Pan-African tectonic-thermal events recorded in Dali area, western Yunnan

There are relatively complete Late Paleoproterozoic Pan-African tectonic-thermal events in Dali area, the isotopic ages of the biotite K-Ar and zircon U-Pb obtained from Haidong Wase granodiorite and granite are 799 Ma and 667 Ma, Cangshan Yunnon-gfeng biotite monzogranite yields the U-Pb age of 748 Ma, and isotopic age of K-Ar obtained from Zhoucheng Bojite is 892.3 Ma.Late Paleoproterozoic Wase granite and Yunnongfeng granite are in sedimentary contact with the Ordovician Dachengcun Forma-tion.Dachengcun Formation siltstone produced brachiopods and gastropods fossils.There is an unconformable contact between the top and Middle Silurian Yinyangshan Formation, with the lack of Lower Silurian strata.Ordovician-Silurian strata of Xiangyang Vil-lage are developed well and contain abundant trilobites, graptolite fossils, with lots of standard molecules of Early Ordovician.The stratigraphic structure in Dali area is different from that of Lijiang area and hence cannot be compared, but it can be compared with things of southern Qinghai and eastern Tibet.The Paleoproterozoic Cangshan Group is equivalent to Ningduo Formation, and the Late Proterozoic Luopingshanyan Group is equivalent to Caoqu Formation, with the lack of the Sinian-Cambrian strata.The Lower Ordovician Xiangyang and Yingfengcun formations are equivalent to the Qingniudong Formation and Zengziding Formation.There-fore, the Dali plate structure should be assigned to the multi-island-arc-basin system on the western margin of the Yangtze of the Ti-bet-Sanjiang orogenic system.The boundary between the Tibet-Sanjiang orogenic system and the Yangtze-Southern China block should be transferred to the Honghe-Chenghai fault.