Home – Home – Jornals – Russian Geology and Geophysics 2005 number 5

Study is given to the petrography, geochemistry, ⁴⁰Ar/³⁹Ar age, and geodynamic settings of the formation of volcanics from boreholes drilled in the Uralian part of the West Siberian syncline (upper reaches of the Severnaya Sos'va River) in recent years. Carboniferous and Permo-Triassic basalts and scarcer basaltic andesites, trachybasalts, and basaltic tuffs have been recognized here. Heterochronous basalts differ in the degree of paleohypergene and greenstone alteration and in geochemical parameters.
The Carboniferous and Permo-Triassic basalts are rocks of calc-alkalic series with normal or, less often, moderate alkalinity. They have moderate contents of K, but some Carboniferous samples are poor and some Permo-Triassic samples are rich in it. Both types of basalts, particularly the Permo-Triassic ones, are enriched in incompatible elements relative to N-MORB.
According to geochemistry, the Carboniferous basalts are island-arc volcanics, and the Permo-Triassic ones are rift trap rocks, which are widespread in the Upper Permian and Triassic strata of the West Siberian syncline.