SHRIMP U-Pb zircon geochronology of igneous rocks from southern margin of the Alataw mountains, Xinjiang, China.

Volcanic and granitic rocks occur widespread on the southern margin of the Alataw Mountains near the border of China and Kazakstan.Rhyolites are widely distributed and outcrop up to 370.8km~2in study area.The rhyolites have zircon U-Pb SHRIMP age of 300±5Ma,and are underlain unconformably by the Early Carboniferous Akeshake Formation and the Late Carboniferous Dongtujinhe Formation.The Wulasitai granite,the largest pluton in study area,outcrops about 82km~2 and intruded into the Akeshake Formation Dongtujinhe Formation and Early Permian volcanic rocks of the Wulang Formation with clear contact relationships.This pluton is irregular in shape and consists of four intmsive bodies.The fourth-intrusion granodioritic body has zircon U-Pb SHRIMP age of 294± 4Ma.The Xiaer'aola pluton is elliptical in shape and composed mainly of monzogranite with outcrop area about 10km~2.This pluton consists of four bodies,which intruded into Early Carboniferous strata.The sixth-intrusion body is the largest one and has zircon U-Pb SHRIMP age of 299±6Ma.Our investigations suggest that the igneous rocks on the southern margin of the Alataw Mountains have zircon U-Pb SHRIMP ages around 300Ma(Late Carboniferous Early Permian);these rocks formed in the same tectono-magmatic environment.