大兴安岭中段天险沟石英二长斑岩的成因——锆石U-Pb年龄、地球化学和Sr—Nd同位素特征  

Petrogenesis of the quartz monzonite porphyry in Tianxiangou,central Great Hinggan Mountains——Constraints from zircon U-Pb dating,geochemical and Sr—Nd isotopic characteristics

作　　者：贺晓天 黄海涛 俎新许[1,2] 张焕 何鹏[1,2] 刘朝阳 赵亚南 李福斌[1,2] HE Xiaotian;HUANG Haitao;ZU Xinxu;ZHANG Huan;HE Peng;LIU Chaoyang;ZHAO Yanan;LI Fubin(Science and Technology Innovation Centre of Nature Resources of Henan Provinces/Research on Technique and Method of Deep Investigation and Evaluation,Zhengzhou,450000;The Second Geo-exploration Institute of Mineral Prospecting and Development,Bureau of Henan Province,Zhengzhou,450000)

机构地区：[1]河南省自然资源科技创新中心(深部调查与评价技术方法研究),郑州450000 [2]河南省地质矿产勘查开发局第二地质勘查院,郑州450000

出　　处：《地质论评》2022年第5期1789-1800,共12页Geological Review

基　　金：内蒙古自治区地质勘查基金项目“呼伦贝尔市沃力嘎沟等四幅1:5万区域矿产地质调查”(编号:NMKD2014-22)的成果。

摘　　要：笔者等通过岩石学、锆石U⁃Pb年代学和地球化学等研究,对大兴安岭中段天险沟石英二长斑岩的成因、物质来源和构造背景进行了探讨。通过锆石LA⁃ICPMS U⁃Pb定年法,得到天险沟石英二长斑岩的年龄为124.4±1.0 Ma,时代为早白垩世早期。天险沟石英二长斑岩属碱性、准铝质岩,里特曼指数σ为3.86~5.10,K_(2)O+Na_(2)O=9.14%~10.35%,钾钠比为0.93~1.0,A/CNK=0.76~0.93,成因类型为I型花岗岩。岩石富集La、Ba、Ce、U等大离子亲石元素,相对亏损Hf、Zr等高场强元素;(La/Yb)_(N)=11.72~13.90,分馏明显,轻稀土富集,而重稀土亏损,Nb、Ta负异常,具岛弧花岗岩的地球化学特征。δEu=1.00~1.59。[n(^(87)Sr)/n(^(86)Sr)]_(i)=0.705065,ε_(Nd)(t)=1.93,源区可能为上地幔。结合大兴安岭地区中生代地壳演化背景,认为天险沟石英二长斑岩形成于与洋壳俯冲有关的火山弧环境,区域应力场由挤压向伸展转换,岩浆源区为上地幔。Based on petrology,zircon U-Pb chronology and geochemistry,this article discusses the genesis,material source and tectonic background of tianxiangou quartz monzonite porphyry in central section of Great Hinggan Mountains.According to zircon LA-ICPMS U-Pb dating method,the age of Tianxiangou quartz monzonite porphyry is 124.4 ± 1.0 Ma and the age is Early Cretaceous.Tianxiangou quartz monzonite porphyry belongs to alkaline and quasi aluminous rocks with Rittman index σ= 3.86 ~ 5.1,total alkali(Na_(2)O + K_(2)O) =9.14% ~ 10.35%,K_(2)O/Na_(2)O = 0.93 ~ 1.0,A/CNK=0.76 ~ 0.93,and the genetic type is Ⅰ-type granite.The rocks are rich in large ion lithophile elements such as La,Ba,Ce and U,and relatively deficient in high field strength elements such as Hf and Zr;(La/Yb)_(N)=11.72 ~ 13.90,with obvious fractionation,enrichment of light rare earths,loss of heavy rare earths,negative Nb and Ta anomalies,showing the geochemical characteristics of island arc granites.δ Eu=1.00~1.59.[n(^(87)Sr)/n(^(86)Sr)]_(i)=0.705065,ε _(Nd)(t) =1.93,the source area may be the upper mantle.Combined with the Mesozoic crustal evolution background in the Great Hinggan Mountains,it is considered that the Tianxiangou quartz monzonite porphyry was formed in a volcanic arc environment related to the subduction of the oceanic crust,the regional stress field was transformed from compression to extension,and the magma source was the upper mantle.

关 键 词：锆石U-PB年龄 Sr—Nd同位素 Ⅰ型花岗岩 天险沟石英二长斑岩 大兴安岭中段 

分 类 号：P588.13[天文地球—岩石学] P597.3[天文地球—地质学]