Variscan orogeny of Central Tianshan Mountains:Constrains from zircon U-Pb chronology of high-grade metamorphic rocks

In this paper,the authors have studied zircon U-Pb chronology of the high-grade metamorphic rocks on the northern margin of the Central Tianshan Microplate.The dating results show that the detrital zircons from the meta-sedimentary rocks have recorded the variable magmatic thermal events from Archean to Neoproterozoic(3320 to 530 Ma),the magmatic zircons of the meta-igneous rocks were crystallized in late Neoproterozoic of 550 Ma,whereas the metamorphic zircons were formed in Devonian of 385-360 Ma.These data demonstrate that the Central Tianshan block was probably formed in Precambrian,and subsequently subjected to Varsican orogeny.Unlike the Tarim Craton with multi-stage Proterozoic tectono-thermal events,the Central Tianshan Microplate which occurred as a single continent did not experience the Precambrian metamorphism.