White Inclusions Research Articles

Microstructural Study of Medieval Crucible Steels from Archaeological Sites in Central and Northwest Asia: Identifying the Bulat

The microstructure of 9th–15th century artifacts made of crucible steel, found at sites in Central and Northwest Asia, is described. Metallographic study of items from settlements and burials with precise data on chronology, location, and accompanying artifacts is important for reconstructing the history of bulat steel and the technology of melting and processing ultra-high-carbon crucible steel. The study of the macro- and microstructure, and the chemical analysis of such items indicate an extremely high content of carbon—1.7–2.1 %. The characteristic feature of their microstructure is a dark matrix with white inclusions of ledeburite and iron carbides. The combination of structural components is reflected in the patterned structure of the metal. These properties suggest that such metal is identical to bulat steel. Findings of macrostructural analysis extend our knowledge of the varieties of this metal, its structural features, phase composition of separate groups of ultra-high-carbon crucible steel, smelting technology, plastic and thermal treatment, and physical properties.

Development of recipes for sweet processed cheese for medical and preventive purposes with “Vynograd” cryopowder

Processed cheeses have always aroused great interest and liking in a significant part of the population. They can be used for business trips, numerous picnics, and to prepare many dishes that could not be done without them. Another advantage of processed cheeses is their low cost. Therefore, in modern nutrition, processed cheeses have occupied a significant part of the food basket for a long time. The use of processed cheeses makes it possible to significantly expand not only the assortment of these products but also to improve the content of nutrients and the active, therapeutic and preventive role of food. The work aimed to develop sweet processed cheese recipes for medical and preventive purposes with cryopowder “Vynograd”. Scientific research was carried out in the conditions of the scientific laboratory of the department of technology of milk and dairy products of the Stepan Gzhytskyi National University of Veterinary Medicine and Biotechnologies Lviv and in production. The proposed technological scheme for the production of this product. The main organoleptic and technical characteristics of sweet processed cheese with cryopowder domestically produced “Vynograd” were studied. Experimental samples of processed cheese kept a delicate, elastic consistency, had a shine on the outside, and had a characteristic original taste and smell (fresh and sweet). The color of the test samples was light gray, with red-black and white inclusions of various sizes. The test samples had a crust outside and a solid ointment-like mass on the cross-section. The mass fraction of fat in the dry matter in the product was 28.0 %. The experimental cheese samples were characterized by the mass fraction of moisture – 29.8 %; sucrose – 24 %. The pH of experimental pieces of processed cheese with cryopowder was 5.6, respectively. The vitamin composition of the processed sweet cheese with Phyto-additive “Grapes” was also evaluated. Experimental samples with “Vynohrad” cryopowder are characterized by increased indicators of the biological value of the product. Testing samples of combined types of processed cheese preserved technological characteristics and regulatory safety indicators during the regulatory storage time.

Classification of arboreal taxa for landscaping in Central Russia based on leaf coloristics

Color affects the psychological and physiological state of a person and is one of the powerful factors that form a comfortable visual environment. Currently, color-leaved taxa are actively offered by nurseries and are used in landscaping. At the same time, the color characteristics of taxa are very diverse, are quite subjective, which makes their selection and application difficult. The purpose of the work is to analyze and classify the modern varietal variety of the wood assortment for the middle part of Russia by the color of ripened leaf blades. The analysis was carried out according to descriptions and photographs presented in information sources and catalogues of nurseries. It has been established that the modern coloristic diversity of arboreal taxa is great, there are discrepancies in the description of foliage color, there is no classification. The classification of the colorist of taxa by visual perception, convenient from a practical point of view, has been developed, reduced to the main color groups: green, blue (silver), whitish, whitish-pink, yellow, purple. The peculiarity is that variegated taxa are included in these groups in accordance with their color perception: yellow-mottled and yellow–bordered taxa are classified as yellow, taxa with white inclusions and fringing are whitish, and so on. It can be recommended to nursery farms to apply the developed classification when selling planting material, landscape firms and gardeners when selecting and composing plant compositions.

