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排序方式: 共有93条查询结果,搜索用时 15 毫秒
61.
Henri E. Gaudette Annie Vitrac-Michard Claude J. Allègre 《Earth and Planetary Science Letters》1981,54(2):248-260
Zircons separated from the Cambrian Potsdam sandstone of New York yield four distinct populations which can be defined by a number of analytical techniques. U-Pb isotopic analyses of small samples and monozircons of each population reveal a fine chronology not apparent in milligram-sized sample analysis, and define source area ages of 1180, 1320, 2100 and 2700 m.y. for the Cambrian detrital suite. These ages correspond to well-defined sources in the Superior and Grenville Provinces of the Canadian Shield (2700 and 2100 m.y.) and the well established Grenville age rocks of the Adirondack Mountains (1180 m.y.). The 1320-m.y. age appears to be derived from the Adirondacks, and suggests the existence of pre-Grenville basement in that massif. Our techniques allow the interpretation of the Precambrian history of a large portion of eastern North America from a single sample, and thus should be valuable in the definition of source areas in paleogeographic reconstruction, and in studies of continental crustal evolution. 相似文献
62.
Annie Souriau Antoni M. Correig Marc Souriau 《Physics of the Earth and Planetary Interiors》1980,23(1):62-71
Rayleigh wave attenuation is investigated for periods ranging from 20 to 90 s, along a 450 km-long profile following the Oligocene tensile zone of the French Massif Central. A model is deduced by inversion, assuming that the S-wave intrinsic quality factor Qβ is frequency-independent, and yields a mean value Qβ = 43 ± 10 for the first 100 km in the upper mantle. This value, far lower than the mean value obtained in Eurasia, is close to those obtained in other recent tensile areas, e.g., the western United States or mid-oceanic ridges.A velocity-depth model for S-waves, deduced in a previous study from surface-wave propagation, has been corrected for the attenuation effect. We find a discrepancy between the corrected S-model and P-wave residuals in the same area, implying that Qβ must be frequency-dependent. This can be a clue for partial melting in the upper mantle beneath this region. 相似文献
63.
Mademoiselle Annie Bouchard 《International Journal of Earth Sciences》1966,55(1):113-118
Résumé Le but de mon travail est de vérifier dans quelle mesure l'analyse chimique et spectrographique des poteries antiques peut permettre de différencier entre elles ces poteries, et apporter des élémentes susceptibles de résoudre certains problèmes archéologiques de localisation.J'ai analysé un certain nombre échantillons de poteries antiques — 300 échantillons environ — qui ont été mis à ma disposition par MonsieurVallet, professeur à la Faculté des Lettres de Clermont-Ferrand. Ces échantillons sont de provenance diverse: France, Italie, Sicile, Grèce propre et îles grecques, Asie Mineure, Afrique du Nord.L'analyse chimique a porté sur les éléments suivants: Fer, Titane et Manganèse. L'analyse spectrographique porte sur les oligoéléments métalliques suivants: Plomb, Etain, Argent, Cuivre, Chrome, Nickel et Cobalt.Les teneurs en Titane, Plomb, Etain et Argent ne montrent pas de différences significatives. Par contre, les teneurs en Fer, Manganèse d'une part, Cuivre, Chrome, Nickel et Cobalt d'autre part, apportent des éléments de différenciation.
The aim of this study is to verify to what extent chemical and spectrochemical analysis can distinguish among sherds from various localities and to give new data to solve some of the archaeological problems about location.About 300 sherds have been analysed; I got them from D.Vallet, Professor at the Faculté des Lettres in Clermont-Ferrand, Auvergne — These samples come from various countries, namely from: France, Italy, Greece, Greek Islands, Asia Minor, North Africa.The chemical analysis was for: Iron, Titanium and Manganese. The determination of trace elements such as: Lead, Tin, Silver, Copper, Chronium, Nickel, Cobalt, is now being carried out by means of spectrochemical analysis.The amount of Titanium, Lead, Tin and Silver shows no significant differences — On the contrary the amount of Iron, Manganese, Copper, Chronium, Nickel and Cobalt, give a good criterion for comparing and contrasting sherds of different provenance.
Zusammenfassung Das Ziel meiner Arbeit ist, zu untersuchen, in welchem Maße es die chemische und spektrographische Analyse von antiken Tonwaren erlaubt, zwischen diesen Tonwaren zu unterscheiden und Lösungen für archäologische Ortsprobleme zu finden.Ich habe eine bestimmte Anzahl von antiken Tonwaren — ungefähr 300 Proben — analysiert die mir M.Vallet, Professor an der Geisteswissenschaftlichen Fakultät von Clermont-Ferrand, zur Verfügung gestellt hat. Diese Proben sind verschiedener Herkunft: Frankreich, Italien, Sizilien, Griechisches Festland, Griechische Inseln, Kleinasien und Nordafrika.Die chemische Analyse betraf die folgenden Elemente: Eisen, Titan, Mangan. Durch die spektrographische Analyse wurden die folgenden Elemente untersucht: Blei, Zink, Silber, Kupfer, Chrom, Nickel und Kobalt.Der Gehalt an Titan, Blei, Zink und Silber der einzelnen Proben zeigte keine wesentlichen Differenzen. Im Gegensatz dazu schwankte der Gehalt an Eisen und Mangan einerseits und Kupfer, Chrom, Nickel und Kobalt anderseits.
