Granitoids in the Rozvadov Pluton,Western Bohemia and Oberpfalz     

Karel Breiter  Wolfgang Siebel 《International Journal of Earth Sciences》1995,84(3):506-519

The Rozvadov Pluton is a complex of mainly Variscan granitoid rocks situated near the Bohemian-Bavarian border between Bärnau, Tachov, Rozvadov and Waidhaus, 25 km ESE of the KTB site. Five mappable units can be distinguished, which intruded as folows: (1) slightly deformed leucocratic meta-aplite/metapegmatite dykes with garnet and tourmaline; (2) a complex of cordierite-bearing granitoids, which have been divided into three facies (a) biotite granite with cordierite (at the margin of the complex), (b) biotite-cordierite granite and (c) cordierite tonalite (in the centre of the complex; (3) fine-grained biotite granite of the Rozvadov type with associated pegmatite bodies; (4) two-mica Bärnau granite; and (5) geochemically specialized albite-zinnwaldite-topaz granite (Kríový kámen/Kreuzstein granite) with indications of Sn-Nb-Ta mineralization and associated phosphorus-rich pegmatite cupolas. Rare earth element data suggest that meta-aplite/pegmatite dykes are the result of a batch partial melting process, whereas the compositional variation of the other rock types was mainly controlled by fractional crystallization. The genesis of the cordierite granitoid suite is best explained in terms of a batch melting of metapelitic source followed by crystallization of a cordierite-rich cumulate and K-feldspar enriched melt. The leucocratic pluton constituents — the meta-aplites and the Bärnau and Kíový kámen granites are rich in phosphorus (0.5–0.8%). The main carriers of phosphorus are alkali feldspars, especially K-feldspar (up to 0.8% P₂O₅). The presence of P-rich leucocratic granites is one of the features distinguishing the Variscan granitoids within the Moldanubian zone from the nearly contemporaneous granitoids in the Saxothuringian zone.  相似文献   

A model for galactic centres     

Wolfgang Kundt 《Astrophysics and Space Science》1979,62(2):335-345

A rotating Supermassive Magnetized Disk is proposed as a model for all the violent phenomena occurring in the nuclei of galaxies, in the form of quasars, Lacertids, radio galaxies, Seyferts, exploding galaxies, etc. The cold disk feeds a fast-rotating supermassive core (some 10³ Schwarzschild radii in extent), which emits (1) an unsteady thermal wind of filamentary geometry, (2) Low-Frequency magnetic Waves, and (3) relativistic electrons and positrons. The latter reach high -factors by phase-riding the LFWs, emit synchro-Compton radiation on crossing scattered waves (from -ray energies down to radio frequencies), and are eventually focused into two antipodal relativistic beams by their frozen-in toroidal magnetic field. Torsional oscillations between the core and disk give rise to a pulsed injection, and a breathing double-onion shape of the LFW windzone can explain the superluminal jetlike appearance. A big nuclear explosion ends each duty cycle, but many smaller explosions prevent the settling core from collapsing. In this model, the helium production of galactic centres is comparable to the observed cosmic helium.  相似文献   

The main problem of lunar theory solved by the method of Brown     

Dieter S. Schmidt 《Earth, Moon, and Planets》1980,23(2):135-164

Brown's method for solving the main problem of lunar theory has been adapted for the computation by machine with the help of an algebraic processor. Brown's results are first recovered and refined. The solution is then expanded to include most terms of order nine. The terms in the series for the longitude and latitude are listed with an accuracy of 0.000 01 and of 0.000 001 for the parallax.This research was supported in parts by the National Science Foundation grant MCS 78-01425.  相似文献   

Amphibole composition in tonalite as a function of pressure: an experimental calibration of the Al-in-hornblende barometer   总被引：66，自引：3，他引：63  

