Crustal structure of the Rhinegraben area     

S. Mueller  E. Peterschmitt  K. Fuchs  D. Emter  J. Ansorge 《Tectonophysics》1973,20(1-4):381-391

Numerous ge ological and geophysical investigations within the past decades have shown that the Rhinegraben is the most pronounced segment of an extended continental rift system in Europe. The structure of the upper and lower crust is significantly different from the structure of the adjacent “normal” continental crust.

Two crustal cross-sections across the central and southern part of the Rhinegraben have been constructed based on a new evaluation of seismic refraction and reflection measurements. The most striking features of the structure derived are the existence of a well-developed velocity reversal in the upper crust and of a characteristic cushion-like layer with a compressional velocity of 7.6–7.7 km/sec in the lower crust above a normal mantle with 8.2 km/sec. Immediately below the sialic low-velocity zone in the middle part of the crust, an intermediate layer with lamellar structure and of presumably basic composition could be mapped.

It is interesting to note that the asymmetry of the sedimentary fill in the central Rhinegraben seems to extend down deeper into the upper crust as indicated by the focal depths of earthquakes. The top of the rift “cushion” shows a marked relief which has no obvious relation to the crustal structure above it or the visible rift at the surface.  相似文献   

Chromium and phosphorus enrichment in the metal of type II (C2) carbonaceous chondrites     

Edward Olsen  Louis H Fuchs  Warben C Forbes 《Geochimica et cosmochimica acta》1973,37(9):2037-2042

Electron microprobe analyses of metal grains in nine C2 meteorites show consistently high Cr and P contents, with large grain to grain variations within individual meteorites. Cr ranges from 0.16 to 1.0 wt.% (average 0.6 per cent for 43 analyses). P ranges from 0.00 to 3.2 wt.% (average 0.42 per cent). In addition, metal grains in seven C3 meteorites show a lesser enrichment of Cr, 0.00 to 0.7 per cent (average 0.13 per cent for 59 analyses), with no P present. Both of these elements, Cr and P, are generally below detection in the metal of other chondrite groups, equilibrated and unequilibrated. C2 metal grains occur typically as spherical to ovate blebs contained within single, euhedral forsterite crystals or crystal fragments that are either isolated in the black C2 matrix or are in clusters making up white inclusions. Metal is rare within true chondrules. Calculations of the expected Cr contents in metal condensing directly from a solar nebular gas agree remarkably well with the observed values. Unfortunately, no calculation is possible for P because of insufficient data at the present time. The composition and the textural relationships indicate this Cr, P rich metal, and the enclosing forsterite are direct condensates from a cooling solar nebula. Cr and P, in the quantities reported here, characterize C2 metal.  相似文献   

The copper-silver occurrences of Rahmani,Western Sahara,Algeria     

Y. Fuchs  F. Arbey  T. Bouima 《Mineralium Deposita》1996,31(4):340-342

The copper-silver occurrences of Rahmani (Western Sahara, Algeria) are located in paleochannel facies of Cambrian sandstones deposited onPan-African volcanics and intrusives. Sulfur isotope analyses were performed on pyrite and copper sulfides in order to trace the origin of the copper-silver mineralization. S isotopic data preclude that bacterial reduction of Cambrian sulfate could have induced the formation of the sulfides. Non-bacterial reduction of sulfate during burial diagenesis is the most valuable explanation for disseminated pyrite. Isotopic ratios on copper sulfides indicate that they result from the reaction of actual or subactual sulfate-bearing surface water with the disseminated pyrite. The origin of copper and silver remains unclear. They are thought to be brought by the downward migrating surface water but their origin could be either the leaching of the Cambrian sandstones or of the weathered volcanics.  相似文献   

Wave propagation in a multiple-scattering upper mantle—observations and modelling     

M. Tittgemeyer  F. Wenzel  K. Fuchs  T. Ryberg 《Geophysical Journal International》1996,127(2):492-502

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Characterization of tourmalines by FTIR absorption spectrometry     

