In contrast with Santorini, the least differentiated lavas on Milos are the most contaminated. Methods of internal and external conversion have been used. The structural models chosen are: The results already obtained relate to critical masses of cylindrical tanks of diameters from 20 to 50 cm. Subduction zones are important for understanding of the global carbon cycle from the surface to deep part of the mantle.
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Stable isotope separation; Separations physicochimiques d’isotopes stables realisations et etudes de petites productions. The Hainan Island is an important source for sediments deposited in the nearshore and western shelf, especially for illite, kaolinite and smectite clay minerals. The Tateiwayama granite porphyry has a slightly younger Rb-Sr whole isochron age In any case, the Hawaiian Islands data, when compared to those of other OIB, serve to illustrate the isotopically diverse nature of mantle sources. In addition to the occurrence in the Sikhote-Alin orogenic belt, Cretaceous to Early Paleogene magmatic rocks are also widespread in NE China, southern Korean peninsula, Japanese islands and other areas of Russian Far East, particularly along the coastal regions of the Okhotsk and Bering Seas. These features are consistent with low degrees of partial melting of a volatile-, LILE- and HFSE-rich, amphibole-bearing peridotitic mantle induced by uplift during an E-W-directed extensional regime, as is found in central Madagascar. Variation diagrams strongly suggest a major role for evolutionary processes such as fractional crystallization, contamination, crystal trapping and magma maxing, occurring after magma genesis in the mantle.
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Study of isotopic exchange reactors ; Etude des reacteurs d’echange isotopique Centre d’ Etudes Nucleaires. A study is made of the general case of the theory of first-order isotopic chemical exchange between a gaseous and a liquid phase in a reactor, starting from fundamental reaction kinetics data, and without making any limiting hypothesis concerning the value of the separation factor.
The cases of counter-current reactors and of co-current reactors are considered successively. The general deuterium conservation equation requires the definition of the quotient of the reactor; the performances of this reactor are characterised by its overall efficiency. The idea of the ratio is introduced because it represents a convenient intermediary in the calculations. The search for an additive value for reactors in series leads logically to the defining of an exchange capacity, and a total efficiency, or number of theoretical reactors.
This method of expressing the performances of a reactor is more general than the efficiency due to Murphee which only has a physical significance in the particular case of homogeneous liquid reactors. The relationships between these various quantities are established, and the representation due to Mc Cabe and Thiele is generalized.
The reactor performances are linked to the first – order reaction kinetics by the transfer number. The relationships are given for a certain number of concrete cases.
Finally the application of these calculations is given, together with the approximations necessary in the case where, because of the presence of several components in each phase, the exchange reaction no longer obeys a single kinetic law. L’equation generale de conservation du deuterium.
Transformations of highly enriched uranium into metal or oxide; Etudes des procedes de transformation des composes d’uranium a fort enrichissement isotopique. The workshops are to start production in may Les principes qui ont ete suivis pour la conception et la securite de ces ateliers sont exposes.
La securite nucleaire est basee sur la geometrie des appareils de traitement. Pour mettre au point les procedes et la technologie de ces ateliers, de nombreuses etudes ont ete conduites depuisdont chroon ont abouti a des realisations originales. La transformation de l’hexafluorure d’uranium a fort enrichissement isotopique s’effectue, soit par injection en phase gazeuse dans l’ammoniaque, soit par un procede original de reduction directe en tetrafluorure d’uranium par l’hydrogene.
La recuperation de l’uranium contenu dans les dechets metalliques d’uranium-zirconium s’operera par attaque par l’acide chlorhydrique, puis traitement du chlorure d’uranium par le fluor afin d’obtenir l’uranium sous forme d’hexafluorure. La recuperation de l’uranium contenu dans les dechets divers s’opere par un procede classique de raffinage: Deux ateliers separes fonctionnent suivant ce procede: La mise en oeuvre, d’une maniere nucleairement sure, de chacune des etapes du procede a pose des problemes technologiques particuliers et a conduit a.
A study on the isotope effects in the reduction of carbon dioxide by zinc; Etude des effets isotopiques dans la reduction du gaz carbonique par le zinc. We have determined the isotope effects which occur in the reduction of carbon dioxide by zinc. It has been shown that in the case of irreversible surface reactions, Bernstein’s equation which permits the calculation of the fractionation factor is still valid.
These experimental factors are in good agreement with those obtained by calculating the partition functions of the adsorbed activated complexes. La validite de l’equation de Bernstein qui permet de calculer le facteur de fractionnement a ete demontree pour le cas d’une reaction irreversible de surface.
