Search

The work function of 75W25Re alloy has been determined by the thermionic emission method aided by computer simulation of resistive heating of a cathode made of the alloy wire. The obtained values are temperature dependent, which is due to desorption of oxygen atoms which enhance the work function. The lowest value of 4.7 eV was obtained for the highest temperature of 2550 K. The value calculated on the basis of the image-force model is 4.65 eV. In addition, the resistivity as a function of temperature, knowledge of which is necessary for work function determination, has been measured for this alloy. [ABSTRACT FROM AUTHOR]

The curative waters of HCO3-SO4-Mg-Na+H2S chemical type and 0.6-0.8 g/dm3 total dissolved solids are exploited in Horyniec Spa located at the northern boundary of the Carpathian Foredeep, near the Polish-Ukrainian border. Although these waters occur at relatively shallow depths (their aquifer is encountered about 30 m below the ground surface), they are quite well protected from surface pollutants by a cover of clayey sands. This paper revises and discusses the origin of specific chemical components of these waters based on the following analyses of stable isotopes: (a) δ34S in [image omitted] , H2S, and CaSO4·2H2O, (b) δ18O in [image omitted] , H2O, and CaSO4·2H2O, and (c) δ2H in H2O and CaSO4·2H2O. The most important process which takes place in the aquifer is the dissolution of gypsum present in the Miocene formation and subsequent bacterial reduction of sulphate ion to hydrogen sulphide in the presence of an organic matter. This process shifts both δ34S and δ18O of sulfate ions towards higher concentration of heavy isotopes by several per mil in comparison to that in the original Miocene gypsum. The hydrogen sulphide generated this way (up to a concentration of 45 mg/dm3) is highly depleted in a heavy isotope by about 41 ‰ with respect to a sulphate ion. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to determine the sources of in groundwater of the Olkusz–Zawiercie Major Groundwater Body. The quality of groundwater was relatively good in the past, but fluctuations of the water table level have caused degradation of water quality. Variations in the water table level and the formation of the depression cone have resulted from both groundwater withdrawal and Zn–Pb mine dewatering. As a result within the extended vadose zone of the aquifer, weathering of pyrite and accompanying sulfides has taken place. Since 1992 the water table has risen and this process has been associated with an increase in concentrations of , Ca and Mg. At the same time, the pH has decreased and periodically high Fe concentrations have been detected. High concentrations of Mg and Sr have been observed and, since gypsum layers are known to be present, a de-dolomitisation process has been hypothesized. The PHREEQC program for Windows was used to estimate saturation indices for calcite, dolomite, gypsum and epsomite. Isotopic data for dissolved in the groundwater and archival data on isotopic composition of ore sulfides were used to solve the isotope balance equation and to estimate the fraction of dissolved that originated from pyrite oxidation and gypsum dissolution. The results have shown that dissolution of pyrite oxidation products has a significant influence on chemical composition of groundwater, especially in the southern part of the cone of depression. By solving the additional, combined mass transfer and isotope balance equations it was inferred that a variation in isotopic composition of weathered sulfides must also occur. [ABSTRACT FROM AUTHOR]

K-Ar determinations have been conducted on the background of the earlier radiometric data in the eastern part of the northern Karkonosze-Izera envelope of the granite massif, composed of different varieties of granites, gneisses and mica schists. The values of the K-Ar age for minerals and rocks from the Karkonosze-Izera block lie in the wide interval ranging from 226.0±6.7 Ma to 386.1±3.0 Ma. The K-Ar age data obtained by volumetric method oscillate between 308±21 and 372±26 Ma. Most biotite K-Ar age values of the Izera granite-gneisses complex give an average age of 316.1±3.3 Ma. They correspond to the cooling age of the Karkonosze pluton while the data below 300 Ma are minimum age values that postdate the last granite intrusion of the Krkonoše-Jizera pluton. The obtained results over 300 Ma are mixed apparent ages between the age of the Karkonosze and the Izera granite ages. The K-Ar dates in the studied region have been compared with fission-track (FT) ages of zircon and titanite in the same area which display another distribution pattern. [ABSTRACT FROM AUTHOR]

