We report here preliminary Rb-Sr whole rock data for Archaean gneisses from the Gorur-Hassan area, South Indian Craton which yield the oldest age yet reported from the Indian subcontinent (3,35866Myr) with a very unradiogenic initial Sr/Sr ratio
(0.70000.0004) which implies that the igneous precursors of these gneisses were derived from a relatively Rb-depleted source within the mantle.
Amérique du Sud ; DatationRb-Sr ; Géochronologie ; Géographie de l'Amérique ; Précambrien
Division du temps précambrien en Amérique du Sud, fondée sur les nouvelles connaissances géologiques et les datations par méthode des isochrones Rb-Sr, des événements les plus importants dans l'évolution tectonique du continent.
Le granite peralcalin du lac Brisson est daté à 1189 32 Ma par une isochrone Rb/Sr de roches totales. Ce résultat est confirmé par des mesures K/Ar sur amphiboles qui donnent un âge moyen de 1163 21 Ma. Cet âge permet d'assimiler le magmatisme
Dix échantillons de dolérites ont été analysés par la méthode Rb-Sr. L'âge est de 160945MA (Rb=1,42.10 au). Quatre de ces échantillons donnent des âges K-Ar de 1750, 1610, 832 et 1468M.A. Les données complétées par l'étude des paramètres chimiques
Variation of Rb/Sr ratios in the loess-paleosol sequences of Central China during the last 130,000 years and their implications for monsoon paleoclimatology
Rb, Sr, and magnetic susceptibility have been measured in the last interglacial-glacial loess profiles at Luochuan and Huanxian, central China. A high degree of similarity between the parameters in both profiles suggests that variations of Rb/Sr
ratios in the sequence can be regarded as an indicator of East Asian summer monsoon strength. Matching the Rb/Sr record with the SPECMAP δ18 O curve suggests that the Rb/Sr ratio responds sensitively to changes of the East Asian monsoon induced by global
A Rb/Sr record of catchment weaathering response to Holocene climate change in Inner Mongolia
Variation in the rubidium to strontium (Rb/Sr) ratio of the loess-palaeosol sequences has been proposed to reflect the degree of pedogenesis and weathering in the northwestern region of China. To characterize the Rb/Sr ratio of the dissolved loads
of a single catchment, the AA. analysed a 12.08 m sediment core from Daihai Lake in Inner Mongolia. Dating control was provided by Pb 210, Cs 137 and AMS C 14. The Rb/Sr ratios of the Holocene lake sediments are interpreted to be the direct results of changes
Description de plagio-migmatites du complexe Partizanskij. Détermination de leur âge par la méthode Rb-Sr. Schéma des régions tectoniques. La formation des granitoïdes et des migmatites remonte, peut-être, au Protérozoïque inférieur.
U-Pb, Sm-Nd and Rb-Sr systematics of mid-ocean ridge basalt glasses
The measurement of Pb, Nd and Sr isotopes isotropes in basalt glasses from mid-ocean ridges reveals correlations in isotope parameters which have important implications for the differentiation history of the mantle.
Environmental change inferred from Rb and Sr of lacustrine sediments in Huangqihai Lake, Inner Mongolia
Based on the geochemical elements Rb and Sr in sediments with 3 different grain size fractions from profile H3 on the northern lacustrine bottomland 13 m above the Huangqihai Lake surface in 1986, the paper investigates the record of palaeolake
stand state, sedimentary environmental evolution, and winter monsoon change. The results showed that the elements and the ratios varied regularly with the grain size. The ratio of Rb/Sr in the fraction