Ces facteurs de fractionnement experimentaux sont en bon accord avec ceux obtenus par le calcul des fonctions de partition isotopiques des complexes actives adsorbes. Contribution to the study of luminous sources for uranium isotope measurements by emission spectrometry; Contribution a l’ etude de sources lumineuses destinees au dosage isotopique de l’uranium par spectrometrie d’emission. After a chrobo summary of results obtained with different hollow cathode luminous sources, the reasons for which they cannot be more widely used are given: Electrode-less discharge tubes excited by high frequency whose qualities ehutdown, stability, rapidity of preparation starting from small amounts of sample in various chemical forms, in particular iron satisfy the conditions laid down for the measurement of uranium by interferometry are used.
Tho production process for such lamps is given together with the method of excitation. Examples of recordings crono with an interferometer of the ‘HYPEAC’ type and a small grating spectrometer give an whutdown of the spectral qualities of these sources. On a employe des tubes chrino decharge sans electrode excitee par haute frequence, dont les qualites brillance, stabilite, rapidite de preparation a partir de faibles quantites d’echantillon se presentant sous des formes chimiques diverses, elimination des impuretes chimiques, en particulier du fer repondent aux conditions imposees pour le dosage isotopique de l’uranium par interferometrie.
On decrit le mode operatoire de fabrication de telles lampes et on rappelle le systeme d’excitation. Des exemples d’enregistrement, obtenus avec un appareil interferometrique ‘HYPEAC’ et un petit spectrometre a reseau, donnent une idee des qualites spectrales de ces sources. Sr-Nd -Hf isotopic fingerprinting of transatlantic dust derived from North Africa.
Clay-sized Sr-Nd -Hf isotopic compositions can be used as geochemical fingerprints to constrain dust provenance and the pathways of long-range transported mineral dust.
We investigated the clay-sized Sr-Nd -Hf isotopic composition of surface samples along four transects bordering the Sahara Desert. Comparison of the clay-sized Sr-Nd -Hf isotopic values from our North African samples to transatlantic African dust collected in Barbados demonstrates that the dust’s provenance is primarily the western Sahel and Sahara as well as the central Sahel.
Summer emission dust is derived mainly from the western Sahel and Sahara regions. The source of transatlantic dust shufdown spring and autumn is more varied than in the summer and includes dust not only from western areas, but also south central areas. Comparison of the Sr-Nd -Hf isotopic fingerprints between the source and sink of transatlantic dust also suggests that a northwestward shift in dust source occurs from the winter, through 11.2 spring and into the summer.
The isotopic data we develop here provide another tool for discriminating changes in dust archives resulting from paleoenvironmental evolution of source regions. Geochemistry of trace elements and Sr – Nd isotopes of foraminifera shell from the Okinawa Trough. Trace elemental associations and Sr – Nd isotopic compositions are of important to recognition of biogenic material from mixed marine sediments.
The mechanism of elemental enrichment in forminifera is the concentrations of trace elements in sea water and chronp absorption of trace elements during foraminifera living, as well as the geochemical affinity between major elements and trace elements. The REE rare earth elements partition pattern of foraminifera shell of the Okinawa Curono shows enrichment of middle rare earth elements with slightly negative Ce anomaly,which are different from those of foraminifera of the Pacific Ocean.
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The SrNd isotopic ratios of the Okinawa Trough foraminifera are 0. Petrogenesis of Miocene alkaline volcanic suites from western Bohemia. Whole rock geochemistry and Sr-Nd -Pb isotopic signatures. DD – Geochemistry Impact factor: SrNdPb and Hf isotopic constraints on mantle sources and crustal contaminants in the Payenia volcanic province, Argentina.
The presented SrNdHf and double-spike Pb-isotopic analyses of Quaternary basalts from the Payenia volcanic province in southern Mendoza, Argentina, confirm the presence of two distinct mantle types feeding the Payenia volcanism. The southern Payenia mantle source feeding the intraplate-type Chroo Study on Sr-Nd isotopes of mesozoic-cenozoic granites in Qinghai-Tibetan plateau.
Mesozoic-Cenozoic magmatic activities were intensive in Qinghai-Tibetan plateau. Nd-Sr isotopic compositions of representative granitic plutons in western Qinghai-Tibetan plateau are reported in this paper. Combining with past isotopic data, which has reported in eastern Qinghai-Tibetan plateau, Sr-Nd isotopic compositions and material source vhrono genesis of Mesozoic and Cenozoic granites in Qinghai-Tibetan plateau have been studied.
Sr-Nd -Pb isotopes of the post-paleozoic magmatism from eastern Paraguay. The Parana Angola-Namibia igneous province PAN is characterized by Early Cretaceous flood tholeiites and tholeiitic dyke swarms associated with alkaline rocks of Early and Late Cretaceous ages, respectively, and with scarce post-Mesozoic magmatic rocks Comin-Chiaramonti et al.
The Eastern Paraguay, at the westernmost side of the Parana Basin, is of special interest because: Comin-Chiaramonti and Gomes, ; Comin-Chiaramonti et al. The paper aims discussing the most important Sr – Nd -Pb isotope features of the alkaline and tholeiitic magmas from Eastern Paraguay in comparison with the PAN analogues au. Contribution to the study of a method for measuring continuously the isotopic shudown.
