Adakites related to subduction in the northern margin of Junggar arc for the Late Paleozoic: Products of slab melting

Volcanic rocks with adakitic compositional signature have been recognized i n the northern margin of ancient Junggar island are for the Late Paleozoic. These adakites for the early Devonian from the Tuoranggekudouke Group (D-1 t) are characteristic of high Sr, Sr/Y and (La/Yb)(N) but low Y, Yb and HRE E. Their compositional characteristics are much similar to those of the typ ical adakites in the world but distinct from those of the normal arc volcan ic rocks from the same Group. We conclude that these adakitic volcanic rock s were produced by slab melting during the early period of Paleoasia-ocean lithosphere subduction. This infers that the Paleoasia Ocean in the north J unggar area began a new subduction process in the early Devonian.