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21.
The polarized single-crystal Raman spectra of synthetic H2O-containing alkali-free beryl were recorded at room and low temperatures, and the polarized single-crystal IR spectra at
room temperature. The H2O molecule in the channel cavities is characterized by a Raman-active symmetric stretching vibration (ν1) at 3607 cm−1 and an IR-active asymmetric stretch (ν3) at 3700 cm−1 at room temperature. At low temperatures this ν3 mode is observed in the Raman. Weak ν1 and ν3 modes of a second type of H2O are also observed in the Raman spectra but only at 5 K. The H⋯·H vector of the most abundant type of H2O is parallel to the channel axis of beryl along [0 0 0 1]. The components of the polarizability tensor of the ν1 mode of H2O are similar to, but not exactly the same as, those of a free H2O molecule. The Raman measurements indicate that the H2O molecule is rotationally disordered around [0 0 0 1]. External translation and librational modes of H2O could be observed as overtones with the internal H2O-stretching modes. In the case of the librational motions, normal modes could also be observed directly in the Raman spectra
at ∼200 cm−1. The energies of the translational modes can be determined from an analysis of the overtones and are about 9 cm−1 in energy (i.e., Tz). The energies of the librational modes are about 210 cm−1 for Rx and 190 cm−1 for Ry.
Received: 8 April 1999 / Accepted: 5 April 2000 相似文献
22.
Abstract— The Sahara is an extraordinary area for recovering meteorites. Between 1989 and 1993, 471 meteorites were collected in Algeria and Libya. Studies of 465 samples have been done. In addition to the classifications of the meteorites that were published in various “Meteoritical Bulletins” in past years, we present here the results on the determination of the shock metamorphism and the degree of weathering. Also, we have tried to solve the pairing problem by considering the find locations, the degree of shock metamorphism, the degree of weathering, and the mineral compositions of olivine and pyroxene. A comprehensive table listing all samples contains references about previous work on these meteorites. 相似文献
23.
J. Newton A. Bischoff J. W. Arden I. A. Franchi T. Geiger A. Greshake C. T. Pillinger 《Meteoritics & planetary science》1995,30(1):47-56
Abstract— The Saharan meteorite Acfer 094 is a unique type of carbonaceous chondrite. Mineralogical and petrological considerations and O isotopes are unable to distinguish unambiguously between a CO3 vs. CM2 classification. The other important light elements, C and N, have systematics that do not match any previously recognised meteorite group. Particularly important in this respect is the very low C/N ratio and δ13C of the macromolecular C. Acfer 094 has more diamond and SiC, especially X type grains, than any other specimen studied, suggesting minimal thermal or aqueous processing to decrease its very primitive status. 相似文献
24.
Valentin R. Troll Juan Carlos Carracedo Beatrice Jägerup Michael Streng Abigail K. Barker Frances M. Deegan Francisco Perez‐Torrado Alejandro Rodriguez‐Gonzalez Harri Geiger 《Geology Today》2017,33(4):148-154
Volcanic pyroclasts of small size, such as lapilli and small pumice stones, are widely used in agriculture, gardening, and for pot plants as natural inorganic mulch. The technique of using pyroclasts to enhance topsoil stems from the eighteenth century, and specifically from the ad 1730–1736 eruption on Lanzarote. Critical observations on plant development during and after the eruption showed that the vegetation died when buried under a thick layer of lapilli, but grew vigorously when covered thinly. While the agriculture of Lanzarote was restricted to cereals before the eruption, it diversified to many kinds of fruit and vegetables afterwards, including the production of the famous Malvasía wines in the Canaries. The population of Lanzarote doubled in the years after the eruption, from about 5000 in 1730 to near 10 000 in 1768, predominantly as a result of the higher agricultural productivity. This outcome led to widespread use of lapilli and pumice fragments throughout the islands and eventually the rest of the globe. Lapilli and pumice provide vesicle space for moisture to be retained longer within the planting soil, which can create an environment for micro‐bacteria to thrive in. Through this route, nutrients from volcanic matter are transported into the surrounding soil where they become available to plant life. The detailed processes that operate within the pyroclasts are less well understood, such as the breakdown of nutrients from the rock matrix and transport into the soil by biological action. Further studies promise significant potential to optimize future agricultural efforts, particularly in otherwise arid areas of the globe. 相似文献
25.
