0Polyphase tectonothermal events recorded in "metamorphic basement" from the Altyn Tagh, the southeastern margin of the Tarim basin, western China: Constraint from U-Pb zircon geochronology
塔里木盆地东南缘(阿尔金山)"变质基底"记录的多期构造热事件:锆石U-Pb年代学的制约

The Altyn Tagh, located on the southeastern margin of the Tarim basin, is a main region where metamorphic basement of the Tarim craton is exposed. In this paper, zircon U-Pb isotopic data of sedimentary rocks unconformably overlying on Archaean-Early Paleoproterozoic metamorphic basement and high grade metamorphic rocks from the Cental-South Altyn Tagh are used to investigate the nature and ployphase tectonothermal events of the metamorphic basement in the southeastern margin of the Tarim basin. Detrital zircons from Neoproterozoic Annanba Group overlying on the Tarim basement yield mainly an age at ca. 1.92Ga, with a few grains between 2.0Ga and 2.4Ga, suggesting that detrital material of the Annanban Group shed from the underlying Milan Group and associated plutonic rocks. In the Central Altyn Tagh massif and South Altyn Tagh subduction-collision complex belt, zircon U-Pb chronological data show that high grade metamorphic rocks recorded three phase tectonothermal events: Early Neoproterozoic event (900~940Ma), Late Neoproterozoic event (760Ma) and Early Paleozoic event. Early Neoproterozoic tectonothermal event can be linked to the Tarim (or Jinning) orogeny, which was commonly recognized in the metamorphic basement around the Tarim basin and the South China block (or Yangtze craton), and was related to the formation of the Rodinia supercontinent. Late Neoproterozoic tectonothermal event has been also commonly recognized around the Tarim basin and Yangtze craton and was related to the breakup of Rodinia supercontinent. Therefore, in Neoproterozoic era, the Altyn Tagh has a similar evolution history to the Yangtze craton, differing from the North China craton. Zircon U-Pb chronological data also indicate that the high grade metamorphic rocks from the Central-South Altyn Tagh commonly experienced Early Paleozoic metamorphic overprint related to subduction and collision.