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51.
Ohne Zusammenfassung 相似文献
52.
Fabio Bellatreccia Giancarlo Della Ventura Luisa Ottolini Eugen Libowitzky Anton Beran 《Physics and Chemistry of Minerals》2005,32(1):65-76
A well-characterized suite of vesuvianite samples from the volcanic ejecta (skarn or syenites) from Latium (Italy) was studied by single-crystal, polarized radiation, Fourier-transform infrared (FTIR) spectroscopy and secondary-ion mass-spectrometry (SIMS). OH-stretching FTIR spectra consist of a rather well-defined triplet of broad bands at higher-frequency (3,700–3,300 cm–1) and a very broad composite absorption below 3,300 cm–1. Measurements with E//c or Ec show that all bands are strongly polarized with maximum absorption for E//c. They are in agreement with previous band assignments (Groat et al. Can Mineral 33:609, 1995) to the two O(11)–H(1) and O(10)–H(2) groups in the structure. Pleochroic measurements with changing direction of the E vector of the incident radiation show that the orientation of the O(11)–H(1) dipole is OHc~35°, in excellent agreement with the neutron data of Lager et al. (Can Mineral 37:763, 1999). A SIMS-based calibration curve at ~10% rel. accuracy has been worked out and used as reference for the quantitative analysis of H2O in vesuvianite by FTIR. Based on previous SIMS results for silicate minerals (Ottolini and Hawthorne in J Anal At Spectrom 16:1266, 2001; Ottolini et al. in Am Mineral 87:1477, 2002) the SiO2 and FeO content of the matrix were assumed as the major factors to be considered at a first approximation in the selection of the standards for H. The lack of vesuvianite standards for quantitative SIMS analysis of H2O has been here overcome by selecting low-silica elbaite crystals (Ottolini et al. in Am Mineral 87:1477, 2002). The resulting integrated molar absorption FTIR coefficient for vesuvianite is i=100.000±2.000 l mol–1 cm–2. SIMS data for Li, B, F, Sr, Y, Be, Ba REE, U and Th are also provided in the paper. 相似文献
53.
Ibrahim M. Shalaby Eugen Stumpfl Hassan M. Helmy Mahmoud M. El Mahallawi Omar A. Kamel 《Mineralium Deposita》2004,39(5-6):608-621
The Um Samiuki Zn–Cu–Pb–Ag mineralisation, south Eastern Desert, Egypt is hosted by felsic volcanic rocks which form part of the 712-Ma-old, east-west-trending Shadli Volcanic Belt. Two major occurrences of massive sulphides are present at the top of rhyolitic breccia in the Western and Eastern mine areas. In each occurrence, a bornite-bearing zone is overlain by a pyrite-chalcopyrite-bearing zone and underlain by a disseminated, Cu-depleted zone. In the massive sulphide ore, sphalerite, chalcopyrite, pyrite, galena, bornite and tetrahedrite–tennantite are major minerals, whereas arsenopyrite, pyrrhotite, molybdenite and magnetite are accessory phases. Covellite and digenite are common secondary minerals. Bornite, tetrahedrite–tennantite and covellite contain high amounts of silver (averages of 1.97, 1.39 and 1.82 wt% respectively). Based on mineralogical balance calculations, bornite and covellite accommodate 80% of silver in the Um Samiuki deposit. Ag was incorporated in the crystal structure of the early-crystallised copper sulphides and sulphosalts and silver minerals. The temperature, sequential precipitation of the fluids and the structure of the crystallising phases control the distribution of silver. Post-depositional deformation and metamorphic processes caused liberation, remobilisation and redeposition of silver within the massive sulphides.Editorial handling: D. Lentz 相似文献
54.
Prof. Dr. Eugen A. Von Thomas Dr. Christer G. Örn 《Aquatic Sciences - Research Across Boundaries》1982,44(1):117-148
Hypolimnetic oxygen in the highly eutrophic Swiss lake Greifensee (area 8 km2, maximum depth 33 m) was almost entirely depleted during summer stratification. We found a strong empirical relation between
wind action across the lake surface and hypolimnetic reoxygenation in the cold half year. Long periods of ice cover severely
limited anemogenic reoxygenation.
相似文献
55.
Summary FTIR spectroscopy was used to study the vibrational behaviour of the hydrogen bond system of the H3O2 unit, present with widely varying O-H...O distances in natrochalcite-type compounds, MeCu2(H3O2)(ZO4)2 (Me = Na, K; Z=S, Se). Absorption bands of powder and polarized single-crystal spectra of non-deuterated and partially deuterated natrochalcite phases are assigned to stretching and bending modes of clearly divided OH– and H2O groups. These results are indicative for a not centro-symmetric configuration of the H3O2 unit and confirm the presence of a very strong hydrogen bond with a split hydrogen atom position.
