Zircon SHRIMP U-Pb geochronology of the Neoproterozoic Chengjiang Formation in central Yunnan Province(SW China) and its geological significance  

作　　者：JIANG XinSheng WANG Jian CUI XiaoZhuang ZHUO JieWen XIONG GuoQing LU JunZe LIU JianHui 

机构地区：[1]Chengdu Institute of Geology and Mineral Resources,Ministry of Land and Resources,Chengdu 610081,China [2]Graduate School of Chinese Academy of Geological Sciences,Beijing 100037,China [3]Beijing SHRIMP Center,Chinese Academy of Geological Sciences,Beijing 100037,China

出　　处：《Science China Earth Sciences》2012年第11期1815-1826,共12页中国科学（地球科学英文版）

基　　金：supported by National Natural Science Foundation of China (Grant Nos. 41030315,41072088);the China Geological Survey(Grant No. 1212011121105)

摘　　要：The Chengjiang Formation is the earliest continental clastic deposit after the Jinning Orogeny in central Yunnan Province,and therefore its accurate depositional age is significant for understanding the formation and evolution of the Neoproterozoic rift basins in southern China.However,hampered by accuracy of the dating technique,the existing age data for the Chengjiang Formation are not very reliable.A large number of magmatic zircons were obtained from the tuff interbed in the lower part of the Chengjiang Formation in Jinyang area and the bottom part of the Chengjiang Formation in Dongchuan area,central Yunnan Province,and high-precision SHRIMP U-Pb dating was carried out on these zircons.The results show that the weighted mean 206 Pb/238 U ages are 797.8±8.2 and 803.1±8.7 Ma respectively.In combination with related geological evidence,it has been demonstrated that the bottom boundary age of the Chengjiang Formation should be 800±5 Ma,whereas the top boundary age could be ca 725 Ma.By synthetically analyzing the latest age data for the relevant strata,it has been confirmed that the Chengjiang Formation should be correlated with the Suxiong Formation and the Kaijianqiao Formation in western Sichuan Province,the Liantuo Formation in the middle and lower Yangtze,the Hongchicun Formation and the Shangshu Formation in northern Zhejiang Province,the Puling Formation in southern Anhui Province,the Luokedong Formation and the Majianqiao Formation in northwestern Jiangxi Province,the Wuqiangxi Formation in northwestern Hunan Province,the Fanzhao Formation and the Qingshuijiang Formation in southeastern Guizhou Province,and the Sanmenjie Formation and the Gongdong Formation in northern Guangxi Province.Sedimentary cycle analysis shows that the sedimentary filling sequence of the Neoproterozoic rift basins in southern China can be divided into four cycles.Among them,Cycle II began at ca.800 Ma,accompanied by intensive tectonic-thermal events.The zircon U-Pb ages from the bottom of the Chengjiang Formation reported in tThe Chengjiang Formation is the earliest continental clastic deposit after the Jinning Orogeny in central Yunnan Province,and therefore its accurate depositional age is significant for understanding the formation and evolution of the Neoproterozoic rift basins in southern China.However,hampered by accuracy of the dating technique,the existing age data for the Chengjiang Formation are not very reliable.A large number of magmatic zircons were obtained from the tuff interbed in the lower part of the Chengjiang Formation in Jinyang area and the bottom part of the Chengjiang Formation in Dongchuan area,central Yunnan Province,and high-precision SHRIMP U-Pb dating was carried out on these zircons.The results show that the weighted mean 206 Pb/238 U ages are 797.8±8.2 and 803.1±8.7 Ma respectively.In combination with related geological evidence,it has been demonstrated that the bottom boundary age of the Chengjiang Formation should be 800±5 Ma,whereas the top boundary age could be ca 725 Ma.By synthetically analyzing the latest age data for the relevant strata,it has been confirmed that the Chengjiang Formation should be correlated with the Suxiong Formation and the Kaijianqiao Formation in western Sichuan Province,the Liantuo Formation in the middle and lower Yangtze,the Hongchicun Formation and the Shangshu Formation in northern Zhejiang Province,the Puling Formation in southern Anhui Province,the Luokedong Formation and the Majianqiao Formation in northwestern Jiangxi Province,the Wuqiangxi Formation in northwestern Hunan Province,the Fanzhao Formation and the Qingshuijiang Formation in southeastern Guizhou Province,and the Sanmenjie Formation and the Gongdong Formation in northern Guangxi Province.Sedimentary cycle analysis shows that the sedimentary filling sequence of the Neoproterozoic rift basins in southern China can be divided into four cycles.Among them,Cycle II began at ca.800 Ma,accompanied by intensive tectonic-thermal events.The zircon U-Pb ages from the bottom of the Chengjiang Formation reported in t

关 键 词：NEOPROTEROZOIC Chengjiang Formation zircon SHRIMP U-Pb age rift basin sedimentary cycle southern China 

分 类 号：P597[天文地球—地球化学] P534.3[天文地球—地质学]