Fission product speciation in the VERDON-3 and VERDON-4 MOX fuels samples

Within the framework of the International Source Term Programme, the VERDON-3 and VERDON-4 complementary tests were devoted to studying MOX fuel and fission product (FP) behaviour at very high temperature (>2300 °C) under oxidising and reducing atmospheres. Post-test qualitative and quantitative characterisations of the VERDON-3 and VERDON-4 samples were carried out in the LECA-STAR facility at the CEA Cadarache centre. This article focuses on the impact of the atmosphere on fission product speciation and more precisely on the behaviour of Cs, Mo and Ba. The well-known white inclusions composed of metallic Mo, Ru, Rh, Pd and Tc underwent transformations during the two tests implying melting and/or composition changes. The semi-volatile behaviour of Mo was once again confirmed. Almost no Cs was seen to remain in the samples after the VERDON-3 and VERDON-4 tests, which is consistent with its volatile behaviour. The behaviour of Ba, which is known to be released in high quantities in reducing atmospheres, provided complex to assess as significant releases seems to have taken place in both VERDON-3 and VERDON-4 tests.

Influence of Cellulosic Fluxes on the Chemical Composition, Microstructure, Inclusions and Micro-Hardness of SMAW Multi-Pass Welds of X42 Steel

This paper studied the influence of cellulosic flux on the chemical composition, microstructure, formation of inclusions and micro hardness of X42 welded steel. The chemical compositions of the used fluxes are FA: E6010 and FB: E8010-P1, with electrodes has low carbon content. The welding conditions are not constant. The fluxes (FA and FB) have a high content of TiO2and SiO2and a low Ti and Si content was also detected in the internal (P1) and external (P3) passes. But there was an increase in the Ti content in the fusion zone (P1, P2 and P3) of the different passes gradually, compared to the base metal. The microstructure of the fusion zone (P1, P2 and P3) for each flux is mainly composed of acicular ferrite. The mass concentration variation of Mn is more elevated through the centers of the fusion zone passes (P1, P2 and P3) with the used fluxes. White and black non-metallic inclusions are observed, regardless of used flux. The micro-hardness in fusion zone varies according to the variation of the equivalent carbon in the different electrodes.

Are tin oxides inclusions in early archaeological bronzes a marker of metal recycling?

Bronze artifacts from Early Bronze Age in Europe often contain white inclusions in the metallic matrix, that are identified as tin oxides (SnO2 or Cassiterite). These inclusions are interpreted as un-smelted residues coming from the copper ore and are generally mixed with more complex oxidized inclusions, which contain sulfur, antimony, arsenic, silver, nickel and cobalt. The nature, shape and distribution of these partially smelted tin inclusions give information on the alloying process. Depending on the technological context and the geographical areas, the presence of such inclusions might indicate that the material has been produced by selecting and supplementing of raw materials containing SnO2 (e.g. co-smelting). In order to understand the role of tin oxide inclusions in the production of bronzes and possible recycling procedures, a crosscutting investigation has been carried out, based on experimental researches. The results show that tin oxides do not completely reduce after four re-melting cycles (recycling) and such a fact is deeply related to the oxygen availability and the dwell time that influences the kinetics of the reaction.

Effect of the cryopowder "beet" on quality indicators of new curd desserts

Natural plant bio-additives deserve special attention, because due to their natural properties they provide dairy products with functional properties. The use of such additives makes it possible to fill the shortage of essential nutrients, increase non-specific resistance of an organism to the effect of unfavorable environmental factors. A skillful combination of cryopowders and the dairy base are very promising both in technological and social terms.The technology of curd desserts with varying fat mass fraction using the cryopowder Beet was developed. The expedience of using the cryopowder Beet in the technology of new sweet curd mass was substantiated. The optimal dose of the cryopowder Beet was proposed. The possibility of using the cryopowder Beet as a component of health promoting curd desserts was studied. The amount of the specified cryo-additive varies depending on the fat mass fraction of the dairy base. The organoleptic, physical, and chemical and microbiological characteristics were studied in the experimental samples. An analysis of organoleptic characteristics of curd masses with the cryopowder Beet shows that they did not have any substantial changes and fully comply with regulatory requirements. Thus, the color of the sweet curd mass was light-beet, raspberry with separate white inclusions of crushed powder-like cryogenic bio-additive. The curd masses retained the smell of fresh sour milk. When introducing the cryopowder Beet into the curd mass, the energy value grew.The revealed changes in the amino acid composition of curd masses indicate that the use of cryopowder Beet makes it possible to enhance nutritional and biological value of the protein component. In particular, we established an increase in the total amount of amino acids by 1.73 %; by 1.16 % in the composition of essential amino acids, and by 2.17 % in the composition of non-essential amino acids.The proposed product expands the domestic range of dairy products for functional purposes.