New results of isotope analysis of light elements (H, C and S) of a dozen Baltic amber samples are described and discussed. Carbon isotope composition was nearly constant (ca. -23‰), whereas sulphur and hydrogen varied in their isotope compositions from +4 to -28‰ and from -171 to -213‰, respectively. The formation and subsequent evolution of this material since its origin in Paleogene time until present is outlined. [ABSTRACT FROM AUTHOR]

Aim of an extensive research project is an analysis of surface properties of Moon's regolith covering and the assessment of the possible existence of usable water on the Moon. In the present paper a short historical survey on Moon's exploration and recent and planned missions is given. Recent recognitions are discussed on the basis of origin and history of the Moon and the import of water from other celestial bodies. Characteristic data and chemical composition of the Moon's surface are summarised with respect to possible water or ice preservation. Experimental investigations have been made on three typical lunar regolith powder samples from the Apollo 11, 12 and 16 missions. The experiments include spectroscopic and thermal analysis, density measurements and sorptometry. In the present paper we give a survey on measuring methods applied and discuss some results. The measurements confirm results of investigations made with less sensitive equipment shortly after the missions. With regard to water occurrence we found that the regolith cover of the Moon surface is rather hydrophobic and can hardly store water as adsorbed layers. [ABSTRACT FROM AUTHOR]

Samples from Fiodoro-Pansky massif were investigated by polarized light microscopy, EDS electron microscopy and isotope ratio mass spectrometry. We have observed four-stage ore mineralization: (1) magmatic Fe-Ti-oxides, (2) sulfide-ferrous oxide, (3) hydrothermal Cu-Ni-sulfide with haycokite, talnakhite and galena admixture, (4) tiosulfates formed from pyrrhotite. A few sulfide samples from generations (2) and (4) were investigated isotopically. The second generation is isotopically homogenous with δ34S close to zero, whilst the third generation shows significantly negative δ34S values. [ABSTRACT FROM AUTHOR]

A new semi-empirical formula was devised for liquid-vapour fractionation at thermodynamic equilibrium, which is valid for the whole temperature range, i.e. from the freezing to the critical temperature, Tc. The new formula contains three parameters (A, B and C) only: [image omitted] where X is the ratio of saturated vapour pressure at temperature T to the critical pressure. Physical reasons for the above formula are presented. The following numerical values of the parameters have been obtained by fitting the above expression to the experimental data from literature: A=1.3781×106, B=1.8876×103, C=3655.8 for 18O/16O, and A=18.993×106, B=40.798×103, C=18405 for D/H isotope fractionation. In both cases, X was calculated from the Van der Waals semi-empirical formula for vapour pressure, which has only one crude parameter: [image omitted] [ABSTRACT FROM AUTHOR]

The Gossendorf volcanic body is the only one in the Styrian basin that shows extensive hydrothermal alteration. K-Ar dating of primary volcanic biotite and alteration products (alunite) suggests that the emplacement of the volcanic body and hydrothermal alteration took place synchronously, 15 Ma ago. The stable isotope compositions of the alteration products such as opal, barite, pyrite and alunite combined with crystallographia investigations indicate temperatures between 150 and 200 °C for the formation of the alteration zones. The calculated stable isotopic compositions of the parent fluid, responsible for the alteration, show an exogene marine component, which interacted with the host rock. Sulphur isotopic compositions of sulphur, sulphides and sulphates indicate disequilibrium, and progressive oxidation. This fact, combined with the mineral zonation of the alteration zone, reflects not only change in the pH but also change in the fO2 of the ascending fluids. [ABSTRACT FROM AUTHOR]

A newly acquired mass spectrometer MI 1201 by the Mass Spectrometry Laboratory will be adapted to determine rhenium and osmium isotope concentrations using negative thermal ionization mass spectrometry (NTIMS). We describe the principle of the Re-Os dating technique and the thermal ionization phenomena which lead to high precision isotope analysis on NTIMS. [ABSTRACT FROM AUTHOR]

