河南大庄铌稀土矿床褐钇铌矿的发现及其地质意义

大庄铌稀土矿床赋存于双山碱性岩体中。岩石地球化学分析结果表明,岩体中SiO2含量53.68%~57.80%,Al2O3含量19.17%~22.61%,Na2O+K2O含量10.95%~16.40%,A/NK比值1.38~1.83,分异指数(DI)91.23%~96.33%,具有高分异、富硅和富碱特征,是典型的A型花岗岩。少量的霞石伟晶岩脉和晶洞的出现,说明含矿碱性正长岩的形成与岩浆-热液阶段有关。铌矿的富集与萤石、钠长石化密切相关,含矿碱性正长岩比无矿碱性正长岩分异程度高,该矿床属岩浆分异型矿床类型。矿床可利用的独立矿物主要为褐钇铌矿,富含钇族稀土元素,钽的含量较低,具有其独特性。矿石伴生稀土∑REE含量为791.24×10^-6~1831.70×10^-6,有一定的综合利用价值。

Discovery of fergusonite from Dazhuang niobium rare earth deposit in Henan Province and its geological significance

The Dazhuang niobium rare earth deposit occurs in Shuangshan alkaline rock body.The results of rock geochemistry analysis show that the rock mass consists of 53.68%~57.80%of SiO 2,19.17%~22.61%of Al 2O 3 and 10.95%~16.40%of Na 2O+K 2O,with A/NK ratio of 1.38~1.83 and DI of 91.23%~96.33%.It is with high differentiation,rich in silicon and alkali,and is a typical A-type granite.The occurrence of small amounts of nepheline pegmatite veins and crystal cavities indicates that the formation of ore-bearing alkali syenite is related to magmatic-hydrothermal stage.The enrichment of niobium ore is closely related to fluorite and albitization,the ore-bearing alkaline syenite is more differentiated than the alkaline syenite without niobium ore,the deposit belongs to the type of magmatic differential deposit.The main available independent mineral of the deposit is fergusonite,it is rich in yttrium rare earth elements with low tantalum content.The∑REE content in ore is 791.24×10^-6~1831.70×10^-6,with certain value for comprehensive utilization.