Effect of E6010 and E8018-G Fluxes Utilization on SMAW Multi-Pass Welded Steel

The aim of this work is to study the influence of the E6010 and E8018-G fluxes on the chemical composition, microstructure, formation of inclusions and micro hardness in different passes (P1, P2 and P3) of X42 welded steel. The marketed chemical composition of used fluxes is: E6010 and E8018-G, which have a low carbon electrodes. The fusion zone microstructure consists of acicular ferrite. The fluxes (FA and FC) have the high TiO2 and SiO2 contents respectively. The high content of Ti and Si, was also detected in the melted zones (P1 ,P2 and P3). The MnO2 oxide proportion in the fluxes (E6010, and E8018-G) is constant (0.94-0.99). However, the Mn content increases in the melted zones (P3 and P1). The highest percentages of Si and Mn was detected in the outer and inner passes respectively of melted zone, relatively to the base metal. The variation of the elements mass concentrations (Mn, Cr, Si and Ti) shows a contradictory variation on the three points in the melted zone passes (P1 and P3). White and black non-metallic inclusions are observed regardless the used flux. The micro-hardness in the multi-pass melting zone with the fluxes (E6010 and E8018-G) varies according to the variation of the equivalent carbon in the different filler metals.

A kabai meteorit újravizsgálatának fontosabb eredményei

A kabai meteoritban többféle eredetű és összetételű hőálló (refraktorikus) ásvány, hőállóásvány-társulás mutatható ki. Legtöbbet és legjellegzetesebbeket a fehérzárványhalmazok, továbbá a kerekded–ovális kondrumszerű képződmények, valamint a 100–200 μm átmérőjű „kondrumok” tartalmaznak. A meteorit felszínén is látható – általában 10–18 mm hosszú – sárgásfehér „zárványokat” a mikroszkópi vizsgálatok szerint többnyire teljesen szabálytalan alakú, „szaggatott” szerkezetű, szemcsés halmazok alkotják. Helyenként egymás közvetlen közelében több különböző méretű halmazból álló csoport alakult ki, valószínűleg egy nagyobb darab széttöredezése eredményeképpen. A halmazok mozaikos szerkezete is ezzel magyarázható. Az uralkodóan 100–400 μm méretű, gyakran különböző összetételű, részben alapanyagot is tartalmazó szemcsék általában bonyolult zónás szerkezetűek. Leggyakoribb, illetve legnagyobb mennyiségű összetevője a magot alkotó, de kisebb mennyiségben rendszerint a többi övben is megjelenő közönséges spinell. A következő öveket részben gehlenit, de uralkodó mennyiségben, titánban és alumíniumban gazdag monoklin piroxének alkotják. Egyes szemcsék körül záró övként a forsterit is megjelenik.
 A kerekded–ovális megjelenésű, kondrumszerű képződmények, valamint a kis méretű kondrumok az előzőekkel megközelítőleg, illetve részben azonos ásványi összetételűek, az alkotók mennyiségi arányában, valamint a képződési sorrendben azonban jelentős különbségek mutatkoznak. Az uralkodó magalkotó fázisok általában változó mennyiségű zárványt tartalmaznak. Például a gehlenitben rendszerint kevés perovszkit és részben spinell, a közönséges spinellben pedig többnyire sok perovszkit mutatható ki. Külön kiemelkedő a kerek „felhőszerű” halmaz magjának túlnyomó részét alkotó magnéziumtartalmú gehlenit nagy mennyiségű, mégpedig 72% platinát, továbbá — többek között — irídiumot és kevés hafniumot is tartalmazó „zárványa”. A kerekded–ovális képződményeken belül az alakzat, a szerkezet, valamint a jellemző ásványok alapján gehlenitet, közönséges spinellt, valamint normatív hercinitet és korundot tartalmazó változatot különböztethetünk meg. A jellemző uralkodó ásványok rendszerint az adott változat magját alkotják, és általában jelentős mennyiségű „zárványt” — főleg kerekded perovszkitot tartalmaznak. A mag körüli övezetet főleg spinell és monoklin piroxének alkotják. Egyes változatokban azonban az 5–7% Na2O-t tartalmazó — esetenként önálló övet alkotó — amorf anyag („mezosztázis”) is jelentős mennyiséget képvisel. Ez az öv valószínűleg a Mokoia-meteoritban kimutatott (MACPHERSON et al. 1983) filloszilikátokhoz hasonló összetételű (normatív) rétegszilikátokat is tartalmaz.