J. -L. Robert  Y. Fuchs  J. -P. Gourdant 《Physics and Chemistry of Minerals》1996,23(4-5):309-309

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START — the road from Bellagio     

Roland J Fuchs 《Global Environmental Change》1995,5(5)

The START initiative (co-sponsored by IGBP, WCRP and HDP) has as its primary objective development of regional frameworks to support regional research related to global change, associated capacity building and synthesis scientific assessments related to policy development. START now has six regional networks under development in South-East Asia, Northern Africa, East Asia, South Asia, the Meditteranean, and Southern Africa. Issues before START include the coordination of regional activities with that of sponsoring programmes, the need for a more elaborated HDP, and the development of thematic programming that will secure multi-donor, multi-year support.  相似文献   

Massif Central (France): new constraints on the geodynamical evolution from teleseismic tomography   总被引：2，自引：0，他引：2  

M. Granet  G. Stoll  J. Dorel  U. Achauer  G. Poupinet  K. Fuchs 《Geophysical Journal International》1995,121(1):33-48

The Massif Central, the most significant geomorphological unit of the Hercynian belt in France, is characterized by graben structures which are part of the European Cenozoic Rift System (ECRIS) and also by distinct volcanic episodes, the most recent dated at 20 Ma to 4000 years BP. In order to study the lithosphere-asthenosphere system beneath this volcanic area, we performed a teleseismic field experiment.
During a six-month period, a joint French-German team operated a network of 79 mobile short-period seismic stations in addition to the 14 permanent stations. Inversion of P -wave traveltime residuals of teleseismic events recorded by this dense array yielded a detailed image of the 3-D velocity structure beneath the Massif Central down to 180 km depth. The upper 60 km of the lithosphere displays strong lateral heterogeneities and shows a remarkable correlation between the volcanic provinces and the negative velocity perturbations. The 3-D model reveals two channels of low velocities, interpreted as the remaining thermal signature of magma ascent following large lithospheric fractures inherited from Hercynian time and reactivated during Oligocene times. The teleseismic inversion model yields no indication of a low-velocity zone in the mantle associated with the graben structures proper. The observation of smaller velocity perturbations and a change in the shape of the velocity pattern in the 60–100 km depth range indicates a smooth transition from the lithosphere to the asthenosphere, thus giving an idea of the lithosphere thickness. A broad volume of low velocities having a diameter of about 200 km from 100 km depth to the bottom of the model is present beneath the Massif Central. This body is likely to be the source responsible for the volcanism. It could be interpreted as the top of a plume-type structure which is now in its cooling phase.  相似文献   

Micro-sized enterprises: vulnerability to flash floods     

Konstantinos Karagiorgos  Micha Heiser  Thomas Thaler  Johannes Hübl  Sven Fuchs 《Natural Hazards》2016,81(2):1091-1106

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XXIII INTERNATIONAL GEOGRAPHICAL CONGRESS,U.S.S.R.     

Roland J. Fuchs 《The Professional geographer》1977,29(3):296-297

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Comparison of Dimensionless Parameters in Astrophysical MHD Systems and in Laboratory Experiments     

E. P. Kurbatov  D. V. Bisikalo  M. V. Starodubtsev  A. Ciardi  J. Fuchs  A. A. Solov’ev  K. F. Burdonov  G. Revet  S. Chen 《Astronomy Reports》2018,62(8):483-491

Estimates of typical parameters of accretion flows in the representative intermediate polar EX Hydrae, the polar AM Herculis, and the “hot Jupiter” WASP-12b are presented. Dimensionless parameters of astrophysical systems are compared with those of laboratory experiments on laser ablation in magnetic fields. It is shown that laboratory simulations of astrophysical flows is possible in principle, provided that some adjustment to the magnetic field, plasma density, and plasma velocity are made.  相似文献