摘要
湖南仁里铌钽矿床位于燕山期幕阜山复式岩体西南缘,是我国近年来新发现的超大型花岗伟晶岩型铌钽矿床,伟晶岩脉产在花岗岩内部裂隙或灌入冷家溪群片岩中。矿区伟晶岩可分为微斜长石型、微斜长石钠长石型、钠长石型和钠长石锂辉石型四个类型分带,且脉体呈NE-SW向分布。相对于北东部的伟晶岩,南西部的伟晶岩具有较高的分异度,铌钽矿化程度高,仁里矿区为幕阜山地区铌钽矿化浓集中心,是幕阜山地区铌钽等稀有金属主要产地。较大规模伟晶岩脉具有较完善的分带,铌钽矿化主要产在伟晶岩内部的中-粗粒白云母钠长石带和锂云母石英带。各伟晶岩脉总体上具有地表品位低,深部品位升高的特点,在标高411 m时,品位达到最高值(Ta_2O_5品位0.438%),说明仁里矿区深部具有较大找矿潜力。本文在总结仁里矿床成矿特征和成矿规律的基础上,分析了周边及深部的找矿方向,建立了复式岩体"体中体"成矿模型。区域找矿需要重视浅部低品位伟晶岩脉的深部评价,按照"北找钽铌、南找锂"的原则开展外围找矿工作。
The Renli super-large rare metal deposit, which is located at the western-southern part of the Mufushan granitic complex in Hunan province, is a newly explored granitic pegmatite type Nb-Ta deposit. Most pegmatite dykes are intruded into the Neoproterozoic schists. The pegmatite dykes can be divided into microcline type, microcline-albite type, albite type and albite-spodumene type. These types of pegmatite dykes exhibit north-west to south-east zonation. Usually, the pegmatites in the south-east are more fractionated than those in the north-west part of the ore field, and are the ore-forming concentration center of rare metal elements in the Mufushan area. The large pegmatites commonly have clear internal zoning, and the Ta-Nb mineralization mainly occurs in the coarse muscovite-albite zone and lepidolite-quartz zone. Ta-Nb mineralization is closely associated with lepidolite, muscovite and leaf-shape albite. In most of the pegmatites, the Ta_2O_5 contents are lower at the surface part and higher at the deep part. Usually, the Ta_2O_5 contents reach the maximum values(Ta_2O_5: 0.438%) at the elevation of about 411 m. These features indicate a great ore-prospecting potential at the depth of the Renli Nb-Ta deposit. Based on these ore-forming features, an ore-forming model of the Renli deposit is established, and attention should be paid to the deep part of pegmatites with low Ta-Nb contents at the shallow parts in ore-prospecting. In addition, the neighboring areas in the north and south part of the orefield may also be promising for Ta-Nb and Li prospecting.
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