Upper Riphean and Vendian sandstones of the Bashkirian anticlinorium |
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Authors: | A V Maslov E Z Gareev V N Podkovyrov |
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Institution: | (1) Forschungsstelle Archäometrie der Heidelberger Akademie der Wissenschaften am Max-Planck-Institut für Kernphysik, Postfach 103980, 69029 Heidelberg, Germany;(2) Geologisches Institut, RWTH Aachen, Wüllnerstrasse 2, 52056 Aachen, Germany;(3) Centre de Géochimie de la Surface (CNRS-ULP), 1 rue Blessig, 67084 Strasbourg, France;(4) Geological Institute of the Ufimian Geoscience Center, Russian Academy of Sciences, Karl Marx Str. 16/2, 450000 Ufa, Russia |
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Abstract: | The analysis of lithogeochemical data on the Upper Riphean and Vendian sandstones from the Bashkirian anticlinorium showed
that sandstone associations formed in a passive sluggish tectonic regime in the middle Late Vendian were replaced by associations
accumulated in the more active tectonic settings. This is well seen in the SiO2-K2O/Na2O and (Fe2O3* + MgO)-TiO2 diagrams reflecting the particular and median compositions of psammites. The lithochemical characteristics of sandstones
were examined to determine the compositional variation of rock complexes eroded on paleodrainage areas. Quartz-rich sedimentary,
metasedimentary, and metamorphic rocks, as well as felsic igneous rocks prevailed in the paleodrainage areas throughout the
entire Late Riphean and Early Vendian, while the main sources of clastic material in the Late Vendian were igneous intermediate
and basic rocks. With allowance made for the previous comparative-lithological data and some other materials, significant
similarity in the position and orientation of compositional fields of psammites from the middle and upper levels of the Asha
Group (Bashkirian anticlinorium) with fields of psammites from different syncollisional (flysch and molasse) basins in the
SiO2-K2O/Na2O, K2O/Na2O-SiO2/Al2O3, F1–F2 and other diagrams suggests that the middle Late Vendian (beginning from the Basa level) was marked by a variation
in tectonic/geodynamic settings of sandstone accumulation and in composition of the eroded paleodrainage systems. The revealed
trend agrees well with concept of the existence of the Late Riphean-Vendian Pechora paleocean. |
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