新疆南天山洋大陆弧岩浆作用:乌瓦门早泥盆世火山岩地球化学及Lu-Hf同位素特征  

Continental Arc Magmatism in the Southern Tianshan Ocean,Xinjiang:Constraints from Geochemistry and Lu-Hf Isotopes of the Early Devonian Wuwamen Volcanic Rocks

作　　者：田昊 刘希军[1,2] 刘潇 刘鹏德 宋宇嘉 肖尧 张治国 TIAN Hao;LIU Xijun;LIU Xiao;LIU Pengde;SONG Yujia;XIAO Yao;ZHANG Zhiguo(Guilin University of Technology,Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources,Guilin 541004,Guangxi,China;Xinjiang Research Center for Mineral Resources,Xinjiang Institute of Ecology and Geography,Chinese Academy of Sciences,Urumqi 830011,Xinjiang,China;College of Civil Engineering,Hexi University,Zhangye 734000,Gansu,China)

机构地区：[1]桂林理工大学,广西隐伏金属矿产勘查重点实验室,有色金属矿产勘查与资源高效利用协同创新中心,广西桂林541004 [2]中国科学院新疆生态与地理研究所新疆矿产资源研究中心,新疆乌鲁木齐830011 [3]河西学院土木工程学院,甘肃张掖734000

出　　处：《大地构造与成矿学》2025年第2期437-453,I0024,I0025,共19页Geotectonica et Metallogenia

基　　金：国家自然科学基金项目(92055208);广西战略性关键矿产资源成矿与勘查科技创新基地建设项目(桂科ZY21195031);广西八桂学者项目(2018-有色金属成矿理论与勘查技术);广西研究生教育创新计划项目(YCBZ2024172、YCBZ2023145);甘肃省青年科技基金项目(23JRRG0017);甘肃省教育厅博士基金项目(2023QB-084);河西学院博士科研启动基金项目(KYQD2023010)联合资助。

摘　　要：中天山地块位于天山造山带中部,广泛发育泥盆纪火山岩,记录了南天山洋的构造演化历史。本次研究对新疆中天山乌瓦门泥盆纪火山岩中的玄武岩、玄武安山岩和安山岩进行了年代学、地球化学及锆石Lu-Hf同位素组成研究,以约束新疆天山造山带构造演化。LA-ICP-MS锆石U-Pb定年结果显示,玄武岩的^(206)Pb/^(238)U年龄为398±3 Ma,为早泥盆世。火山岩SiO_(2)平均含量为53.38%、Al_(2)O_(3)平均含量为16.80%,K_(2)O平均含量为1.19%,Na_(2)O平均含量为3.60%,为钙碱性岩,具有类似岛弧岩浆的地球化学特征,如轻稀土元素(LREE)相对重稀土元素(HREE)较富集,HREE分配模式平坦,富集大离子亲石元素(LILE)Ba、Th和U,相对亏损高场强元素(HFSE)Nb、Ta和Ti。乌瓦门玄武岩中锆石的ε_(Hf)(t)值为−13.0~−10.6,表明其源区相对富集,具有壳源特征,可能是由于俯冲流体交代岩石圈地幔发生部分熔融而产生。综合分析表明,乌瓦门火山岩可能形成于南天山洋俯冲至中天山地块之下的大陆弧环境。The central Tianshan-Yili block,situated within the middle of the Tianshan Orogenic Belt,is characterized by widespread Devonian volcanic rocks.The Wuwamen volcanic rocks mainly comprise basalt,basaltic andesite,and andesite.To elucidate the tectonic evolution of the Tianshan Orogenic Belt in Xinjiang,we conducted zircon U-Pb dating,Lu-Hf isotopes,and geochemical analysis of the volcanic rocks.LA-ICP-MS zircon U-Pb dating yielded an Early Devonian age of 398±3 Ma.The volcanic rocks belong to the calc-alkaline series,and exhibit island-arc geochemical characteristics,such as LREE enrichment,flat HREE pattern,LILE enrichment(e.g.,Ba,Th,and U),and HFSE depletion(e.g.,Nb,Ta,and Ti).The Lu-Hf isotopic analyses revealed ^(176)Hf/^(177)Hf ratios ranging from 0.282138 to 0.282635,with correspondingε_(Hf)(t)values ranging from-13.0 to-10.6.The geochemical and isotopic data suggest that the Wuwamen basalts were derived from a mantle source that experienced significant crustal contamination.It is inferred that the basalts originated from the partial melting of a lithospheric mantle metasomatized by subduction fluid,with subsequent incorporation of Paleoproterozoic crustal materials during magma ascent.The results suggest that the Wuwamen volcanic rocks formed in a continental arc setting associated with the northward subduction of the Southern Tianshan Ocean beneath the Central Tianshan Block during the Early Devonian.

关 键 词：火山岩 中天山 乌瓦门 地球化学 锆石Lu-Hf同位素 

分 类 号：P581[天文地球—岩石学]