内蒙古科右前旗一带梅勒图组火山岩U-Pb测年及地球化学特征  

A study of geochronology and geochemistry of volcanic rocks from Meiletu Formation in Horqin Right Wing Front Banner, Inner Mongolia

作　　者：吴昊[1] 陈满[1] 龚全德[1] 曹元宝[1] 张力强[1] 刘学元[1] 杜士澍 秦越强 陈彪[1] 张钧贵 孙浩[1] 郝森[1] WU Hao;CHEN Man;GONG Quande;CAO Yuanbao;ZHANG Liqiang;LIU Xueyuan;DU Shishu;QIN Yueqiang;CHEN Biao;ZHANG Jungui;SUN Hao;HAO Sen(The Fourth Detachment of Gold Headquarters,Chinese Armed Police Force,Liaoyang 111000,Liaoning,China)

机构地区：[1]武警黄金第四支队

出　　处：《地质通报》2019年第11期1836-1845,共10页Geological Bulletin of China

基　　金：中国地质调查局项目《内蒙古东部复兴屯、树木沟、特格乌拉、苑家街1∶5万地质矿产综合调查》（编号：12120115041901）

摘　　要：通过对科右前旗一带梅勒图组火山岩LA-ICP-MS锆石U-Pb定年和元素地球化学分析,获得梅勒图组安山质晶屑熔结凝灰岩及安山岩的喷发年龄分别为125.6±1.6Ma和120.2±2.2Ma,指示梅勒图组火山岩的形成时代介于120~126Ma之间,形成于早白垩世中期。岩石具有高的SiO2(60.4%~65.3%)和全碱(7.0%~9.5%)含量,铝饱和指数A/CNK为0.89~0.98,属于钾玄岩及高钾钙碱性系列;稀土元素总量为124×10^-6~169×10^-6,(La/Yb)N值为5.83~13.4,负Eu异常微弱(δEu=0.84~1.05);在原始地幔标准化微量元素蛛网图上,样品富集Rb、Ba、Th、U、K、La、Nd,亏损Nb、Ta、P和Ti,Sr/Y值介于19.4~29.7之间。其岩石源区为富集地幔,岩浆上升过程中受到地壳物质的混染,岩石形成于板内伸展环境,其地球动力学背景可能与古太平洋板块的俯冲有关。Through LA-ICP-MS zircon U-Pb dating and elemental geochemical analysis of Meiletu Formation volcanic rock in Horqin Right Wing Front Banner, the authors obtained the eruption ages of 125.6 ± 1.6 Ma and 120.2 ± 2.2 Ma for andesite crystallinoclasitc welded tuff and andesite in Meiletu Formation, indicating that the forming ages of Meiletu Formation volcanic rock are between 120 and 126 Ma in the Early Cretaceous. The rock has high SiO2(60.4%~65.3%) and total alkali content(7%~9.5%),with aluminum index A/CNK being 0.89~0.98, suggesting shoshonitic and high-K calc alkaline series;rare earths range from 124×10^-6 to 169×10^-6, and(La/Yb)Nvalues are in the range of 5.83~13.4, with weak negative Eu anomalies(δEu=0.84~1.05);on the primitive mantle normalized trace element spider diagram, there exist enrichment of Rb, Ba, Th, U, K, La and Nd and depletion of Nb, Ta, P and Ti, with Sr/Y ratio between 19.4 and 29.7. The rock source area should be enriched mantle, and the magma was contaminated by crustal material during the process of magma rising. The rock was formed in an intraplate extensional environment,and its geodynamic background might have been related to subduction of paleo-Pacific plate.

关 键 词：LA-ICP-MS锆石U-PB定年 地球化学 梅勒图组 火山岩 内蒙古科右前旗 

分 类 号：P597[天文地球—地球化学] P588.14[天文地球—地质学]