Conditions of formation of Paleozoic picrite basalt complexes of the basement of the Western Siberian Plate

Abstract

The carried out researches with the help of 40Ar/39Ar analysis have shown a coincidence of formation (about 490 million years) of Paleozoic picrite and basalt complexes of the basement of the Western Siberian Plate. The data on petrochemistry, geochemistry of rare and rare-earth elements, and also on compositions of clinopyroxenes, testifies to formation of picrites of borehole № 11 (Chkalovsky area) as a result of action of intra plate magmatic systems of oceanic islands - OIB. Calculations on the basis of clinopyroxene compositions speak about considerable parameters of crystallization of picrite porphyrite minerals: 1215-1275 °C, 4.5-8 kbar. As a whole, it is established that considered picrite basalt complexes were formed with the assistance of enriched plume magmatic systems in intra plate conditions of ancient ocean near to its active margin.