额济纳旗地区晚石炭-晚二叠世地层沉积学和年代学研究及其构造背景分析  

Sedimentary and geochronology study on the Late Carboniferous-Late Permian strata from Ejin Banner area and its tectonic setting

作　　者：杜一滨 张焱杰 徐备 杨振宁 王志伟 王智慧 DU YiBin;ZHANG YanJie;XU Bei;YANG ZhenNing;WANG ZhiWei;WANG ZhiHui(Key Laboratory of Regional Geology and Mineralization,Hebei GEO University,Shijiazhuang 050031,China;College of Resources,Hebei GEO University,Shijiazhuang 050031,China)

机构地区：[1]河北地质大学区域地质与成矿作用重点实验室,石家庄050031 [2]河北地质大学资源学院,石家庄050031

出　　处：《岩石学报》2020年第4期1253-1273,共21页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41672214、41802053);中国地质调查局项目(DD20189612、DD20190004)联合资助.

摘　　要：对额济纳旗地区红石山-额济纳旗坳陷带和马鬃山-切刀隆起带晚石炭世-晚二叠世地层进行了沉积学和年代学研究。红石山-额济纳旗坳陷带的大狐狸山地区干泉组下段碎屑岩可分为滨海相、前三角洲相和三角洲前缘相等三种沉积相类型,具有向上粒度变粗的特征,表明该带属于以三角洲快速供应为主的滨海带沉积环境。碎屑锆石年代学分析表明其形成时代为322~305Ma,主要集中在428~520Ma和336~373Ma两个时期,分别代表红石山-额济纳旗坳陷带边缘古亚洲洋俯冲及其结束后早石炭世伸展过程的两期岩浆活动记录。马鬃山-切刀隆起带的八道桥地区二叠系由巨厚的紫红色砾岩、砂岩重复组成多个旋回,沉积及层序特征表明该套地层形成于干旱条件下的快速沉积,属陆相洪冲积环境产物,沉积时代为280~268Ma。碎屑锆石年龄谱也记录了早古生代岩浆活动峰期(424~515Ma)和古老基底年龄(950Ma和1700~1900Ma)。阿拉善旗埋汗哈达地区埋汗哈达组从下向上分为洪冲积相、滨海泻湖相和滨海相等三种沉积相,构成从陆相到海相变化的沉积序列,形成时代为279~270Ma。该组的碎屑锆石分析主要记录了三个连续的峰期年龄即280Ma、287Ma和294Ma,说明早二叠世发生频繁的岩浆活动。沉积学及年代学研究揭示哈尔苏海组为滨海环境,形成于晚二叠世,其碎屑锆石年龄分布广泛,除273~329Ma的年龄代表晚石炭世-中二叠世岩浆活动外,其余锆石集中在383Ma、468~517Ma、800~913Ma和1485Ma等四个峰期,表明马鬃山-切刀隆起带在晚二叠世接受了来自早古生代造山带和古老基底的复杂物源。八道桥及埋汗哈达地区的研究揭示晚二叠世马鬃山-切刀隆起带的古地理环境为从陆相到滨海相。上述沉积学和年代学分析表明额济纳旗地区红石山-额济纳旗坳陷带和马鬃山-切刀隆起带对沉积环境和古地理格局有关键控制作用�Sedimentology and geochronology study for the Late Carboniferous-Late Permian strata in Ejin Banner area has been carried out.The clastic rocks in the lower part of the Ganquan Formation in the Hongshishan-Ejin Banner sag belt can be divided into three sedimentary facies types:coastal,pre-delta and delta front facies,indicating that this sag belt belongs to a coastal sedimentary environment dominated by rapid supply of delta.The geochronology of detrital zircons shows that the Ganquan Formation was formed between 322Ma and 305Ma.With an age range of 322~801Ma of the detrital zircons,the age peaks of 428~520Ma and 336~373Ma represent two records of magmatic activities of the Early Paleozoic subduction of the Paleo-Asian Ocean and the Early Carboniferous extension in the Hongshishan-Ejin Banner sag belt,respectively.The Permian in Badaoqiao area of the Mazongshan-Qiedao uplift belt is composed of thick purplish conglomerate and sandstone.The sedimentary and sequence characteristics indicate that these clastic rocks formed in a rapid deposition during arid climate conditions,belonging to the continental flood alluvial environment.Detrital U-Pb zircon dating limited the depositional age of the Badaoqiao Formation between 280Ma and 268Ma.The Early Paleozoic(412~515Ma)and Precambrian(950Ma and 1700Ma)detrital zircons from this formation were derived from ancient basement.The Maihanhada Formation is divided into three sedimentary facies from bottom to top:flood alluvial,coastal lagoon and coastal facies.The youngest ages of detrital zircons are 279~270Ma in the Maihanhada Formation including three consecutive peak ages of 280Ma,287Ma and 294Ma,indicating that there was frequent magmatic activities in the Early Permian.The Late Permian Haersuhai Formation was formed in a coastal environment and analysis of the detrital zircons in it exhibits ages of 273~329Ma,which records the Late Carboniferous to Permian magmatism.Other ages of 383Ma,468~517Ma,800~913Ma and 1485Ma represent complex sources from the Early Paleozoic orog

关 键 词：沉积古地理 地质年代学 晚石炭世-晚二叠世 额济纳旗地区 

分 类 号：P531[天文地球—古生物学与地层学] P597.3[天文地球—地质学]