With 4 Figures 相似文献
Das Wasserstoffbrückensystem in Verbindungen des Natrochalcit-Typs - eine FTIR spektroskopische Untersuchung der H3O 2 – Gruppe
Zusammenfassung FTIR Spektroskopie wurde zur Untersuchung des Schwingungsverhaltens des Wasserstoff-Brückenbindungssystems der H302 Gruppe herangezogen, die mit stark variierenden O-H... 0 Abständen in Verbindungen des Natrochalcit-Typs, MeCu2(H3O2)(ZO4)2 (Me = Na, K; Z = S, Se) auftritt. Absorptionsbanden von Pulverund polarisierten Einkristallspektren nicht deuterierter und teilweise deuterierter Natrochalcit-Phasen, werden den Streck- und Knickschwingungen klar getrennter OH– und H2O Gruppen zugeordnet. Diese Ergebnisse weisen auf einen nichtzentrosymmetrischen Aufbau der H3O 2 – -Gruppe hin und bestätigen das Auftreten einer sehr starken Wasserstoffbrücke mit einer aufgespaltenen Position des Wasserstoffatoms.
With 4 Figures 相似文献
56.
Patterns and trends in the perception of seismic risk. Case study: Bucharest Municipality/Romania 总被引:1,自引:1,他引:0
This research looks at the very nature of perception of seismic risk, an issue that is not only academically important, but
also it can save lives and reduce injury and community costs. The background idea is that citizens in big cities, vulnerable
to seismic hazard are living with latent and permanent concerns about a possible earthquake. We were interested in revealing
significant aspects of Bucharest citizens’ orientations and tendencies in relation to the possible seismic event. Bucharest,
the capital of Romania, is exposed to the greatest seismic hazard compared with other European capitals. The dimensions of
study were: the anticipations of seism occurrence, the behavior during the event, evaluations of consequences, support factors,
and individual vulnerability. This article is an example of the low cost approach on a sample of 190 citizens, understood
as an exercise in attempting to relate population characteristics to various aspects of risk perception. The methodology used
was based on a field investigation, where the research agents’ applied one questionnaire containing free/post codified/fan
answers concerning: demographic variables, the buildings’ features, and perceptions about the possible earthquake event. The
findings of this study showed that the hazard perception significantly associates with aspects concerning the subjects’ orientation
toward institutional factors/human relations/negativism, and toward financial/material/moral support in case of disaster etc.
It is hoped that this issue will serve to inspire further investigations into this very important and socially sensitive field,
due to the fact that hazard analysis and mitigation would be more effective when it takes into account the human dimension
of disasters. 相似文献
57.
Th. Armbruster E. Libowitzky M. Auernhammer P. Bauerhansl Ch. Hoffmann E. Irran A. Kurka H. Rosenstingl L. Diamond 《Mineralogy and Petrology》1995,52(1-2):113-126
Summary The crystal structure of blue bazzite (space group P6/mcc, Z = 2, = 9.501(1),c = 9.178(1) Å) with the composition Be3(Sc1.25Fe3+
0.43Mg0.32Mn0.03Al0.02)=2.05 Si6O18[Na0.32(n H2O)] was refined from X-ray single-crystal data with 422 unique reflections to R = 2.2%. The structure is of the beryl type with octahedra strongly compressed parallel to the c-axis. The octahedral Me-O distance in bazzite is 2.080 A compared to 1.904 Å in beryl. The flattening of octahedra leads to a larger a cell dimension in bazzite compared to beryl (9.209 A). Two-valent cations (mainly Mg) in octahedral coordination are charge balanced by Na at (0, 0, 0) in the structural channels. Polarized single-crystal IR-spectra recorded between 400 and 8000 cm–1 indicate that H2O in the structural channels is oriented with the H-H vector perpendicular to thec-axis. The IR-spectra show more absorption bands than known for type II H2O in beryl thus the existence of more than one H2O species or even OH-groups is very likely.Refractive indices of the same bazzite were measured using a spindle-stage and employing the wavelength-temperature variation method yielding no = 1.6279(3), ne = 1.6066(5) for 589 nm at 25°C. The birefringence = 0.0213 is significantly larger than the one of near end-member beryl ( = 0.0047). This high birefringence of bazzite is related to the electronic polarizability of octahedral Sc and Fe which increase no at a stronger rate than ne. Transition metals in bazzite are also responsible for a higher refractive index dispersion than found for beryl.
