Home – Home – Jornals – Russian Geology and Geophysics 2001 number 3

We have studied endogenic processes in the southeastern part of the Major Sayan Fault zone at the boundary of the Siberian Platform and Sayan-Baikal folded region. This is a zone of repeated occurrence of deformations, silica-alkaline metasomatism, and granite formation, which proceeded under moderate pressures no higher than 5.5-6 kbar. Some silica-alkaline metasomatites replacing each other with time include products of high-temperature granitization and quartz-albite-microcline (±magnetite, biotite, riebeckite, aegerine-augite) metasomatites and albitites. Early granitization took place under normal alkalinity with participation of rather reduced fluids, and postmagmatic fluid systems are carbon-enriched. Quartz-albite-microcline metasomatites formed at elevated alkalinity and F and f(O₂) activity. There is a clear difference between granitoids of the early tectonometamorphic cycles and the latest granites of the stage of marginal-suture activity, which are characterized by elevated concentrations of Nb, Y, Be, Sn, Pb, Th, and U.