Effect of Fe3+-bearing point defects on the UV-spectra of two natural olivines   总被引：1，自引：0，他引：1  

N. R. Khisina  K. Langer  G. Partzsch 《Physics and Chemistry of Minerals》1992,18(8):514-516

Polarized near-UV spectra have been recorded on 20 μm diameter spots on oriented crystals of microprobe-analyzed olivines from Baikhal Rift, Fa_8.8 (I) and Seberget, Fa_9.3 (II), which have formed under different fO₂ and, therefore, are expected to contain Fe³⁺-bearing point defects in different concentrations. These should be reflected in the UV-spectra of such minerals (Cemic et al. 1986). The spectra obtained confirm these predictions: The difference in α _{Y, 26500} in both samples indicates a difference in Fe³⁺-site fractions of ΔX_Fe. = 1.78-10⁻⁴, which may be related to an fO₂ about ten times higher for the formation of olivine II compared to I.  相似文献   

Waste disposal in rock by R. Pusch. Developments in geotechnical engineering, 76, Elsevier, Amsterdam, 1994, hardcover, 472 pp., US$ 177.25, ISBN 0-444-89449-7     

M. Langer 《Engineering Geology》1995,39(3-4):266-267

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Sedimentpetrographische und mineralogische Untersuchungen an glaukonitführenden Kreidegesteinen Bayerns     

Prof. Dr. Heinrich M. Köster  Dipl.-Min. Ewald E. Kohler 《International Journal of Earth Sciences》1973,62(2):521-535

Zusammenfassung Der Lösungsrückstand glaukonitführender Gesteine des bayerischen Helvetikums und der Regensburger Oberkreide enthÄlt Glaukonit der 1-M-Glimmermodifikation in den Glaukonitkörnern und in der Feintonfraktion < 2 Ø. Die einige zehntel- gro\en Glaukonitglimmer sind in den helvetischen Gesteinen als unregelmÄ\ig oder hexagonal begrenzte BlÄttchen ausgebildet, in den OberpfÄlzer Gesteinen als unregelmÄ\ig begrenzte oder leistenförmige Kristallite. Bei den helvetischen Gesteinen ist der Glaukonitglimmer in den Körnern und in der Feintonfraktion mit Chlorit (± Montmorillonit), in den oberpfÄlzischen Gesteinen dagegen mit Montmorillonit vergesellschaftet. Die Assoziation Glaukonit/Chlorit oder Glaukonit/Montmorillonit dürfte durch unterschiedliche marine Fazies bedingt sein. Es fehlt eine Korrelation zwischen dem diagenetisch gebildeten Dolomit und dem Chloritgehalt der Gesteine. Die Morphologie der Glaukonitkörner in allen helvetischen Gesteinen und im Regensburger Grünsandstein deutet auf eine authigene Bildung der Körner, dagegen sind im turonen Regensburger Glaukonitmergel die Körner abgerollt.

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The residue of glauconite-bearing rocks from the Bavarian Helvetic zone and the Upper Cretaceous of Regensburg contains glauconitic mica of the 1 M mica-type in the glauconite pellets as well as in the clay fraction < 2 Ø. The glauconite mica of the helvetic rocks are developed as irregular or hexagonaly shaped flakes, those from the rocks of the Upper Palatinate are irregular or form ledges. In the helvetic rocks the glauconitic mica of the fraction < 2 is associated with chlorite (± montmorillonite), in the rocks of the Upper Palatinate on the contrary only montmorillonite could be detected besides glauconitic mica. The association glauconite/chlorite or glauconite/ montmorillonite may be caused by differing marine facia. There is no correlation between dolomite formed by diagenesis and content of chlorite in the rocks. The morphology of the glauconite pellets in all Helvetic rocks and in the Grünsand from Regensburg indicates an authigenic formation of the pellets, whereas the pellets of the Turonic glauconitic marl from Regensburg are rounded by transport.

