上扬子地区两条下寒武统底部剖面的差异及其对沉积环境的启示  

Variations Between Two Lower Cambrian Prof iles in the Upper Yangtze Region and Their Implications for Depositional Environments

作　　者：王国志 张灿 刘大永[1,2] 邱林飞 李子颖[5] 彭平安[1,2,3] WANG Guozhi;ZHANG Can;LIU Dayong;QIU Linfei;LI Ziying;PENG Ping’an(State Key Laboratory of Organic Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China;CAS Center for Excellence in Deep Earth Science,Guangzhou 510640,China;University of Chinese Academy of Sciences,Beijing 100049,China;Zhaoqing Real Estate Registration Center,Zhaoqing 526199,China;Beijing Research Institute of Uranium Geology,China National Nuclear Corporation,Beijing 100029,China)

机构地区：[1]有机地球化学国家重点实验室,中国科学院广州地球化学研究所,广州510640 [2]中国科学院深地科学卓越创新中心,广州510640 [3]中国科学院大学,北京100049 [4]肇庆市不动产登记中心,肇庆526199 [5]核工业北京地质研究院,北京100029

出　　处：《高校地质学报》2024年第6期660-667,共8页Geological Journal of China Universities

基　　金：国家自然科学重点基金“砂岩型铀矿铀及伴生元素与有机质迁移富集机理”(U2167210)资助。

摘　　要：选择贵州遵义松林黑砂坡采石场剖面和渝东南酉阳丹泉采石场剖面,系统采集了下寒武统牛蹄塘组底部富有机质富微量金属元素的页岩样品,进行有机地球化学、矿物学及主微量元素测试。结果表明虽然两个剖面的直线距离约300公里,但同处于上扬子地台,可以进行对比研究。根据两条剖面垂向有机质丰度、有机质碳同位素以及主、微量元素丰度等各参数的垂向变化及差异性,可判定两个剖面位于不同的陆架坡折位置。同松林剖面相比,丹泉剖面样品总体距物源区更近,碎屑输入通量更高。虽然两条剖面自牛蹄塘组底部向上不到9 m的范围内出现多次沉积环境的变化,但总体随海平面上升,两个剖面沉积环境趋同。两条剖面页岩有机质丰度(TOC)和有机质碳同位素(δ^(13)C_(org))与某些和热液关系密切的微量元素(如As、Ni、Sb)之间的关系表明有机质对微量元素的吸附是松林剖面牛蹄塘组底部微量元素富集的主要机制;而同沉积热液流体的混合是丹泉剖面牛蹄塘组底部微量元素富集的主要机制。Sampling of two quarry sections occurred at Zunyi,Guizhou,and Youyang,southeastern Chongqing.These samples were systematically collected from organic-rich,polymetal-enriched shales at the base of the Lower Cambrian Niutitang Formation.Analysis encompassed organic geochemistry,mineralogy,and major and trace element compositions.Despite being approximately 300 kilometers apart,both sections are situated within the Upper Yangtze Platform,facilitating comparative study.Vertical variations in TOC,δ13Corg,and major and trace element abundances suggest that these sections occupy distinct positions on the continental shelf slope.Compared to the Songlin section,samples from the Danquan section indicate proximity to the source area,characterized by higher clastic input fluxes.Although multiple depositional environment changes occurred within less than a 9-meter range from the Niutitang Formation’s base upwards in both sections,the depositional environments tended to converge with rising sea levels.The relationship between shale organic matter abundance(TOC),organic carbon isotopes(δ^(13)C_(org)),and certain trace elements associated with hydrothermal activity(e.g.,As,Ni,Sb)in both sections indicates different mechanisms for trace element enrichment.In the Songlin section,organic matter adsorption primarily drives trace element enrichment at the Niutitang Formation’s base,whereas in the Danquan section,mixing with codepositional hydrothermal fluids is the primary mechanism.

关 键 词：上扬子地区 牛蹄塘组 沉积环境 热液流体 有机质碳同位素 金属元素 

分 类 号：P588.2[天文地球—岩石学]