辽北地区早-中二叠世变质火山-碎屑岩年代学和地球化学特征:对华北板块北缘东段构造演化的启示  

Geochronology and geochemistry of the Early-Middle Permian metamorphic volcano-clastic rocks,northern Liaoning Province:Implications for the tectonic evolution of the eastern segment of the northern margin of the North China Craton

作　　者：张丽 刘永江[4,5] 张超 刘晓燕[1,3] 李伟民 葛锦涛[2] 梁琛岳 赵英利[6] ZHANG Li;LIU YongJiang;ZHANG Chao;LIU XiaoYan;LI WeiMin;GE JinTao;LIANG ChenYue;ZHAO YingLi(Gollege of Earth Sciences,Institute of Disaster Prevention,Sanhe 065201,China;Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China;Hebei Key Laboratory of Earthquake Dynamics,Sanhe 065201,China;Frontiers Science Center for Deep Ocean Multispheres and Earth System,Key Lab of Submarine Geoscience and Prospecting Techniques,College of Marine Geosciences,Ocean University of China,Qingdao 266100,China;Laboratory for Marine Mineral Resources,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266237,China;College of Earth Sciences,Jilin University,Changchun 130061,China)

机构地区：[1]防灾科技学院地球科学学院,三河065201 [2]中国地质调查局沈阳地质调查中心,沈阳110034 [3]河北省地震动力学重点实验室,三河065201 [4]深海圈层与地球系统前沿科学中心,海底科学与探测技术教育部重点实验室,中国海洋大学海洋地球科学学院,青岛266100 [5]青岛海洋科学与技术国家实验室海洋矿产资源评价与探测技术功能实验室,青岛266237 [6]吉林大学地球科学学院,长春130061

出　　处：《岩石学报》2022年第8期2510-2538,共29页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(42130305、42102259、42102271);中央高校基本科研业务费专项资助项目(ZY20220212);中国地质调查局项目(DD20190042-03、DD20221632-02);国家重点研发计划项目(2017YFC0601300-01)联合资助。

摘　　要：新识别的“下二台”构造杂岩作为华北板块北缘东段分布的构造混杂岩带重要组成部分,其物质组成、形成时代和构造属性仍需进一步研究,这将为探讨华北板块北缘东段晚古生代构造演化提供重要依据。作者在“下二台”构造杂岩中识别出一套早-中二叠世变质火山-碎屑岩,其以变质碎屑岩为主,并夹变质火山岩,二者在野外产出上混杂在一起。变质火山岩原岩类型包括流纹岩、英安岩、安山岩、玄武安山岩,为一套钙碱性火山岩,属于准铝质-弱过铝质岩石。根据岩相学和地球化学特征,将其分为变质酸性火山岩和变质中-基性火山岩;二者均相对富集轻稀土元素,亏损重稀土元素,轻重稀土元素分馏明显,Eu负异常不明显,但变质酸性火山岩明显亏损P、Ti元素,结合高场强元素相关性特征,认为二者不是同一基性岩浆分异的产物。变质火山岩锆石LA-ICP-MS U-Pb同位素年龄为272~288Ma,代表其原岩结晶年龄,时代为早二叠世;变质酸性火山岩原始岩浆来源于地壳物质的部分熔融,变质中-基性火山岩原始岩浆来源于岩石圈地幔(俯冲带附近),并遭受了地壳物质的混染,二者均形成于活动大陆边缘火山弧环境。变质碎屑岩原岩恢复为泥砂质沉积岩和砂泥质沉积岩,相对亏损轻稀土元素,富集重稀土元素,轻重稀土元素分馏较明显,Eu异常不明显。两件碎屑岩样品锆石LA-ICP-MS U-Pb同位素年龄主要介于267~347Ma,推断其沉积下限为267Ma和269Ma,均为中二叠世;泥砂质沉积岩可能来源于再旋回的以长英质岩石为母岩的沉积岩,砂泥质沉积岩可能来源于再旋回的以长英质和镁铁质岩石为母岩的沉积岩,二者分别形成于活动大陆边缘大陆岛弧和大洋岛弧环境。下二台地区早-中二叠世变质火山-碎屑岩为“下二台”构造杂岩重要组成部分,它表明二叠纪时期华北板块北缘东段经历了三个构造演化阶�As an important part of the tectonic mélange belt distributed in the eastern segment of the northern margin of the North China Craton(NCC),the material composition,formation age and tectonic attributes of the“Xia’ertai”tectonic complex still need to be further studied,since it may provide an important scientific basis for exploring the tectonic evolution of the eastern segment of the northern margin of the NCC.We have identified a set of Early-Middle Permian metamorphic volcano-clastic rocks in the“Xia’ertai”tectonic complex which is mainly composed of meta-clastic rocks interbedded with meta-volcanic rocks,and the two mingled in the field.The protoliths of meta-volcanic rocks include rhyolite,dacite,andesite,basaltic andesite.They are a set of calc-alkaline volcanic rocks that are metaluminous-weak peraluminous.According to petrographic and geochemical characteristics,they are divided into metamorphic acid volcanic rocks and metamorphic intermediate-basic volcanic rocks.Both of them were relatively enriched in LREEs and depleted in HREEs,indicating an obvious fractional distillation of light and heavy rare earth elements,while the Eu anomaly was not obvious.The metamorphic acid volcanic rocks are obviously deficient in P and Ti.Combined with the correlation characteristics of high field strength elements,it is considered that they are not the products of the same magma differentiation.The LA-ICP-MS U-Pb ages of zircons from the meta-volcanic rocks range from 272 Ma to 288 Ma,representing their crystallization ages of Early Permian.The original magma of metamorphic acid volcanic rocks came from the partial melting of crustal materials,while the original magma of metamorphic intermediate-basic volcanic rocks came from the lithospheric mantle near the subduction zone and suffered from the mixing of crustal materials.Both of them are formed in a volcanic arc environment at the active continental margin.The protoliths of the meta-clastic rocks are argillo-arenaceous and arenopelitic.In meta-clastic rocks

关 键 词：中亚造山带 华北板块北缘 “下二台岩群” 构造杂岩 早-中二叠世 

分 类 号：P588.14[天文地球—岩石学] P588.212[天文地球—地质学] P597.3