Abstract: Late Paleozoic volcanic strata are widely distributed in the Gangdise belt. Petrological and geochemical characteristics show that remarkable change of the Gangdise belt had already taken place in late Paleozoic. The authors found volcanics intercalation in Late Carboniferous-Early Permian Laka Formation within Tarezeng area along central and western segment of the Gangdise belt. Petrological and geochemical characteristics show that it belonged to an island arc environment and marked the first arc-producing action of the Gangdise belt that took place in Late Paleozoic. During that period, central and western segment of the Gangdise belt had already experienced the conversion from the passive continental margin to active continental margin.