内蒙古狼山宝音图群变沉积岩碎屑锆石年代学特征:华北北缘西段中-新元古代构造演化记录  

Detrital zircon geochronology of the metasedimentary rock in the Baoyintu Group from Langshan,Inner Mongolia:Implications of the tectonic evolution in the western segment of the northern margin of the North China during Meso-Neoproterozoic

作　　者：唐爽 张晋瑞 初航 魏春景[3] 卞昊达 TANG Shuang;ZHANG JinRui;CHU Hang;WEI ChunJing;BIAN HaoDa(College of Earth Sciences,Jilin University,Changchun 130061,China;Tianjin Center,China Geological Survey(North China Center for Geoscience Innovation),Tianjin 300170,China;School of Earth and Space Sciences,Peking University,Beijing 100871,China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]中国地质调查局天津地质调查中心(华北地质科技创新中心),天津300170 [3]北京大学地球与空间科学学院,北京100871

出　　处：《岩石学报》2024年第11期3568-3585,共18页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42072073、41702049);国家重点研究发展计划项目(2021YFA0715104)联合资助.

摘　　要：宝音图群分布于内蒙古中西部狼山的格尔敖包沟、宝音图、巴音前达门和图古日格一带,构造位置处于华北克拉通、阿拉善地块和中亚造山带的交界部位,主要由云母片岩、石英岩、变基性岩和大理岩组成。关于宝音图群的沉积时代下限和物源亲缘性一直存在争议。本文对狼山地区宝音图群不同地区碎屑锆石进行了LA-ICP-MS U-Pb定年分析。结果显示,宝音图群变沉积岩中的碎屑锆石多为岩浆锆石,多数发育变质增生边,其中格尔敖包沟地区碎屑锆石呈现5个主峰值年龄段(950Ma、1300Ma、1500Ma、1800Ma和2500Ma附近)和2个次峰值年龄段(720Ma和2100Ma附近),最年轻的碎屑锆石谐和年龄为700±8Ma,形成于新元古代,可以代表宝音图群最大沉积年龄,是目前发现的宝音图群最年轻碎屑锆石。获各琦地区碎屑锆石呈现2个主峰值年龄段(1500Ma和1700Ma附近)和3个次峰值年龄段(840Ma、1300Ma和1900Ma附近)。宝音图地区碎屑锆石呈现1个主峰值年龄段(1700Ma附近)和4个次峰值年龄段(840Ma、1000Ma、1400Ma和2200Ma附近)。巴音前达门地区碎屑锆石呈现3个主峰值年龄段(1800Ma、1900Ma和2500Ma附近)和3个次峰值年龄段(770Ma、970Ma和1300Ma附近)。帮帮敖瑞地区碎屑锆石呈现3个主峰值年龄段(920Ma、1200Ma和1500Ma附近)和1个次峰值年龄段(710Ma附近)。图古日格地区碎屑锆石呈现1个主峰值年龄段(1900Ma附近)和5个次峰值年龄段(1100Ma、1300Ma、2300Ma、2500Ma和3100Ma附近)。通过碎屑锆石年龄图谱对比及年龄χ2分布分析发现,宝音图群变沉积岩原岩整体都沉积于离散背景中,狼山北部的宝音图群变沉积岩(图古日格和巴音前达门地区)的物源来自于华北克拉通,可能记录了哥伦比亚超大陆裂解事件;狼山西南部的宝音图群变沉积岩(格尔敖包沟、帮帮敖瑞、获各琦和宝音图地区)的物源来自于阿拉善地块,可能记录了罗迪尼亚超大陆的The Baoyintu Group is distributed in Langshan region,central western Inner Mongolia,specifically along Geeraobao Valley,Baoyintu,Bayinqiandamen,and Tugurige areas.The tectonic location of this group is at the junction of the North China Craton(NCC),the Alxa Block and the Central Asian Orogenic Belt.The Baoyintu Group mainly comprises mica schists,quartzites,metabasic rocks and marbles.There has been considerable debate regarding the specific sedimentary age and the provenance affinity of the Baoyintu Group.In this study,we conducted LA-ICP-MS U-Pb dating analysis on detrital zircons from the Baoyintu Group in different areas of Langshan.The results indicate that most detrital zircons in the metasedimentary rocks of the Baoyintu Group are magmatic zircons,and most of them with metamorphic overgrowths.At Geeraobao Valley,detrital zircons exhibit five primary age peaks(ca.950Ma,1300Ma,1500Ma,1800Ma and 2500Ma)and two secondary peaks(ca.720Ma and 2100Ma).The youngest concordant age of the detrital zircons is 700±8Ma,belonging to the Neoproterozoic,which represents the maximum depositional age of the Baoyintu Group and is currently the youngest detrital zircon found in the Baoyintu Group.At Huogeqi,detrital zircons exhibit two primary age peaks(ca.1500Ma and 1700Ma)and three secondary peaks(ca.840Ma,1300Ma and 1900Ma).At Baoyintu,there is one main age peak(ca.1700Ma)and four secondary peaks(ca.840Ma,1000Ma,1400Ma and 2200Ma).At Bayinqiandamen,detrital zircons exhibit three main primary peaks(ca.1800Ma,1900Ma and 2500Ma)and three secondary peaks(ca.770Ma,970Ma and 1300Ma).At Bangbangaorui,there are three primary age peaks(ca.920Ma,1200Ma and 1500Ma)and one secondary peaks(ca.710Ma).At Tugurige,detrital zircons exhibit one main age peak(ca.1900Ma)and five secondary peaks(ca.1100Ma,1300Ma 2300Ma,2500Ma and 3100Ma).By comparing detrital zircon age spectra and analyzing chi square distribution of the age,we suggest that the protolith of the metasedimentary rocks of the Baoyintu Group was deposited in an extensional settin

关 键 词：变沉积岩 碎屑锆石 沉积构造属性 宝音图群 狼山 

分 类 号：P542[天文地球—构造地质学] P597.3[天文地球—地质学]