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51.
Zusammenfassung Eine uns vom Naturhistorischen Museum in Wien freundlicherweise zur Verfügung gestellte Probe des Meteoriten von Steinbach wurde mit einem Elektronenstrahl-Mikroanalysator vom Typ CAMECA qualitativ und quantitativ auf die chemische Zusammensetzung der einzelnen Phasen untersucht.Besonders eingehend wurde dabei die Metallphase analysiert, da diese sich durch die Anwesenheit einer gut ausgebildeten Widmanstättenschen Struktur in Gegenwart von Tridymit als Druckindikator auszeichnet.Die nichtmetallischen Phasen wurden ebenfalls quantitativ bestimmt und ergeben leicht abweichende Ergebnisse von den Analysen vonN. Story-Maskelyne, O. Winkler undF. Heide. Interessant sind vor allem der relativ hohe Mangangehalt in Bronzit und Chromit sowie der Chromgehalt des Troilits.Die Anwendung der neuen Berechnungen über die Abkühlungsgeschichte der Meteoritenmutterkörper vonWood auf unsere quantitativen Analysen ergab eine Abkühlungsgeschwindigkeit von 10°/Million Jahre, was einem Mutterkörper von ca. 50–90 km Durchmesser und einem Zentraldruck von 200 b entspricht.
Mit 8 Textabbildungen
Herrn Professor Dr.F. Machatschki zum 70. Geburtstag gewidmet. 相似文献
Summary A sample of the meteorite of Steinbach, made available by the Naturhistorisches Museum at Vienna, has been analyzed qualitatively and quantitatively by a CAMECA electron-beam microanalyzer.Detailed examination has been made on the structure of the metal phase, as the presence of a well-grown Widmanstätten-structure in contact with trydimite as a pressure-indicator is a direct proof for the formation of the Widmanstätten-structure without pressure.The nonmetallic phases have been analyzed quantitatively and the results are slightly different from those ofStory-Maskelyne, Winkler andHeide. Very interesting is the relatively high content of manganese in bronzite and chromite, also the chromium content of troilite.The application of the new computations ofWood, dealing with the cooling history of meteorite-parentbodies to our quantitative analyses indicate a cooling rate of 10° C/Million years, according to a parentbody of appr. 50–90 km diameter and a central pressure of appr. 200 b.
Mit 8 Textabbildungen
Herrn Professor Dr.F. Machatschki zum 70. Geburtstag gewidmet. 相似文献
52.
S.B. Lyakhov A.D. Maiorov G.G. Managadze O.A. Povalyaev A.I. Chmil L.Yu. Kochmarev E.G. Shustin M.F. Friedrich W.K. Riedler A.N. Laliashvili A. Kiraga Z. Kłoss Z. Kravchic N.A. Leonov 《Planetary and Space Science》1982,30(4):347-357
Laboratory results of beam plasma discharge (BPD) (dimensions several metres) in a homogeneous atmosphere and a jet of neutral gas are presented. The beam was obtained by an electron gun of the same type as used in rocket experiments.The BPD parameters glow intensity, electromagnetic field and its spectrum, electron density as well as the flux of scattered electrons were measured. In addition, photographs of the BPD were taken. The threshold of BPD ignition was determined as a function of gas pressure and beam parameters. The initial stage of BPD formation as well as various types of oscillatory processes in the discharge were studied. A possible process of BPD initiation is presented. 相似文献
53.
Dissolution and precipitation rates of brucite (Mg(OH)2) were measured at 25°C in a mixed-flow reactor as a function of pH (2.5 to 12), ionic strength (10−4 to 3 M), saturation index (−12 < log Ω < 0.4) and aqueous magnesium concentrations (10−6 to 5·10−4 M). Brucite surface charge and isoelectric point (pHIEP) were determined by surface titrations in a limited residence time reactor and electrophoretic measurements, respectively. The pH of zero charge and pHIEP were close to 11. A two-pK, one site surface speciation model which assumes a constant capacitance of the electric double layer (5 F/m2) and lack of dependence on ionic strength predicts the dominance of >MgOH2+ species at pH < 8 and their progressive replacement by >MgOH° and >MgO− as pH increases to 10-12. Rates are proportional to the square of >MgOH2+ surface concentration at pH from 2.5 to 12. In accord with surface speciation predictions, dissolution rates do not depend on ionic strength at pH 6.5 to 11. Brucite dissolution and precipitation rates at close to equilibrium conditions obeyed TST-derived rate laws. At constant saturation indices, brucite precipitation rates were proportional to the square of >MgOH2+ concentration. The following rate equation, consistent with transition state theory, describes brucite dissolution and precipitation kinetics over a wide range of solution composition and chemical affinity:
54.
55.
Giuseppe D. Saldi Guntram Jordan Jacques Schott Eric H. Oelkers 《Geochimica et cosmochimica acta》2009,73(19):5646-5657
Magnesite growth rates and step velocities have been measured systematically as a function of temperature from 80 to 105 °C and saturation state in 0.1 M NaCl solutions using hydrothermal atomic force microscopy (HAFM). The observations indicate that at these conditions magnesite precipitation is dominated by the coupling of step generation via spiral growth at screw dislocations and step advancement away from these dislocations. As these two processes occur in series the slowest of these dominates precipitation rates. At 100 °C magnesite growth rates (r) determined by HAFM are consistent with
r=k(Ω-1)2,