地质学报2017，Vol.91Issue(8)：1760-1775,16.
河北怀来龙凤山青白口系长龙山组碎屑锆石LA-ICP-MS U-Pb年龄及其构造古地理意义
Detrital Zircon LA-ICP-MS U-Pb Dating of the Changlongshan Formation of Qingbaikou System in Huailai County, Hebei Province and Its Tectonic-Paleogeographic Significance
摘要
Abstract
The Changlongshan Formation (also called the Luotuoling Formation) of Qingbaikou System in Huailai County,Hebei Province receives much concern for the discovery of the Longfengshan Biota.The study reports an LA-ICP-MS U-Pb age of detrital zircons from siltstone occurring in the middle Longshan Formation (near to the strata bearing the Longfengshan Biota) in the west slope of Longfengshan Mountain.The result shows that U-Pb ages yielded are distributed between 1573 Ma～2931 Ma,with a distinct peak at～ 1.85 Ga,and several other secondary age peaks responding to some geological events of the North China Craton (NCC) in the Pre-Cambrian.The main peak age of 1.85 Ga reveals the amalgamation event of the western and eastern blocks of the NCC,2.6 Ga (2.603 Ga and 2.556 Ga) and 2.9 Ga (2.935 Ga) correspond to the important continental crust growth time of the NCC,and especially the former (2.6 Ga) correspond to the most prominent time of continental rapidly growth of the NCC.Detrital zircon ages of between 2.4～2.0 Ga (2.07 Ga,2.177 Ga,2.228 Ga,2.286 Ga,2.324 Ga and 2.388 Ga) record intracontinental extension and rifting events of the NCC.1.6 Ga (1.580 Ga) age peak reflects the Gaoyuzhuang period magmatic event,roughly corresponding to the Columbia supercontinent breakup.Widespread lack of 2.5 Ga age peak of the NCC may be due to the Changlongshan transgression,which likely covers all the 2.5 Ga outcrop.Referring to the bentonite age (1.36～1.38 Ga) of underlying Xiamaling Formation,the minimum concordia age (1.573 Ga) of the detrital zircon ages obtained in this study can not effectively constrain the deposition time of the Changlongshan Formation.Comparative study on the detrital zircon ages of Changlongshan Formation or comparable strata within the Yan-Liao aulacogen indicates that internal differences response to the above tectonic events in the Yan-Liao Aulacogen,suggesting considerable complexity of the geography within the Yan-Liao Aulacogen in the Changlongshan period.The age distribution of detrital zircons from the Changlongshan Formation of Qingbaikou System in the Liujiang region and the Liaodong Peninsula has obvious differences with that in the Yan-Liao Aulacogen,which is largely restrained by the paleo-geographical background.关键词
长龙山组/青白口系/碎屑锆石/燕辽裂陷槽/华北克拉通Key words
Changlongshan Formation/Qingbaikou System/detrital zircon/Yan-Liao Aulacogen/North China Craton引用本文复制引用
王振涛,沈阳,王训练,马伯永,黄晓宏..河北怀来龙凤山青白口系长龙山组碎屑锆石LA-ICP-MS U-Pb年龄及其构造古地理意义[J].地质学报,2017,91(8):1760-1775,16.基金项目
本文由中央高校基本科研业务费专项资金(批准号:2652014005)资助. （批准号:2652014005）
