U-Pb geochronology of the detrital zircons from the southern segment of the Changning-Menglian suture zone in western Yunnan: Constraints on sedimentary age and tectonic environment

Clarify the evolution characteristics of the Lincang Block, it is necessary to restrict the sedimentary age and tectonic environment of the Nanduan Formaiton.The U-Pb geochronology of detrital zircon in the Nanduan Formaiton is studied in this paper.The study shows that the age of the youngest group from the Nanduan Formation are 512 Ma and 509.6 Ma.The source has the characteristics of three age groups: Pan African period (680~530 Ma), late Greenville period (980~900 Ma) and early Greenville period (1300~1100 Ma).The results show that it is considered that the maximum sedimentary lower limit of the Nanduan Formaiton is Cambrian, and the upper limit of the middle and the upper part is Carboniferous.The provenance comes from at least three orogenic belts in the East Gondwana supercontinent, which is mainly the Pinjarra orogenic belt in Antarctica, the Albany Fraser orogenic belt in Western Australia and the Paterson-Peterman orogenic belt in eastern Australia, with a pro-Gondwana continental nature.In the reconstruction of Gondwana continent in Paleozoic, the Nanduan Formation is located on the northern edge of the Australian plot, which expervenced an evolutionary process from the western Australia Block to the eastern Australia Block, moving north to East, and transforming from the passive continental margin to the active continental margin.The early sedimentary environment was coastal shallow sea or delta, and the later stage is forearc accretionary wedge sedimentary environment.