Petrology of a xenolith of ferro-aluminous gneiss from the Nain complex     

Jonathan H. Berg  Robert A. Wiebe 《Contributions to Mineralogy and Petrology》1985,90(2-3):226-235

Several gneissic xenoliths occur in granite which has been intruded along the contact between an anorthosite body and gneisses in the Nain complex, Labrador. One of these xenoliths is a ferro-aluminous gneiss with ovoids, 1–3 cm in diameter, consisting of an intimate mixture of fine, granular cordierite-olivine-spinel-orthopyroxene-plagioclase-ilmenite-pyrrhotite enclosed by poikilitic grains of garnet and orthoamphibole. Biotite occurs as both granular and poikilitic grains. The textures indicate a two-stage contact metamorphic history characterized by the simplified reaction: cordierite+olivine+spinel+plagioclase +orthopyroxene→garnet+orthoamphibole Although, on the basis of texture, the reactants represent the early stage assemblage and the products represent the final stage, the distribution coefficient data for Fe-Mg indicate that, except for orthopyroxene, all of the minerals were stable and in equilibrium during the final stage. The coexistence of cordierite and olivine indicates that pressure was less than 3 kbar. The phase relationships agree well with the experimental work of Hsu and Burnham (1969) on the almandine-pyrope join at 2 kbar and indicate a temperature of 800° C for the first stage and 615° C for the second stage of contact metamorphism. This close agreement also suggests that the ovoids at one time may have been garnet porphyroblasts that were decomposed during the first stage. These data correlate well with the field relations: the first-stage, high-temperature effects were likely caused by the intrusion of the anhydrous anorthositic body and the second-stage, low-temperature effects by the invasion of the volatile-rich granite.  相似文献   

Die Eigenschwingungen der durch den Kanal im Damm von Melide gekoppelten Becken des Luganersees     

Jürg Trösch  Giorgio Salvadè  Kurt Stocker 《Aquatic Sciences - Research Across Boundaries》1987,49(1):16-28

The northern and the southern basin of Lake Lugano, Switzerland, are separated by an artificial dam. The flow of the water is not only influenced by the outflow of the northern basin but also by gravitational oscillations (seiches) of both basins. A longperiodic peak around 100 minutes can be explained by a mathematical model. The interaction of the internal waves is a coupled oscillation with a period of 74 hours.   相似文献   

Connections of the West Pacific subtropical high and some hydroclimatic regimes in China with Antarctic ice-snow indices     

G. Peng  Prof. Dr. M. Domrös 《Meteorology and Atmospheric Physics》1987,37(2):61-71

Summary On the basis of 10 years monthly and long-term annual data the importance of the antarctic ice-snow cover and correlated indices has been discussed. By computing time-lag correlation analyses of the ice-snow indices and different atmospheric indices of the northern hemisphere and some hydroclimatic regimes in China, it could be shown that a close relationship between sea-ice in the Antarctic and the intensity and area indices of the subtropical West Pacific high exists. It was also possible to prove a close relationship between antarctic ice-snow indices and the annual run-off of the Yellow River at Sanmenxia, and between rainfall over North China and the lower sections of the Yellow river.With 3 Figures  相似文献   

Seismic activity preceding the 1983 eruption of Mt. Etna     

G. Patanè  S. Gresta  S. Imposa 《Bulletin of Volcanology》1984,47(4):941-952

The March–August, 1983 eruption of Mt. Etna can be considered as one of the most important in the last years.The analysis of seismic activity during the three months immediately before the eruption showed interesting variations of theb coefficient, in the frequency-magnitude relationship, that have been linked to possible changes of the stress field in the Etnean region.The eruption start was also preceded by a strong seismic crisis with epicenters mostly on the southern, eastern and southwestern flanks of the volcano, and characterized by the shallowness of most of the events (h3 km).The data analysis has led to a hypothesis on the eruption occurrence based on a model of dynamic evolution of the stress field acting on Mt. Etna.  相似文献   