Max W. Schmidt 《Contributions to Mineralogy and Petrology》1992,110(2-3):304-310

The Al-in-hornblende barometer, which correlates Al^tot content of magmatic hornblende linearly with crystallization pressure of intrusion (Hammarstrom and Zen 1986), has been calibrated experimentally under water-saturated conditions at pressures of 2.5–13 kbar and temperatures of 700–655°C. Equilibration of the assemblage hornlende-biotite-plagioclase-orthoclasequartz-sphene-Fe-Ti-oxide-melt-vapor from a natural tonalite 15–20° above its wet solidus results in hornblende compositions which can be fit by the equation: P(±0.6 kbar) = –3.01 + 4.76 Al _hbl ^tot r ²=0.99, where Al^tot is the total Al content of hornblende in atoms per formula unit (apfu). Al^tot increase with pressure can be ascribed mainly to a tschermak-exchange ( ) accompanied by minor plagioclase-substitution ( ). This experimental calibration agrees well with empirical field calibrations, wherein pressures are estimated by contact-aureole barometry, confirming that contact-aureole pressures and pressures calculated by the Al-in-hornblende barometer are essentially identical. This calibration is also consistent with the previous experimental calibration by Johnson and Rutherford (1989b) which was accomplished at higher temperatures, stabilizing the required buffer assemblage by use of mixed H₂O-CO₂ fluids. The latter calibration yields higher Al^tot content in hornblendes at corresponding pressures, this can be ascribed to increased edenite-exchange ( ) at elevated temperatures. The comparison of both experimental calibrations shows the important influence of the fluid composition, which affects the solidus temperature, on equilibration of hornblende in the buffering phase assemblage.  相似文献   

Sunspot photometry and the total solar irradiance deficit measured in 1980 by ACRIM     

M. Steinegger  P. N. Brandt  J. Pap  W. Schmidt 《Astrophysics and Space Science》1990,170(1-2):127-133

Until now a simple Photometric Sunspot Index (PSI) model was used (e.g. Willsonet al., 1981) to describe the contribution of sunspots to the solar irradiance deficit measurement by ACRIM. In this work we replace this model by a photometry of sunspot pictures for the period of 19 August to 4 September, 1980 taking into account the individual features, like lightbridges or umbral dots, of each spot. The main results of this preliminary analysis are: (1) theA _u/A _p ratios and alsos the values vary in a wide range and are by no means constant as in the PSI model; (2) the general trend of the irradiance deficit from our analysis agrees well with the ACRIM measurements; (3) on some days there are differences of more than 50% between the deficits derived from our measurements and from the PSI model.Paper presented at the 11th Eurpean Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife, Canary Islands, Spain  相似文献   

Seismic lamination and anisotropy of the Lower Continental Crust   总被引：2，自引：3，他引：2  

Rolf Meissner  Wolfgang Rabbel  Hartmut Kern 《Tectonophysics》2006,416(1-4):81

Seismic lamination in the lower crust associated with marked anisotropy has been observed at various locations. Three of these locations were investigated by specially designed experiments in the near vertical and in the wide-angle range, that is the Urach and the Black Forrest area, both belonging to the Moldanubian, a collapsed Variscan terrane in southern Germany, and in the Donbas Basin, a rift inside the East European (Ukrainian) craton. In these three cases, a firm relationship between lower crust seismic lamination and anisotropy is found. There are more cases of lower-crustal lamination and anisotropy, e.g. from the Basin and Range province (western US) and from central Tibet, not revealed by seismic wide-angle measurements, but by teleseismic receiver function studies with a P–S conversion at the Moho. Other cases of lamination and anisotropy are from exhumed lower crustal rocks in Calabria (southern Italy), and Val Sesia and Val Strona (Ivrea area, Northern Italy). We demonstrate that rocks in the lower continental crust, apart from differing in composition, differ from the upper mantle both in terms of seismic lamination (observed in the near-vertical range) and in the type of anisotropy. Compared to upper mantle rocks exhibiting mainly orthorhombic symmetry, the symmetry of the rocks constituting the lower crust is either axial or orthorhombic and basically a result of preferred crystallographic orientation of major minerals (biotite, muscovite, hornblende). We argue that the generation of seismic lamination and anisotropy in the lower crust is a consequence of the same tectonic process, that is, ductile deformation in a warm and low-viscosity lower crust. This process takes place preferably in areas of extension. Heterogeneous rock units are formed that are generally felsic in composition, but that contain intercalations of mafic intrusions. The latter have acted as heat sources and provide the necessary seismic impedance contrasts. The observed seismic anisotropy is attributed to lattice preferred orientation (LPO) of major minerals, in particular of mica and hornblende, but also of olivine. A transversely isotropic symmetry system, such as expected for sub-horizontal layering, is found in only half of the field studies. Azimuthal anisotropy is encountered in the rest of the cases. This indicates differences in the horizontal components of tectonic strain, which finally give rise to differences in the evolution of the rock fabric.  相似文献   

