After summarizing the vast analytical material it was possible to establish the differences in rare-earth element (REE) distribution in geosynclines and on platforms. It is shown that the heavier REE composition in sediments of geosynclines and the lighter one in sediments of platforms was initially created by processes of endogenic differentiation and then inherited by sedimentary series of these zones. On the basis of the calculation of the REE content in rocks of various shells of the Earth crust the increase of the role of heavy lanthanides into the depths of the crust is shown. The obtained estimate of REE abundance in the lithosphere led to the conclusion that the crust of our planet, despite the repeated reworking of its matter by sedimentary processes, metamorphism and granitization, has inherited features peculiar to products of tholeiitic magmatism-the most widely spread type of mantle fusion.A . B. Ronov et al.Caucasus geosyncline, comparing that distribution to the distribution of REE i n platform areas generally, and estimating the relative influence of tectonism and difference in source to that distribution. By supplementing our new data with that already in the literature, we believe it is now possible to construct a model which not only summarizes the REE distribution in the sedimentary shell and in the crust of the earth, but which also traces the changes in REE content and composition within the crust from shell to shell throughout geological time.To estimate the distribution of REE in geosynclinal zones, 150 composite samples (37,000 specimens) of aleuro-sands, clay, carbonate, and volcanogenic rocks were analysed. The samples represent each division of the Jurassic, Cretaceous, Palaeogenic and Neogenic systems in the main structural zones of the Caucasian geosyncline and the adjacent Scythian and Russian platforms. Rare-earth element determinations were carried out from preliminary isolated sums of TR oxides (Balashov, 1970) by the X-ray spectral method (Turanskaya, 1958). Carbonates were treated with hot 2% HCI and REE were measured separately in an acidic extract and in the insoluble residue.Rare-earth element distribution for the Phanerozoic sedimentary assemblage of the Russian platform, for recent sediments and volcanic rocks of the ocean floor, and for the intrusive and metamorphic rocks of the continental shield are taken from the literature. This published data is compiled and compared with our new data to complete the model. DIFFERENCES IN REE DISTRIBUTION IN GEOSYNCLINAL FACTORS AND PLATFORM SEDIMENTS AND CONTROLLINGPrevious studies have demonstrated that the chemical composition of geosynclinal sedimentary assemblages changes systematically across geosynclinal belts from their inner zone to their outer and then to the adjoining platform (Ronov et al., 1965, 1966). These compositional changes parallel a decrease in the rates of sedimentation and erosion and in the intensification of sedimentary differentiation. These results led us to assume that REE distribution might also show defi...

No abstract

No abstract

No abstract