Multistage alkaline permanganate degradation of a type II kerogen     

Dragomir Vitorovi&#x;  Mirjana Djordjevi&#x;  Andr Ambls  Jean C. Jacquesy 《Organic Geochemistry》1984,5(4):259-265

The products of a 27-step alkaline permanganate degradation of a type II kerogen from a sample of Toarcian shale, Paris Basin, have been studied. The high yield of oxidation products consisted of 1.86% neutrals and bases, 24.48% ether-soluble acids, and 45.95% precipitated, ether-insoluble acids, based on weight of original kerogen. The ether-soluble acids and the soluble products of further permanganate degradation of precipitated acids were found to consist mostly of saturated unbranched C₆–C₂₂ α,ω-dicarboxylic and C₉–C₂₅ monocarboxylic acids. Significant amounts of aromatic monocarboxylic, dicarboxylic and tricarboxylic acids were also found. Alkane tri- and tetracarboxylic acids were obtained in small concentration.  相似文献   

Speciation of boron with Cu2+, Zn2+, Cd2+ and Pb2+ in 0.7 M KNO3 and in sea-water     

Constant M.G. van den Berg 《Geochimica et cosmochimica acta》1984,48(12):2613-2617

The stability constants, $\text{K}{}^1{}_{\mathrm{MB}}$, for borate complexes with the ions of Cu, Pb, Cd and Zn are determined in this work by DPASV in 0.7 M KNO₃ at metal concentrations of 10^?7 M. The acidity constants of the Cu²⁺ ion are determined by DPASV in the same conditions. The following values for log $\text{K}{}^1{}_{\mathrm{MB}}$ () have been obtained: CuB: 3.48, CuB₂: 6.13, PbB: 2.20, PbB₂: 4.41, ZnB: 0.9, ZnB₂: 3.32, CdB: 1.42, and CdB₂: 2.7, while the values for the acidity constants of Cu are $\text{pK}{}^1{}_{\mathrm{CuOH}}\text{= 7.66}$ and . At the low concentration of boron in 35%. S sea-water complexes with borate represent only about 0.2% Cu, 0.03% Pb, 0.02% Zn and 0.003% Cd.  相似文献   

The last interglacial ocean     

William F. Ruddiman  Rose Marie L. Cline  James D. Hays  Warren L. Prell  William F. Ruddiman  Ted C. Moore  Nilva G. Kipp  Barbara E. Molfino  George H. Denton  Terence J. Hughes  William L. Balsam  Charlotte A. Brunner  Jean-Claude Duplessy  James L. Fastook  John Imbrie  Lloyd D. Keigwin  Thomas B. Kellogg  Peter R. Thompson 《Quaternary Research》1984,21(2):123-224

The final effort of the CLIMAP project was a study of the last interglaciation, a time of minimum ice volume some 122,000 yr ago coincident with the Substage 5e oxygen isotopic minimum. Based on detailed oxygen isotope analyses and biotic census counts in 52 cores across the world ocean, last interglacial sea-surface temperatures (SST) were compared with those today. There are small SST departures in the mid-latitude North Atlantic (warmer) and the Gulf of Mexico (cooler). The eastern boundary currents of the South Atlantic and Pacific oceans are marked by large SST anomalies in individual cores, but their interpretations are precluded by no-analog problems and by discordancies among estimates from different biotic groups. In general, the last interglacial ocean was not significantly different from the modern ocean. The relative sequencing of ice decay versus oceanic warming on the Stage 6/5 oxygen isotopic transition and of ice growth versus oceanic cooling on the Stage 5e/5d transition was also studied. In most of the Southern Hemisphere, the oceanic response marked by the biotic census counts preceded (led) the global ice-volume response marked by the oxygen-isotope signal by several thousand years. The reverse pattern is evident in the North Atlantic Ocean and the Gulf of Mexico, where the oceanic response lagged that of global ice volume by several thousand years. As a result, the very warm temperatures associated with the last interglaciation were regionally diachronous by several thousand years. These regional lead-lag relationships agree with those observed on other transitions and in long-term phase relationships; they cannot be explained simply as artifacts of bioturbational translations of the original signals.  相似文献   