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Résumé Le résidu de dissolution des roches glauconieuses provenant de l'Helvétien bavarois et du Crétacé supérieur de Ratisbonne contient des micas glauconieux de la modification micacée 1 M dans les grains de glaucome et dans la fraction < 2 Ø. Les micas glauconieux de quelques dizaines de des roches de l'Helvétien ont des contours irréguliers ou des silhouettes hexagonales, tandis que les roches glauconieuses du Haut Palatinat ont des micas irréguliers ou montrent des agrégats de mica de forme plus allongée. Dans les roches helvétiques, le mica glauconieux est associé dans les grains de glauconie et dans la fraction < 2 Ø avec de la chlorite (± montmorillonite); dans les roches du Haut Palatinat au contraire, il est associé avec de la montmorillonite. L'association glauconite/chlorite ou glauconita/montmorillonite semble Être due à des différences de faciés marin. Il n'existe pas de corrélation entre la dolomie d'origine diagénétique et la teneur en chlorite des roches. La morphologie des grains de glauconie dans les roches helvétiques et dans les grès verts de Ratisbonne démontre une formation authigène des grains; par contre les grains des marnes à glauconie turoniennes de Ratisbonne sont arrondis.

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Der Deutschen Forschungsgemeinschaft danken wir für die Unterstützung der Arbeit durch eine Sachbeihilfe. Herrn Dr. W.Schmitt vom Institut für Technische Chemie der TU München verdanken wir die Erlaubnis zur Benutzung des Elektronenmikroskopes. Die Herren Dr. J.Kröger, Dr. M.Freimoser und Dr. A.Buchner stellten uns dankenswerterweise Probenmaterial zur Verfügung.  相似文献   

Monte Carlo Radiative Transfer Modeling of Lightning Observed in Galileo Images of Jupiter   总被引：1，自引：0，他引：1  

U.A. DyudinaA.P. Ingersoll  A.R. VasavadaS.P. Ewald  the Galileo SSI Team 《Icarus》2002,160(2):336-349

We study lightning on Jupiter and the clouds illuminated by the lightning using images taken by the Galileo orbiter. The Galileo images have a resolution of ∼25 km/pixel and are able to resolve the shape of single lightning spots, which have half widths (radii) at half the maximum intensity in the range 45-80 km. We compare the shape and width of lightning flashes in the images with simulated flashes produced by our 3D Monte Carlo light-scattering model.The model calculates Monte Carlo scattering of photons in a 3D opacity distribution. During each scattering event, light is partially absorbed. The new direction of the photon after scattering is chosen according to a Henyey-Greenstein phase function. An image from each direction is produced by accumulating photons emerging from the cloud in a small range (bins) of emission angles. The light source is modeled either as a point or a vertical line.A plane-parallel cloud layer does not always fit the data. In some cases the cloud over the light source appears to resemble cumulus clouds on Earth. Lightning is estimated to occur at least as deep as the bottom of the expected water cloud. For the six flashes studied, we find that the clouds above the lightning are optically thick (τ>5). Jovian flashes are more regular and circular than the largest terrestrial flashes observed from space. On Jupiter there is nothing equivalent to the 30-40-km horizontal flashes that are seen on Earth.  相似文献   

Calcium isotope fractionation in coccoliths of cultured Calcidiscus leptoporus, Helicosphaera carteri, Syracosphaera pulchra and Umbilicosphaera foliosa     

Nikolaus Gussone  Gerald Langer  Markus Geisen  Blair A. Steel  Ulf Riebesell 《Earth and Planetary Science Letters》2007,260(3-4):505-515