Joyce Schmatz Marc Holland Steffen Giese Wouter van der Zee Janos. L. Urai 《Journal of the Geological Society of India》2010,75(1):74-88
The aim of this study is to improve our knowledge of the processes that lead to clay smear during faulting of a layered sand-clay
sequence in an analogue sandbox model. We carefully characterized mechanical properties of the materials used by a series
of geotechnical tests. Displacement field was quantified using PIV (Particle Image Velocimetry). The model is water-saturated
to allow the deformation of wet clay and sand in one experiment comprising a sand package with a horizontal layer of clay
above a predefined rigid basement fault. The thickness and rigidity of the clay layer are the parameters varied in this study.
The model shows a range of structures that are related to competence contrast between sand and different clay types. Results
show ductile shearing of soft clay with a transition to brittle fracturing of stiff clay accompanied by the formation of rotating
clay blocks in the fault zone. Localized deformation is observed through time showing (i) the propagation of one active fault
migrating laterally through the sediment package, and (ii) the formation of a stable prism between two or more active faults
that gets progressively smaller with minor rotation of the hanging wall fault. Continuous clay smear is observed resulting
from the lateral injection of clay as well as from a reworked mixture of sand and clay. 相似文献
26.
Ohne Zusammenfassung
Herrn Professor Dr. Fritz Baltzer zum 80. Geburtstag gewidmet 相似文献
27.
C. A. Geiger 《Mineralogy and Petrology》1999,66(4):271-299
Summary The thermodynamic properties of garnets in the system (Fe2+, Mn2+, Mg, Ca)3A12Si3O12 are reviewed. The thermodynamic properties of the three end-member garnets pyrope, almandine and grossular, including their volume, enthalpy of formation, entropy, compressibility and thermal expansion have been well determined. For spessartine enthalpy of formation and heat capacity at low temperatures are needed. Pyrope's unusual behavior in some of its properties is probably related to the presence of the small, light Mg cation, which has a large anisotropic thermal vibration. The thermodynamic mixing properties of the six binaries are also discussed. Good volume of mixing data exist now for all of the binaries, but much work is still required to determine the enthalpies and third-law vibrational entropies of mixing. It is shown that the magnitude of the positive deviations in the volumes of mixing is related to the volume difference between the two end-member components. It is probable that excess entropies, if present, originate at low temperatures below 200 K. Recent29Si NMR experiments have demonstrated the presence of short-range ordering (SRO) of Ca and Mg in pyrope-grossular solid solutions. Short-range order will have to be considered in new models describing the entropies of mixing. Its possible presence in all garnet solid solutions needs to be examined. The mixing properties of pyrope-grossular garnets, which are the best known for any garnet binary, can, in part, be described by the Quasi-Chemical approximation, which gives insight into the microscopic interactions which determine the macroscopic thermodynamic mixing properties. Microscopic properties are best investigated by spectroscopic and computational approaches. Hard mode IR measurements on binary solid solutions show that the range of local microscopic structural distortion is reflected in the macroscopic volumes of mixing. The nature of The contents of this contribution was presented at the IMA Meeting in Toronto in August, 1998. It precedes issues of Mineralogy and Petrology containing thematic sets of IMApapers strain tiields and site relaxation needs to be studied in order to obtain a better understanding of the solid-solution process and energetics in garnet. Critical areas for future experimentation are also addressed.[/p]
