湖南仁里超大型稀有金属矿床的成矿特征与成矿模型

Metallogenic Characteristics and Prospecting Direction of Renli Super-Large Rare Metal Deposit in Hunan Province, China

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 northwest to southeast zonation.Usually,the pegmatites in the southeast are more fractionated than those in the northwest 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 2 O 5 contents are lower at the surface part and higher at the deep part.Usually,the Ta 2 O 5 contents reach the maximum values(Ta 2 O 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.