Four species of marine calcifying algae, the coccolithophores Calcidiscus leptoporus, Helicosphaera carteri, Syracosphaera pulchra and Umbilicosphaera foliosa were grown in laboratory cultures under temperatures varying between 14 and 23 °C, and one species, C. leptoporus, under varying [CO₃²⁻], ranging from 105 to 219 μmol/kg. Calcium isotope compositions of the coccoliths resemble in both absolute fractionation and temperature sensitivity previous calibrations of marine calcifying species e.g. Emiliania huxleyi (coccolithophores) and Orbulina universa (planktonic foraminifera) as well as inorganically precipitated CaCO₃, but also reveal small species specific differences. In contrast to inorganically precipitated calcite, but similar to E. huxleyi and O. universa, the carbonate ion concentration of the medium has no statistically significant influence on the Ca isotope fractionation of C. leptoporus coccoliths; however, combined data of E. huxleyi and C. leptoporus indicate that the observed trends might be related to changes of the calcite saturation state of the medium. Since coccoliths constitute a significant portion of the global oceanic CaCO₃ export production, the Ca isotope fractionation in these biogenic structures is important for defining the isotopic composition of the Ca sink of the ocean, one of the key parameters for modelling changes to the marine Ca budget over time. For the present ocean our results are in general agreement with the previously postulated and applied mean value of the oceanic Ca sink (Δ_sed) of about − 1.3‰, but the observed inter- and intra-species differences point to possible changes in Δ_sed through earth history, due to changing physico-chemical conditions of the ocean and shifts in floral and faunal assemblages.  相似文献   

Electronic absorption and luminescence spectroscopic studies of kyanite single crystals: differentiation between excitation of FeTi charge transfer and Cr3+ dd transitions     

A. N. Platonov  A. N. Tarashchan  K. Langer  M. Andrut  G. Partzsch  S. S. Matsyuk 《Physics and Chemistry of Minerals》1998,25(3):203-212

A selected set of five different kyanite samples was analysed by electron microprobe and found to contain chromium between <0.001 and 0.055 per formula unit (pfu). Polarized electronic absorption spectroscopy on oriented single crystals, R₁, R₂-sharp line luminescence and spectra of excitation of λ₃- and λ₄-components of R₁-line of Cr³⁺-emission had the following results: (1) The Fe²⁺–Ti⁴⁺ charge transfer in c-parallel chains of edge connected M(1) and M(2) octahedra shows up in the electronic absorption spectra as an almost exclusively c(||Z′)-polarized, very strong and broad band at 16000 cm⁻¹ if <, in this case the only band in the spectrum, and at an invariably lower energy of 15400 cm⁻¹ in crystals with  ≥ . The energy difference is explained by an expansion of the O_f–O_k, and O_b–O_m edges, by which the M(1) and M(2) octahedra are interconnected (Burnham 1963), when Cr³⁺ substitutes for Al compared to the chromium-free case. (2) The Cr³⁺ is proven in two greatly differing crystal fields a and b, giving rise to two sets of bands, derived from the well known dd transitions of Cr^{3+ 4}A_2g→⁴T_2g(F)(I), →⁴T_1g(F)(II), and →⁴T_1g(P)(III). Band energies in the two sets a and b, as obtained by absorption, A, and excitation, E, agree well: I: 17300(a, A), 17200(a, E), 16000(b, A), 16200(b, E); II: 24800(a, A), 24400(a, E); 22300(b, A), 22200(b, E); III: 28800(b,A) cm⁻¹. Evaluation of crystal field parameters from the bands in the electronic spectra yield Dq(a)=1730 cm⁻¹, Dq(b)=1600 cm⁻¹, B(a)=790 cm⁻¹, B(b)=620 cm⁻¹ (errors ca. ±10 cm⁻¹), again in agreement with values extracted from the λ³, λ⁴ excitation spectra. The CF-values of set a are close to those typical of Cr³⁺ substituting for Al in octahedra of other silicate minerals without constitutional OH⁻ as for sapphirine, mantle garnets or beryl, and are, therefore, interpreted as caused by Cr³⁺ substituting for Al in some or all of the M(1) to M(4) octaheda of the kyanite structure, which are crystallographically different but close in their mean Al–O distances, ranging from 1.896 to 1.919 A (Burnham 1963), and slight degrees of distortion. Hence, band set a originates from substitutive Cr³⁺ in the kyanite structural matrix. The CF-data of Cr³⁺ type b, expecially B, resemble those of Cr³⁺ in oxides, especially of corundum type solid solutions or eskolaite. This may be interpreted by the assumption that a fraction of the total chromium contents might be allocated in a precursor of a corundum type exsolution. Received: 3 January 1997 / Revised, accepted: 2 May 1997  相似文献   

