辽北开原地区晚古生代—早中生代混杂岩的厘定及其地质意义  

Determination and geological significance of Late Paleozoic-Early Mesozoic melanges in Kaiyuan area,northern Liaoning Province

作　　者：郑常青[1,2] 耿志忠 段东 宋志伟 孙晓蕾 ZHENG Changqing;GENG Zhizhong;DUAN Dong;SONG Zhiwei;SUN Xiaolei(College of Earth Sciences,Jilin University,Changchun 130061,China;Key laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources,Jilin University,Changchun 130061,China)

机构地区：[1]吉林大学地球科学学院,长春130061 [2]吉林大学东北亚矿产资源评价自然资源部重点实验室,长春130061

出　　处：《世界地质》2023年第3期444-460,共17页World Geology

基　　金：国家自然科学基金项目(42172213)。

摘　　要：辽宁省开原地区地处华北克拉通北缘,域内沿清河断裂出露一套中浅变质岩系,前人先后将其称为“辽河群”、“清河镇群”、“开原岩群”、“清河构造混杂岩”,但对其物质组成和形成时代尚未形成统一认识。通过系统总结不同岩石锆石U-Pb测年结果和地球化学数据,该套变质岩系是由新太古代、古元古代、晚二叠世-中三叠世不同时代地质体组成,其中早三叠世的海相沉积盖层和大面积的晚二叠世-中三叠世活动大陆边缘岛弧岩块指示古亚洲洋的闭合过程,碰撞背景下形成的变质英安岩(244 Ma)将古亚洲洋的最终闭合时间限定为中三叠世。综合对比区域地质资料,古亚洲洋在开原地区的俯冲闭合作用导致形成这套变质程度不同以新太古代华北板块基底岩石、晚二叠世-中三叠世火山岩为“岩块”,变粒岩、浅粒岩等变质碎屑岩为“基质”的混杂岩系。Kaiyuan area of Liaoning Province is located in the northern margin of North China Craton,in which a set of medium-to-low metamorphic rock series is exposed along the Qinghe fault.It was successively named as“Liaohe Group”,“Qinghezhen Group”,“Kaiyuan rock group”,and“Qinghe tectonic mélange”,and a unified understanding about its composition and age has not yet been reached.By systematically summarizing the zircon U--Pb dating results and geochemical data with different lithologies,this set of metamorphic rock series is composed of geological bodies with different ages from Neoarchaean,through Paleoproterozoic to Late Permian--Middle Triassic,among which the Early Triassic marine sedimentary covers and the large area of Late Permian--Middle Triassic arc-type blocks formed within an active continental margin indicate the closure process of the Paleo--Asian Ocean.The collision-related metamorphosed dacite(244 Ma)constrained the final closure time of the Paleo--Asian Ocean at the Middle Triassic.A comprehensive comparison of regional geological data shows that the subduction and closure of the Paleo--Asian Ocean in the Kaiyuan area resulted in the formation of a set of mélange series with different degrees of metamorphism,including the Neoarchean basement rocks of the North China Craton,the Late Permian-Middle Triassic volcanic rocks as“rock blocks”and metamorphic clastic rocks such as metamorphic leptynite and leptits as“matrix”.

关 键 词：晚古生代-早中生代 华北克拉通北缘 混杂岩 古亚洲洋闭合 开原地区 辽北 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]