川西苏地二长花岗岩地球化学、锆石年代学及Lu-Hf同位素特征——对松潘——甘孜地块构造背景的限定  

Geochemistry, zircon geochronology and Lu-Hf isotopic characteristics of the Sudi monzogranite in the Western Sichuan: Implications for tectonic setting of the Songpan-Ganze terrane

作　　者：周玉 周雄[2] 张贻[1] 秦志鹏 贾志泉[4] 梁兵[4] ZHOU Yu;ZHOU Xiong;ZHANG Yi;QIN Zhipeng;JIA Zhiquan;LIANG Bing(Urumqi Natural Resources Comprehensive Survey Center of China Geological Survey,Urumqi 830057,Xinjiang,China;Institute of Multipurpose Utilization of Mineral Resources,Chinese Academy of Geological Sciences,Chengdu 610041,Sichuan,China;Chengdu University of Technology,Chengdu 610059,Sichuan,China;No.108 Geological Team,BGEEMRSP,Chongzhou 611230,Sichuan,China)

机构地区：[1]中国地质调查局乌鲁木齐自然资源综合调查中心,新疆乌鲁木齐830000 [2]中国地质科学院矿产综合利用研究所,四川成都610041 [3]成都理工大学,四川成都610059 [4]四川省地矿局一〇八地质队,四川崇州611230

出　　处：《中国地质》2022年第6期1984-2001,共18页Geology in China

基　　金：中国地质调查局二级项目(DD20160074、DD20190185、DD20211550、ZD20220316);国家青年自然科学基金项目(41602072);西藏自治区科技厅重大科技专项(XZ201801-GB-01);新疆维吾尔自治区自然科学基金资助项目(2022D01A148)联合资助。

摘　　要：【研究目的】查明松潘—甘孜地块东南部花岗岩地球化学及构造演化特征,对在该区寻找稀有金属矿产具有重要意义。【研究方法】在野外地质调查基础上,采集了地块东南部前人研究未涉及的苏地岩体二长花岗岩样品开展了镜下鉴定、岩石地球化学及锆石LA-(MC)-ICP-MS U-Pb和Lu-Hf同位素测试工作。【研究结果】结果表明,苏地岩体二长花岗岩SiO_(2)含量为63.72%~66.48%,中—高钾、富钠、贫钙,AR值为1.44~1.83,A/CNK值为0.98~1.16,为中—高钾钙碱性系列;岩石相对富集K、Rb、Cs等大离子亲石元素(LILE),亏损Nb、Ta、Ti等高场强元素(HFSE);岩石稀土总量为157.16×10^(-6)~187.88×10^(-6),LREE/HREE为6.26~9.46,δEu为0.62~0.74,具有弱—中等的负铕异常;锆石U-Pb定年结果为(221.1±1.5)Ma(MSWD=0.30,n=22)和(214.5±1.5)Ma(MSWD=0.22,n=22),表明苏地岩体原始岩浆初始结晶时代为晚三叠世中期;锆石Lu-Hf同位素εHf(t)和TDM2分别为-6.56~-4.12和1.67~1.51 Ga。【结论】综合分析认为苏地二长花岗岩为较为典型的I型花岗岩,其可能为源于下地壳的初始岩浆于晚三叠世中期在造山碰撞闭合转入伸展体制下上升侵位过程中形成。松潘—甘孜地块东南部在晚三叠世中期处于后碰撞造山环境。This paper is the result of geological survey engineering.[Objective]It is of great significance to find out the geochemical and tectonic evolution characteristics of granite in the southeast of the Songpan-Ganze terrane for searching for rare metal minerals in this area.[Methods]we have carried out field geological survey and conducted whole-rock geochemistry and zircons LA-(MC)-ICP-MS U-Pb and Lu-Hf isotope analyses on the monzogranite of the Sudi pluton in the southeast part of the Songpan-Ganze terrane.[Results]The results show that the samples were mediumhigh potassium,sodium rich and calcium deficiency.The values of AR were 1.44-1.83 and values of A/CNK were 0.98-1.16,which were medium-high potassium calcareous alkaline series.The rocks show relatively enriched large ion lithophile element(LILE),negative high field-strength elements (HFSE),and high REE content (the total amount of REE=157.16×10^(-6)-187.88×10^(-6)) with the LREE enrichement (LREE/HREE=6.26-9.46) and weak negative Eu anomaly europium anomaly (δEu=0.62-0.74).The results of zircon U-Pb dating were (221.1±1.5) Ma (MSWD=0.30,n=22) and (214.5±1.5) Ma (MSWD=0.22,n=22),indicating that the primitive magma of the Sudi pluton crystallized in the middle of the Late Triassic.Its zircon Lu-Hf isotope εHf(t)and TDM2are-6.56--4.12 and 1.67-1.51 Ga.[Conclusions]According to the comprehensive analysis,we believe that the monzogranite in Sudi pluton is a typical I-type granite and it may be formed by the upwelling and emplacement of the initial magma from the lower crust in the middle of Late Triassic in the process of orogenic collision to post-collisional extensional tectonic setting.The southeastern margin of Songpan-Ganze terrane was under post-collisional orogenic environment in Late Triassic.

关 键 词：二长花岗岩 岩石地球化学 锆石U-Pb定年 LU-HF同位素 松潘—甘孜地块东南部 苏地 四川 

分 类 号：P581[天文地球—岩石学] P591[天文地球—地质学]