西准噶尔晚古生代地壳组成与生长:来自Sr-Nd-Pb同位素填图的证据  

Late Paleozoic crustal composition and growth in West Junggar:Evidence from Sr-Nd-Pb isotopic mapping

作　　者：徐盛林[1] 丁伟翠[1] 陈宣华[1] 李廷栋[2] 韩乐乐 刘勇[2] 马飞宙[4] 王叶 XU Shenglin;DING Weicui;CHEN Xuanhua;LI Tingdong;HAN Lele;LIU Yong;MA Feizhou;WANG Ye(SinoProbe Center,Chinese Academy of Geological Sciences,Beijing 100037 China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037 China;School of Earth Sciences and Resources,China University of Geosciences(Beijing),Beijing 100083 China;China Geological Survey,Beijing100037 China)

机构地区：[1]中国地质科学院深部探测中心,北京100037 [2]中国地质科学院地质研究所,北京100037 [3]中国地质大学(北京)地球科学与资源学院,北京100083 [4]中国地质调查局,北京100037

出　　处：《地学前缘》2022年第2期261-280,共20页Earth Science Frontiers

基　　金：中国地质调查局地质调查项目(DD20160083,DD20221643,DD20221645,DD20221648);科学技术部国家重点研发计划项目(2018YFC0603700);中国地质科学院基本科研业务费专项经费资助项目(JKY202011)。

摘　　要：西准噶尔地区晚古生代岩浆活动剧烈,地壳的垂向和侧向增生显著,地壳生长和演化存在多阶段性。本文重点通过Sr-Nd-Pb同位素填图研究,发现西准噶尔地区ε_(Nd)(t)值为2.29~8.75,(^(87)Sr/^(86)Sr)_(i)值为0.697397~0.708336,(^(206)Pb/^(204)Pb)_(i)值为17.4975~19.0352,整体表现为高正ε_(Nd)(t)、低(^(87)Sr/^(86)Sr)_(i)和年轻的地壳模式年龄特征,源区以古生代新生地壳为主,地幔贡献值整体大于50%,深部地壳几乎不存在古老的结晶基底,可以与区域构造地质、地球物理资料作较好匹配。区域晚古生代主要经历3个时期的造山阶段,分别对应造山带演化的第一阶段(中晚石炭世,岛弧为代表的侧向生长为主)、第二阶段早期(晚石炭世—早二叠世,后碰撞阶段的垂向生长为主)和第二阶段晚期(早二叠世—早三叠世,壳幔混源背景下的垂向生长),区域造山作用结束于早三叠世。The West Junggar region has experienced intense Late Paleozoic magmatic activity,where vertical and lateral crustal accretion is significant and crustal growth and evolution is multi-stage.Focusing on Sr-Nd-Pb isotopic mapping,this study found that the West Junggar region has the isotopic characteristics of high positiveε_(Nd)(t)value of 2.29-8.75,low(^(87)Sr/^(86)Sr)_(i) ratio of 0.697397-0.708336,and(^(206)Pb/^(204) Pb)_(i) ratio of 17.4975-19.0352;it has a young crustal model age by calculation.The source area is dominated by Paleozoic new crust,with mantle contribution greater than 50%,and there is almost no old crystalline basement in the deep crust,which is in agreement with regional tectonic geological and geophysical data.The West Junggar region mainly experienced three orogenic stages in the Late Paleozoic:arc-dominated lateral growth in the Middle-Late Carboniferous;post-collision vertical growth in the Late Carboniferous-Early Permian;and vertical growth in the Early Permian-Triassic with crust-mantle mixed source.Regional orogenesis ends in the Early Triassic.

关 键 词：晚古生代 同位素填图 地壳组成 地壳生长 造山演化 西准噶尔 

分 类 号：P542[天文地球—构造地质学] P597[天文地球—地质学]