Experiments on silicate melt immiscibility in the system Fe2SiO4–KAlSi3O8–SiO2–CaO–MgO–TiO2–P2O5 and implications for natural magmas     

M. Bogaerts  M. W. Schmidt 《Contributions to Mineralogy and Petrology》2006,152(3):257-274

The effect of CaO and MgO, with or without TiO₂ and P₂O₅, on the two-melt field in the simplified system Fe₂SiO₄–KAlSi₃O₈–SiO₂ has been experimentally determined at 1,050°–1,240°C, 400 MPa. Despite the suppressing effect of MgO, CaO, and pressure on silicate melt immiscibility, our experiments show that this process is still viable at mid-crustal pressures when small amounts (0.6–2.0 wt%) of P₂O₅ and TiO₂ are present. Our data stress that the major element partition coefficients between the two melts are highly correlated with the degree of polymerisation (nbo/t) of the SiO₂-rich melt, whatever temperature, pressure, or exact composition. Experimental immiscible melt compositions in natural systems at 0.1 MPa from the literature (lunar and tholeiitic basalts) plot on similar but distinct curves compared to the simplified system. These relations between melt polymerisation and partition coefficients, which hold for a large range of compositions and fO₂, are extended to various volcanic and plutonic rocks. This analysis strengthens the proposal that silicate melt immiscibility can be important in volcanic rocks of various compositions (from tholeiitic basalts to lamprophyres). However, the majority of proposed immiscible compositions in plutonic rocks are at least not coexisting melts, but may have suffered accumulation of early crystallized minerals.  相似文献   

Assembly of Proterozoic Australia: implications of a revised pole for the ∼1070 Ma Alcurra Dyke Swarm, central Australia     

Phillip W. Schmidt  George E. Williams  Alfredo Camacho  James K. W. Lee 《Geophysical Journal International》2006,167(2):626-634

  相似文献   

Surface waves image the top of the Eifel plume   总被引：1，自引：0，他引：1  

Jan P. Mathar  Joachim R. R. Ritter  Wolfgang Friederich 《Geophysical Journal International》2006,164(2):377-382

  相似文献   

Jurassic strike slip versus subduction in the Eastern Alps     

Wolfgang Frank  Wolfgang Schlager 《International Journal of Earth Sciences》2006,95(3):431-450

Late Jurassic formations of the Northern Calcareous Alps (NCA) contain ample evidence of synsedimentary tectonics in the form of elongate basins filled with turbidites, debris flows and slumps. Clasts are derived from the Mesozoic of the NCA; they commonly measure tens of metres in diameter and occasionally form kilometre-size bodies. These sedimentologic observations and the presumed evidence of Late Jurassic high-pressure metamorphism recently led to the hypothesis of a south-dipping Jurassic subduction zone with accretionary wedge in the southern parts of the NCA. We present new ⁴⁰Ar/³⁹Ar dates from the location of the postulated high-pressure metamorphism that bracket the age of this crystallization not earlier than 114–120 Ma. The event is therefore part of the well-documented mid-Cretaceous metamorphism of the Austro-alpine domain. Thus, there is currently no evidence of Late Jurassic high-pressure metamorphism to support the subduction hypothesis. The sediment record of the Late Jurassic deformation in the NCA, including the formation of local thrust sheets, is no conclusive evidence for subduction. All these phenomena are perfectly compatible with synsedimentary strike-slip tectonics. Large strike-slip fault zones with restraining and releasing bends and associated flower structures and pull-apart basins are a perfectly viable alternative to the subduction model for the Late Jurassic history of the NCA. However, in contrast to the Eastern Alps transect, where arguments for a Jurassic subduction are missing, a glaucophane bearing Jurassic high-pressure metamorphism in the Meliatic realm of the West Carpathians is well documented. There, the high-pressure/low-temperature slices occur between the Gemeric unit and the Silica nappe system (including the Aggtelek-Rudabanya units), which corresponds in facies with the Juvavic units in the southern part of the NCA. To solve the contrasting palaeogeographic reconstructions we propose that the upper Jurassic left lateral strike-slip system proposed here for the Eastern Alps continued eastwards and caused the eastward displacement of the Silica units into the Meliatic accretionary wedge.  相似文献