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湘西下寒武统牛蹄塘组地球化学特征及其对沉积-构造环境的响应 被引量:4

Geochemical Characteristics and Sedimentary Tectonic Setting of the Lower Cambrian Niutitang Formation in Western Hunan Province
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摘要 为深入探讨湘西地区下寒武统牛蹄塘组黑色岩系沉积-构造环境,对三岔剖面黑色岩系进行了详细采样测试,并重点分析了主量、微量及稀土元素地球化学特征。研究结果表明,牛蹄塘组黑色岩系不仅有机碳含量高,而且相比于北美页岩更富集V、Ni、Cr等微量元素。δ^(13) C_(org)及微量元素判别指标V/(V+Ni)、V/Cr、Ni/Co、δU、Ce/La、Ce_(anom)等特征的变化均反映牛蹄塘组沉积期水体属缺氧还原的浅水环境,且Mo/TOC与U_(EF)-Mo_(EF)协同模式表明沉积区当时为一局限海盆环境。稀土元素(REE)中轻稀土相对重稀土富集,且北美页岩标准化分布模式呈近水平略微左倾状,结合元素比值特征和La/Yb-Ce/Yb、La/Yb-ΣREE图解,牛蹄塘组黑色岩系的母岩以长英质岩石为主,但沉积过程也受到海底热液作用影响。同时,根据δCe、δEu的特征与K_(2)O/Na_(2)O-SiO_(2)图解,认为沉积区在早寒武世为被动大陆边缘构造背景。 The purpose of this work is to further explore the sedimentary tectonic environment of the black rock series of the Lower Cambrian Niutitang Formation in the Early Cambrian System of western Hunan Province.Detailed sampling and tests were performed on such rock series in the Sancha section,and geochemical characteristics of major,trace,and rare earth elements of these rocks were analyzed.The results show that the Niutitang Formation has a high organic carbon content,and more trace elements such as V,Ni,and Cr than the shale in North America.Variations of δ^(13)C_(org) and trace element identification indicators V/(V+Ni),V/Cr,Ni/Co,δU,Ce/La,and Ce anom reflect that the water mass of the Niutitang Formation was in an anoxic reduction state.And both the Mo/TOC and U_(EF)-Mo_(EF) synergistic models suggest that the sedimentary area was a limited basin environment during that time.LREE in rare earth elements(REE)are relatively rich compared with HREE,and the NASC-normalized pattern is slightly left-inclined.Combined with geochemical element ratio characteristics,La/Yb-Ce/Yb,and La/Yb-ΣREE diagrams,the source rock of the Niutitang Formation is dominated by felsic rocks,but the deposition process was affected by hydrothermal fluid.In the meantime,according to the characteristics of δCe,δEu and K_(2)O/Na_(2)O-SiO_(2) diagrams,the sedimentary area is considered to be a passive continental margin tectonic setting in the Early Cambrian.
作者 吴育平 刘成林 龚宏伟 柳永军 Awan Rizwan Sarwar 阳宏 曾晓祥 WU Yuping;LIU Chenglin;GONG Hongwei;LIU Yongjun;AWAN Rizwan Sarwar;YANG Hong;ZENG Xiaoxiang(State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum(Beijing),Beijing 102249;College of Geosciences,China University of Petroleum(Beijing),Beijing102249;SIOPEC Dongsheng Petroleum Development Group Co Ltd ofShengli Oilfield,Dongying,Shandong 257000)
出处 《地质与勘探》 CAS CSCD 北大核心 2021年第5期1065-1076,共12页 Geology and Exploration
基金 国家自然科学基金项目(编号:41572099、41872127)资助。
关键词 地球化学 沉积环境 构造背景 牛蹄塘组 湘西地区 geochemistry sedimentary environment tectonic setting Niutitang Formation western Hunan Province
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