南天山地块塔格拉克地区二长花岗岩锆石U-Pb年代学、地球化学特征:对壳源岩浆成因和构造背景的限定  

Zircon U-Pb geochronology and geochemistry of the Tagelake monzogranites in South Tianshan block:Constraints on crustal magmatic origin and tectonic setting

作　　者：李生喜 何碧 杨博[2] 魏志福[3] 陶刚 甘保平 赵飞 孙平原 赵振琯 黄鹏飞 LI Shengxi;HE Bi;YANG Bo;WEI Zhifu;TAO Gang;GAN Baoping;ZHAO Fei;SUN Pingyuan;ZHAO Zhenguan;HUANG Pengfei(The Second Institute of Geology and Minerals Exploration Team,Gansu Provincial Bureau of Geology and Minerals Exploration and Development,Lanzhou 730020,Gansu,China;Xi'an Center,China Geological Survey,Xi′an 710054,Shaanxi,China;Lanzhou Center for Oil and Gas Resources,Institute of Geology and Geophysics,Chinese Academy of Sciences,Lanzhou 730000,Gansu,China;School of Environment and Resource,Southwest University of Science and Technology,Mianyang 621010,Sichuan,China;State Key Laboratory of Continental Dynamics,Northwest University,Xi'an 710069,Shaanxi,China)

机构地区：[1]甘肃省地质矿产勘查开发局第二地质矿产勘查院,甘肃兰州730020 [2]中国地质调查局西安地质调查中心,陕西西安710054 [3]中国科学院地质与地球物理研究所兰州油气资源研究中心,甘肃兰州730000 [4]西南科技大学环境与资源学院,四川绵阳621010 [5]西北大学大陆动力学国家重点实验室,陕西西安710069

出　　处：《中国地质》2023年第2期622-639,共18页Geology in China

基　　金：中国地质调查局(12120115021701)资助。

摘　　要：提要:【研究目的】西南天山造山带内塔格拉克地区的长条状岩体位于南天山地块,由二长花岗岩组成。厘定该二长花岗岩的形成机制,对南天山壳源岩浆成因的限定、洋盆俯冲消减及碰撞闭合时限等问题的研究具有重要意义。【研究方法】本文首次报道了塔格拉克地区二长花岗岩的全岩主量元素、微量元素、锆石U-Pb年代学结果。【研究结果】LA-ICP-MS锆石年代学研究揭示出塔格拉克地区二长花岗岩成岩年龄为(284.0±1.9)~(284.3±3.2)Ma,为早二叠世花岗岩。岩石主量元素和微量元素分析结果揭示该二长花岗岩具有A型花岗岩特征:(1)SiO_(2)(70.92%~72.78%)含量高,碱质(K_(2)O+Na_(2)O=7.91%~8.44%)含量较高,A/CNK(0.89~0.99)较高,表明二长花岗岩为准铝质岩石,属于高钾钙碱性系列;(2)LREE(196×10^(-6)~280×10^(-6))相对富集,HREE(22.8×10^(-6)~28.2×10^(-6))相对亏损,负Eu异常(δEu为0.51~0.64)明显,球粒陨石标准化配分模式呈右倾Ⅴ型特征;(3)富集Rb、Th和K等大离子亲石元素,相对亏损Nb、Ta、Zr、P和Ti等高场强元素。【结论】结合区域构造演化,认为塔格拉克地区二长花岗岩形成于后碰撞构造背景。This paper is the result of geological survey engineering.[Objective]The Tagelake strip pluton,outcropped at the south Tianshan terrane in Southwestern Tianshan orogenic belt,is composed of monzogranites.Determining the formation mechanism of the monzogranites has important implications for the crust-derived magma origin and the time limit of subduction and ocean basin closure in South Tianshan Mountains.[Methods]In order to determine the formation mechanism of the monzogranites,detailed zircon U−Pb geochronology,major elements and trace elements were firstly conducted.[Results]LA-ICP-MS zircon geochronology study reveals that the monzogranites in the Tagelake area crystallized at(284.0±1.9)-(284.3±3.2)Ma,indicative of an Early Permian pluton.The results of major elements and trace elements reveal that the monzogranites display the characteristics of A-type granite:(1)The contents of SiO_(2)(70.92%-72.78%),K_(2)O+Na_(2)O(7.91%-8.44%)and A/CNK(0.89-0.99)are high,indicating that monzogranites are metaluminous rock and belongs to the high potassium calcium alkaline series;(2)The monzogranites are enriched in LREE(196×10^(-6)-280×10^(-6))and depleted in HREE(22.8×10^(-6)-28.2×10^(-6)).Negative Eu anomaly is obvious,withδEu values of 0.51-0.64,and the monzogranites are characterized by fractionated chondrite-normalized REE patterns;(3)The monzogranites are enriched in Rb,Th,K and other large ion lithophile elements and depleted in Nb,Ta,Zr,P,and other high field strength elements.[Conclusions]Combined with the regional tectonic evolution,it is considered that the Tagelake monzogranites were formed in the post-collision tectonic setting.

关 键 词：锆石U-PB年代学 地球化学 二长花岗岩 地质调查工程 塔格拉克地区 南天山地块 

分 类 号：P581[天文地球—岩石学] P597[天文地球—地质学]