Evaluation of the Effects of Fluoride Prophylactic Agents on Mechanical Properties of Nickel Titanium Wires using Scanning Electron Microscope

Orthodontic treatment these days is increasing in demand, and therefore, it is relatively imperative for the orthodontist to prescribe the use of fluoride-containing products, such as mouthwashes and gels, to help prevent dental caries and maintain healthy oral health. The aim of the study was to assess and evaluate the effects of fluoride prophylactic agents on mechanical properties of nickel titanium (NiTi) wires during orthodontic treatment using scanning electron microscope (SEM). We used the commercially available round preformed NiTi orthodontic archwire (3M company) and three different mouthwash solutions, i.e., Phos-Flur gel (1.1% sodium acidulated phosphate fluoride, APF, 0.5% w/v fluoride, pH = 5.1; Colgate Oral Pharmaceuticals) and Prevident 5000 (1.1% sodium fluoride neutral agent, 0.5% w/v fluoride, pH = 7; Colgate Oral Pharmaceuticals). All the specimens were subjected to a three-point bending test on a universal testing machine. To observe the surface morphological changes, one wire from each group was randomly selected and observed under a SEM. It was observed that there was not much difference in the values of both modulus of elasticity and yield strength obtained after loading of stress on the wires in all the three experimental conditions. A significant difference in both modulus of elasticity and yield strength was observed during unloading of stress. Further, when the surface characteristics were observed for all the specimens using SEM images, it was observed that NiTi wires treated with Phos-Flur showed large surface defects which appeared as round, pitted areas depicting corrosion, numerous white inclusions, and overall damaged surface structure of the wire as compared with the control. Thus, fluoridated mouthwashes are essential to maintain good oral hygiene and decrease instance of caries in patients undergoing orthodontic treatment. The prophylactic usage of topical fluoride agents on NiTi wire seems to diminish the mechanical properties of the orthodontic wire that could significantly affect future treatment outcomes. It has been proved that fluoride mouthwashes/gels do affect the structural surface qualities and strength of wires used during the orthodontic treatment irrespective of the composition of the wires. Therefore, it is the responsibility of the clinician to prescribe these prophylactic agents carefully while keeping in mind their pH so that the overall result of the treatment may not be hampered and delayed due to change in properties of the wires used.

Activated ceramic compositions with the addition of serpentinite

The article describes the loam of the Kubekovsky deposit of the Krasnoyarsk Territory, which is widely used in the production of ceramic bricks in factories that produce wall materials. In the studies described in the article, mechanoactivation and modification were used to improve its technological and physico-mechanical characteristics. Mechanoactivation was carried out in a hydrodynamic dispersant. As the additive-modifier used waste stoneplant serpentinites of the Perevalnoye deposit. The effect of the additive-modifier on the properties of ceramic compositions is shown. It is shown that a small amount of serpentinite up to three percent -significantly increases the compressive strength of fired ceramic samples.If the composition has an additive of more than three percent, a decrease in strength characteristics is observed, this is related, probably due to the fact that most of the magnesium oxide remains unreacted. White inclusions areobserved visually in the structure of calcined samples throughout the volume. The combined effect of mechanoactivation and modification is shown, which makes it possible to improve the technological and physicomechanical characteristics of the ceramic shard. The results of electron microscopy are presented, suggesting that the microstructure of a ceramic shard activated with the addition of serpentinite contains moremullite-rich mixed crystals, as well as devitrified areas. Inclusions of magnesium oxide are not observed. Magnesium oxide in the ceramiccomposition serves as a primer capable of making the melt more liquid,accelerating its devitrification.

