华北板块北缘东段晚古生代-早中生代造山带构造演化:来自辽北开原地区尖山子变质火山岩的证据  

Tectonic evolution of the Late Paleozoic-Early Mesozoic orogenic belt in the eastern segment of the northern margin of the North China Block:Evidence from meta-volcanic rocks of Jianshanzi,northern Liaoning Province

作　　者：张诺 王长兵 刘正宏[1,3] 徐仲元 李刚[1] 玄雨菲[1] 高煜 王晨 ZHANG Nuo;WANG ChangBing;LIU ZhengHong;XU ZhongYuan;LI Gang;XUAN YuFei;GAO Yu;WANG Chen(College of Earth Sciences,Jilin University,Changchun 130061,China;No.209 Geological Party,Geological Bureau of Yunnan Nuclear Industry,Kunming 650106,China;Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources,Changchun 130061,China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]云南省核工业二〇九地质大队,昆明650106 [3]自然资源部东北亚矿产资源评价重点实验室,长春130061

出　　处：《岩石学报》2022年第8期2323-2344,共22页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41872203)资助。

摘　　要：本文对辽北开原地区尖山子火山岩进行了LA-ICP-MS U-Pb年代学、全岩地球化学和Hf同位素的研究,探讨华北板块北缘东段晚古生代-早中生代的构造演化历史。尖山子变质火山岩原岩包括流纹岩、英安岩、安山岩等,为一套钙碱性火山岩,属于准铝质-弱过铝质岩石,变质流纹岩和变质安山岩的形成时代分别为256.1±1.5Ma、252.4±1.7Ma和222.4±1.8Ma、227.9±1.2Ma,相对富集轻稀土和大离子亲石元素,亏损重稀土和高场强元素。变质流纹岩明显Eu负异常,ε(t)值为-10.83~+8.10,多为正值,二阶段模式年龄为698~1967Ma,主要来源于新生玄武质下地壳的部分熔融,还有少量古老地壳物质的混染;变质安山岩无明显Eu异常,ε(t)值为+4.54~+6.79,二阶段模式年龄为825~968Ma,可能是由新生基性下地壳部分熔融的产物。尖山子火山岩存在两期岩浆作用:晚二叠世-早三叠世(247~256Ma)和晚三叠世(~225Ma),由不同时代、不同构造环境下形成的火山岩叠置混杂而成。综合认为,华北板块北缘东段在二叠世期间处于活动大陆边缘构造环境中,古亚洲洋双向俯冲;晚二叠世-早三叠世俯冲板片的断离诱发软流圈地幔熔融以及幔源岩浆上升侵位,形成新生地壳并导致地壳加厚。古亚洲洋在中三叠世早期最终闭合,碰撞造山的影响可能一直持续到晚三叠世早期。LA-ICP-MS U-Pb dating,whole-rock geochemistry and Hf isotopic analyses for the Jianshanzi volcanic rocks in the Kaiyuan area are presented to explore the Late Paleozoic-Early Mesozoic tectonic evolution history of the eastern segment of the northern margin of the North China block.The detailed research indicates that the protolith of Jianshanzi metamorphic volcanic rocks includes rhyolite,dacite and andesite,they are calc-alkaline series and metaluminous-weak peraluminous rocks.According to the zircon U-Pb dating,the metamorphic rhyolite and metamorphic andesite formed in the Late Permian(256.1±1.5 Ma,252.4±1.7 Ma)and the Late Triassic(222.4±1.8 Ma,227.9±1.2 Ma),respectively.They are characteristized by enrichment in light rare earth elements and large ion lithophile elements,and depletion of heavy rare earth elements and high field strength elements.Metamorphic rhyolite has an obvious negative Eu anomaly withε(t)values of-10.83~+8.10 and the second-stage model are 698~1967 Ma.They are mainly due to the partial melting of the juvenile basaltic lower crust and the contamination of a small amount of ancient crustal materials.Metamorphic andesite has no obvious Eu anomaly,and theε(t)value and the second-stage model are+4.54~+6.79 and 825~968 Ma,which may be the product of partial melting of basic lower crust.There are two periods of magmatism in Jianshanzi volcanic rocks:Late Permian-Early Triassic(247~256 Ma)and Late Triassic(~225 Ma).The material composition of the Jianshanzi volcanic rocks is characterized by different times and different tectonic backgrounds.It is comprehensively believed that the eastern segment of the northern margin of the North China block was in an active continental margin tectonic environment during the Permian,and the Palaeo-Asian Ocean subducted in both directions;Mantle-derived magma ascends and emplaces,forming a nascent crust and causing crustal thickening.The Paleo-Asian Ocean finally closed in the early Middle Triassic,and the impact of collisional orogeny may have continued

关 键 词：华北板块北缘东段 晚古生代 古亚洲洋 火山岩 锆石U-PB年代学 

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