稀有金属花岗岩结晶分异过程中铷的富集与成矿:来自江西甘坊岩体的矿物学证据  

Rb mineralization during magmatic differentiation:Insight from mineralogical study on the Ganfang rare metal granite,Jiangxi Province

作　　者：徐净 侯文达 王力圆 赵太平[2] 陈素余 田立明 XU Jing;HOU Wenda;WANG Liyuan;ZHAO Taiping;CHEN Suyu;TIAN Liming(Zijin School of Geology and Mining,Fuzhou University,Fuzhou,Fujian 350108,China;Key Laboratory of Mineralogy and Metallogeny,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou,Guangdong 510640,China;Geophysical and Geochemical Exploration Brigade of Jiangxi,Nanchang,Jiangxi 330000,China)

机构地区：[1]福州大学紫金地质与矿业学院,福建福州350108 [2]中国科学院广州地球化学研究所矿物学与成矿学重点实验室,广东广州510640 [3]江西省地质矿产勘查开发局物化探大队,江西南昌330000

出　　处：《地质学报》2023年第11期3766-3785,共20页Acta Geologica Sinica

基　　金：南京大学内生金属矿床成矿机制研究国家重点实验室(编号2021-LAMD-K07);中国地质调查局花岗岩成岩成矿地质研究中心开放基金(编号PMGR202004)联合资助的成果。

摘　　要：内容提要:铷的成矿与稀有金属花岗岩密切相关。由于稀有金属花岗岩中普遍存在晚阶段热液蚀变,很难厘清岩浆过程与热液过程,稀有金属成矿起主导作用的是岩浆分异作用,还是热液交代作用,目前的认识尚不清晰。江西甘坊岩体是一个重要的稀有金属成矿区,当前在甘坊岩体内发现了一系列花岗岩型和细晶岩脉型锂铷稀有多金属矿床(点),其稀有金属成矿机制仍不明确。本文选择甘坊岩体内的白果、大港、楠木坑花岗岩型铷矿和富华、同安细晶岩型铷矿为研究对象,采用矿物自动扫描系统、电子探针、LA-ICP-MS等方法对多种花岗岩中的长石类和云母类矿物进行精细结构和成分分析。结果表明:云母类矿物是铷的主要载体(Rb=1683×10^(-6)~12047×10^(-6)),长石类矿物中铷含量低,其中钾长石铷含量为1683×10^(-6)~4051×10^(-6),而钠长石几乎不含铷(1.82×10^(-6)~89.94×10^(-6))。富铷锂的云母由白云母经锂多硅白云母和铁锂云母向锂云母转变,其中锂主要通过2Li^(+)+^(Ⅳ)Si^(4+)←→^(Ⅵ)Al^(3+)+^(Ⅵ)Al^(3+)+□和Li^(+)+Fe^(2+)←→^(Ⅵ)Al^(3+)+□,铷主要以Rb^(+)/Na^(+)/Cs^(+)←→K^(+)的方式进入云母。矿物结构和成分特征显示,甘坊岩体中铷、锂等稀有金属的富集与岩浆分异作用有关,结晶分异作用可能是晚阶段熔体中铷、锂等稀有金属富集的关键,而流体交代作用对稀有金属的富集作用不明显。The Rb mineralization is associated with rare metal granites.However,widespread hydrothermal alteration in the late evolution of rare metal granites makes it difficult to distinguish the magmatic process from the hydrothermal process.It is still unclear whether the rare metal mineralization is dominated by magmatic differentiation or hydrothermal metasomatism.The Ganfang intrusion in the Jiangxi Province is an important rare metal metallogenic area,where a series of Li-Rb rare metal deposits(mineralization)have been discovered,and the mineralization mechanism of rare metals is not yet clear.This paper takes both granite-type Rb(Baiguo,Dagang,and Nanmukeng)and aplite-type Rb(Fuhua,Tongan)mineralization from the Ganfang intrusion for case studies.The detailed mineralogy texture and composition of feldspars and micas have been analyzed by automatic mineral scanning system,electron probe and LA-ICP-MS.The results show that micas are the main carriers of Rb(1683×10^(-6)~12047×10^(-6)),and the contents of Rb in feldspars are lower.The Rb content of K-feldspar is 1683×10^(-6)~4051×10^(-6),whereas albite contains almost no Rb concentration(1.82×10^(-6)~89.94×10^(-6)).The Rb-bearing micas transfer from muscovite,though Li-phengite and zinnwaldite,to lepidolite,in which substituted mechanisms for Li are 2Li^(+)+^(Ⅳ)Si^(4+)←→^(Ⅵ)Al^(3+)+^(Ⅵ)Al^(3+)+□ and Li^(+)+Fe^(2+)←→↔^(Ⅵ)Al^(3+)+□,and for Rb is Rb^(+)/Na^(+)/Cs^(+)←→K^(+).The mineral textures and compositions record both magma crystallization differentiation and fluid metasomatism for Ganfang granites;however,the former was the key enrichment mechanism for Rb as well as Li.

关 键 词：稀有金属 花岗岩 铷 富集机制 甘坊岩体 江西 

分 类 号：P618.6[天文地球—矿床学]