Phát hiện vi khuẩn Aeromonas schubertii gây đốm trắng ở nội quan cá lóc (Channa striata) bằng phương pháp PCR

The PCR procedure to detect Aeromonas schubertii bacteria, which causes white inclusions in internal organs of snakehead fish, was carried out and standardized. The primer pairs Schubertii-16S- (UF-2) F and Schubertii-16S- (UF-2) R (Demarta et al., 1999) were used to amplify the 16s rDNA gene for A. schubertii with a 322-bp PCR product was used in order to shorten the detection time and specific to the causative agent. The optimized PCR procedure includes 1 mM MgCl 2, 1U Taq DNA polymerase and 0.2 mM dNTPs. The detection limit of this PCR protocol is approximately of 30 ng DNA. The specificity of the primer pair is determined to detect only A. schubertii bacteria without detection of some common bacterial pathogens in aquaculture such as Streptococcus agalactiae, Aeromonas hydrophila, Vibrio parahaemolyticus, Edwardsiella ictaluri and Flavobactertium columnare.

Powder Iron–Glass Material: Mechanism of Wear in Vacuum

The wear mechanism of powder iron–glass material is analyzed. The behavior of PS5GSh–PS5GSh and of PS5GSh–hardened steel 45 during friction in vacuum is studied. It is established that the glass inclusions and “white layer” formed on the friction surface influence the wear-resistance of the iron-glass material. It is noted that increased hardness leads the glass inclusions to form a near-surface framework, resisting the plastic deformation on the surface and inside the material. It is shown that the white inclusions have low friction adhesion and thus prevent seizure with steel. The “white layer” adheres strongly to the material. It acts as a solid lubricant and, along with the glass inclusions, increases the wear resistance. Extreme gross wear is accompanied by active growth and failure of the “white layer” as scales on dislocation slip planes located at an angle to the friction surface. The wear mechanism of the powder iron–glass materials under simultaneous contact of steel and glass is studied.

Interactions between TiAl Alloy and Different Oxide Moulds under High-temperature and Long-time Condition

AbstractInteractions between Ti-47Al-2Cr-2Nb (at.%) alloy and alumina, zirconia and yttria moulds were studied under high-temperature and long-time condition, and the reaction mechanisms were explored. The moulds were prepared by traditional precision casting technique, and the experiments were carried out in a carbon resistance furnace at 1550°C for 30 min. The results indicated that the interfacial reactions between TiAl alloys and alumina and zirconia moulds were serious. Obvious reaction layers composed of Ti-rich phases and Al2O3 inclusions were formed on the alloy-mould interfaces, and a large amount of dark Al2O3 inclusions were found in the alloy matrixes. Interaction between TiAl and yttria mould was mild. No obvious reaction layer was formed on the alloy-mould interface, and only a small amount of white inclusions inferred as Al-Y oxide were found in the alloy matrix. Al2O3 and ZrO2 cannot be used as mould materials for the directional solidification of TiAl alloys. Y2O3 mould possesses a higher stability, which can be used in the directional solidification of TiAl alloys by the proper choice of more stable binder.

Large silica‐rich igneous‐textured inclusions in the Buzzard Coulee chondrite: Condensates, differentiates, or impact melts?

Abstract–We studied three large (2–4 mm diameter) igneous‐textured inclusions in the Buzzard Coulee (H4) chondrite using microanalytical techniques (OLM, SEM, EMPA, SIMS) to better elucidate the origins of igneous inclusions in ordinary chondrites. The inclusions are clasts that come in two varieties (1) white inclusions Bz‐1 and Bz‐2 represent a nearly holocrystalline assemblage of low‐Ca and high‐Ca pyroxene (63–66 area%) and cristobalite (33–36%) and (2) tan inclusion Bz‐3 is glass‐rich (approximately 60%) with low‐Ca and high‐Ca pyroxene phenocrysts. The bulk compositions of the inclusions determined by modal reconstruction are all SiO2‐rich (approximately 67 wt% for Bz‐1 and Bz‐2, approximately 62% for Bz‐3), but Bz‐3 is enriched in incompatible elements (e.g., REE approximately 4–5 × CI abundances), whereas Bz‐2 and Bz‐1 are depleted in those elements that are most incompatible in pyroxene (e.g., La‐Ho approximately 0.15–0.4 × CI abundances). These bulk compositions do not resemble what one would expect for partial or complete shock melting of a chondritic precursor, and show no evidence for overall volatility control. We infer that the inclusions originated through igneous differentiation and FeO reduction, with Bz‐3 forming as an “andesitic” partial melt (approximately 30–40% partial melting of an H chondrite precursor), and Bz‐1 and Bz‐2 forming as pyroxene‐cristobalite cumulates from an Si‐rich melt. We suggest that both types of melts experienced a period of transit through a cold, low‐pressure space environment in which cooling, FeO reduction, and interaction with a vapor occurred. Melts may have been lofted into space by excavation or splashing during collisions, or by pyroclastic volcanism. Our results indicate intriguing similarities between the inclusions in Buzzard Coulee and the silicates in some iron (IIE‐type) and stony iron (IVA‐type) meteorites, suggesting a genetic relationship.