Kristallchemie und optische eigenschaften des bazzits aus dem Furkabasistunnel
Zusammenfassung Die Kristallstruktur eines blauen Bazzits (Raumgruppe P6/mcc, Z = 2,a = 9.501(1),c = 9.178(1) Å) mit der Zusammensetzung Be3(Sc1.25Fe3+ 0.43Mg0.32Mn0.03Al0.02)2=2.05 Si6)O18[Na0.32(n H2O)] wurde von Röntgeneinkristalldaten mit 422 Reflexen zu R = 2.2% verfeinert. Die Struktur ist die des Berylltyps mit der Besonderheit, daß die Oktaeder entlang der c-Achse stark zusammengedrückt sind. Die oktaedrischen Me-O Abstände im Bazzit betragen 2.080 Å, im Gegensatz zu 1.904Å im Beryll. Die Stauchung der Oktaeder im Bazzit führt zu einer längeren a-Achse als im Beryll (9.209 Å). Zweiwertige Kationen (vor allem Mg) in oktaedrischer Koordination werden durch Na auf (0, 0, 0), in den strukturellen Kanalen, neutralisiert. Polarisierte Einkristall-IR-Spektren zwischen 400 and 8000 cm–1 zeigen, daß H2O Moleküle in den strukturellen Kanalen mit dem H-H Vektor senkrecht zur c-Achse orientiert sind. Die IR-Spektren weisen außerdem mehr Absorptionsbanden auf, als für den H2O Typ II bekannt sind, sodaß entweder mehr als eine H2O Spezies oder sogar OH-Gruppen sehr wahrscheinlich sind.Brechungsindizes am gleichen Bazzit wurden auf einem Spindeltisch mit der Wellenlängen-Temperatur Variationsmethode gemessen und ergaben no = 1.6279(3), ne = 1.6066(5) bei 589 nm und 25 °C. Die Doppelbrechung A = 0.0210 ist deutlich höher als für einen nahezu Endgliedberyll (A = 0.0047). Diese hohe Doppelbrechung des Bazzits wird durch die elektronische Polarisierbarkeit von oktaedrischem Sc und Fe verursacht, die no starker ansteigen läßt als ne. Übergangselemente im Bazzit sind auch für die höhere Dispersion der Brechungsindizes als im Beryll verantwortlich.相似文献
58.
E. Libowitzky 《Mineralogy and Petrology》1990,43(2):147-160
Summary A complex of Precambrian chlorite-micaschists in the Moravian zone of the Bohemian massif contains up to 20 vol.% of fine grained magnetite and ilmenite. The rocks are characterized by high Fe, Ti and V contents (averages: 13 wt %, 1.6 wt% and 200 ppm), showing a strong positive correlation. SiO2 contents amount to 60 wt.%; together with relatively high K and low Ca and Mg values this is considered to be evidence for metapelites and -psammites. Relictic sedimentary layers of magnetite and chlorite, as well as relictic titano-magnetites were occasionally observed. Magnetite contains up to 0.5 wt.% V2O3 and Cr2O3 each, and up to 1.2 wt.% TiO2. Ilmenites show up to 5 wt.% MnO.The unusual bulk chemistry of the metasediments, the relictic layered structures and the composition of the magnetites (in relation to magnetites of different genesis) suggest a clastic sedimentary origin of the ore minerals, eroded probably from some basic magmatic complex. Hence a Precambrian black-sand is proposed as a precursor rock and compared with different blacksands known from the literature.
With 5 Figures 相似文献
Präkambrische Blacksands als Precursors von Ilmenit führenden Chlorit-Glimmerschie fern der Böhmischen Masse, österreich
Zusammenfassung Eine Serie prdkambrischer Chlorit-Glimmerschiefer im Moravikum der Böhmischen Masse enthält bis zu 20 Vol.% feinkörnigen Magnetit und Ilmenit. Die Gesteine sind durch hohe Gehalte an Fe, Ti and V (durchschnittlich 13 Gew.%, 1.6 Gew.% und 200 ppm), die cine starke positive Korrelation untereinander aufweisen, charakterisiert. Die SiO2-Gehalte betragen 60 Gew.%; dies wird, gemeinsam mit relativ hohen K- und niedrigen Ca- und Mg-Werten, als Hinweis auf Metapelite und -psammite angesehen. Gelegentlich wurden reliktische Lagen von Magnetit und Chlorit, wie auch reliktische Titano-Magnetite beobachtet. Der Magnetit enthält bis zu jeweils 0.5 Gew.% V2O3 und Cr2O3, und bis zu t.2 Gew.% TiO, Die Ilmenite zeigen bis zu 5 Gew.% MnO.Die ungewöhnliche Gesamtzusammensetzung der Metasedimente, die reliktisch gebänderten Strukturen und die Zusammensetzung der Magnetite (verglichen mit Magnetiten verschiedenster Genese) legen einen klastisch-sedimentären Ursprung der, wahrscheinlich von einem basischen Magmatit abgetragenen, Erzminerale nahe. Folglich wird der Einfluß eines präkambrischen Blacksands im Ausgangsgestein vorgeschlagen und mit unterschiedlichen Blacksands aus der Literatur verglichen.
With 5 Figures 相似文献
59.
Eugen Wegmann 《International Journal of Earth Sciences》1948,36(1):48-50
Ohne Zusammenfassung 相似文献
60.
Eugen Seibold 《International Journal of Earth Sciences》1951,39(1):141-142
Ohne Zusammenfassung 相似文献