四川冕宁地区苏雄组火山岩地球化学、年代学特征及其意义  

Geochemical and Chronological Characteristics of Volcanic Rocks of Suxiong Formation in Mianning Area,Sichuan Province and Their Significance

作　　者：吴广彬 徐争启[1,2,3] 孙岳 田建民 阚磊 张苏恒 Wu Guangbin;Xu Zhengqi;Sun Yue;Tian Jianmin;Kan Lei;Zhang Suheng(College of Earth Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059;Sichuan Key Laboratory of Earth Science and Technology,Chengdu,Sichuan 610059;Key Laboratory of Earth Exploration and Information Technology,Ministry of Education,Chengdu,Sichuan 610059;Institute No.209 of CNNC,Kunming,Yunnan 650101)

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]地学核技术四川省重点实验室,四川成都610059 [3]地球勘探与信息技术教育部重点实验室,四川成都610059 [4]云南省核工业二○九地质大队,云南昆明650101

出　　处：《资源环境与工程》2024年第2期121-129,共9页Resources Environment & Engineering

基　　金：国家自然科学基金项目“康滇地轴粗粒晶质铀矿标型特征及形成机理”(41872079);成都理工大学珠峰科学研究计划项目“青藏高原东缘热液铀矿成矿机理”(2022ZF11413);中国核工业地质局科研项目“康滇地轴新元古代铀成矿关键控矿因素研究”(2018-07)、“康滇地轴前寒武纪地质构造演化及其对铀成矿的制约”(2023-16)。

摘　　要：扬子板块西缘广泛发育苏雄组火山岩,其岩石地球化学及年代学特征对探讨该区苏雄组火山岩与铀成矿关系具有重要意义。采集四川冕宁地区苏雄组流纹岩样品,通过分析其全岩主量、微量、稀土元素及锆石U-Pb-Lu-Hf同位素组成,对苏雄组流纹岩的岩石类型、岩浆源区以及构造演化背景进行研究。苏雄组流纹岩锆石U-Pb年龄为(823.8±3.7)Ma(MSWD=3.4),表明其形成于新元古代早期。流纹岩具有高硅(SiO_(2)=70.14%~76.75%,平均74.19%)、高碱(K_(2)O+Na_(2)O=6.66%~7.67%,平均7.25%)、低铝(Al_(2)O_(3)=11.36%~13.12%,平均12.10%)、低钙(CaO=0.26%~2.39%,平均1.08%)、低镁(MgO=0.18%~0.74%,平均0.37%)的特征,属于过铝质碱性系列岩石;相对富集Th、Rb、U、Zr、Hf,相对亏损Ba、P、Nb、Ti、Sr,具有轻稀土元素相对富集、重稀土元素相对亏损、Eu明显负异常、稀土元素配分曲线呈海鸥型分布的特征,并具有较高的10000 Ga/Al值、Y/Nb值和锆石饱和温度,指示其属于A_(2)型长英质岩浆岩;流纹岩的锆石Lu-Hf同位素组成指示其来源于新增生地壳的部分熔融,并受到地幔物质的混入。综合分析认为苏雄组火山岩形成于新元古代早期后碰撞活动大陆边缘的拉张伸展环境,构造演化过程中洋壳俯冲后退导致的富钠软流圈上涌促进了U的富集,苏雄组火山岩具有提供铀源的良好条件。The volcanic rocks of the Suxiong Formation are widely developed in the western margin of the Yangtze Plate,and their geochemical and chronological characteristics are of great significance for exploring the relationship between the volcanic rocks of the Suxiong Formation and uranium mineralization in this area.Collect rhyolite samples from the Suxiong Formation in Mianning area,Sichuan,and analyze their major,trace,and rare earth element compositions,as well as zircon U-Pb-Lu-Hf isotope compositions,to study the rock type,magma source area,and tectonic evolution background of the Suxiong Formation rhyolite.The zircon U-Pb age of the Suxiong Formation rhyolite is(823.8±3.7)Ma(MSWD=3.4),indicating that it was formed in the early Neoproterozoic.Rhyolite has the characteristics of high Si(SiO_(2)=70.14%~76.75%,average 74.19%),high alkali(K_(2)O+Na_(2)O=6.66%~7.67%,average 7.25%),low Al(Al_(2)O_(3)=11.36%~13.12%,average 12.10%),low Ca(CaO=0.26%~2.39%,average 1.08%),and low Mg(MgO=0.18%~0.74%,average 0.37%),and belongs to the peraluminous alkaline series rocks.Relatively enriched in Th,Rb,U,Zr,and Hf,and relatively deficient in Ba,P,Nb,Ti,Sr,it has the characteristics of relatively enriched light rare earth elements,relatively deficient heavy rare earth elements,obvious negative anomalies in Eu,and a seagull shaped distribution of rare earth element distribution curves.It also has high values of 10000 Ga/Al,Y/Nb,and zircon saturation temperature,indicating that it belongs to A_(2)type rhyolite.The zircon Lu-Hf isotope composition of rhyolite indicates that it originated from partial melting of newly accreted crust and was mixed with mantle material.It is believed that the volcanic rocks of the Suxiong Formation were formed in the extensional environment of the collision active continental margin in the early Neoproterozoic.During the tectonic evolution process,the subduction and retreat of the oceanic crust led to the upwelling of the enriched sodium asthenosphere,which promoted uranium enrichment.The volcanic rocks

关 键 词：苏雄组 A型花岗岩 锆石U-PB年龄 LU-HF同位素 铀矿 

分 类 号：P588.14[天文地球—岩石学] P59[天文地球—地质学]