华北板块北缘东段古洋盆的消亡过程:来自辽北地区中-基性岩浆岩的启示  

The extinction process of the paleo-oceanic basin in the eastern part of the northern margin of the North China Block:Implications from the intermediate-mafic magmatic rocks in the northern Liaoning,NE China

作　　者：时溢[1,2] 石绍山 陈旭 桓凤明[4] SHI Yi;SHI ShaoShan;CHEN Xu;HUAN FengMing(Shenyang Center of Geological Survey,China Geological Survey,Shenyang 110034,China;Northeast Geological S&T Innovation Center of China Geological Survey,Shenyang 110034,China;Survey of Regional Geological and Mineral Resource of Jilin Province,Changchun 130022,China;Liaoning Metallurgical Geological Exploration Research Institute Co.,Anshan 114000,China)

机构地区：[1]中国地质调查局沈阳地质调查中心,沈阳110034 [2]东北地质科技创新中心,沈阳110034 [3]吉林省区域地质矿产调查所,长春130022 [4]辽宁省冶金地质勘查研究院有限责任公司,鞍山114000

出　　处：《岩石学报》2022年第8期2292-2322,共31页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41902234);中国地质调查局地质调查项目(DD20190042-02、DD20221779、DD20221632-02)联合资助。

摘　　要：本文对辽宁北部地区原“佟家屯岩组、磨盘山组、照北山岩组”等地层进行了解体,从中识别出了多处晚古生代-早中生代中-基性火山岩及侵入岩,通过对其进行岩相学、地球化学、年代学以及Lu-Hf同位素研究,以此制约华北板块北缘东段古洋盆演化-消亡过程。锆石测年结果显示,关家屯东变玄武岩及王家店北变安山岩形成于中二叠世(265.5±1.7Ma~260.6±2.7Ma),老陵山变玄武安山岩及五龙山变闪长岩形成于晚二叠世-早三叠世(251.5±2.1Ma~251.4±1.4Ma),五龙山正长岩及红土砬子辉长岩形成于中三叠世早期(247±1.3Ma~245.4±1.4Ma)。岩石地球化学表明,关家屯东变玄武岩、王家店北变安山岩及老陵山变玄武安山岩具有相对高的Zr/Y比值和低Ta/Yb比值,显示出大洋岛弧玄武岩的亲缘性。老陵山变玄武安山岩富Mg^(#)、Cr、Ni,与赞岐岩的地球化学特征相一致,其Zr、Ti含量较高,可能形成于弧后盆地环境;五龙山变闪长岩富碱、Al_(2)O_(3),贫Mg、Cr,具有大陆裂谷型玄武岩的地球化学特征;五龙山正长岩具有高Sr/Y比值及低Sr、低Yb的特征,类似于喜马拉雅型花岗岩,应形成于裂谷伸展期向碰撞回返期过渡的中-高压环境;红土砬子辉长岩与五龙山变闪长岩地球化学特征相近,而前者与后者相比具有相对低的Ba/Nb和Ba/Ta比值,暗示其成岩过程中并未遭受俯冲板块的改造作用,可能形成于造山后伸展环境。综合前人研究,本文认为辽北地区在晚古生代期间处在弧后有限洋盆环境,该洋盆属于古亚洲洋南侧的分支洋盆。在中二叠世-中三叠世期间,研究区经历了弧后洋盆的俯冲-消亡过程。本研究不仅为华北板块北缘东段古洋盆的构造属性、形成演化机制、洋-陆格局重建及限制古缝合带空间位置提供重要线索,而且对重塑东北大地构造格局具有重要的指示意义。In this paper,the Tongjiatun,Mopanshan and Zhaobeishan formations in northern Liaoning,NE China,have been disintegrated,and a number of Late Paleozoic-Early Mesozoic middle-basic volcanic rocks and intrusive rocks were identified.Through carries on the petrographical,geochemical,geochronological and Lu-Hf isotope research,the evolution and extinction process of the ancient ocean basin in the eastern part of the northern margin of the North China Block(NCB)will be restricted.Zircon dating results indicate that the Guanjiatun meta-basalt and the Wangjiadian meta-andesite were formed in the Middle Permian(265.5±1.7Ma~260.6±2.7Ma),the Laolingshan meta-basaltic andesite and the Wulongshan meta-diorite were formed in the Late Permian-Early Triassic(251.5±2.1Ma~251.4±1.4Ma),and the Wulongshan syenite and the Hongtulazi gabbro were formed in the Middle Triassic(247±1.3Ma~245.4±1.4Ma).Petrogeochemical characteristics indicate that the Guanjiatun meta-basalt,the Wangjiadian meta-andesite and the Laolingshan meta-basaltic andesite have relatively high Zr/Y ratios and low Ta/Yb ratios,indicating the affinity of oceanic island arc basalts.The Laolingshan meta-basaltic andesite displays enrichment in Mg^(#),Cr and Ni,which are relatively consistent with the geochemical characteristics of sanukite,with high Zr and Ti contents,and may have been formed in the back-arc oceanic basin setting.The Wulongshan meta-diorite is enriched in alkali,Al_(2)O_(3),Mg,Cr and has the geochemical characteristics of Continental Rift Basalt(CRB).The Wulongshan syenite is characterized by high Sr/Y ratio,low Sr and low Yb,which is similar to the Himalayan granite.It should have been formed in a medium-high pressure environment during the transition from rift extension to collision period.The geochemical characteristics of the Hongtulazi gabbro,which are similar to those of the Wulongshan meta-diorite,has lower Ba/Nb and Ba/Ta ratios,suggesting that the Hongtulazi gabbro was not affected by subduction plate during its petrogenesis,and formed in

关 键 词：华北板块 辽北地区 弧后洋盆 地球化学 锆石U-PB定年 

分 类 号：P588.12[天文地球—岩石学] P588.14[天文地球—地质学] P597.3