Abstracts of papers held at the IMA symposium physics of minerals,novosibirsk, USSR, 1978 (appendix)     

K. Langer  John K. Winter  Fujio P. Okamura  Subrata Ghose 《Physics and Chemistry of Minerals》1979,4(1):101-103

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Optical absorption and mössbauer spectra of purple and green yoderite,a kyanite-related mineral     

R. M. Abu-Eid  K. Langer  F. Seifert 《Physics and Chemistry of Minerals》1978,3(3):271-289

Mössbauer and polarized optical absorption spectra of the kyanite-related mineral yoderite were recorded. Mössbauer spectra of the purple (PY) and green yoderite (GY) from Mautia Hill, Tanzania, show that the bulk of the iron is Fe³⁺ in both varieties, with Fe²⁺/(Fe²⁺+Fe³⁺) ratios near 0.05. Combining this result with new microprobe data for PY and with literature data for GY gives the crystallochemical formulae: $$\begin{gathered} ({\text{Mg}}_{{\text{1}}{\text{.95}}} {\text{Fe}}_{{\text{0}}{\text{.02}}}^{{\text{2 + }}} {\text{Mn}}_{{\text{0}}{\text{.01}}}^{{\text{2 + }}} {\text{Fe}}_{{\text{0}}{\text{.34}}}^{{\text{3 + }}} {\text{Mn}}_{{\text{0}}{\text{.07}}}^{{\text{3 + }}} {\text{Ti}}_{{\text{0}}{\text{.01}}} {\text{Al}}_{{\text{3}}{\text{.57}}} )_{5.97}^{[5,6]} \hfill \\ {\text{Al}}_{{\text{2}}{\text{.00}}}^{{\text{[5]}}} [({\text{Si}}_{{\text{3}}{\text{.98}}} {\text{P}}_{{\text{0}}{\text{.03}}} ){\text{O}}_{{\text{18}}{\text{.02}}} ({\text{OH)}}_{{\text{1}}{\text{.98}}} ] \hfill \\ \end{gathered}$$ and PY and $$\begin{gathered} ({\text{Mg}}_{{\text{1}}{\text{.98}}} {\text{Fe}}_{{\text{0}}{\text{.02}}}^{{\text{2 + }}} {\text{Mn}}_{{\text{< 0}}{\text{.001}}}^{{\text{2 + }}} {\text{Fe}}_{{\text{0}}{\text{.45}}}^{{\text{3 + }}} {\text{Ti}}_{{\text{0}}{\text{.01}}} {\text{Al}}_{{\text{3}}{\text{.56}}} )_{6.02}^{[5,6]} \hfill \\ {\text{Al}}_{{\text{2}}{\text{.00}}}^{{\text{[5]}}} [({\text{Si}}_{{\text{3}}{\text{.91}}} {\text{O}}_{{\text{17}}{\text{.73}}} {\text{(OH)}}_{{\text{2}}{\text{.27}}} ] \hfill \\ \end{gathered}$$ for GY. The Mössbauer spectra at room temperature contain one main doublet with isomer shifts and quadrupole splittings of 0.36 (PY), 0.38 (GY) and 1.00 (PY), 0.92 (GY) mm s^?1, respectively. These values correspond to Fe³⁺ in six or five-fold coordination. The doublet components have anomalously large half widths indicating either accomodation of Fe³⁺ in more than one position (e.g., octahedraA1 and five coordinatedA2) or the yet unresolved superstructure. Besides strong absorption in the ultraviolet (UV) starting from about 25,000 cm^?1, the polarized optical absorption spectra are dominated by strong bands around 16,500 and 21,000 cm^?1 (PY) and a medium strong band at around 13,800 cm^?1 (GY). Position and polarization of these bands, in combination with the UV absorption, explain the colour and pleochroism of the two varieties. The bands in question are assigned to homonuclear metal-to-metal charge transfer transitions: Mn²⁺(A1) Mn³⁺(A1′) ? Mn³⁺(A1) Mn²⁺(A1′) and Mn²⁺(A1) Mn³⁺(A2 ? Mn³⁺(A1) Mn²⁺(A2) in PY and Fe²⁺(A1) Fe³⁺(A1′) ? Fe³⁺(A1) Fe²⁺(A1′) in GY. The evidence for homonuclear Mn²⁺ Mn³⁺ charge transfer (CTF) is not quite clear and needs further study. Heteronuclear FeTi CTF does not contribute to the spectra. In PY, additional weak bands were resolved at energies around 17,700, 18,700, 21,000, and 21,900 cm^?1 and assigned to Mn³⁺ in two positions. Weak bands around 10,000 cm^?1 in both varieties are assigned to Fe²⁺ spin-alloweddd-transitions. Very weak and sharp bands, around 15,400, 16,400, 21,300, 22,100, 23,800, and 25,000 cm^?1 are identified in GY and assigned to Fe³⁺ spin-forbiddendd-transitions.  相似文献   

