辽阳河栏地区辽河群中变质基性熔岩的锆石U-Pb年龄与形成构造背景  

Zircon U-Pb Age and Tectonic Setting of Meta-Basalts of Liaohe Group in Helan Area,Liaoyang,Liaoning Province

作　　者：王惠初 陆松年[1] 初航 相振群[1] 张长捷[2] 刘欢 

机构地区：[1]中国地质调查局天津地质调查中心,天津300170 [2]中国地质调查局沈阳地质调查中心,沈阳110034

出　　处：《吉林大学学报（地球科学版）》2011年第5期1322-1334,1361,共14页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(40772120);国家地质矿产调查评价专项项目(1212010911005;1212011120154)

摘　　要：在海城—草河口的北辽河群中分布大量变质基性火山岩和基性岩墙,其中辽阳河栏镇南部大石桥组中的基性火山岩保存有良好的枕状构造。这些变质枕状熔岩化学成分上低碱低钾富铁,具有岛弧拉斑玄武岩的特征,岩石稀土和微量元素特征指示变质枕状熔岩形成于与岛弧相关的构造背景,很可能是弧后盆地环境的产物,而非大陆裂谷。锆石年代学研究显示:变质枕状熔岩的锆石SHRIMP U-Pb年龄为(1 869±28)Ma;变辉绿岩墙的形成年龄为(1 828±13)Ma,并有一组～2 080Ma的捕获锆石年龄;花岗伟晶岩锆石U-Pb年龄为(1 869.7±7.6)Ma。结合岩石的产出状态和前人研究资料:推测变质枕状熔岩形成年龄为～1 880Ma,可以代表北大石桥组的形成时代;花岗伟晶岩的年龄为～1 860Ma,可作为造山作用结束的标志;变基性岩墙为～1 830Ma,可作为后造山伸展张裂的标志。A lot of meta-basalts and mafic dykes occurred in the Northern Liaohe Group in Haicheng-Caohekou area,among which,the meta-basalts of Dashiqiao Formation in south Helan,Liaoyang,preserved a good pillow structure.The meta-pillow lava is chemically characterized by low alkaline,low K2O/Na2O ratios and iron-rich,which suggest that it belongs to island-arc tholeiite series.The REE and trace element characteristics indicate that the meta-pillow lava formed in the tectonic setting associated with the island-arc,likely back-arc basin rather than the continental rift.The study of isotopic chronology show that zircon SHRIMP U-Pb age of the meta-pillow lava is（1 869±28） Ma,of meta-diabase dyke is（1 828±13） Ma with a group of ~2 080 Ma captured zircon ages,and the zircon LA-ICP-MS U-Pb age of granite pegmatite is（1 869.7±7.6） Ma.Based on their occurrence,zircon dating and previous research data,it is suggested that the meta-pillow lava is formed at ~1880 Ma which could represent the forming age of Dashiqiao Formation,and the granite pegmatite is at ~1860 Ma which can be considered as a marker of the end of orogeny,and the meta-diabase dyke at ~1830 Ma which may indicates the beginning of post-orogeny extension.

关 键 词：辽吉活动带 辽河群 枕状熔岩 锆石U-PB年龄 构造背景 构造 辽阳 

分 类 号：P597.1[天文地球—地球化学]