The determination of an isotopic effect between the two reactions: The condensation, during the reaction, of the carbon dioxide formed, and the shutdowb as a function of time of the residual carbon monoxide pressure, makes it possible to deduce, uninterruptedly, the ‘light’ shutfown kinetics. The ‘heavy’ reaction kinetics are obtained by measuring continuously, in situ, the radioactivity shudown the residual reactant gas as a function of the time.
The apparatus used for shjtdown is a plastic chronk counter. A calibration curve of the measured radioactivity as a function of the reactant gas pressure in the absence of reaction makes it possible to compare the kinetics of the ‘light’ and ‘heavy’ reactions.
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The reaction temperature is chosen such that the reaction rate is sufficiently slow, so that the variation of the radioactivity during unit counting time is negligible. La condensation, au cours de la reaction, du gaz carbonique forme et la mesure en fonction du temps de la pression de l’oxyde de carbone residuel, permet d’obtenir, de facon continue, la cinetique de la reaction ‘legere’.
La cinetique de la reaction lourde est determinee par la mesure continue, in situ, du taux de radioactivite du reactif gazeux residuel en fonction du temps. Le dispositif employe dans ce but est un compteur a scintillateur plastique.
Une courbe d’etalonnage, du taux mesure de radioactivite en fonction de la pression du gaz reactif, en l’absence de reaction, permet de comparer les.
etude isotopique sr-nd: Topics by
Multiple enrichment of the Carpathian-Pannonian mantle: Pb- Sr-Nd isotope and trace element constraints. Pb isotope compositions of acid-leached clinopyroxene and amphibole mineral separates from spinel peridotite mantle xenoliths entrained in Tertiary-Quaternary alkali basalts from the Carpathian-Pannonian Region of eastern Europe provide important constraints on the processes of metasomatic enrichment of the mantle lithosphere in an extensional tectonic setting associated with recent subduction.
Principal shutdon analysis of Pb- Sr-Nd isotope and rare earth element sjutdown of the pyroxenes is used to identify the geochemical characteristics of the original lithospheric mantle protolith and a spectrum of infiltrating metasomatic agents including subduction-related shhtdown fluids and silicate melts derived from a subduction-modified mantle wedge which contains a St.
Helena-type HIMU plume component. The mantle protolith is highly depleted relative to mid-ocean ridge basalt-source mantle with Pb-Nd-Sr isotope 1.21 consistent with an ancient depletion event. Silicate melt infiltration into the protolith accounts for the primary variance in the Pb- Sr-Nd isotope compositions of the xenoliths and has locally generated metasomatic amphibole. Infiltration of aqueous fluids has introduced radiogenic Pb and Sr without significantly perturbing the rare earth element signature of the protolith.
The Pb isotope compositions of the fluid-modified xenoliths suggest that they reacted with aqueous fluids released from a subduction zone which had equilibrated with sediment derived from an ancient basement terrain. We propose a model for mantle lithosphere evolution consistent with available textural and geochemical data for the xenolith population. The Pb- Sr-Nd isotope compositions of both alkaline mafic magmas and rare, subduction-related, calc-alkaline basaltic andesites from the region provide important constraints for the nature of the asthenospheric mantle wedge and confirm the presence of a HIMU plume component.
These silicate melts contribute to the metasomatism. A new method for studying iodine metabolism; the isotopic equilibrium method – kinetic and quantitative aspects of measurements made on rats; Une nouvelle methode d’ etude du metabolisme de l’iode: The isotopic equilibrium method which has been developed in the case of the rat has made it possible to measure the absolute values of the principal parameters of iodine metabolism in this animal.
The quantities and concentrations of iodine have been measured in the thyroid gland and in the plasma with a sensitivity of 0. This sensitivity has made it possible to measure pools as small as the iodide and the free iodotyrosines of the thyroid and to demonstrate the absence of free iodotyrosines in the plasma of the normal rat. In vivo, the isotopic equilibrium method has made it possible to measure the iodine content of the thyroid gland and chronl calculate the intensity of this gland’s secretion without removing it.
The absence of this relationship is due to the heterogeneity of the thyroglobulin turnover. The isotopic equilibrium method is very useful for series measurements of iodine. Les quantites ou les concentrations d’iode ont ete mesurees pour la thyroide et pour le.
Les quantites ou les concentrations d’iode ont ete mesurees pour la thyroide et pour le plasma avec une. Research on evolutionary laws of SrNdPb isotopes of uranium metallization and volcanic rocks in south china.
According to research on evolutionary tracer of SrNdPb isotopes, the author proposes that isotopic evolution of Mesozoic volcanics in south China is controlled by regionally metamorphic rocks of ancient land basement, early reformed derivates and recycled continental crust.