98% of the observed BCSDs, presenting a correlation coefficient larger than 0.9 with observation. The parameterized BC number concentration is also very well represented, with a correlation coefficient of 0.91 and a slope of 0.99 in comparison with observations. This work also studies how soot particles are incorporated in the CCN population and propose a parameterization to represent it. Simulations suggest that the larger BC particles are only partially incorporated as CCN and BC is a constraint to the fraction of aerosols that can act as CCN in all size ranges. The simulations also suggest that the incorporation of BC as CCN is probably only effective through coagulation in the presence of the wet phase. In addition, the work compares different strategies to predict observed NCCN from ASD. It is shown that the strategy presented can substantially improve the results of comparison of modeled and measured data from as bad as 2.14 ± 0.65 to as good as 1.02 ± 0.17. This study shows that the knowledge of the bulk chemical composition can be used to predict both the size-resolved chemical composition and mixing state, reducing the number of parameters needed to predict NCCN.