SHRIMP U-Pb dating for a K-bentonite bed in the Tieling Formation,North China  

作　　者：SU WenBo LI HuaiKun HUFF W D ETTENSOHN F R ZHANG ShiHong ZHOU HongYing WAN YuSheng 

机构地区：[1]School of Earth Sciences and Resources, China University ofGeosciences (Beijing), Beijing 100083, China [2]Tianjin Institute of Geology and Mineral Resources, China Geological Survey, Tianjin 300170, China [3]Department of Geology, University of Cincinnati, Cincinnati, OH 45221-0013, USA [4]Department of Earth and Environment Sciences, University of Kentucky, Lexington, KY 40506-0053, USA [5]Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China

出　　处：《Chinese Science Bulletin》2010年第29期3312-3323,共12页

基　　金：supported by the National Natural Science Foundation of China (40372057 and 40772076);the SINOPEC Project (G0800-06-ZS-319);the China Geological Survey (CGS) project (1212010611802)

摘　　要：A SHRIMP U-Pb zircon age of 1437±21 Ma was obtained for a recently discovered K-bentonite bed in the Tieling Formation,situated northeast of Beijing at the boundary between Liaoning and Hebei provinces,on the northern margin of the North China Craton(NCC).The SHRIMP U-Pb age places Tieling Formation near the end of the Calymmian Period of the early Mesoproterozoic Era.In addition,a SHRIMP U-Pb zircon date of 1372±18 Ma was acquired for K-bentonite beds in the overlying,dark-shale-dominated Xiamaling Formation from the same location northeast of Beijing.This date assigns a similar Mid-Mesoproterozoic(Ectasian Period) age for the Xiamaling Formation,as have previously determined dates from other sections northwest of Beijing.These dates indicate that the Tieling and Xiamaling formations,as well as the related succession in the eastern part of the Yanshan Mountains,represented by the well-known Meso-to Neoproterozoic standard section in Jixian,can be correlated well with sections northwest of Beijing in the western part of the Yanshan Mountains.In other words,the boundary between the Calymmian and Ectasian periods in the northern parts of the NCC is marked by the unconformity between the Tieling and Xiamaling formations in the northern NCC.This boundary was previously ascribed to the "Qinyu Orogeny" and thought to be of Grenville age.In this regard,the conventional "Qinyu Orogeny" should now be regarded as a short-lived regional uplift during Early Mesoproterozoic time,rather than a result from the Grenvillian assembly of the NCC to the Rodinia Supercontinent(～1.0 Ga).A SHRIMP U-Pb zircon age of 1437±21 Ma was obtained for a recently discovered K-bentonite bed in the Tieling Formation, situated northeast of Beijing at the botmdary between Liaoning and Hebei provinces, on the northern margin of the North China Craton （NCC）. The SHRIMP U-Pb age places Tieling Formation near the end of the Calymmian Period of the early Mesoproterozoic Era. In addition, a SHRIMP U-Pb zircon date of 1372±18 Ma was acquired for K-bentonite beds in the overlying, dark-shale-dominated Xiamaling Formation from the same location northeast of Beijing. This date assigns a similar Mid-Mesoproterozoic （Ectasian Period） age for the Xiamaling Formation, as have previously determined dates from other sections northwest of Beijing. These dates indicate that the Tieling and Xiamaling formations, as well as the related succession in the eastern part of the Yanshan Mountains, represented by the well-known Meso- to Neoproterozoic standard section in Jixian, can be correlated well with sections northwest of Beijing in the western part of the Yanshan Mountains. In other words, the boundary between the Calymmian and Ectasian periods in the northern parts of the NCC is marked by the unconformity between the Tieling and Xiamaling formations in the northern NCC. This boundary was previously ascribed to the ＂Qinyu Orogeny＂ and thought to be of Grenville age. In this regard, the conventional ＂Qinyu Orogeny＂ should now be regarded as a short-lived regional uplift during Early Mesoproterozoic time, rather than a result from the Grenvillian assembly of the NCC to the Rodinia Supercontinent （-1.0 Ga）.

关 键 词：SHRIMP 铁岭组 膨润土 Pb 锆石 中国 RODINIA超大陆 中元古代早期 

分 类 号：P588.121[天文地球—岩石学] P588.2[天文地球—地质学]