An integrated north–south paleo-Dadu-Anning River: New insights from bulk major and trace element analyses of the Xigeda Formation  

作　　者：Yong Zheng Hai-bing Li Jia-wei Pan Ping Wang Ya Lai Zheng Gong 

机构地区：[1]Key Laboratory of Deep-Earth Dynamics,Institute of Geology,Chinese Academy of Geological Sciences,China Geological Survey,Ministry of Natural Resources,Beijing 100037,China [2]Jiangsu Donghai Continental Deep Hole Crustal Activity National Observaion and Research Station,Lianyungang 222300,China [3]Southern Marine Science and Engineering Guangdong Laboratory,Guangzhou 511458,China [4]Geophysical Exploration Center,China Earthquake Administration,Zhengzhou 450002,China [5]Institute of Geophysics,China Earthquake Administration,Beijing 100081,China

出　　处：《China Geology》2024年第1期91-103,共13页中国地质（英文）

基　　金：financially supported by the Natural Science Foundation of China(41941016,42072240,41830217);Ministry of Science and Technology of China(2019QZKK0901,2021FY100101);Key Special Project for Introduced Talents Team of the Southern Marine Science and Engineering Guangdong Laboratory(GML2019ZD0201);China Geological Survey(DD20221630);Special Fund of the Institute of Geophysics,China Earthquake Administration(DQJB20B21).

摘　　要：The Xianshuihe-Anninghe fault extends SE–S and constitutes the southeastern margin of the Tibetan Plateau.However,the Dadu River which is associated with the fault does not flow following the path,but makes a 90ºturn within a distance of 1 km at Shimian,heading east,and joins the Yangtze River,finally flowing into the East China Sea.Adjacent to the abrupt turn,a low and wide pass near the Daqiao reservoir at Mianning separates the N–S course of the Dadu River from the headwater of the Anning River which then flows south into the Yunnan Province along the Anninghe fault.Therefore,many previous studies assumed southward flow of the paleo-Dadu River from the Shimian to the Anning River.However,evidences for the capture of the integrated N–S paleo-Dadu-Anning River,its timing,and causes are still insufficient.This study explored the paleo-drainage pattern of the Dadu and Anning Rivers based on bulk mineral and geochemical analyses of the large quantities of fluvial/lacustrine sediments along the trunk of the Dadu and Anning Rivers.Similar with sands in the modern Dadu River,the Xigeda sediments also exhibit a granitoid affinity with the bulk major mineral compositions of quartz(>50%),anorthite(about 10%),orthoclase(about 5%),muscovite(about 5%),and clinochlore(about 4%).Correspondingly,bulk major elements show high SiO_(2),with all samples>60%,and some of them>70%,low TiO_(2)(≤0.75%),P_(2)O_(5)(≤0.55%),FeO*(≤5%),and relatively high CaO(1.02%–8.51%),Na_(2)O(1.60%–2.52%),and K_(2)O(2.17%–2.71%),with a uniform REE patterns.Therefore,synthesizing all these results indicate that these lacustrine sediments have similar material sources,which are mainly derived from its course in the Songpan-Ganzi flysch block,implying that the paleo-Dadu originally flowed southward into the Anning River and provided materials to the Xigeda ancient lake.The rearrangement of the paleo-Dadu River appears to be closely related to the locally focused uplift driven by strong activities of the XianshuiheXiaojiang fault system.

关 键 词：Dadu River Anninghe fault River diversion Xigeda Formation Tectonic uplift PROVENANCE Songpan-Ganzi flysch Ancient lake Xianshuihe-Xiaojiang fault system Tibetan Plateau 

分 类 号：P531[天文地球—古生物学与地层学] P548[天文地球—地质学]