华北燕辽地区串岭沟组黑色页岩对中元古代早期海水氧化还原环境的制约  

Black shales of the Chuanlinggou Formation in the northern North China Craton and its constraints on redox state of seawater during the Early Mesoproterozoic

作　　者：刘书琪 祝禧艳[2,3] 苏文博 赵太平[3,4] 仇一凡[3,4] 何雨婷 张华锋 LIU ShuQi;ZHU XiYan;SU WenBo;ZHAO TaiPing;QIU YiFan;HE YuTing;ZHANG HuaFeng(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;Key laboratory of Mineral Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Innovation Academy of Earth Science,Chinese Academy of Sciences,Beijing 100029,China;Key Laboratory of Mineral and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]中国科学院地质与地球物理研究所,中国科学院矿产资源研究重点实验室,北京100029 [3]中国科学院地球科学研究院,北京100029 [4]中国科学院广州地球化学研究所,中国科学院矿物学与成矿学重点实验室,广州510640

出　　处：《岩石学报》2022年第6期1667-1684,共18页Acta Petrologica Sinica

基　　金：国家重点研发计划项目(2020YFA0714803);国家自然科学基金项目(41630211、41872198)联合资助.

摘　　要：燕辽地区串岭沟组中上部保存有华北克拉通中元古代第一套大面积发育的黑色页岩,沉积于潮间带中下部,标志着该克拉通自形成以来最重要的海进过程,也是地球中年期早期阶段大气-海洋环境状态的特殊记录者。本文对蓟县八仙山剖面串岭沟组三段黑色页岩和顶部碳质白云岩开展了全岩主、微量元素和总有机碳(TOC)含量测定,认为其源区主要来自风化的长英质陆源碎屑物质。黑色页岩的TOC含量(平均值1.12%)、氧化还原敏感金属元素V(平均值82.6×10^(-6))、Cr(平均值73.9×10^(-6))、Ni(平均值29.8×10^(-6))含量明显高于碳质白云岩(TOC、V、Cr、Ni含量均值分别为0.47%、29.6×10^(-6)、26.4×10^(-6)、11.7×10^(-6))。此外,二者的氧化还原参数C_(org)/P分别为62.94和39.44,V/Cr值与沉积层位明显负相关,表明不同深度海水的氧化还原状态略有变化,但V/Cr-Th/U仍均落入富氧范围。研究结果表明,至少串岭沟组黑色页岩沉积时(不早于1.64Ga),较高的大气氧水平加剧了陆源物质风化及向海洋的输送量,并已经使得潮间带中下部静水进入到了相对氧化状态,从而可以为1.57~1.56Ga大型多细胞生物的出现提供持续含氧的发育环境。The 1.64~1.63Ga Chuanlinggou Formation preserves the first sequence of Mesoproterozoic black shale in the North China Craton.They could reveal the big transition of atmospheric and oceanic environment since the Middle Age of the Earth.In this study,the black shale and carbonaceous dolomite,forming in the middle to lower intertidal zone,of the third member of the Chuanlinggou Formation at the Jixian section of the Yanliao Aulacogen,have been analyzed systematically.Their major and trace elements characteristics suggest these successions should originate mainly from weathered terrigenous clastic materials of felsic parental rocks.The REDOX sensitive metal elements V(average 82.6×10^(-6)),Cr(average 73.9×10^(-6))and Ni(average 29.8×10^(-6))in black shales are significantly higher than those in carbonaceous dolomite(average contents of V,Cr and Ni are 29.6×10^(-6),26.4×10^(-6) and 11.7×10^(-6),respectively).The V/Cr ratio is negatively correlated with the sedimentary horizon,indicating that the REDOX state of seawater varies slightly at different depths,although all the ratios correspond to the oxygen-rich range in the V/Cr-Th/U discrimination diagram.In addition,their average Total Organic Carbon(TOC)content is 1.12%and 0.47%,and REDOX parameter C_(org)/P is 62.94 and 39.44,respectively,showing the seawater is of relative high oxygen concentration.It is supposed that,at least,when the black shale of Chuanlinggou Formation deposited(no earlier than~1.64Ga),a higher atmospheric oxygen level intensified the aerobic weathering,resulting in a dramatic rise of terrigenous materials into the sea.Furthermore,it has caused the static shallow water to be in a relative oxidation state,which may contribute a continuous oxygen-containing environment for the emergence of 1.57~1.56Ga large multicellular organisms since the earlier Calymmian Period.

关 键 词：黑色页岩 中元古代 串岭沟组 海水氧化还原状态 华北克拉通 

分 类 号：P588.22[天文地球—岩石学]