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151.
Geissler Wolfram Plenefisch Thomas Kind Reiner Klinge Klaus Kämpf Horst Boušková Alena Nehybka Vladimír Skácelová Zuzana Jacob Brian 《Studia Geophysica et Geodaetica》2000,44(2):188-194
We used teleseismic recordings of a temporary deployment of seismic stations and of permanent short period stations in the western Eger Rift system to study the lithosphere with the help of Receiver Functions. The crust-mantle boundary (Moho) is observed at almost all stations by strong P-to-S converted phases. The Moho is basically flat between about 26 – 30 km depth in the entire region. At one station in the Eger Rift (BOH-1, Loket castle) no Moho is observed. We interpret this with the existence of a broad gradient zone there, instead of a sharp discontinuity. This observation, however, needs to be confirmed by more data. 相似文献
152.
Ohne Zusammenfassung 相似文献
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154.
Horst Purwin Stefan Lauterbach Gerhard P. Brey Alan B. Woodland Hans-Joachim Kleebe 《Contributions to Mineralogy and Petrology》2013,165(4):623-639
Samples with eclogitic composition in the system CaO–FeO–Fe2O3–MgO–Al2O3–SiO2 were produced from various kinds of starting materials held in graphite-lined Pt capsules at a pressure of 2.5–3.0 GPa and temperatures of 800–1,300 °C using a piston-cylinder or Belt apparatus. Garnets and clinopyroxenes were characterized by analytical transmission electron microscopy and electron probe micro-analysis (EPMA). Fe3+/ΣFe ratios determined by electron energy-loss spectroscopy (EELS) decrease in clinopyroxene from 22.2 ± 3.4 % at 800 °C to 13.3 ± 5.4 % at 1,300 °C, while in garnet, they vary between 10.8 ± 1.5 and 15.4 ± 4.7 %, respectively. Temperature estimates according to Krogh (Contrib Mineral Petrol 99:44–48, 1988) reproduce the experimental temperature to ±60 °C without systematic deviations if total iron is used in the calculation. If only the Fe2+ content is used, which was obtained by combining EPMA and EELS results, the experimental temperature is underestimated by 33 °C on average at 800–1,200 °C and overestimated by 77 °C on average at 1,300 °C. These systematic deviations can be explained by the temperature-dependent ratio of Fe2+/ΣFe in garnet divided by that in clinopyroxene. Since the difference between the calculated and experimental temperature is relatively small, a Fe2+-based recalibration of the thermometer appears not to be necessary for the investigated system in the range of pressure, temperature and composition covered by the experiments of this study. 相似文献
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157.
Horst Balthasar 《Solar physics》1983,84(1-2):371-376
From 63 mostly unblended Fraunhofer lines measured along the solar east-west diameter the rotation velocity has been determined. The mean value is 1986 km s#X2212;1. The velocity decreases with the optical depth in the photosphere. Over a range of 700 km the difference of the velocities is 41 m s#X2212;1 for the Holweger-Müller atmosphere or 34 m s#X2212;1 for the Harvard Smithsonian reference atmosphere. 相似文献
158.
Horst Balthasar 《Solar physics》1985,99(1-2):31-38
From the comparison of 59 iron lines at the center of the solar disk with laboratory wavelenghts, the mean vertical velocity of solar granulation and its depth dependence is determined. These values are used to calculate limb-effect curves. The differences to observed curves are interpreted as mean horizontal motions. These motions yield again a depth dependence showing Doppler shifts toward the observer in deep layers and away from the observer in high layers for regions away from the disk center. Values from - 400 m s–1 through + 500 m s–1 are obtained. 相似文献
159.
Luiz?Alberto?Ribeiro?Mendon?a Horst?FrischkornEmail author Maria?Marlúcia?Freitas?Santiago Josué?Mendes Filho 《Environmental Geology》2004,46(2):295-302
The Araripe Plateau in northeastern Brazil has an area of about 8,000 km2, confined by 39°05E and 40°55E, and 7°10S and 7°50S. Due to high permeability of soils, a surface drainage system is practically inexistent. Water is stored in excavations with clayey soil, the barreiros. Monthly samples were taken for 18O measurements, from September 1999 to August 2000, from four barreiros, three dug wells and five drilled wells. Results show that (1) groundwaters in the eastern part of the plateau are derived from present-day rainfall (18O–3.2), whereas groundwaters in the western portion are isotopically different (18O–5.0); (2) barreiros are strongly marked seasonally by elevated 18O during the dry period due to elevated evaporation; (3) a dug well at a distance of 30 m from a barreiro exhibits 18O similar to that of the reservoir, indicating a strong interaction between groundwater and surface water; and (4) a tubular well of 242-m depth, located in a fault, exhibits strong seasonal changes in 18O and electrical conductivity, revealing downward leakage between aquifers. 相似文献
160.
Horst R. Marschall Rainer Altherr Angelika Kalt Zsolt Kasztovszky 《Geochimica et cosmochimica acta》2006,70(18):4750-4769
Partitioning and budget of Li, Be and B in high-pressure metamorphic rocks from the island of Syros (Greece) were studied, using secondary ion mass spectrometry, inductively coupled plasma optical emission spectrometry and prompt gamma neutron activation analysis. Partitioning between coexisting mineral phases was found to be rather constant and independent of element concentrations. For several mineral pairs, apparent partition coefficients vary in a narrow range, while concentrations vary by more than an order of magnitude. Hence, it was possible to establish sets of inter-mineral partition coefficients for Li, Be and B among 15 different high-pressure minerals. This data set provides important information on the behaviour of the light elements in different lithologies within subducting slabs from the onset of metamorphism to the eclogite stage. It is essential for modelling trace-element and isotope fractionation during subduction and dehydration of oceanic crust. 相似文献