新疆加尔塔斯克斯套斑岩锆石U-Pb-Hf同位素特征及其对洋脊俯冲的制约  

Characteristics of zircon U-Pb-Hf isotopes for the Gartasksitao porphyritic rocks and constraints on ridge subduction,Xinjiang

作　　者：陶明荣 陆一敢 方科 周奇明 陈青云 TAO Mingrong;LU Yigan;FANG Ke;ZHOU Qiming;CHEN Qingyun(Institute of Minerals Resources and Geology,China Nonferrous Metals(Guilin)Geology and Mining Co.,Ltd.,Guilin 541004,Guangxi,China;CAS Key Laboratory of Crust-Mantle Materials and Environments,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,Anhui,China)

机构地区：[1]中国有色桂林矿产地质研究院有限公司矿产地质研究所,广西桂林541004 [2]中国科学院壳幔物质与环境重点实验室/中国科学技术大学地球和空间科学学院,安徽合肥230026

出　　处：《地质通报》2022年第4期611-625,共15页Geological Bulletin of China

基　　金：国家自然科学基金项目《地壳岩浆活动中的镁同位素分馏及其意义——以喜马拉雅地区典型岩石为例》(批准号:41729001)。

摘　　要：新疆加尔塔斯克斯套斑岩铜矿床位于西准噶尔斑岩成矿带西段,目前研究程度很低。对该矿床花岗闪长斑岩体进行LA-ICP-MS锆石U-Pb年龄、岩石地球化学及Hf同位素组成测试分析。结果显示,该岩体的锆石U-Pb年龄为299.2±5.3 Ma,形成于晚石炭世末—早二叠世初;岩石具有富SiO_(2)、Al_(2)O_(3)、Na,贫K,Mg#值较高,以及高Sr、低Y和Yb含量的特点,显示埃达克岩特征;富集大离子亲石元素Cs、Ba、U和轻稀土元素,亏损高场强元素Ti、Nb、Ta和重稀土元素,无明显Eu异常。斑岩具有高的^(176)Hf/^(177)Hf值,正高ε_(Hf)(t)值(+10.1~+15.6,平均+12.8),以及年轻的两阶段模式年龄(T_(DM2)=307.4~687.1 Ma),显示亏损地幔源区属性,鲜有壳源混染。研究认为,该斑岩体可能形成于洋脊俯冲,并伴有明显的Cu、Au矿化,指示该斑岩铜矿床有良好的找矿潜力。The Gartasksitao porphyry copper deposit is located in the western part of the porphyry metallogenic belt in West Junggar.The LA-ICP-MS zircon U-Pb age,geochemistry,and Hf isotopic compositions of the granodiorite porphyry for this deposit have been analyzed.The results show that the zircon U-Pb age of the granodiorite porphyry is 299.2±5.3 Ma,formed between the Late Carboniferous and the Early Permian.The samples have high SiO_(2),Al_(2)O_(3),Na_(2)O,and low K_(2)O,high Mg#and Sr,low Y,Yb,indicating affinity with the adakitic feature.Trace elements are characterized by enrichment of Cs-Ba-U LILEs and LREEs,depletion of in Ti-Nb-Ta and HREEs,and rarely Eu anomaly.The ^(176)Hf/^(177)Hf ratios are high,with positive ε_(Hf)(t)values(+10.1~+15.6,Avg.+12.8)and young T_(DM2)(307.4~687.1 Ma),indicating that the granodiorite porphyry was derived from a depleted mantle source.It could be suggested that the porphyry was formed by the oceanic ridge subduction,accompanied by considerable Cu and Au mineralization,which indicates that the Gartasksitao porphyry copper deposit has promising prospecting potential.

关 键 词：西准噶尔 斑岩铜矿 锆石U-PB定年 HF同位素 地球化学 加尔塔斯克斯套 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]