内蒙东部晚古生代构造格局:来自中、晚二叠-早三叠世砂岩碎屑锆石U-Pb年代学的证据

发布时间：2018-04-02 22:01

本文选题：内蒙东部　切入点：中亚造山带　出处：《岩石学报》2016年09期

【摘要】：内蒙东部的克旗-林西-阿鲁科尔沁-扎鲁特-索伦-蘑菇气地区位于华北板块与西伯利亚板块所夹持的中亚造山带东段,西拉木伦缝合带与贺根山-黑河缝合带之间,是古亚洲洋晚古生代残余海盆最后消失的地区,保存了上述两缝合带构造演化过程的相关信息。本文针对中、晚二叠-早三叠世砂岩开展碎屑锆石LA-ICP-MS U-Pb年代学研究。测试的上二叠统林西组与下三叠统陶海营子组、老龙头组砂岩均具有成分成熟度低,近源快速沉积的特点,碎屑骨架成分显示多为火山岩区物源供给。锆石CL图和Th/U值也指示了绝大多数锆石为岩浆成因锆石。结合前人研究成果,区域内已获得的2533粒碎屑锆石U-Pb年龄主要分为3组:约230~570Ma(峰值年龄为270~315Ma、430Ma和500Ma)、700~1100Ma(峰值970Ma)及1500Ma(峰值1800Ma和2500Ma)。较古老的峰值年龄1800Ma和2500Ma,暗示了华北克拉通基底的物源信息。其余两组年龄则与西拉木伦缝合带北侧的额尔古纳-兴安-锡林浩特地块内部岩浆事件的时间相吻合。对比分析内蒙东部不同区域(克旗-林西地区、阿鲁科尔沁-扎鲁特地区和索伦-蘑菇气地区)、不同时代(中、晚二叠世-早三叠世)沉积物碎屑组分变化趋势,推测古亚洲洋最终沿西拉木伦缝合带自西向东呈"剪刀"式闭合,时间持续至早三叠世。此外,索伦-蘑菇气地区中、晚二叠-早三叠世相对稳定的物源供给,证实了额尔古纳-兴安地块与松辽-锡林浩特地块至少在中二叠世沉积以前就已经沿贺根山-黑河缝合带完成拼贴,应为前人提出的早石炭世末。
[Abstract]:The Keqi-Linxi-Arukeqin-Sarut-Sauron-mushroom gas area in eastern Inner Mongolia is located in the eastern segment of the Central Asian orogenic belt between the North China plate and the Siberian plate, and between the West Lamuron suture zone and the Hegen Shan-Heihe suture zone.It is the last area of the Paleo-Paleozoic remnant basin in the Paleo-Asian Ocean, which preserves the relevant information about the tectonic evolution of the two suture zones mentioned above.In this paper, the LA-ICP-MS U-Pb chronological study of detrital zircon has been carried out for the middle and late Permian-early Triassic sandstone.The sandstone of the Upper Permian Linxi formation and the Lower Triassic Taohaiyingzi formation and Laotou formation have the characteristics of low compositional maturity and fast deposition near source. The detrital skeleton compositions are mostly supplied from volcanic rocks.The CL diagram and Th/U values also indicate that the vast majority of zircons are magmatic zircon.Combined with the previous research results, the U-Pb ages of 2533 zircons obtained in the region are divided into three groups: about 230 Ma 570 Ma (peak ages 270 Ma, 315 Ma, 430 Ma and 500 Ma, 700 1 100 Ma (peak 970 Ma) and 1500 Ma (peak 1800Ma and 2 500 Ma), respectively).The older peak ages 1800Ma and 2500 Maindicate the provenance information of the North China Craton basement.The other two ages coincide with the magmatic events in the Erguna-Xin-Xilinhaote massif north of the Silamuron suture belt.The variation trends of detrital components of sediments in different regions of eastern Inner Mongolia (Keqi-Linxi area, Aru Keerqin-Zarut area and Sauron-mushroom gas area) in different ages (middle, late Permian-early Triassic) were compared and analyzed.It is inferred that the Paleo-Asian Ocean was finally closed with scissors from west to east along the West Lamuron suture zone, which lasted until the early Triassic.In addition, the late Permian-early Triassic material supply in the Soren-mushroom gas area was relatively stable.It is confirmed that the Erguna-Xingan block and the Songlio-Xilinhaote block were collaged along the Hegenshan-Heihe suture zone at least before the Middle Permian deposition, which should be the end of the early Carboniferous put forward by the predecessors.
【作者单位】：吉林大学古生物学与地层学研究中心;吉林大学地球科学学院;东北亚矿产资源评价国土资源部重点实验室;太原理工大学地球科学与工程系;
【基金】：科技部“973”项目(2013CB429802) 国家自然科学青年基金项目(41502207、41302175)联合资助
【分类号】：P542;P597.3

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