Most of them represent near-primary magmas, although some alkali basalts were derived from the minor fractionation of olivine and diopside phenocrysts. A Pb- Sr-Nd isotope study of South West and East Indian Ridges confirms that the Indian Ocean belongs to a specific regional isotopic domain, as previously suggested by the results from islands of this ocean. Finally, investigation to date in the CEA on recombination circuits for power reactors is also discussed. The Sr , Nd isotopic ratios of the Okinawa Trough foraminifera are 0. Despite much active research, the fundamental questions still remain elusive regarding when and where the Indian plate collided with the Asian plate. Posterosional basalts are derived from the depleted asthenosphere, but their isotopic characteristics have been slightly modified by either the plume or the source of previously erupted volcanics. Both the geochemical signature and Sr-Nd -Hf isotopic composition of the gabbroic rocks reveal that the magma of the studied rocks was formed by the partial melting of a depleted mantle wedge metasomatized by slab-derived fluids.
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Research on evolutionary laws of SrNdPb isotopes of uranium metallization and volcanic rocks in south china. Materials and methods – Preparation of thin sections of rock samples for study of petrography and alteration of the intrusive rocks. Chrino, the subduction of a colder oceanic crust south of the Grijalva Fracture Zone and higher crustal assimilation lead to the reduction of slab contribution in southern part of the arc. The characters of each type of curono arising from both mechanisms are described in some detail. The front arc volcanoes also show two major latitudinal trends:
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 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 shutdowh confirm the presence of a HIMU shjtdown component.
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The major- and trace-element and Sr-Nd isotopic signatures show heterogeneous geochemical characteristics of the granitic rocks and suggest a suutdown geotectonic setting. On donne le mode operatoire complet et des exemples d’application. Posté le dimanche 03 septembre Felsic volcanic rocks mainly rhyolite, dacite and ignimbrite that overlay all tectonostratigraphic terranes were erupted during Ma, postdating the accretionary process in the Sikhote-Alin belt.
We present the first record of Katawaz chronology that constrained the Khojak Formation to be current study revealed that the Katawaz sedimentary sequence shutdoqn in age from Eocene to the earliest Miocene. Infiltration of aqueous fluids has introduced radiogenic Pb and Sr without significantly perturbing the rare earth element signature of the protolith.
Petrographic, petrochemical and Sr-Nd isotopic data are presented for granitoids and microdioritic enclaves from two Cretaceous stocks Togouchi granodiorite and Tateiwayama granite porphyry from the Togouchi-Yoshiwa district, northwest Hiroshima prefecture, SW Japan.
Isotopic composition of uranium metallization shows the characteristics of crust sources, and Yanshanian accretion of continental margin caused the crust movement such as magmatic activity in lower crust within continent, extension-down-faulting, etc. Le Yoruba du Nigeria et L’itsa Parle en. A la suite d’une deuxieme etudequi a mene a la conclusion que la contamination ne provient pas d’une dispersion des energies initiales des ions, on propose deux mecanismes comme etant les plus importants; la diffusion et l’instabilite du regime des sources.
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Lead isotope data have characteristics of a lower crust shjtdown with minor contamination by upper crustal material. Moreover, they are slightly enriched in large ion lithophile elements Rb, Ba, Th and K and light rare earth elements and depleted in high field strength elements Nb and Ti.
A new zhutdown 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: SrNdPb and Hf isotopic constraints on mantle sources and crustal contaminants in the Payenia volcanic province, Argentina.
La temperature du fil chaud est de l’ordre de deg C entretenue par courant redresse. Linked to a numerical model, these gas diffusion experiments through a shale porous plug allowed us to correlate porosity and diffusivity of the migration medium. Les modeles structuraux choisis sont: Les quantites ou les concentrations d’iode ont ete mesurees pour la thyroide et pour le plasma avec une.
These basalts probably originate from near the asthenosphere-lithosphere boundary.
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. We constructed the Cenozoic chronology in the Katawaz Basin based on our newly collected detrital zircon U-Pb ages and fission track ages.
These rocks constitute an extended magmatic belt along the continental margin of NE Asia. Chemical and isotopic heterogeneities in such xenoliths are usually interpreted to reflect melt extraction followed by metasomatic re-enrichment.
Using a linear interpolation method applied to two standards it is possible to correct for this inaccuracy as long as the isotopic concentrations are less than about 10 per cent in U Instead, we interpret this trend as reflecting the dilution of an early stage contaminated magma by several reinjections of fresh basalt in the chamber. These experimental factors are in good agreement with those obtained by calculating the partition functions of the adsorbed activated complexes.
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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. Hydrothermal activity associated with emplacement of the intrusions within the Jurassic limestones modified the elemental and the Sr isotopic composition of the hydrothermally altered rocks In particular the monzonitic to syenitic dykes underwent an alkali metasomatism marked by depletion in K and Rb and enrichment in Na and Sr.
Isotopic data to study the mechanism of the oxidation of mercaptoacetic acid; Donnees isotopiques pour l’ etude du mecanisme d’oxydation de l’acide mercaptoacetique; Izotopnyj metod snutdown mekhanizma okisleniya chroni kisloty; Estudio del mecanismo de oxidacion del acido mercaptoacetico por medio de datos obtenidos con radioisotopos. Physico-Chemical Study of the Separation of Calcium Isotopes by Chemical Exchange Between Amalgam and Salt Solutions; Etude physico-chimique de la separation des isotopes du calcium par echange chimique entre amalgame et solution saline.
This suggests that both G1 and G2 are highly differentiated peraluminous rocks with strong hydrothermal interaction. Criticality studies made at the Commissariat a l’Energie atomique deal on the one hand with experiments on plutonium and uranium solutions, on the other hand with theoretical work on the development and cjrono of computation, methods for the resolution of problems concerning the nuclear safety of chemical and metallurgical plants.
A method for reducing memory errors in the isotopic analyses of uranium hexafluoride by mass spectrometry; Methode de reduction des erreurs de memoire dans les analyses isotopiques de l’hexafluorure d’uranium par spectrometrie de masse.