The Strzegom-Sobótka Variscan Massif (Fore-Sudetic Block, NE Bohemian Massif) consists of various post-kinematic Variscan granitoids emplaced into Palaeozoic low grade metamorphic rocks. Biotite from five samples representing the homblende-biotite monzogranite, biotite monzogranite and biotite granodiorite has been dated using the K-Ar method for two size-fractions (0.25–0.35 and 0.35–0.5 mm). Finer fractions show more intense chloritization and therefore the results for them were rejected in further discussion. Coarser fractions with higher potassium content were accepted as yielding a maximum estimate approaching the true K-Ar biotite cooling ages. The results are clustered in two groups. The older age group (308.8±4.6 Ma and 305.5±4.3 Ma) comprises results obtained from the biotite granodiorites. They are generally consistent with the zircon crystallization age of 308.4±1.7 Ma reported by Tumiak el al. (2005) and imply rapid cooling of the biotite granodiorite from magmatic temperatures down to the closure temperature of K-Ar isotopic system in biotite. The younger group is defined by 29 1.0±4.4 Ma and 298.7±5.2 Ma ages for the hornblende-biotite monzogranite and 294.2±4.3 Ma age for the biotite monzogranite. In the absence of precise U-Pb or Pb-Pb zircon data further geochronological studies are needed to decipher precisely the cooling history of the monzogranites. [ABSTRACT FROM AUTHOR]

Refinements have been made to achieve over 99% yield in the conversion of CO to CO2 in order to improve the reproducibility and accuracy of δ18 O measurements in sulfates. BaSO4 (10-15 mg) was mixed with an identical amount of spectrographic-grade graphite and loaded into a Pt boat. The mixture was gradually heated to 1100 °C to reduce sulfate to CO and CO2; the former gas was simultaneously converted to CO2 by a glow discharge between Pt electrodes immersed in a magnetic field (produced by a pair of external neodymium magnets). A small memory effect was noticed during the analysis (less than 0.3‰ per 10‰ difference in δ18 O between two subsequently analysed samples). The memory effect, however, was suppressed by repetitive preparation of the same specimen. CO2 produced in this way from sulfate reference samples was analysed on a dual inlet and triple collector mass spectrometer along with CO2 equilibrated with VSMOW, GISP and SLAP water reference samples. To avoid large departures of measured isotope ratios from 18O/16O of the working calibrator we used CO2 gas prepared from ocean water sulfate for this purpose. The calibrated δ18 O values (in ‰) obtained in this way for NBS-127, IAEA SO-5 and IAEA SO-6 reference materials were 8.73 ± 0.05, 12.20 ± 0.07 and -10.43 ± 0.12, respectively. [ABSTRACT FROM AUTHOR]

A slice of black shale rock cut by various metal sulphide veins of different generations from the Kupferschiefer deposits of Lubin, Poland was subjected to bombardment in a Laser Microprobe Combustion Reactor to produce SO2 for S-isotope analyses. The δ34S values ranged from-22 to-29 ‰ consistent with previous findings using conventional IRMS and attributable to primary generation of H2S by bacterial sulphate reduction. Systematic trends in δ34S values of a few per mil over distances of the order of mm attest to low temperatures of mineralization with accompanying change in the isotope composition of the fluids due to kinetic or equilibrium isotope fractionation.†Revised version of a paper presented at the VIII Isotope Workshop of the European Society for Isotope Research (ESIR), June 25 to 30, 2005, Leipzig-Halle, Germany [ABSTRACT FROM AUTHOR]

Tree rings can be used as archives of climatic and environmental data with annual resolution. Tree rings widths, maximum late wood density and other parameters as stable composition in tree rings can be used for the reconstruction of past climatic and environmental changes. Stable carbon isotope ratios in tree rings may provide valuable information on past climatic conditions. 13 C/ 12 C ratios of plant organic matter can reflect corresponding 13 C/ 12 C ratio of atmospheric CO 2 during formation of the rings. Investigations of isotopic carbon composition in tree rings from in the ecologically clean the Augustów Wilderness region in the north-eastern part of Poland (22°58′E, 53°51′N) (nowadays a sanctuary) were undertaken. Series of δ 13 C in α-cellulose and in wholewood were acquired. Those measurements constituted a part of more complex investigations of carbon isotope composition in tree rings including the measurements of radiocarbon concentration and tree ring widths. This article presents preliminary results. It is argued that contrary to the tree ring widths and δ 13 C in wholewood that do not reveal significant correlation with temperature, the variation of δ 13 C in the latewood α-cellulose is correlated with combined July and August temperatures. [ABSTRACT FROM AUTHOR]

