尼日利亚中部纳萨拉瓦地区卡马伟晶岩型锂铌钽矿床锆石与锡石U-Pb年代学、Hf同位素组成及其地质意义  

Zircon and Cassiterite U-Pb Geochronology and Hf Isotopes of Kama Li-Nb-Ta Pegmatite Deposit and Its Geological Significance in Nasarawa,Central Nigeria

作　　者：曹亮 胡鹏[1,2] 姜军胜 陈鑫[3,4] 向鹏 李乐广[5] 卢山松 赵凯 童喜润[1] 王建青 Cao Liang;Hu Peng;Jiang Junsheng;Chen Xin;Xiang Peng;Li Leguang;Lu Shansong;Zhao Kai;Tong Xirun;Wang Jianqing(Wuhan Center,China Geological Survey(Central South China Innovation Center for Geosciences),Wuhan 430205,China;Research Center for Petrogenesis and Mineralization of Granitoid Rocks,China Geological Survey,Wuhan 430205,China;School of Earth Resources,China University of Geosciences,Wuhan 430074,China;State Key Laboratory of Geological Processes and Mineral Resources,Wuhan 430074,China;School of Earth Sciences,China University of Geosciences,Wuhan 430074,China;Tianjin North China Geological Exploration General Institute Co.,Ltd,Tianjin 300170,China)

机构地区：[1]中国地质调查局武汉地质调查中心(中南地质科技创新中心),湖北武汉430205 [2]中国地质调查局花岗岩成岩成矿地质研究中心,湖北武汉430205 [3]中国地质大学资源学院,湖北武汉430074 [4]地质过程与矿产资源国家重点实验室,湖北武汉430074 [5]中国地质大学地球科学学院,湖北武汉430074 [6]天津华北地质勘查总院,天津300170

出　　处：《地球科学》2024年第11期3971-3994,共24页Earth Science

基　　金：中国地质调查局地质调查项目(No.DD20230576);中国地质调查局花岗岩成岩成矿地质研究中心开放基金项目(No.PMGR202103).

摘　　要：尼日利亚中部纳萨拉瓦地区是典型的含锂铌钽稀有金属伟晶岩脉发育的地区.卡马花岗伟晶岩型稀有金属矿床位于尼日利亚锂铌钽锡多金属成矿带的中部,是新发现的以锂为主,伴生铌钽矿的大型矿床,为限定其成矿年龄,探讨其矿化过程的来源及演化,对含矿伟晶岩脉开展了岩石学、矿物学、锆石及锡石U-Pb年代学、锆石微量元素和Lu-Hf同位素等研究.锆石和锡石的U-Pb年代测定结果表明,锆石U-Pb定年为(577.3±2.5)Ma(n=18,MSWD=6.4),锡石U-Pb定年为(582.6±8.6)Ma(n=25,MSWD=0.72),推断马锂矿床伟晶岩形成于577~583 Ma,矿床成矿作用主要发生在新元古代晚期.微量地球化学研究表明,研究区伟晶岩在俯冲‒碰撞作用中形成,其岩浆源区主要为变质沉积岩,起源自陆壳.岩浆演化过程可能经历了斜长石、磷灰石、锆石等矿物的分离结晶作用.岩浆的强烈分离结晶演化作用导致岩石具有高分异演化特征.伟晶岩的锆石、锡石和铌钽铁矿Hf同位素组成表明,锆石的εHf(t)值在‒20.6和‒19.0之间,TDM2值为2.7 Ga;锡石的εHf(t)值在‒17.7和‒14.9之间,TDM2值在2.4 Ga和2.6 Ga之间变化.铌钽铁矿的εHf(t)值在‒15.9和‒7.4之间,TDM2值在2.0 Ga和2.4 Ga之间变化,表明伟晶岩的母体熔体主要起源于新太古代‒古元古代基底岩的重熔作用.尼日利亚稀有金属伟晶岩矿床成矿与冈瓦纳造山运动关系密切,与冈瓦纳形成造山运动的碰撞后伸展期相对应.The Nasarawa region in central Nigeria is a typical area with developed lithium-niobium-tantalum rare metal pegmatite veins.The Kama granitic pegmatite-type rare metal deposit,located in the central part of the Nigerian lithiumniobium-tantalum-tin polymetallic metallogenic belt,is a newly discovered large deposit mainly containing lithium with associated niobium and tantalum ores.To define its metallogenic age and explore the sources and evolution of its mineralization process,this paper conducts a study of petrology,mineralogy,zircon and cassiterite U-Pb geochronology,zircon trace elements,and Lu-Hf isotopes on the ore-bearing pegmatite veins The zircon U-Pb dating yields the ages of(577.3±2.5)Ma(n=18,MSWD=6.4),and the cassiterite U-Pb dating yields the ages of(582.6±8.6)Ma(n=25,MSWD=0.72),therefore the pegmatite of the Kama deposit is inferred to have formed between 577 and 583 Ma,with the main mineralization occurring in the late Neoproterozoic.Trace elementsgeochemical analyses indicate that the pegmatites in the study area were formed during subduction-collision processes,with their magma source primarily being metamorphic sedimentary rocks,originating from the continental crust.The magma evolution process may have involved fractional crystallization of minerals such as plagioclase,apatite,and zircon.The intense fractional crystallization evolution of the magma results in rocks with highly differentiated evolutionary characteristics.The Hf isotopic compositions of zircon,cassiterite and columbite-tantalite in pegmatite show that theεHf(t)value of zircon is between‒20.6 and‒19.0,and the TDM2 value is 2.7 Ga;TheεHf(t)value of cassiterite is between‒17.7 and‒14.9,and the TDM2 value varies between 2.4 Ga and 2.6 Ga.TheεHf(t)value of Columbite-tantalite is between‒15.9 and‒7.4,and the TDM2 values are between 2.0 Ga and 2.4 Ga,indicating that the parent melt of pegmatite mainly originated from the remelting of Neoarchean-Proterozoic basement rocks.The mineralization of rare metal pegmatite deposit

关 键 词：锆石U-Pb定年 锡石U-Pb定年 微量元素 Hf 同位素 伟晶岩 成矿时代 尼日利亚 地球化学. 

分 类 号：P611[天文地球—矿床学] P585[天文地球—地质学] P597