京西坳陷周口店地区洪水庄组地球化学特征及其地质意义  

Geochemical characteristics and geological significance of the Hongshuizhuang Formation in the Zhoukoudian Area of Jingxi Depression

作　　者：曾金华 兰晓东[1] 司晨晨 ZENG Jinhua;LAN Xiaodong;SI Chenchen(School of Ocean Science,China University of Geosciences(Beijing),Beijing 100083,China)

机构地区：[1]中国地质大学(北京)海洋学院,北京100083

出　　处：《东北石油大学学报》2021年第6期52-67,I0004,I0005,共18页Journal of Northeast Petroleum University

基　　金：中央高校基本科研优秀教师基金项目(35832019010)。

摘　　要：洪水庄组是华北中元古界主力烃源岩之一,生烃潜力巨大,物源和沉积环境存在争议。根据微量元素及碳、氧同位素资料,分析京西坳陷周口店地区洪水庄组地球化学特征,明确物源特征及沉积环境。结果表明:京西坳陷洪水庄组物源具有多源性,陆源贡献主要分布于洪二段和洪三段。洪二段页岩明显富集高场强元素和轻稀土元素,轻、重稀土元素分异严重,反映碎屑物质可能来自华北中元古代岛弧背景下的大陆岛弧长英质物源区。洪一段沉积期,京西坳陷处于半潮湿气候下,盐度相对较高,在弱氧化—弱还原的浅水环境下形成白云岩;洪二段沉积期,气候潮湿,海侵导致京西坳陷海平面上升,碳酸盐岩台地消亡,长英质碎屑搬运至低盐、厌氧、中等分层的深水环境沉积而形成黑色页岩;洪三段沉积期,沉积环境与洪一段的类似,水体环境重新变咸但低于洪一段的,泥质白云岩沉积于弱还原、弱分层水体环境。总体上,周口店地区洪水庄组发育局限浅海相沉积,在潮湿气候的厌氧—缺氧环境下,经历海水由浅变深再变浅的沉积过程,洪二段具备烃源岩发育的最佳地质条件。该结果为京西坳陷洪水庄组古气候及古地理的重建和烃源岩的评价提供地质依据。As one of main Mesoproterozoic source rocks in North China,the Hongshuizhuang Formation has great hydrocarbon generation potential.However,the provenance and sedimentary environment are still controversial.Based on the data of trace elements and carbon-oxygen isotopes,we analyzed the geochemical characteristics of Hongshuizhuang Formation in the Zhoukoudian Area of Jingxi Depression and clarified its provenance and sedimentary environment.The results show the Hongshuizhuang Formation in Jingxi Depression is multi-source and the terrigenous contribution is mainly distributed in the second and third member.Among them,the shale is obviously rich in high field strength elements and light rare earth elements,with serious difference between light and heavy rare earth elements,which indicates that the terrestrial clastics of Hongshuizhuang Formation comes from felsic source area of the continental island arc in the Middle Proterozoic Era in North China.During the deposition of the first member of Hongshuizhuang Formation,the Jingxi Depression was in a subhumid climate.The salinity was relatively high,and dolomites was deposited in the shallow water environment of weak oxidation and weak reduction.During the deposition of the second member of Hongshuizhuang Formation,the transgression caused the rising of sea level rise and the extinction of carbonate platform in Jingxi Depression.The felsic clastics were transported to the deep seawater with low salinity,anoxic conditions and moderate stratification and the black shales were deposited in it.The climate of the third member of Hongshuizhuang Formation was similar to the first member.The seawater became salty again but lower than that of the first member and the dolomites interbed with thin shales was deposited in the seawater with weakly oxidation and weakly stratification.Generally speaking,the Hongshuizhuang Formation in the Zhoukoudian Area developed restricted neritic deposits and experienced the deposition process of seawater from shallow to deep and then shallow.The

关 键 词：构造环境 母岩类型 沉积环境 地球化学特征 洪水庄组 周口店地区 京西坳陷 

分 类 号：P595[天文地球—地球化学] TE122.1[天文地球—地质学]