Development of glaciolacustrine basins and varved clay sedimentation in Lithuania are closely connected with the course of ice retreat during Daniglacial time from 16,000 till 13,000 BE Isotopic composition (δ13C and δ18O) of chemogenic carbonaceous samples from glaciolacustrine varved clays, which spread near glacier edge of South-Lithuanian (Balbieriškis section), Middle-Lithuanian (Girininkai section) and North-Lithuanian (Joniškêlis section) Phases of the Baltija (Pomeranian) Stage of Nemunas (Vistulian) Glaciation, has been studied. The obtained stable isotope data well confirm climatic changes of Daniglacial time in Lithuania. The gradual warming of climate is connected with the South-Lithuanian to Middle- Lithuanian and the Middle-Lithuanian to North-Lithuanian Interphasials as well as with the South Lithuanian interoscillations. The Interphasial lacustrine sedimentation with rhythmical lamination of carbonaceous sediments was observed in the middle part of the Balbieriškis section (at a depth of 3.1-5.9 m). The following climatic changes of Daniglacial time in Lithuania are distinguished: (1) stadial (3000-6000), (2) glaciophasial (500-1000), (3) glacio- oscillation (500-1000) years and (1) interstadial (1000-2000), (2) interphasial (250-450), (3) glacio-interoscillation (20-40) years. Regular succession of Daniglacial climatic and sedimentation changes in the local periglacial glaciolacustrine lakes, conditioned by recession of the last Scandinavian ice sheet, was revealed in the glaciolacustrine-lacustrine sediments for the first time. [ABSTRACT FROM AUTHOR]

Describes a fast and safe method of direct SO2 extraction from BaSO4 for sulfur isotopic analysis by mass spectrometry. Use of pure NaPO3 and copper foil as reagents; Testing of the reproducibility of the method; Relationship between measured ion beam ratios and the isotopic ratios for respective SO+ and SO2+ spectra.

We performed stepwise heating experiments for determination of the two stable isotope ratios of argon fractions and total concentrations of the three stable isotopes 36Ar, 38Ar and 40Ar in lunar regolith acquired from the Apollo 11, Apollo 12 and Apollo 16 missions. Also the concentration of in situ formed radiogenic 40Ar was estimated on the basis of known ages and potassium concentrations determined by isotope dilution method. The observed excess of 40Ar concentration is interpreted to be due to variable (over geological time) flux of solar energetic particles which were implanted into the material at the Moon surface. [ABSTRACT FROM AUTHOR]

The new version of a double-vacuum crucible for fusion of small samples of refractoty minerals has been described recently by Halas (2006). This novel type of high temperature crucible was further improved in the following important points: (1) The expensive material, tantalum, was replaced by much cheaper molybdenum which also appears to be significantly less corrosive in the presence of hot boron nitride ceramic used as the insulator, and (2) a versatile temperature controller was assembled from commercially available components. [ABSTRACT FROM AUTHOR]

Presents a study which discussed the use of Cu2O - NaPO3 mixtures for sulfur dioxide extraction from BaSO4 for sulfur isotope analysis. Method to extract sulfur dioxide from sulfates; Assessment of the amount of extracted sulfur dioxide and reaction time; Information on the plots of sulfur dioxide yield as a function of reaction time.

Temporal and spatial variations of the concentration and the isotopic composition of groundwater sulfate in an unconfined sandy aquifer covered by peatland have been studied to better understand the sources and biogeochemical processes that affect sulfate distribution in shallow groundwater systems influenced by organic rich sediments. The groundwater monitoring was carried out for one year at hydrogeological station Pożary located within the protected zone of the Kampinos National Park. Sulfur (δ34SSO4) and oxygen (δ18OSO4) isotopic composition of dissolved sulfates were analyzed together with oxygen (δ18OH2O) and hydrogen (δ2HH2O) isotopic composition of water and major ions concentration at monthly intervals. The research revealed three main sources of sulfates dissolved in groundwater, namely, (a) atmospheric sulfates—supplied to the aquifer by atmospheric deposition (rain and snow melt), (b) sulfates formed by dissolution of evaporite sulfate minerals, mainly gypsum—considerably enriched in 34S and 18O, and (c) sulfate formed during oxidation of reduced inorganic sulfur compounds (RIS), mainly pyrite—depleted in 34S and 18O. The final isotopic composition and concentration of dissolved SO42− in groundwater are the result of overlapping processes of dissimilatory sulfate reduction, oxidation of sulfide minerals, and mixing of water in aquifer profile. [ABSTRACT FROM AUTHOR]