摘要
云南省建水县普雄风化壳离子吸附型铌稀土多金属矿床(简称普雄矿床)是在滇东南长岭岗碱性岩风化壳中发现的大型铌稀土(Nb-REE)矿床,以稀土为主,共/伴生Nb_(2)O_(5)资源量5.7万吨。本文利用XRD、TIMA、SEM、EPMA、LA-ICP-MS、ICP-MS等测试方法对采自3个钻孔、2条剖面的风化壳及霞石正长岩样品开展矿物学和地球化学研究,旨在揭示Nb的来源、赋存状态和富集规律。结果表明,风化壳中Nb主要来自霞石正长岩中的Nb-U矿物(贝塔石、铌钙矿、烧绿石等)、榍石和片榍石。在弱风化层和半风化层Nb主要赋存于正长石、含铌矿物以及云母类矿物中,而在全风化层和黏土层则主要赋存于高岭石、伊利石、铁锰(氢)氧化物和云母类矿物中,整个风化壳中可能普遍存在携带着全岩一半以上铌含量的含铌矿物(如残留的贝塔石、次生的铌钽铀矿等)。碱长正长岩风化壳中Nb的含量普遍低于霞石正长岩风化壳。在风化壳纵向上,Nb的平均含量总体从弱风化层的99.2×10^(−6)向上逐渐升高到黏土层的160×10^(−6),但单个钻孔中黏土层相较全风化层顶部有所降低。此外,从山顶到山脊、山脚,相同风化层中Nb含量明显升高。综上表明基岩贡献、风化壳矿物组合以及地形地貌差异共同制约了普雄矿床铌的富集规律。
The Puxiong deposit is a large niobium-rare earth(Nb-REE)polymetallic deposit found in the weathering crust of the Changlinggang alkaline rocks in Jianshui County,Southeast Yunnan.It hosts 57,000 t of Nb_(2)O_(5) besides the huge REE reserve.To determine the source,occurrence,and enrichment mechanism of Nb,the mineralogical and geochemical compositions of samples from the weathered crust and nepheline syenite bed rock collected from three drills and two profiles were analyzed by using XRD,TIMA,SEM,EPMA,LA-ICP-MS,and ICP-MS methods.The results show that the primary sources of Nb in the weathering crust are Nb-U minerals(betafite,fersmite,pyrochlore,etc.),titanite,and hiortdahlite in the nepheline syenite.Niobium mainly occurs in residual orthoclase,Nb-bearing minerals,and secondary mica minerals in the weakly and semi-weathered layers.In the completely weathered and humic layers,niobium is generally enriched in kaolinite,illite,iron manganese(hydro-)oxide,and mica.Niobium-bearing minerals(e.g.,residual betafite,secondary liandratite)accounting half of the Nb content of the whole rock occur throughout the weathered crust.The content of Nb in the weathering crust of the alkali-feldspar syenite is generally lower than that in the weathering crust of nepheline syenite.And the average content of Nb increases vertically from 99.2×10^(−6) in the weakly weathered layer to 160×10^(−6) in the humic layer.Furthermore,the Nb concentration in the same layers increases significantly from the hilltop to the footslope.In summary,the bedrock,the mineral assemblage,and topography and landform constrain the enrichment of Nb in the Puxiong deposit.
作者
王敏
周家喜
周美夫
肖嵩
李音
张子军
WANG Min;ZHOU Jiaxi;ZHOU Meifu;XIAO Song;LI Yin;ZHANG Zijun(School of Earth Sciences,Yunnan University,Kunming 650500,Yunnan,China;Key Laboratory of Critical Minerals Metallogeny in Universities of Yunnan Province,Kunming 650500,Yunnan,China;State Key Laboratory of Deposit Geochemistry,Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550081,Guizhou,China;No.209 Geological Team of Yunnan Nuclear Industry,Kunming 650034,Yunnan,China)
出处
《大地构造与成矿学》
EI
CAS
CSCD
北大核心
2022年第6期1057-1074,共18页
Geotectonica et Metallogenia
基金
国家自然科学基金重大研究计划重点项目(91962216)
云南大学与核工业二〇九地质大队合作科研项目(2019-2021)
云南大学科研启动项目(YJRC4201804)联合资助。
关键词
矿物学
地球化学
铌(Nb)
普雄矿床
长岭岗碱性岩
霞石正长岩
mineralogy
elemental geochemistry
niobium(Nb)
Puxiong deposit
Changlinggang alkaline rocks
nepheline syenite