With 11 Figures 相似文献
Eine kritische Zusammenstellung und Analyse der thermodynamischen Daten der (Fe2+, Mn2+, Mg, Ca)3Al2Si3O12 granate
Zusammenfassung In dieser Studie werden die thermodynamischen Eigenschaften der Granate im System (Fe2+,Mn2+, Mg, Ca)3Al2Si3O12 kritisch zusammengestellt. Die thermodynamischen Eigenschaften der drei Endglied-Granate Pyrop, Almandin und Grossular, einschließlich ihrer Volumina, Bildungswärmen, Entropien, Kompressibilitäten und thermischen Ausdehnungen wurden bereits hinreichend gut bestimmt. Dagegen müssen die Bildungswärme und Tieftemperatur-Wärmekapazität von Spessartin noch gemessen werden. Die Eigenschaften des Pyrops sind wahrscheinlich mit den großen anisotropen Schwingungen des kleinen, leichten Mg-Kations verbunden. Die thermodynamischen Mischungseigenschaften der sechs binären Mischkristallreihen werden ebenfalls diskutiert. Während die Mischungs-Volumendaten der binären Mischreihen gut bekannt sind, müssen ihre Mischungs-Enthalpien und Standard-Mischungsentropien noch ermittelt werden. Es wurde gezeigt, daß die Größe der positiven Exzeß-Volumina mit dem Volumen-Unterschied der zwei Endglied-Komponenten der jeweiligen Mischreihe verknüpft ist. Es ist wahrscheinlich, daß Exzeß-Entropien, wenn vorhanden, erst bei Tieftemperaturen unter 200 K auftreten. Neue29Si NMR-Experimente belegen, daß in Pyrop-Grossular-Mischkristallen Nahordnung von Mg und Ca vorliegt. Der Effekt der Nahordnung muß in künftigen thermodynamischen Modellen berücksichtigt werden. Hieraus ergibt sich die Notwendigkeit, alle Granat-Mischreihen auf mögliche Nahordnung hin zu untersuchen. Die Mischungseigenschaften der Pyrop-Grossular-Mischreihe, die von sämtlichen Granat-Mischreihen am besten bestimmt wurden, können teilweise mit dem Quasi-Chemical-Model beschrieben werden. Dieses Modell ermöglicht die Beschreibung der mikroskopischen Wechselwirkungen, die die makroskopischen thermodynamischen Eigenschaften bestimmen. Mikroskopische Eigenschaften werden am besten mit spektroskopischen Messungen und theoretischen Berechnungen untersucht. Hard-mode IR-Spektroskopie-Messungen an binären Mischreihen zeigen, daß die lokalen mikroskopischen strukturellen Verzerrungen in den makroskopischen Mischungs-Volumina widergespiegelt werden. Die Art der Spannungsfelder und Platz-Relaxationen muß detaillierter untersucht werden, um ein besseres Verständnis des Mischkristall-Bildungsprozsses und der Energetik der Granate zu erreichen. Darüber hinaus werden wichtige künftige Forschungsgebiete diskutiert.
With 11 Figures 相似文献
28.
29.
W. Geiger H. J. Meng dipl. Natw. ETH Chr. Ruhlé dipl. Forsting. ETH Chr Ruhlé 《Aquatic Sciences - Research Across Boundaries》1975,37(2):225-234
The effects of periodic, simulated water level fluctuations on northern pike fry produced by pumped-storage operations were examined. Daily fluctuations of 10 cm caused a significant increase in the daily mortality rate. Waves reduced the detrimental effect of water level lfuctuations, at least during the adhesive phase of fry. 相似文献
30.
In the coastal catchments of Shandong Province the water scarcity is aggravated due to saltwater intrusion, reducing the usability of water resources available. Such a situation calls for sustainable integrated water resources management (IWRM). The idea for the objectives and implementation of the IWRM are explained in this paper. The general objective of the planned project disscussed in the present study is to bring together German traditional expertise in water resources management and newer developments in the context of the European Water Framework Directive; the research efforts aim to relieve the desperate water scarcity situation in the costal area of Shandong Province. 相似文献