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71.
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Summary The Tertiary alkaline, nepheline-normative olivine melanephelinite-basanite-phonolite suite in the Labe tectono-volcanic zone, Czech Republic, displays mineralogical and geochemical features indicative of the presence of products of more than one fractionation series and of more than one parental magma. The Mg- and Ni-rich olivine melanephelinites (ankaratrites), which contain disintegrated lherzolite xenoliths, represent low degree (c. 4%) partial melts of a highly enriched mande source. Many of the abundant basanitic rocks also represent primary or near-primary basaltic melts subject to a small but variable degree Fof olivine fractionation. Other basanites with lower mg-numbers and Mg and Ni contents had a crystallization history involving hornblende and phlogopite.Melaphonolites (tephriphonolites) provide a link between basaltic rocks and phonolites with plagioclase fractionation progressively playing a more significant role. The phonolites represent products of crystallization of highly evolved melts but poor correlation between SiO2, MgO, CaO, Na2O and degree of undersaturation as well as between major and trace element contents indicate that a single line of descent cannot have been in operation: the products of different parental magmas showing a wide compositional range that evolved under different conditions of fractionation are represented. A very advanced stage of magma evolution, characterized by the dominance of alkali feldspar fractionation is represented by phonolites that contain the highest Hf, Nb, Rb, Ta, Th, Y, Zr and REE in the whole Tertiary volcanic suite.
With 7 Figures 相似文献
Geochemie und Petrogenese der tertiären alkalischen Vulkanit-Serie der Labe tektonovulkanischen Zone, Tschechische Republik
Zusammenfassung Die tertiäre alkalische Nephelin-normative Olivin Melanephelinit-Basanit-Phonolit Serie in der Labe tektono-vulkanischen Zone, Tschechische Republik, zeigt mineralogische und geochemische Eigenschaften, die auf die Anwesenheit von Produkten von mehr als einer Fraktionierungsserie und von mehr als einem Ausgangsmagma hinweisen. Die Mg- und Ni-reichen Olivin Melanephelinite (Ankaratrite), die umgewandelte LherzolitXenolite enthalten, stellen einen niedrigen Grad (ca. 4%) teilweiser Aufschmelzung einer stark angereicherten Mantelquelle dar. Viele der verbreiteten basanitischen Gesteine stellen auch primäre oder fast-primäre basaltische Schmelzen dar, die in kleinem, aber schwankendem Ausmaß von Olivinfraktionierung betroffen wurden. Andere Basanite mit niedrigen Mg-Zahlen und Mg- und Ni-Gehalten hatten eine Kristallisationsgeschichte in der Hornblende und Phlogopit eine Rolle spielte.Melaphonolite (Tephriphonolite) stellen ein Verbindungsglied zwischen basaltischen Gesteinen und Phonoliten dar, wobei Plagioklas-Fraktionierung eine zunehmend größere Rolle spielt. Phonolite sind Produkte der Kristallisation von Schmelzen, aber die schlechte Korrelation zwischen SiO2, MgO, CaO, Na2O und dem Grad der Untersättigung, wie auch zwischen Haupt- und Spurenelementen weist darauf hin, daß eine einzelne Entwicklungslinie nicht in Frage kommt. Die Produkte verschiedener Ausgangsmagmen zeigen ein weites Spektrum verschiedener Zusammensetzung, das sich unter verschiedenen Bedingungen der Fraktionierung entwickelt hat. Ein sehr fortgeschrittenes Stadium der Magmaentwicklung, charakterisiert durch die Vorherrschaft von Alkali-Feldspat-Fraktionierung wird durch Phonolite dargestellt, die die höchsten Gehalte an Hf, Nb, Rb, Ta, Th, Y, Zr und REE in der gesamten tertiären vulkanischen Abfolge führen.
With 7 Figures 相似文献
74.
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Jaroslav Střeštík Karel Prikner Reviewer M. Hooždara 《Studia Geophysica et Geodaetica》1977,21(2):159-167
Summary The numerical method of Fourier's spectral analysis is used to treat 29 pairs of samples of pc3 pulsations recorded at the observatories of Budkov (Czechoslovakia) and Belsk (Poland). The amplitude, frequency and phase characteristics of their spectra are compared. The polarization characteristics of the spectral frequency components of pulsations recorded at both observatories are compared in a quasi-stationary approximation of a plane oscillation. 相似文献
76.
77.
Ivan Kimák Karel Kudela P. V. Vakulov Reviewer S. Fischer 《Studia Geophysica et Geodaetica》1982,26(2):207-211
Summary Data obtained from apparatus detecting energetic particles on low altitude polar orbiting satellite Intercosmos-13 show enhancement of quiasitrapped proton flux (Ep=1–11 MeV) near L=4 in comparison with both and lower L. This phenomenon persists during intervals with low level of geomagnetic activity. Possibility of influence of false pulses on the result is discussed. 相似文献
78.
In the paper, the mathematical tools, used for the modelling of the electromagnetic field of the harmonic plane wave in the two-dimensional inhomogeneous medium (the case ofE-polarization), are presented. Further, the resolving power of some parameters, that are measured in the VLF and VLF-R methods, is compared in the case of two vertical conductive dykes. To this aim, all the usual parameters of the VLF method and the most important parameter of the VLF-R method () have been chosen. Two groups of models that differ in resistivities have been considered. In each of the groups the distance of the dykes is variable. The parameters |H
y|, which has shown most promising in this respect, is examined also from the point of view of the sensibility to geological noise. The results of the modelling are illustrated by two examples of the results of field measurements. 相似文献
79.
Summary An algorithm is derived to compute the coefficients of a spherical harmonic series for the geoid radius vector that are a solution to a system of linear equations, containing Stokes' constants of the geopotential. 相似文献
80.
Summary Drawing on [6], the height profiles of local complex polarization and local polarization characteristics of electromagnetic waves in several models of the Earth's ionosphere are analysed. The profiles were obtained with the aid of a computer program for modelling propagating [5]. The analysis was carried out a) for a flxed given configuration of the external magnetic field of the EarthB
0 at a number of discrete frequencies f<5 Hz, b) for chosen model of the ionosphere at a fixed given frequency f=1 Hz and in connection with a change of the dip of the lines of force and of the magnitude of the external (homogeneous) magnetic field|B
0|, c) for various models at f=1 Hz and a varying configuration of the external magnetic field, reflecting the change in geomagnetic latitude. The results of the analysis will serve as an aid to the interpretation of the results of solving the problem of wave propagation through the ionosphere. 相似文献