Geological implications of elements of the Pleistocene mudstone with different organism compositions and enrichment environments in the Qaidam Basin,China  

作　　者：Jinqi QIAO Qingyong LUO Chen ZHANG Zhenxue JIANG 

机构地区：[1]State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing 102249,China [2]Basin and Reservoir Research Center,China University of Petroleum,Beijing 102249,China [3]Unconventional Natural Gas Research Institute,China University of Petroleum,Beijing 102249,China

出　　处：《Frontiers of Earth Science》2023年第2期437-454,共18页地球科学前沿（英文版）

基　　金：The study was granted financial support by the National Natural Science Foundation of China(Grant Nos.42202154 and 42002050);the Science Foundation of China University of Petroleum,Beijing(No.ZX20220074).

摘　　要：Trace elements and rare earth elements(REEs)of two kinds of organic facies samples representing marginal and more basin-center deposits from Pleistocene lacustrine mudstones in the central Qaidam Basin were studied to understand the provenance,palaeotectonic setting,hydrothermal activity,palaeoredox conditions and sedimentary rate.The results show that the lacustrine mudstones were mainly derived from felsic sources with little contribution from ancient crustal sediments and no ultramafic(ophiolitic)source.The mudstones were deposited in a continental island arc tectonic setting,which is consistent with the tectonic evolution of the Cenozoic basin.Both two organic facies samples were hydrothermal in origin based on the ternary diagram of Ni–Zn–Co and normalized REE patterns.However,this does not mean that the water column in paleolake was affected by hydrothermal fluids in situ.This signal might indicate hydrothermal origins from hot springs related to active faults around the basin rather than the deep hydrothermal fluids entering the sediments via deep faculties based on the comprehensive analyses of normalized REE patterns,negative E_(uanom)(Eu anomaly),Y/Ho,Sm/Yb,and Eu/Sm.Redox proxies including U/Th,Ni/Co,and Mnanom values,are more sensitive for the studied samples indicating that most of the organic facies A samples were deposited under an oxygen-depleted condition,while the organic facies B samples were deposited under oxygen-rich conditions.Redox proxies of Ceanom values are unavailable for the organic facies B samples due to hypersaline environments,and V/C_(r)and V/(V+Ni)are invalid for the organic facies A samples,possibly because of their organism composition.The low Lan/Ybn values indicate high sedimentation rates,which is consistent with the average sedimentation rates of approximately 0.43 to 1.1 km/Ma.However,the La_(n)/Yb_(n) is more likely affected by the provenance of the studied samples,so it should be used with caution.

关 键 词：ELEMENTS lacustrine mudstone PLEISTOCENE Qigequan Formation Qaidam Basin 

分 类 号：P53[天文地球—古生物学与地层学]