【摘要】 普雄铌稀土矿床位于滇东南建水县,是新发现赋存于长岭岗碱性岩体风化壳中的一个超大型富铌稀土矿床。目前,该矿床探获稀土矿石量3.6亿t,稀土氧化物量47万t,铌金属量5.7万t,以轻稀土元素富集为特征。本文通过对具有代表性的15号勘探线60号钻孔20件各种类型铌稀土矿石样品进行分析测试,初步查明了该矿床的矿物学和元素地球化学特征。显微镜下鉴定和XRD、SEM分析结果显示,该矿床Ⅰ号和Ⅱ号矿体残留造岩矿物主要有正长石、斜长石、霞石、云母和磁铁矿等,次生矿物主要为高岭石、三水铝石和蒙脱石等,主要稀土矿物及含稀土矿物为独居石、氟碳铈矿、铅锰铈矿和方钍石等。稀土矿物和含稀土矿物主要呈他形粒状、针状和板状等分布于高岭石、云母和正长石的裂隙和解理中,部分独立分布。ICP-MS分析结果显示,稀土元素含量变化范围较大,但相对球粒陨石均有不同程度富集,总体表现为Ⅰ号矿体样品∑REE(766×10^-6～8942×10^-6)高于Ⅱ号矿体(1029×10^-6～6043×10^-6)。全部样品轻稀土（∑LREE）总量(748×10^-6～8841×10^-6)明显高于重稀土（∑HREE）总量(14×10^-6～101×10^-6),∑LREE/∑HREE=42～114,（La/Yb）_N=92～1001,且轻稀土内部分异（（La/Sm）_N=21～52）较重稀土内部分异（（Gd/Yb）_N=2～11）更明显。全部样品均具有Eu负异常特征,其δEu值为0.44～0.72。不同类型样品的Ce异常特征不同,Ⅰ号矿体样品具有明显的负Ce异常（δCe=0.02～0.52,仅ZK15-60-02样品的δCe=1.34）,Ⅱ号矿体样品具有弱的负Ce异常（δCe=0.41～0.85,仅ZK15-60-18样品的δCe=1.97）;全部样品中微量元素含量也均有较大变化范围,与上地壳元素平均含量相比,Li、Zn、Ga、Zr、Nb、Cd、Sb、Cs、Tl、Pb、Th和U等有不同程度富集,Sc、V、Cr、Co、Ni、Cu和Sn等有不同程度亏损。综合研究表明,内生成岩作用和外生成矿作用共同导致了该矿床轻、重稀土的分异与富集,内生成岩作用为矿床提供物质来源,外生成矿作用导致铌稀土元素进一步富集。更多还原

【Abstract】 The Puxiong Nb-REE deposit is located in the Jianshui City, southeast Yunnan Province, SW China. It is a large-scale Nb-REE deposit in the weathering crust of Changlinggang granitic alkaline rock body. At present, the deposit has yielded 360 million tons of REE ores, 0.47 million tons of REE oxides, and 57000 tons of Nb metal, which are characterized by the enrichment of light rare earth elements（LREE）. In this paper, the mineralogical and elemental geochemical characteristics of the deposit have been preliminarily identified through the analysis and testing of 20 kinds of niobium rare earth ore samples from No.60 drilling hole in the No.15 exploration line. The results of microscope, XRD and SEM studies show that there are orthoclase, plagioclase, nepheline, mica and magnetite in the remaining rock-forming minerals of the deposit, the secondary minerals are mainly kaolinite, gibbsite and montmorillonite, the main REE minerals and REE-containing minerals are monazite, bastnaesite, mianningite and thorianite. REE minerals and REE-containing minerals are mainly distributed in the fissures and cleavages of kaolinite, mica, and orthoclase, mainly in the shape of granular, needle-like and plate-like, and some of them are distributed independently. ICP-MS analysis results show that the REE contents also change greatly, ∑REE contents(766×10^-6～8942×10^-6) of No.Ⅰ ore body are higher than those of No.Ⅱ ore body(∑REE=1029×10^-6～6043×10^-6). The total contents of LREE(∑LREE=748×10^-6～8841×10^-6) were significantly higher than those of HREE(∑HREE=14×10^-6～101×10^-6), ∑LREE/∑HREE=42～114,（La/Yb）_N=92～1001, and the internal differentiation of LREE（（La/Sm）_N=21～52） was more obvious than that of HREE（（Gd/Yb）_N=2～11）. All the samples have negative Eu anomalies, with δEu values ranging from 0.44 to 0.72. Different ores types have different Ce anomaly characteristics. The samples of No. I ore body have obvious negative Ce anomalies（δCe=0.02～0.52, only δCe=1.34 for sample ZK15-60-02）, and the samples of No.Ⅱ ore body have weak negative Ce anomalies（δCe=0.41～0.85, only δCe=1.97 for sample ZK15-60-18）. The trace elements content also have a large range, but compared with the Clark values of the upper crust, Li, Zn, Ga, Zr, Nb, Cd, Sb, Cs, Tl, Pb, Th and U are relatively enriched, while Sc, V, Cr, Co, Ni, Cu and Sn are relatively depleted. The results show that the differentiation and enrichment of LREE and HREE were caused by the internal diagenesis and the external mineralization. The internal diagenesis provided the material source for the deposit, and the external mineralization resulted in the further enrichment of Nb-REE.更多还原