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大兴安岭中北段原岩锆石U-Pb测年及其与区域构造演化关系
引用本文:佘宏全,李进文,向安平,关继东,杨郧城,张德全,谭刚,张斌.大兴安岭中北段原岩锆石U-Pb测年及其与区域构造演化关系[J].岩石学报,2012,28(2):571-594.
作者姓名:佘宏全  李进文  向安平  关继东  杨郧城  张德全  谭刚  张斌
作者单位:1. 中国地质科学院矿产资源研究所,北京,100037
2. 内蒙古自治区第六地质矿产勘查开发院,海拉尔,021008
基金项目:本文受"十一五"国家科技支撑计划项目(2006BAB01A10)和国家地质调查项目(1212011120992)联合资助.
摘    要:作者认为单个锆石的同位素年龄记录了所在区域单次构造、岩浆或变质事件活动的时间,不同来源的大量原岩单颗粒锆石的测年数据则可以反映研究区总体构造演化历史。本文对近年来在大兴安岭中北段自测和收集的123件原岩样品的2636个锆石U-Pb测年点的同位素年龄进行统计,结果显示研究区的锆石年龄数据总体上出现840~780Ma, 530~440Ma, 330~280Ma, 240~190Ma,180~160Ma和150~120Ma等多个明显高峰值区间和>840Ma, 770~540Ma和440~400Ma三个相对数据较少的空白地段,且岩浆结晶锆石、变质锆石、继承性锆石等不同成因类型的锆石的年龄统计分布有良好的对应性。年龄数据的高峰值区间与该地区基底形成、陆壳生长、主要板块或微板块俯冲、碰撞、拼贴等主要构造事件时间吻合;而年龄空白区间则与主要的洋底扩张、被动陆缘时代相吻合。研究说明大量原岩锆石的测年数据与河流碎屑锆石同位素年代学一样,可以用于研究物源区的地壳生长和构造演化历史。综合大兴安岭中北段大量单颗粒锆石的同位素年代学、岩石组合和构造特征研究,说明该地区经历了古元古代基底形成、新元古代陆壳生长、新元古代末期板块裂解,古生代期间古陆块间的俯冲、拉张、拼贴碰撞,早中生代碰撞造山、晚中生代造山后伸展垮塌、大陆边缘弧后伸展等复杂的构造演化历史;同时表明蒙古-鄂霍茨克洋在早中生代时期(晚三叠世)即已碰撞造山,大兴安岭中北段及额尔古纳地区发育大量与碰撞有关的花岗岩、混合岩及碰撞后伸展跨塌有关的构造和岩石产物(盆岭构造、滑脱构造、变质核杂岩、陆相双峰式火山岩和多金属成矿等),这对于重新认识研究区中生代多金属成矿的地球动力学背景提供了新的依据。

关 键 词:大兴安岭  锆石  U-Pb同位素测年  花岗岩  构造演化  陆陆碰撞
收稿时间:2011/10/1 0:00:00
修稿时间:2012/1/10 0:00:00

U-Pb ages of the zircons from primary rocks in middle-northern Daxinganling and its implications to geotectonic evolution
SHE HongQuan,LI JinWen,XIANG AnPing,GUAN JiDong,YANG YunCheng,ZHANG DeQuan,TAN Gang and ZHANG Bin.U-Pb ages of the zircons from primary rocks in middle-northern Daxinganling and its implications to geotectonic evolution[J].Acta Petrologica Sinica,2012,28(2):571-594.
Authors:SHE HongQuan  LI JinWen  XIANG AnPing  GUAN JiDong  YANG YunCheng  ZHANG DeQuan  TAN Gang and ZHANG Bin
Institution:Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;The Sixth Institute of Geology and Mineral Resources Development, Inner Mongolia Autonomous Region, Hailaer 021008, China;Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China
Abstract:The age of single zircon is thought to be the recording of single tectonic, magmatic or metamorphism activity, the ages of a large amount of zircons got from different types of primary rocks should be able to indicate the geotectonic evolution history. The authors of the paper collected 2636 zircon ages determined by U-Pb dating from 123 samples in middle-northern Daxinganling, dated by authors or gatherd from published data, the statistics on these data has shown that the zircon ages have several peak value ages of 840~780Ma, 530~440Ma, 330~280Ma, 240~190Ma, 180~160Ma and 150~120Ma, and three blank time space of >840Ma, 770~540Ma, 440~400Ma. The ages of different types zircons generated by magmatism, metamorphism, or that inherited from former rocks have similar statistics features. The peak value of zircon ages has a good accordance with the time that important tectonic event took place in middle-northern Daxinganling Mountains, such as, the formation of basement, mircoplate subduction and collision. The blank period of zircon ages is corresponded to that of ocean spread or passive continental margin event. It is concluded that a large amount of zircon ages determined by U-Pb dating method for primary rocks also can be applied to study the geotectonic evolution history, just like the zircon ages from rivers detrita. Study on the statistics on zircon ages, granite association and tetonics indicates a very complicated tectonic evolution history has been taken place in middle-northern Daxinganling Mountain, that is, the formation of basement in Plaeoprotozoic, growth of continental crust in Neoprotozoic, breakdown of plate in the end of Neoprotozoic, subdution, spreading, accretion and collision between miroplates in Paleozoic, continental collision in Early Mesozoic, postorogenic extension and collapse in Late Mesozoic related to the Mongolia-Okhotsk orogeny and continental marginal tectonic-magmatic event related to the subdution of West Pacific Ocean in Mesozoic. The study has also shown that the Mongol-Okhostsk Ocecn has been closed in Late Triassic Period in Transbakal area. There is a large amount of granites, migmatites related to continental collision, and metaomorphic complex, basin-range, continental bimodal volcanic rocks related to postorogenic collapse, occurred in middle-northern Daxinganling. It is suggesting that the geodynamic background for the polymetal mineralizaton in the area need to be reconsidered.
Keywords:Daxinganling  Zircon  Isotope dating  Granite  Geotectonic evolution  Continental collision
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