Strong Calcite-Like Spectra Cathodoluminescence Emission from Allende Meteorite Cai Phases

ABSTRACT Calcium–aluminum-rich inclusions (CAIs) of Allende CV3 chondrite were studied by Environmental Scanning Electron Microscopy (ESEM), Energy Dispersive Spectrometry (EDS), Backscattering (BS), and Spectra Cathodoluminescence (CL). CAI minerals show spectra CL curves exceeding the 450,000 a.u. with a large homogeneity along the white inclusions. CL curve features fit perfectly with terrestrial patterns of stressed specimens of weathered marble and limestone in which hydroxyl groups may be involved. Crypto-clusters of CaCO3, undetectable by means of EPMA, EDS, and Micro-Raman techniques, coupled to the CAI phases are inferred from the spectral CL data and from the carbon and calcium contents provided by the EDS probe.

δ18O and chemical composition of Libyan Desert Glass, country rocks, and sands: New considerations on target material

– Oxygen isotope and chemical measurements were carried out on 25 samples of Libyan Desert Glass (LDG), 21 samples of sandstone, and 3 of sand from the same area. The δ18O of LDG samples range from 9.0‰ to 11.9‰ (Vienna Standard Mean Ocean Water [VSMOW]); some correlations between isotope data and typological features of the LDG samples are pointed out. The initial δ18O of a bulk parent material may be slightly increased by fusion due to the loss of isotopically light pore water with no isotope exchange with oxygen containing minerals. Accordingly, the δ18O of the bulk parent material of LDG may have been about 9.0 ± 1‰ (VSMOW). The measured bulk sandstone and sand samples have δ18O values ranging from 12.6‰ to 19.5‰ and are consequently ruled out as parent materials, matching the results of previous studies. However, separated quartz fractions have δ18O values compatible with the LDG values suggesting that the modern surface sand inherited quartz from the target material. This hypothesis fits previous findings of lechatelierite and baddeleyite in these materials. As the age of the parent material reported in previous studies is Pan-African, we measured the δ18O values of bulk rock and quartz from intrusives of Pan-African age and the results obtained were compatible with the LDG values. The main element abundances (Fe, Mg, Ca, K, Na) in our LDG samples conform to previous estimates; Fe, Mg, and K tend to be higher in heterogeneous samples with dark layers. The hypothesis of a low-altitude airburst involving silica-rich surface materials deriving from weathered intrusives of Pan-African age, partially melted and blown over a huge surface by supersonic winds matches the results obtained.

Effect of redox conditions on the evaporation of oxide melts in the CaO-MgO-FeO-Al2O3-SiO2 system

Physicochemical studies of cosmic substance provide a basis for fundamental concepts of the origin, composition, and structure of planets and meteorites. Of great importance in this context is the experimental study of the properties of oxides and melts in the CaO – MgO – FeO – Al 2 O 3 – SiO 2 system, which is the basic system of meteoritic substance and, in particular, the hightemperature substance of white inclusions (CAI). There is extensive evidence for the significant influence of changes in temperature and pressure on this substance during its formation and evolution. The investigation of its evaporation and condensation is of special interest because of the combination of high-temperature and cooling stages during its evolution. Data on CAI evaporation and condensation, which are required for calculations, can be obtained experimentally. The most efficient approach is a combination of the Knudsen effusion technique with the mass-spectrometric analysis of evaporation products [1‐3]. This study is aimed at determining the influence of redox conditions on oxide melt evaporation by the example of melts in the CaO – MgO – FeO – Al 2 O 3 – SiO 2 system. Note that the evaporation of such multicomponent oxide melts is dominated by the evaporation reactions of simple oxides, because the content of complex gaseous oxide compounds in the vapor is insignificant [3]. Therefore, the evaporation of these melts can be described to a first approximation by the evaporation tendencies of simple oxides.