.相似文献
64.
Annie Souriau 《Earth and Planetary Science Letters》1984,68(1):101-114
Gorringe Ridge is a strong uplifted block of oceanic crust and upper mantle lying at the eastern end of the Azores-Gibraltar plate boundary. The geoid over this structure derived from Seasat altimeter data exhibits a 9-m height anomaly with a north-south lateral extension smaller than 200 km. An attempt is made to interpret this geoid together with the gravity anomalies and with the seismicity, which has been compiled as a function of depth.It is first shown that the flexure of the oceanic lithosphere due to the ridge loading does not provide a good fit of the geoid anomalies and probably should be discarded, as it assumes a continuous unfractured elastic plate.Models involving local heterogeneities are then tested. The comparison of the observed geoid anomalies with the anomalies due to the uncompensated relief indicates that the topographic high has no shallow compensation.Uncompensated models, previously proposed to explain the gravity anomalies, are tested using the geoid. One model (Purdy and Bonnin, in Bonnin [11]), which involves an uplift of upper mantle material at depth, generates too strong geoid anomalies and must be discarded. Another model, which represents a nascent subduction zone (Le Pichon et al. [25]), fits both the gravity and geoid anomalies, but leads to difficulties in explaining the deep seismicity north of Gorringe Ridge.A model in isostatic equilibrium is also able to fit both gravity and geoid anomalies. This model involves a deep root of density 3.0 g cm?3, as has been previously proposed for many oceanic ridges and plateaus. This model is compatible with the deep seismicity, but the origin of this low-density material at great depth is up to now an unresolved question.More likely, dynamical models taking into account the forces induced by the convection related to the slow plate convergence in this area will have to be considered. 相似文献
65.
Age and significance of the North Pyrenean metamorphism 总被引:1,自引:0,他引:1
39Ar-40Ar and 87Rb-87Sr studies of some metamorphic minerals from the North Pyrenean zone indicate that they crystallized about 92–104 m.y. ago on the east, 85 m.y. or older on the west. An amphibole from a lherzolite in the eastern area gives a plateau age at 103 m.y. The North Pyrenean metamorphism is shown to be a thermal effect of forcible lherzolite emplacement along the North Pyrenean zone. This latter process is related to the early breakup of the Europe-Iberia plate during the middle Cretaceous time. 相似文献
66.
A model of population synthesis for our Galaxy is used to estimate the constraints imposed by photometric and astrometric star counts. We construct a statistical method to compute the degree of compatibility of the model with the data in the form of a multidimensional functionf(V, B-V, U-B, ). We apply the method to the determination of the star formation history in the Galaxy from Schmidt plates towards the anticentre. Although the presently available data do not allow us to draw firm conclusions, we show that the same kind of data with a slightly better photometric accuracy and with proper motions would give new constraints on the past star formation rate of the Galaxy. 相似文献
67.
Chemical and biological characterization of particles by flow cytometry in the Krka estuary, Croatia
Flow cytometry was used to characterize suspended particles in the Krka estuary (Croatia). This technique allows a rapid characterization and quantification of individual particles; it is based on the simultaneous measurement of the light scatter and natural or induced fluorescence. The relative size of the particles was determined by light scatter signals and by a calibration with fluorescent beads.The determination of organic particles was carried out by staining with fluorescein isothiocyanate (FITC). The autofluorescence of photosynthetic pigments (chlorophyll and phycoerythrin) present in the phytoplankton population was measured. The carbohydrates (galactose and glucose-mannose) were stained by lectins conjugated to FITC. The abundance of organic coatings or mineral particles and detritus was obtained from the difference between the total number of particles stained by specific carbohydrate fluorochromes and living cells.Results show that the Krka estuary is characterized by the occurrence of very small particles. About 80% of suspended particles are organic, most of these particles being living cells. The only exception is the Guduca River, a small tributary. 相似文献
68.
7-ethylresorufin O-deethylase activity and level of DNA-adducts in trout treated with benzo(a)pyrene
Jean-Franois Masfaraud Annie Pfohl-Leszkowic Christian Malaveille Grard Keith Gilles Monod 《Marine environmental research》1992,34(1-4)
In fish, as well as in mammals, it is well known that the cytochrome P450-dependent oxidative metabolism of xenobiotics can generate DNA-reactive species. Moreover, this metabolism is known to be inducible by several compounds of environmental significance, such as polychlorobiphenyls, polycyclic aromatic hydrocarbons (PAHs) and dioxins. Consequently, we studied the relationship between the degree of induction of the cytochrome P4501A, expressed as that of 7-ethylresorufin O-deethylase (EROD) activity, and the level of DNA-adducts, using the post-labelling assay, in the liver of rainbow trout exposed to benzo(a)pyrene (a representative PAH). The results showed a significant 2- to 4-fold increase in EROD activity 2, 4 and 8 days after treatment, paralleled by an increase in DNA-adduct levels. This work further emphasizes the involvement of cytochrome P4501A in the metabolism of benzo(a)pyrene into genotoxic metabolites in rainbow trout. 相似文献
69.