Synthesis and stability of deerite,Fe 12 2+ Fe 6 3+ [Si12O40](OH)10, and Fe3+⇋Al3+ substitutions at 15–28 kb     

K. Langer  D. Lattard  W. Schreyer 《Contributions to Mineralogy and Petrology》1977,60(3):271-297

Deerite, Fe ₁₂ ²⁺ Fe ₆ ³⁺ [Si₁₂O₄₀](OH)₁₀, thus far known from ten localities in glaucophane schist terranes, was synthesized at water pressures of 20–25 kb and temperatures of 550–600 °C under the of the Ni/NiO buffer. The X-ray powder diagram, lattice constants and infrared spectrum of the synthetic phase are closely similar to those of the natural mineral. A solid solution series extends from this ferri-deerite end member to some 20 mole % of a hypothetical alumino-deerite, Fe ₁₂ ²⁺ Al ₆ ³⁺ [Si₁₂O₄₀](OH)₁₀. The upper temperature breakdown of ferri-deerite to the assemblage ferrosilite +magnetite+quartz+water occurs at about 490 °C at 15 kb, and 610 °C at 25 kb fluid pressure for the of the Ni/NiO buffer. Extrapolation of these data to lower water pressures indicates that deerite can be a stable mineral only in very low-temperature, high-pressure environments.  相似文献   

Convective cores in galactic cooling flows     

Alexei Kritsuk  Tomasz Plewa  Ewald Müller 《Monthly notices of the Royal Astronomical Society》2001,326(1):11-22

We use hydrodynamic simulations with adaptive grid refinement to study the dependence of hot gas flows in X-ray luminous giant elliptical galaxies on the efficiency of heat supply to the gas. We consider a number of potential heating mechanisms including Type Ia supernovae and sporadic nuclear activity of a central supermassive black hole. As a starting point for this research we use an equilibrium hydrostatic recycling model. We show that a compact cooling inflow develops, if the heating is slightly insufficient to counterbalance radiative cooling of the hot gas in the central few kiloparsecs. An excessive heating in the centre, instead, drives a convectively unstable outflow. We model the onset of the instability and a quasi-steady convective regime in the core of the galaxy in two dimensions assuming axial symmetry.
Provided the power of net energy supply in the core is not too high, the convection remains subsonic. The convective pattern is dominated by buoyancy driven large-scale mushroom-like structures. Unlike in the case of a cooling inflow, the X-ray surface brightness of an (on average) isentropic convective core does not display a sharp maximum at the centre. A hybrid model, which combines a subsonic peripheral cooling inflow with an inner convective core, appears to be stable. We also discuss observational implications of these results.  相似文献