太康隆起上古生界稀土元素地球化学特征及其地质意义  

Geochemical characteristics of Upper Paleozoic mudstone in southern North China Basin and their geological significances

作　　者：曾秋楠[1,2] 张交东 于炳松 刘旭锋[2] 周新桂 ZENG Qiunan;ZHANG Jiaodong;YU Bingsong;LIU Xufeng;ZHOU Xingui(China University of Geosciences(Beijing),Beijing 100083,China;Oil and Gas Survey,China Geology Survey,Beijing 100083,China)

机构地区：[1]中国地质大学(北京),北京100083 [2]中国地质调查局油气资源调查中心,北京100083

出　　处：《海洋地质与第四纪地质》2020年第3期132-143,共12页Marine Geology & Quaternary Geology

基　　金：国家重大科技专项“大型油气田和煤层气开发”下属课题4任务6“南华北地区海陆交互相页岩气勘查评价应用试验”(2016ZX05034004-006);地质调查项目“南华北盆地上古生界油气地质调查”(DD20190095)。

摘　　要：南华北盆地晚古生代海陆交互相暗色泥岩较为发育,是该区主要烃源岩层系之一。本文采用电感耦合等离子体质谱仪和X射线荧光光谱(XRF)对太康隆起西部地区上古生界本溪组、太原组、山西组和下石盒子组28件暗色泥岩、粉砂质泥岩样品进行了稀土元素和微量元素测试,基于稀土元素的稳定性和其对沉积水体变化的高敏感度,结合泥岩有机碳含量及宏观沉积特征,探讨太原组、山西组古沉积环境及其对有机质富集的影响。分析结果表明,太康隆起地区太原组和山西组稀土元素总量高,轻、重稀土元素分异程度相近,明显高于本溪组和下石盒子组,同时山西组具有较弱的Ce负异常和较强的Eu负异常。Ce异常表明本溪组至下石盒子组整体形成于缺氧的还原环境。ΣREE和TOC在垂向上的变化表明古气候条件经历了由干冷向温湿的转变,沉积速率先降低再增大,太原期沉积水体深,沉降速率低,环境稳定,对有机质的富集和保存有着重要的地质意义。Marine and continental alternative shale of Upper Paleozoic is important as a source rock in southern North China Basin.In this paper,twenty-eight mudstone and silty mudstone samples collected from Upper Paleozoic Benxi,Taiyuan,Shanxi and Xiashihezi Formations on Taikang Uplift,southern North China Basin were analyzed for REEs and trace elements,by means of ICP-MS and XRF to investigate the characteristics of paleoenvironment and their effect on the enrichment of organic matters.The result shows that mudstone in Taiyuan and Shanxi Formations,especially the latter,has similar features of obvious Eu-anomalies and weak Ce-anomalies,higher total REE contents and higher fractionation between LREE and HREE compared with samples from the Benxi and Xiashihezi Formations.The Ce abnormity,which can be used to reveal redox of lake water,shows that the studied samples are mainly formed in a hypoxic reducing environment.Vertical distribution ofΣREE and TOC suggests a change of climate from cold-arid to warm-humid,and a variation of sedimentation rate of mudstone from high to low to high.Among the four studied Formations,the Taiyuan Formation is the one with a stable sedimentary environment of deep water and low sedimentation rate,which benefits the accumulation and preservation of organic matters.

关 键 词：稀土元素 上古生界 古环境 南华北盆地 

分 类 号：P736.4[天文地球—海洋地质]