Rare earth elemental and Sr isotopic evidence for seawater intrusion event of the Songliao Basin 91 million years ago  

作　　者：Yu-Ke Liu Hua-jian Wang Jin-You Zhang Zhen-Wu Liu Fa-Zi Chen Xiao-Mei Wang Shui-Chang Zhang He Liu 

机构地区：[1]Research Institute of Petroleum Exploration and Development,Beijing,100083,China [2]Key Laboratory of Petroleum Geochemistry,China National Petroleum Corporation,Beijing,100083,China [3]Daqing Oil Field Company,China National Petroleum Corporation,Daqing,Heilongjiang,163000,China [4]School of Ocean Sciences,China University of Geosciences,Bejing,100083,China

出　　处：《Petroleum Science》2023年第3期1347-1362,共16页石油科学（英文版）

基　　金：supported by Project of Basic Science Center of National Natural Science Foundation of China(72088101);the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA14010101);National Key Research and Development Program of China(2017YFC0603101);National Natural Science Foundation of China(41872125,42002158);Scientific and Technological Project of RIPED(2021ycq01);the subject development project of RIPED(yjkt2019-3).

摘　　要：Petrogenesis of lacustrine dolostone is closely related with paleo-lake water conditions.Here we report the high spatial-resolution petrographic and geochemical results of a lacustrine dolomite nodule from the Qingshankou Formation,the Songliao Basin.Sedimentary and elemental signatures confirm the protogenetic origin of this nodule and its effectiveness in recording geochemical characteristics of paleo-lake water during dolomitization.The low Y/Ho ratios,middle rare earth element(MREE)enrichment and subtle positive Eu anomalies within the nodule indicate a fresh water source.However,the Sr isotope values in the core of the nodule(0.7076-0.7080)are close to contemporaneous seawater(0.7074),yet different from the modern river(0.7120)and the host black shale(0.7100).On the premise of excluding the influence of hydrothermal fluids,the significantly low strontium isotope values of the lacustrine dolomite might be caused by seawater interference during dolomitization.Our findings demonstrate that lacustrine dolomite within black shales is not only a faithful tracer of diagenetic water environment,but also a novel and easily identified mineralogical evidence for episodic seawater intrusion event(91 Ma)in the Songliao Basin,which supplements other paleontological and geochemical evidence.

关 键 词：Songliao Basin Lacustrine dolostone Seawater intrusion Rare earth elements Strontium isotope 

分 类 号：P618.13[天文地球—矿床学]