NEW DATA ON THE Rb-Sr AGE OF DIKE BELTS IN WESTERN TRANSBAIKALIA
M.G. Shadaev, V.B. Khubanov, and V.F. Posokhov
Geological Institute, Siberian Branch of the RAS, 6a ul. Sakh'yanovoi,
Ulan Ude, 670047, Russia
Keywords: Rifting, dike belts, bimodal magma series, Rb-Sr isotopic ages, Transbaikalia
Pages: 707-715
Abstract
Dike belts of NE strike, up to 100 km long and 12-15 km wide, have been recognized in the central area of western Transbaikalia. These are subparallel near-vertical dikes of trachybasalts, syenite-porphyries, trachydacites, and trachyrhyodacites. According to chemical composition, the dike rocks form a bimodal alkaline magma series. Rb-Sr isotope dating of the syenite-porphyry dikes showed that the dike belts formed in the Late Carboniferous-Early Permian (300-285 Myr ago), nearly simultaneously with the formation of massifs of alkali A -type granites and volcanic fields composed of bimodal trachybasalt-trachyte and comendite associations of the North Mongolian-Transbaikalian rift belt.
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