湖北鹤峰走马镇地区牛蹄塘组岩石地球化学特征:物源、古风化、沉积环境和构造背景  

Geochemical Characteristics of Niutitang Formation in Zoumazhen Area,Hefeng,Hubei Province:Provenance,Paleoweathering,Sedimentary Environment and Tectonic Setting

作　　者：何谋惷[1,2] 丁振举 王翔[3] 万禹 He Mouchun;Ding Zhenju;Wang Xiang;Wan Yu(School of Earth Resources,China University of Geosciences,Wuhan 430074,China;National Demonstration Center for Experimental Mineral Exploration Education,China University of Geosciences,Wuhan 430074,China;Hubei Branch of China National Geological Exploration Center of Building Materials Industry,Wuhan 430070,China;Institute of Seismology,China Earthquake Administrator,Wuhan 430071,China)

机构地区：[1]中国地质大学资源学院,湖北武汉430074 [2]中国地质大学固体矿产勘查国家级实验教学示范中心,湖北武汉430074 [3]中国建筑材料工业地质勘查中心湖北总队,湖北武汉430070 [4]中国地震局地震研究所,湖北武汉430071

出　　处：《地球科学》2023年第9期3280-3295,共16页Earth Science

基　　金：中国地质调查局项目(No.12120114016601).

摘　　要：鹤峰地区位于湘西‒鄂西地区层控铅锌多金属成矿带内,不仅是我国“扬子型”铅锌矿床重要产区之一,也是我国页岩气资源重要的远景区,为了探讨区内分布的寒武系下统牛蹄塘组黑色岩系沉积物物质来源及其成熟度、古风化特征、沉积环境以及岩石形成的构造环境,对产于鹤峰县走马镇地区下寒武统牛蹄塘组中下部的黑色岩系开展了岩石学和岩石化学成分分析,结果显示:走马镇地区牛蹄塘组岩石的主量元素含量变化比较大,上下不同层位样品化学成分相差较大,其中下部地层除了SiO_(2)和P_(2)O_(5)含量高于PAAS值外,其他组分均低于PAAS值.强烈富集U、Cr,而亏损Th,具有较高的Ni/Co值和较低的V/Cr值.REE总量略高于PAAS,具有明显的Ce负异常和弱‒微弱的Eu负异常以及略偏大的Y/Ho比值.而上部地层中Al_(2)O_(3)含量明显高于下部地层,与PAAS相比,除了SiO_(2)和Na_(2)O略微富集外,其他组分全部亏损.强烈富集V、U和Ba,明显亏损Zn、Th、Ni和Rb,Ni/Co比值低而V/Cr比值高且变化范围大.REE总量与下部地层相差不大,弱‒微弱的Ce和Eu的负异常,Y/Ho比值比下部地层更接近火成岩和陆源碎屑岩值.结果表明该套岩石为陆源碎屑岩和中性火山岩,在潮湿‒半干旱的气候条件下经过强烈的风化作用,沉积于被动大陆边缘构造环境下的缺氧‒贫氧、局部贫氧‒次氧化的海水中,有热水沉积物的参与.The Hefeng area is located in the stratabound-type Pb-Zn polymetallic metallogenic belt in the junctional zone between western Hunan and western Hubei.It is not only one of the important producers of“Yangtze-type”Pb-Zn deposits,but also an important prospecting area of shale gas resources in China.In order to discuss the provenance,paleoweathering,sedimentary environment and tectonic setting of the Niutitang Formation,the petrology and petrochemistry of the black rock series in the middle and lower part of the Niutitang Formation in Zouma Town of Hefeng County are analyzed.The contents of major elements in the rock vary significantly,and the chemical composition of the samples from different layers is quite different.Except for SiO_(2)and P_(2)O_(5),most of the compositions in the lower layer are lower than the PAAS value.The rocks are strongly enriched in U and Cr,but depleted in Th.They have high Ni/Co ratios and low V/Cr ratios.The total amount of REE is slightly higher than that of PAAS,with obvious Ce negative anomaly,weak Eu negative anomaly,and slightly larger Y/Ho ratio.The content of Al_(2)O_(3) in the upper stratum is significantly higher than that in the lower strata.Compared with PAAS,most of the components are depleted except SiO_(2)and Na_(2)O.The rocks are strongly enriched in V,U,and Ba,obviously depleted in Zn,Th,Ni,and Rb,with low Ni/Co ratios and high V/Cr ratios.The content of the total amount of REE is similar to that of the lower strata with the weak negative anomalies of Ce and Eu,and the Y/Ho ratios are similar to the values of igneous and terrigenous clastic rocks.It is considered that the Niutitang Formation were originated from terrigenous clastic rocks and neutral volcanic rocks,which have undergone strong weathering under humid to semi-arid climatic conditions,and were deposited in the palaeogeographic anoxic/dysoxic environment in the passive continental margin setting.

关 键 词：牛蹄塘组 岩石学 地球化学 物源 沉积环境 构造背景 鄂西鹤峰 

分 类 号：P53[天文地球—古生物学与地层学]