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941.
942.
Zusammenfassung Die massenspektrometrische Analyse kleinster Gasmengen von H2, O2, CO, CO2, CH4 und H2O ist infolge der Beeinflussung durch das Meßsystem mit beachtlichen Schwierigkeiten verbunden. Die Beeinflussung erfolgt einerseits durch Reaktionen der Gase mit heißen Metalloberflächen und andererseits durch im System vorhandene Glasoberflächen. Bei einer entprechenden apparativen Anordnung, Erhitzen der Proben und Trennung der Gase durch Kühlfallen, können Gasmengen in und auf Mineralen bis zu 0,005 mm3/NDT quantitativ bestimmt werden. Die Apparatur ist durch thermische Zersetzung von Muskovit-, Calcitkristallen usw. geeicht. Die Anwendung dieser Methode auf das Gebiet der Chemie und Mineralogie sowie die Grenzen und Möglichkeiten einer quantitativen Analyse von Restgasen wird gezeigt.
Mit 5 Abbildungen 相似文献
Mass-spectrometric analysis of gases of the system C-H-O in minerals
Summary The analysis by mass-spectrometer of smallest amounts of gases H2, O2, CO, CO2, CH4 and H2O, respectively, meets with considerable difficulties, because of the influence by the measuring system. The influence is caused by interactions of the gases with hot metal surfaces on one hand, and glass surfaces on the other hand. By a suitable arrangement of apparatus and procedures, such as heating the samples and separating the gases by cooling traps, the gas amounts in and on minerals can be quantitatively determined up to 0.005 mm3/SPT. The apparatus is calibrated by thermal dissociation of crystals like muscovite, calcite etc. The application of this method in chemistry and mineralogy is treated as well as the limits and the possibility of the quantitative analysis of residual gas.
Mit 5 Abbildungen 相似文献
943.
The Hodson mining district is in the westernmost foothills of the Sierra Nevada in California, about 17 km west of the town of Angels Camp. This district is part of the West Gold Belt, which lies about 12–16 km west of, and generally parallel to, the better known Mother Lode Gold Belt in central California. The district produced several million dollars worth of Au between about 1890 and 1940. 相似文献
944.
Fe-rich tholeiitic liquids and their cumulate products in the Pleasant Bay layered intrusion, coastal Maine 总被引:4,自引:0,他引:4
R. A. Wiebe 《Contributions to Mineralogy and Petrology》1997,129(4):255-267
Fe-rich tholeiitic liquids are preserved as chilled pillows and as the chilled base of a 27 meter thick macrorhythmic layer
in the Pleasant Bay mafic-silicic layered intrusion. The compositions of olivine (Fo1) and plagioclase (An13−8) in these extremely fine grained rocks suggest that they represent nearly end stage liquids that formed by fractionation
of tholeiitic basalt. Their major element compositions (∼17.5 wt% FeOT and 54 wt%SiO2) closely resemble highly evolved glasses in the Loch Ba ring dike and some recent estimates of end-stage liquids related
to the Skaergaard layered intrusion, and are consistent with recent experimental studies of tholeiite fractionation. Their
trace element compositions are consistent with extensive earlier fractionation of plagioclase, olivine, clinopyroxene, ilmenite,
magnetite and apatite. The mineral assemblage of the chilled rocks (olivine, clinopyroxene, quartz, ilmenite and magnetite),
apatite saturation temperatures, and very low Fe3+/Fe2+indicate conditions of crystallization at temperatures of about 950 °C and f
O
2
about two log units below FMQ. Cumulates that lie about 3 meters above the chilled base of the macrorhythmic layer contain
cumulus plagioclase, olivine, clinopyroxene, ilmenite, apatite and zircon. This mineral assemblage and the Fe-Mg ratio in
clinopyroxene cores suggest that this cumulate was in equilibrium with a liquid having a composition identical to that of
the chilled margin which lies directly beneath it. The high FeOT and low SiO2 concentrations of this cumulate (23.3 and 45.8 wt%, respectively) are comparable to those in late stage cumulates of the
Skaergaard and Kiglapait intrusions. This association of a chilled liquid and cumulate in the Pleasant Bay intrusion suggests
that late stage liquids in tholeiitic layered intrusions may have been more SiO2-rich than field-based models suggest and lends support to recent experimental studies of tholeiite fractionation at low f
O2 which indicate that saturation of an Fe-Ti oxide phase should cause FeOT to decrease in the remaining liquid.
Received: 17 January 1997 / Accepted: 10 June 1997 相似文献
945.
946.
