浙西北地区上奥陶统物源及古地理意义:来自沉积学、碎屑组成及年代学的证据  

Provenance and Paleogeographic Significance of Upper Ordovician in NW Zhejiang:Evidence from Sedimentology,Clastic Composition and Chronology

作　　者：于涛 王宗起 王东升[3] 刘宣妤 马收先[3] 聂潇 马昌前[5] Yu Tao;Wang Zongqi;Wang Dongsheng;Liu Xuanyu;Ma Shouxian;Nie Xiao;Ma Changqian(Chinese Academy of Geological Sciences,Beijing 100037,China;Development Research Center of China Geological Survey,Beijing 100037,China;MNR Key Laboratory of Metallogeny and Mineral Assessment,Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China;National Engineering Laboratory for Exploration and Development of Low Permeability Oil and Gas Field,Exploration and Development Research Institute of PetroChina Changqing Oilfield Company,Xi’an 710018,China;School of Earth Science,China University of Geosciences,Wuhan 430074,China)

机构地区：[1]中国地质科学院,北京100037 [2]中国地质调查局发展研究中心,北京100037 [3]中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室,北京100037 [4]中国石油长庆油田分公司勘探开发研究院低渗透油气田勘探开发国家工程实验室,陕西西安710018 [5]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学》2023年第10期3649-3670,共22页Earth Science

基　　金：国家自然科学基金项目(No.41902042);战略性矿产重点远景区矿产地质调查(No.DD20221684);浙闽粤火山岩区铜金矿产地质调查(No.DD20201173);国家重点研发计划(No.2016YFC0600202)。

摘　　要：华南板块早古生代构造-沉积演化存在诸多争议.浙西北地区位于毗邻江山-绍兴断裂带的扬子地块,晚奥陶世扬子地块东南缘发生碳酸盐岩与碎屑岩的沉积相转变,其沉积相时空展布与物源分析可为重建扬子地块东南缘古地理格局提供证据.通过沉积相详细解剖,砂岩碎屑组成、重矿物组合、地球化学及碎屑锆石U-Pb年代学分析,综合分析浙西北地区上奥陶统沉积物源,为重建该地区古地理格局及构造演化提供证据.浙西北地区晚奥陶世地层主要由砾岩、瘤状灰岩、砂岩、粉砂岩、泥岩组成,沉积序列、沉积相标志研究表明,研究区沉积于深海斜坡-浅海环境,沉积基底向北西方向倾斜.岩石学特征表明,砂岩以岩屑砂岩和长石岩屑砂岩为主,成分成熟度和结构成熟度较低,主要由石英(29%)、长石(18%)和岩屑(53%)组成.砂岩碎屑及砾石成分为安山岩、流纹岩、凝灰岩、花岗岩、板岩、千枚岩、石英岩、粉砂岩和燧石,表明混合物源的性质.砂岩碎屑重矿物中出现的辉石、铬铁矿、磁铁矿和石榴石颗粒,表明源区岩石含有镁铁质岩石和变质岩.地球化学分析表明,砂岩和粉砂岩沉积于活动陆缘环境,物源具有中酸性岛弧性质.碎屑锆石U-Pb年龄显示812 Ma和460 Ma的混合物源,早古生代物源可与陈蔡群配套.古水流方向指示物源方向为南东,主要来自于岛弧,扬子地块东南缘沉积于活动大陆边缘.There are many controversies about the Early Paleozoic tectono-sedimentary evolution of the South China plate.The NW Zhejiang is located in the Yangtze block adjacent to the Jiangshan-Shaoxing fault zone,where sedimentary facies transformation of carbonate to clastic rocks occurred in SE Yangtze block during the Late Ordovician.The temporal and spatial distribution of sedimentary facies and provenance analysis can provide evidence for the reconstruction of paleogeography of the SE Yangtze block.Based on detailed analyses of sedimentary facies,sandstone clastic composition,heavy mineral assemblage,geochemistry and detrital zircon U-Pb chronology,in this paper it comprehensively analyzes the provenance of the Upper Ordovician in NW Zhejiang,providing evidence for the reconstruction of paleogeography and tectonic evolution of SE Yangtze block.The Late Ordovician strata in NW Zhejiang are mainly composed of conglomerate,nodular limestone,sandstone,siltstone and mudstone.Sedimentary sequence and facies symbol indicate that the study area was deposited in a deep-sea sloped-shallow sea environment,and the sedimentary basement was inclined to NW.The clastic rocks were mainly composed of lithic sandstones and feldspar lithic sandstones with low compositional and structural maturity and were mainly composed of quartz(29%),feldspar(18%)and lithic(53%).Sandstone clasts and gravel are mainly composed of andesite,rhyolite,tuff,granite,slate,phyllite,quartzite,siltstone and chert,indicating a mixed source.The presence of pyroxene,chromite,magnetite and garnet grains indicates that the source rocks contain mafic and metamorphic rocks.The geochemical analysis shows that the sandstones and siltstones were deposited in active continental margin environment,and the provenance is intermediate acid island arc.The detrital zircon U-Pb ages show a mixed source of ca.812 Ma and ca.460 Ma,and the Early Paleozoic provenance can be matched with the Chencai Group.The paleocurrent indicates an SE origin,the provenance comes primarily from the

关 键 词：沉积相 物源 上奥陶统 活动大陆边缘 浙西北地区 地球化学 岩石学 

分 类 号：P534.42[天文地球—古生物学与地层学] P597.3[天文地球—地质学]