四川省汉源地区苏雄组火山岩地球化学特征及其对铀成矿作用的启示  

GEOCHEMICAL CHARACTER ISTICS OF THE SUXIONG FORMATION VOL-CANIC ROCKS IN HANYUAN AREA,SICHUAN PROVINCE AND ITS IMPLI-CATION FOR URANIUM MINERALIZATION

作　　者：阚磊 徐争启[1,2,3] 田建民 吴广彬 KAN Lei;XU Zhengqi;TIAN Jianming;WU Guangbin(College of Earth Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059,China;Key Laboratory of Earth Eploration and Information Technology,Ministry of Education,Chengdu,Sichuan610059,China;Sichuan Key Laboratory of Geoscience and Nuclear Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]地球勘探与信息技术教育部重点实验室,四川成都610059 [3]地学核技术四川省重点实验室,四川成都610059

出　　处：《矿物岩石》2023年第3期48-59,共12页Mineralogy and Petrology

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”(批准号:41872079);成都理工大学珠峰科学研究计划(项目编号:2021ZF11413);四川省应用基础研究项目“四川冕宁一攀枝花地区新元古代铀成矿作用及成矿机理研究”(项目编号:2020YJ0361);中国核工业地质局项目“康滇地轴前寒武纪地质构造演化及其对铀成矿的制约”(项目编号:2023-16)。

摘　　要：为了解扬子陆块西缘铀成矿与苏雄组火山岩年代学特征、构造环境之间的关系,初步建立铀富集机理,对扬子陆块西缘的铀富集与成矿提供新的理论依据,本次研究在结合前人研究的基础上,对汉源地区苏雄组火山岩的元素地球化学特征、锆石U-Pb测年及Lu-Hf同位素进行分析,苏雄组酸性火山岩富硅(SiO_(2)=66.27%~77.02%)、富钾(K_(2)O=2.72%~7.29%)、富铝(Al_(2)O_(3)=11.65%~18.84%),属钙碱性-碱性系列岩石;A/NK为1.43~3.12,A/CNK为1.36~3.01,属强过铝质。岩石相对富集Rb, Th, U,La, Ce,而相对亏损Ba, Nb, Ta, Ti,具有较高的稀土总量(ΣREE=196.83×10^(-6)~2 062.21×10^(-6)),相对富集轻稀土,亏损重稀土,轻重稀土分异明显((La/Yb)N比值为4.10~13.63),具有明显的Eu负异常(δEu=0.27~1.60)。样品具有相对高的10 000 Ga/Al值,锆石饱和温度908~1 003℃,指示其具有A2型花岗岩的地球化学特征。定年结果显示苏雄组酸性火山岩形成于新元古代中期为809.0±6.6 Ma, εHf(t)值为0.5~3.3,平均1.82,TDM1=1 266~1 337 Ma,平均1 303 Ma,为中元古代。苏雄组火山岩来源为中元古代的新增生中基性下地壳部分熔融并有幔源组分加入,形成于俯冲大背景下的弧后伸展环境,表明了扬子陆块西缘俯冲环境的阶段性和复杂性,洋壳的俯冲后退造成富Na软流圈的上涌为铀的富集提供了萃取剂和热点,表明了840~780 Ma弧后发展至弧前的扬子陆块西缘具有一定的铀成矿潜力。Based on previous studies,the elemental geochemical characteristics,zircon U-Pb dating and Lu-Hf isotope analysis of the Suxiong Formation volcanic rocks in the Hanyuan area are analyzed to study the relationship between uranium mineralization in the western margin of the Yangtze Block and the chronology and tectonic environment of the Suxiong Formation volcanic rocks,establishing the uranium enrichment mechanism and providing a new theoretical basis for uranium mineralization in the west margin of the Yangtze Block.The results show that the acid volcanic rocks of Suxiong Formation are rich in silica(SiO_(2)=66.27%-77.02%),potassium(K_(2)O=2.72%-7.29%)and aluminum(Al_(2)O_(3)=11.65%~18.84%),belonging to the calc-alkaline series of rocks.A/NK ranges from 1.43 to 3.12,and A/CNK ranges from 1.36 to 3.01,showing strong peraluminous character.The Suxiong Formation acid volcanic rocks are relatively rich in Rb,Th,U,La and Ce,and relatively deficient in Ba,Nb,Ta and Ti,having a high total amount of rare earths(ZREE=196.83×10^(-6)-2062.21×10^(-6)).It is relatively rich in light rare earths,and relatively deficient in heavy rare earths.The differentiation of light and heavy rare earth is obvious(La/Yb)n ratio=4.10-13.63),with an obvious Eu negative anomaly(δEu=0.27-1.60).The samples of volcanic rocks have a relatively high value of 10,000 Ga/Al,and the saturation temperature of zircon is 908 to 1 o03 C,displaying geochemical characteristics of A2-type granite.Geochronology dating of Suxiong Formation acidic volcanic rocks yields a Mesoproterozoic age(809.0±6.6 Ma,εHf(t)value ranging from 0.5 to 3.3 with an average of 1.82,and TDMi=1266 to 1337 Ma with an average of 1303 Ma).It is considered that the Suxiong Formation volcanic rocks were derived from the partial-melting-induced new accretion of lower basic crust with addition of mantle-derived components in the Mesoproterozoic and were formed in a back arc extensional environment under subduction background,indicating the stage and complexity of the subduction environ

关 键 词：苏雄组火山岩 构造环境 汉源地区 铀富集与成矿 弧后伸展环境 

分 类 号：P619.14[天文地球—矿床学]