The origin and compositions of Mesoarchean oceanic crust: Evidence from the 3075 Ma Ivisaartoq greenstone belt, SW Greenland

The Mesoarchean (ca. 3075 Ma) Ivisaartoq greenstone belt contains well-preserved primary magmatic structures, such as pillow lavas, volcanic breccias, and clinopyroxene cumulate layers (picrites), despite the isoclinal folding and amphibolite facies metamorphism. The belt also includes variably deformed gabbroic to dioritic dykes and sills, actinolite schists, and serpentinites. The Ivisaartoq rocks underwent at least two stages of post-magmatic metamorphic alteration, including seafloor hydrothermal alteration and syn- to post-tectonic calc-silicate metasomatism, between 3075 and 2961 Ma. These alteration processes resulted in the mobilization of many major and trace elements. The trace element characteristics of the least altered rocks are consistent with a supra-subduction zone geodynamic setting and shallow mantle sources. On the basis of geological similarities between the Ivisaartoq greenstone belt and Phanerozoic forearc ophiolites, and intra-oceanic island arcs, we suggest that the Ivisaartoq greenstone belt represents a relic of dismembered Mesoarchean supra-subduction zone oceanic crust. This crust might originally have been composed of a lower layer of leucogabbros and anorthosites, and an upper layer of pillow lavas, picritic flows, gabbroic to dioritic dykes and sills, and dunitic to wehrlitic sills. The Sm–Nd and U–Pb isotope systems have been disturbed in strongly altered actinolite schists. In addition, the U–Pb isotope system in pillow basalts appears to have been partially open during seafloor hydrothermal alteration. Gabbros and diorites have the least disturbed Pb isotopic compositions. In contrast, the Sm–Nd isotope system appears to have remained relatively undisturbed in picrites, pillow lavas, gabbros, and diorites. As a group, picrites have more depleted initial Nd isotopic signatures ( ε Nd = + 4.23 to + 4.97) than pillow lavas, gabbros, and diorites ( ε Nd = + 0.30 to + 3.04), consistent with a variably depleted, heterogeneous mantle source. In some areas gabbros include up to 15 cm long white inclusions (xenoliths). These inclusions are composed primarily (> 90%) of Ca-rich plagioclase and are interpreted as anorthositic cumulates brought to the surface by upwelling gabbroic magmas. The anorthositic cumulates have significantly higher initial ε Nd (+ 4.8 to + 6.0) values than the surrounding gabbroic matrix (+ 2.3 to + 2.8), consistent with different mantle sources for the two rock types.

Electrochemical dissolution of simulated "white inclusions". Kinetics and material balance for Mo, Re, Ru metals and their alloys during electrochemical dissolution in nitric acid

Abstract The kinetics of pure Mo, Re and Ru metals, as well as their alloys 52.5at. Mo – 47.5at. Re and 90at. Mo – 10at. Ru electrochemical dissolution during potential controlled electrolysis at a temperature T=25 °C in 0.5–6.0M HNO3 solutions were studied. The dissolution kinetics for all metal and alloy electrodes under study were found to be of zero order vs. metal concentration in the electrolyte. Rate constants for Mo electrochemical dissolution increased from 1.68×10-3 to 5.99×10-3mol cm-2h-1 with the growth of HNO3 concentration in the electrolyte from 0.5 to 4.0M. Further increase of the acid concentration in the solution to 6.0M did not result in the acceleration of Mo electrochemical dissolution. Rate constants of Re and Ru metals electrochemical dissolution increased monotonously from 4.27×10-4 to 1.7×10-3mol cm-2 h-1 for Re and from 1.28×10-4 to 1.61×10-3mol cm-2 h-1 for Ru with the rise of HNO3 concentration from 0.5 to 6.0M. Dissolution of Mo-Re and Mo-Ru alloys was congruent. With the increase of HNO3 concentration in the electrolyte from 0.5 to 6.0M, the dissolution rate constant of Mo-Re alloy was increasing from 1.33 to 7.60×10-3mol(Mo+Re)cm-2h-1. Maximum rates of Mo-Ru alloy electrochemical dissolution from 2.21×10-3 to 3.28×10-3mol(Mo+Ru)cm-2 h-1 were observed in 2.0–4.0M HNO3 at the electrolysis potential E=1.6V/SCE. The main electrochemical and chemical processes occurring at the metal and alloy electrodes and resulting in the metals dissolution are pointed out.