The violet opacity in the red peculiar stars (II)     

O. Alksnis  L. Začs 《Astrophysics and Space Science》1994,215(1):73-82

Moderate dispersion (25-35 Å mm^–1) spectra were obtained from two carbon stars, V Cyg and WZ Cas, in a wide range of wavelengths (3400-6800 Å) with the echelle-spectrometer, ZEBRA, of the 6 m telescope and two-dimensional photon-counting system. Spectral feature identification was carried out from 3850 to 6200 Å. Most of the bands are due to C₂, SiC₂, and CN, however, particularly in WZ Cas, moderate atomic lines of the iron peak and s-process elements are also found. WZ Cas is a so-called lithium star, however, we have found no evidence for a strong line of Li. The spectra of V Cyg contain an emission line of H.  相似文献   

Dual-porosity elastoplastic analyses of non-isothermal one-dimensional consolidation   总被引：1，自引：0，他引：1  

Jincai Zhang  Jean-Claude Roegiers  Mao Bai 《Geotechnical and Geological Engineering》2004,22(4):589-610

A numerical solution, using the finite difference method, and based on a porothermo-elasto-plastic formulation for dual-porosity one-dimensional consolidation has been presented. The model is fully coupled to ensure the interactive behavior of fluid flow, heat flow and solid deformations in the conservation of momentum, mass and energy equations. A bi-linear stress-strain relationship is used to accommodate elastoplastic deformation behavior. A double effective stress law, proposed by Elsworth and Bai (1992), is applied to describe constitutive relationships among the stresses, pressures and temperatures. In order to examine the dual-porosity and thermal effects on the soil consolidation individually, isothermal and non-isothermal consolidations for a dual-porosity column are analyzed. In comparison to the single porosity approach, the present study shows that the pore pressure dissipation is faster and Mandel's effect (Mandel, 1953) is more pronounced at early times of the source disturbance for dual-porosity consolidation. One of the significant parameters affecting the dual-porosity consolidation is the fracture spacing (fracture density); the smaller the fracture spacing, the faster the column drainage.  相似文献   

Local erosion rates versus active tectonics: cosmic ray exposure modelling in Provence (south-east France)     

Lionel Siame  Olivier Bellier  Rgis Braucher  Michel Sbrier  Marc Cushing  Didier Bourls  Bruno Hamelin  Emmanuel Baroux  Beatrice de Voogd  Grant Raisbeck  Franoise Yiou 《Earth and Planetary Science Letters》2004,220(3-4):345-364

Over the past decade, in situ-produced cosmogenic nuclides have revolutionised the study of landscape evolution. In particular, numerous studies have demonstrated that, in active tectonic settings, cosmic ray exposure dating of deformed or displaced geomorphic features makes it possible to quantify long-term deformation rates. In western European countries, erosion due to climatically driven processes and human activities is probably the factor that most limits the accuracy of exposure ages and landscape modification rates. In this study, we present the results of a depth-profiling technique applied to alluvial terraces located along the Rhône and the Moyenne Durance rivers. The expected decrease with depth of the measured ¹⁰Be concentrations has been modelled using a χ² inversion method in order to constrain the exposure history of the alluvial sediments. The results suggest that: (1) over the Quaternary, the local surface erosion rates including both regional uplift and climatically driven processes acting on landforms are on the order of 30 m/Myr in southeastern France, and (2) providing a fairly good bracketing of the exposure age, the modelled abandonment age of alluvial terraces affected by the Moyenne Durance Fault allows estimating incision rates, comparing the alluvial terrace elevations with topographic river profiles, and a minimum vertical slip rate value of roughly 0.02 mm/yr for the southern segment of the Moyenne Durance Fault.  相似文献