西拉木伦构造带克德河砂砾岩的时代及构造意义  

The geological age of Kedehe sand-conglomerates on the north of Xar Moron suture zone in the eastern Central Asian Orogenic Belt and its geological significance

作　　者：郑月娟[1,2] 张德军[1,2,3] 张海华 张健[1,2] 陈树旺[1,2] 甄甄[1,2] ZHENG Yuejuan;ZHANG Dejun;ZHANG Haihua;ZHANG Jian;CHEN Shuwang;ZHEN Zhen(Shenyang Center of Geological Survey,China Geological Survey,Shenyang,Liaoning 110034,China;Northeast S&T Innovation Center of China Geological Survey.Shenyang,Liaoning 110034,China;MNR Key Laboratory of Stratigraphy and Palaeontology,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)

机构地区：[1]中国地质调查局沈阳地质调查中心,辽宁沈阳110034 [2]中国地质调查局东北地质科技创新中心,辽宁沈阳110034 [3]自然资源部地层与古生物重点实验室,中国地质科学院地质研究所,北京100037

出　　处：《地质学报》2023年第8期2459-2475,共17页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号42294328014,42172024);国家重点研发计划项目(编号2019YFC0605404);中国地质调查项目(编号DD20230220,DD20230022)联合资助的成果。

摘　　要：内容提要:西拉木伦构造带北部双井地区发育一套巨厚的、低成熟度快速堆积的近源粗碎屑沉积建造,与构造环境紧密相关,前人称其为克德河砂砾岩并将其沉积时代分别划为中二叠统(哲斯组)或上二叠统(林西组)。本次工作对该套地层进行了大比例尺剖面测量,对取自剖面下、中、上(1、25、86层)三个部分的砂岩样品进行LA-ICP-MS U-Pb年代学研究,结果显示:3个样品具有类似的碎屑锆石年龄分布特征,多数测年值集中分布在485~405Ma、463~401 Ma、520~363 Ma区间,其峰值年龄分别为427 Ma、445 Ma、440 Ma,锆石数量分别占总量的48.0%、52.5%和38.8%,其次为大于1000 Ma的年龄,锆石数量分别占30.7%、22.5%、45.0%,且均具有1800Ma和2500Ma左右的峰值年龄,明显具有华北板块基底年龄信息。自下而上3个测年样品最年轻峰值年龄分别为312Ma、376Ma,282Ma,最年轻的锆石年龄分别为304Ma、244Ma和245 Ma。在第85层杂色复成分砾岩的灰岩砾石中发现上石炭统—下二叠统阿木山组的■和珊瑚化石,在41及43层发现中生代孢粉化石。依据碎屑锆石测年数据及生物化石鉴定结果,结合其被晚三叠世岩体侵入接触的地质现象,判断克德河砂砾岩的沉积时代可能为中三叠世。推测西拉木伦构造带经历了一个较长的演化过程,从中二叠世开始华北板块和西伯利亚板块进入碰撞造山阶段,克德河砂砾岩可能是山脉快速隆升、山体遭受强烈剥蚀堆积的产物,据此判断华北板块和西伯利亚板块碰撞拼合造山一直延续到中三叠世才结束。In the Shuangjing area on the north of Xar Moron suture zone,there is a suite of rapid accumulation with low maturity,which were called‘Kedehe conglomerate’and previously divided into Middle Permian(Zhesi Formation)and Late Permian(Linxi Formation)respectively.Based on the previous research results,the authors made an another detailed study on the developed strata of Kedehe conglomerate rocks through field measurement.The results of the study of the LA-ICP-MS U-Pb geochronology of sandstone samples from the 1st,25th and 86th layers of the section showed that they had similar primary age ranges.The age spectrum of detrital zircon falls mainly in three intervals of 485~405 Ma、463~401 Ma、520~363 Ma with peak ages of 427 Ma,445 Ma and 440 Ma,additionally,the zircons accounts for 48.0%,52.5%and 38.8%of the total amount respectively.In the second place,the ages of ca.1800 Ma and ca.2500 Ma are more widely distributed,indicating the information of the North China Plate basement.The youngest peak ages of the three bottom-up dating samples are 312 Ma,376 Ma and 282 Ma,and the youngest zircons are 304 Ma,244 Ma and 245 Ma,respectively.Fossils of fusulinid and coral from the Late Carboniferous to Early Permian Amushan Formation were found in limestone gravel of the 85th layers of the section,and Mesozoic sporopollen fossils recovered from the 41st and 43th layers.According to the fossils and detrital zircon U-Pb age,the age of Kedehe conglomerate rocks can be classified as Middle Triassic.It is speculated that Xar Moron suture zone has experienced a long-time accretion and stitching process.The collisional collapse process between the North China plate and the Siberian plate occurred since the Middle Permian.The Paleo-Asian Ocean finally closed along the Xar Moron suture zone at least until the Middle Triassic,and the Kedehe conglomerate rocks are the product of collision on its both sides.

关 键 词：西拉木伦构造带 克德河砂砾岩 碎屑锆石U-PB年龄 生物化石 中三叠世 

分 类 号：P548[天文地球—构造地质学] P534.51[天文地球—地质学]