南岭铋矿床的产出特征及成因探讨

南岭成矿带是我国乃至世界上最重要的铋矿产地。该区铋矿床的研究尽管起步较早,但进展缓慢,其产出特征及成因认识仍很薄弱。本文通过系统搜集、综合分析矿山基础地质资料和前人研究成果,在时空分布规律、含铋矿物类型、矿床成因等方面取得一定认识。南岭成矿带有湘南、粤北、崇-余-犹、于-赣等四大铋矿聚集区;铋矿床类型主要有石英脉型、矽卡岩型、蚀变花岗岩型、破碎带型、充填交代型、斑岩型等六种,以石英脉型铋矿数量最多,矽卡岩型铋矿储量最大;铋矿床形成年龄介于170~150 Ma之间,与相关花岗岩体侵入年龄相近。目前已发现含铋矿物30余种,涵盖自然元素、硫化物、含硫盐、氧化物、含氧盐、碲化物、铋化物、氟化物等类型,以铋的含硫盐最为丰富。含铋矿物组合在不同类型铋矿床中有所差异,但一般产在矿脉中下部,且由浅至深矿物中硫的原子百分比呈下降的趋势。南岭铋矿床的主要成矿物质来自花岗岩浆,在花岗岩浆形成过程中有地幔流体的加入,成矿中晚阶段大气降水的混入可能是铋大量沉淀的重要因素。

The occurrence and genesis of Bi deposits in the Nanling region

The Nanling region is the most important Bi metallogenic area in China and even in the world. Despite early efforts, their occurrence and genesis remain unclear. Ourcomprehensive study of the geological survey data and previous research has allowed us to obtain understanding of their spatial and temporal distribution, bismuth mineral characteristics,ore forming material source, and factors influencing precipitation. There are three metallogenic zones (South Hunan province, Chong Yu You and Yu Gan) and six styles of Bi mineralization (hydrothermal quartz vein, skarn, altered granite, fracturezone, filling metasomatism and porphyry). Hydrothermal quartz vein type has the most extensive distribution, but the skarn type enjoys the largest reserves.Both the Bi mineralization and related granitic magma emplacement in the Nanling region mainly occurred at 170~150 Ma. More than thirty bismuth minerals have been found in this region, including natural element, sulfide, sulfosalt, oxide, oxysalt, telluride, bismuthide and fluoride, with the sulfosalt being the most abundant. The bismuth mineral assemblages vary in different deposits, but show certain spatial zonal rules. The ore forming material was derived mainly from granitic magma with the addition ofmantle fluid. The mixture between magmatic fluid and air saturated water at the middle late fluid evolution stagemay have accounted for the mass Bi precipitation.