The lead isotope composition of 32 lead glasses excavated from strata of the twelfth to early fifteenth century in six countries
of NW Europe made the predominance of the Harz Mountains in this period of the Medieval European lead and silver production
highly probable. Post-Variscan vein type galena, Devonian syngenetic hydrothermal ore (Rammelsberg) and blended ore from both
deposits in the Harz were used. Our evaluation of 200 mining sites in Germany, Britain and Ireland also demonstrated that
minor lead sources for lead glass were located in Bavaria/Bohemia and England. Lead ores from the Rhenohercynian orogenic
belt in Germany are derived from rock sources close to the upper continental crust composition in 238U/204Pb of about 10 and Th/U of about 4. The ores in Central England originated from rocks with 238U/204Pb of about 11.
Received: 24 September 1996 / Accepted: 17 January 1997 相似文献
947.
948.
The granulometric composition and sorting of loesses and interbedded soils are studied for stratigraphic subdivision and correlation of the loess-paleosol sequence in Moldova. Distinctive features of loess and paleosol horizons of different age are identified and general characteristics of the mineral composition are described that together with other lithological characteristics, including the visual ones, improve reliability of stratigraphic operations. 相似文献
949.
Ice-core samples from Upper Fremont Glacier (UFG), Wyoming, were used as proxy records for the chemical composition of atmospheric
deposition. Results of analysis of the ice-core samples for stable isotopes of nitrogen (δ15N, ) and sulfur (δ34S, ), as well as and deposition rates from the late-1940s thru the early-1990s, were used to enhance and extend existing National Atmospheric
Deposition Program/National Trends Network (NADP/NTN) data in western Wyoming. The most enriched δ34S value in the UFG ice-core samples coincided with snow deposited during the 1980 eruption of Mt. St. Helens, Washington.
The remaining δ34S values were similar to the isotopic composition of coal from southern Wyoming. The δ15N values in ice-core samples representing a similar period of snow deposition were negative, ranging from -5.9 to -3.2 ‰ and
all fall within the δ15N values expected from vehicle emissions. Ice-core nitrate and sulfate deposition data reflect the sharply increasing U.S.
emissions data from 1950 to the mid-1970s. 相似文献
950.
L. Beccaluva D. Ohnenstetter M. Ohnenstetter A. Paupy 《Contributions to Mineralogy and Petrology》1984,85(3):253-271
Within the Vourinos ophiolite evidence of two magmatic series has been preserved in cognate cumulates and in effusive and hypabyssal rocks, which constitute the earlier Krapa sequence and the younger Asprokambo sequence. The Asprokambo dyke basic magmas which are poor in incompatible elements and relatively Ni and Cr rich, bear some resemblance to very low Ti basalts (transitional to boninites) found in subduction related arcs or interarc basins. Krapa series magmas from sills, massive and pillow lavas are best equated with low-K tholeiites of island arc suites. Compositions of Al- and Ti- poor Cpx in lavas from both series are comparable to those in island arc basalts, the Asprokambo Cpx being richer in Ca and Cr than those from Krapa.The large volume of cumulates from the Krapa sequence displays the following crystallization order: Ol±Sp, Cpx, Pl±Opx, Mt. Periodic influx of fresh magma batches into the magma chamber occurred mainly during the formation of the lower cumulates (wehrlite, Ol-clinopyroxenite and melagabbro). The upper cumulates, gabbronorite and leucogabbronorite with minor Mt-bearing gabbronorite, crystallized in the upper levels of a magma chamber which became progressively smaller with time. In the Asprokambo sequence, Ol+Sp, Opx, Cpx, PI and Amph are the successively crystallizing phases. The ortho to heteradcumulates consist of websterite, Pl-websterite, gabbronorite, amphibole bearing leuconorite, diorite and granophyre. In cumulates, especially in the lower Krapa sequence, significant subsolidus reaction was probably induced by the persistence of high geothermal gradients linked to continuous magmatism. Petrological features indicate that the evolution of the Krapa series is more compatible with an intermediate fractional/equilibrium crystallization history in an initially open system, whereas nearly perfect fractional crystallization in closed system may have occurred in the small Asprokambo magma chambers. Chemical variations in the lavas of both series can be explained in terms of crystallization of the observed cumulates. Significantly, the Asprokambo intrusives have igneous Mg-hornblende and vanadium bearing, chromian, aluminous titaniferous magnetite, crystallization of which is responsible for the calcalkaline evolutionary trend of these rocks. Major and trace element modelling necessitates a two stage model for the petrogenesis of the Vourinos parental melts, involving high-degree remelting of previously depleted mantle sources favoured by the influx of subduction derived hydrous fluids. The primary magmas parental to the Krapa and Asprokambo series could have been derived respectively by 20 and 30% equilibrium partial fusion of variably depleted lherzolitic sources, leaving residua having a harzburgitic to dunitic composition. 相似文献