大兴安岭北段窝里河早古生代蛇绿岩识别及构造背景  

Identification and tectonic setting of Early Paleozoic ophiolite in Wolihe,northern part of Greater Khingan Mountains

作　　者：付俊彧[1] 杨晓平[1] 崔丹丹 杨浩[2] 那福超[1] 庞雪娇[1] 孙巍[1] FU Junyu;YANG Xiaoping;CUI Dandan;YANG Hao;NA Fuchao;PANG Xuejiao;SUN Wei(Shenyang Center,China Geological Survey,Shenyang 110034,Liaoning,China;College of Earth Sciences,Jilin University,Changchun 130061,Jilin,China)

机构地区：[1]中国地质调查局沈阳地质调查中心,辽宁沈阳110034 [2]吉林大学地球科学学院,吉林长春130061

出　　处：《地质通报》2024年第12期2219-2236,共18页Geological Bulletin of China

基　　金：中国地质调查局项目《东北地区数据更新及地质编图》(编号:DD20230224);《中国大地构造演化和国际亚洲大地构造图编制》(编号:DD20190360)。

摘　　要：大兴安岭北段多宝山地区窝里河一带早古生代火山-沉积地层中出露一套镁铁—超镁铁质岩,其形成时代、构造性质一直不清楚。采用岩石学、岩石地球化学及锆石U−Pb(LA−MC−ICP−MS)年代学方法对其进行了系统研究。研究表明,这套镁铁—超镁铁质岩包括蛇纹岩、蛇纹石化辉橄岩、蚀变辉长岩、角闪辉长岩、玄武安山岩及枕状玄武岩,具有蛇绿岩组合特点;前二者为地幔岩,辉长岩具堆晶岩特点,玄武安山岩相当于基性岩墙,枕状玄武岩为海底喷出岩;它们都呈岩块状分布在早古生代片理化火山碎屑岩-碎屑沉积岩基质中,共同构成一套蛇绿混杂岩。其中,镁铁质岩石属于钙碱性系列,超镁铁岩与镁铁质岩石均富集大离子亲石元素Ba、K、Sr,亏损高场强元素Nb、P、Ti及Th,具有活动大陆边缘弧火山岩特点;获得蛇绿岩上部单元玄武安山岩形成时代447 Ma。总括蛇绿岩岩石组合及地球化特征,认为蛇绿岩属消减型蛇绿岩(SSZ),形成于弧背盆地构造背景;蛇绿岩构造侵位最年轻地质体为早—中奥陶世,推测蛇绿岩构造侵位于晚奥陶世末期。A set of mafic−ultramafic rocks emerged from the Early Paleozoic volcano−sedimentary strata in the Wolihe of Duobaoshan area,northern part of the Greater Khingan Mountains,whose formation age and structural properties are still unclear.In this paper,petrology,petrogeochemistry and zircon U−Pb(LA−MC−ICP−MS)chronology are used to systematically study the set of mafic−ultramafic rocks.The results show that the mafic−ultramafic rocks include serpentinite,serpentinized pyroxene peridotite,altered gabbro,hornblende gabbro,basaltic andesite and pillow basalt,which have the characteristics of ophiolite combination;The first two are mantle rocks,gabbro has the characteristics of cumulates,basalt andesite is equivalent to basic dike,pillow basalt is submarine extruded rock;They are distributed in the matrix of Early Paleozoic stratified pyroclastic rock and clastic sedimentary rock,and together constitute a set of ophiolitic mellitic rocks.Among them,mafic rocks belong to the calc−alkaline series,ultramafic rocks and mafic rocks are rich in large ion lithophile elements Ba,K,Sr,and depleted in high field strength elements Nb,P,Ti and Th,which have the characteristics of active continental margin arc volcanic rocks.The formation age of basalt andesite in the upper unit of ophiolite is 447 Ma.In summary,it is considered that the ophiolite belongs to suprasubduction zone type ophiolite(SSZ),which formed in the tectonic setting of the arc back basin.The youngest geological body of the ophiolite tectonic emplacement is the Early to Middle Ordovician,and it is speculated that the ophiolite tectonic emplacement is located at the end of the late Ordovician,it is inferred that the ophiolite tectonic emplacement was at the end of the Late Ordovician.

关 键 词：多宝山窝里河 SSZ型蛇绿岩 弧背盆地 晚奥陶世 

分 类 号：P534.42[天文地球—古生物学与地层学] P58[天文地球—地质学]