湘西南脉型金矿的地质特征及其矿床成因

湘西南是湖南重要的产金区,该区金矿以脉型金矿为主。按其成矿元素组合,该区脉型金矿可划分为单金石英脉型和金-锑石英脉型;按其矿体产出形态特征,可划分为顺层式和切层式脉型金矿两种。该区脉型金矿受地层、岩性和构造控制明显,矿物组合简单,金主要以自然金形式产出。该区脉型金矿形成主要与脆、韧性剪切作用有关,雪峰山一带加里东期的剪切作用,使该区的浅变质岩发生变形,并促使地层中的成矿物质发生活化、迁移,最终富集形成金矿床,因此,该区金矿的成因类型为与剪切带有关的中低温热液金矿床。

GEOLOGICAL FEATURES AND GENESIS OF VEINED GOLD DEPOSITS IN SOUTHWESTERN HUNAN

Southwestern Hunan is an important Au-producer in Hunan Province. Among all gold deposits, the quartz-veined gold deposits are most important in southwestern Hunan. The veined gold deposits there can be sub-divided into the Au-single quartz veined type and the Au-Sb quartz veined type in accordance with their element associations; based on the orebody occurrence, the veined deposits also can be sub-divided into the concordant type and the discordant type, the former generally coincides with the wall rocks in occurrence, while the latter cuts through the wall rocks at a high angle. The gold deposits in southwestern Hunan are strictly controlled by the strata, lithology and structure; mineral association usually is simple, gold is present predominantly as native gold. The formation of gold deposits in this area is closely connected with the brittle-ductile shearing. The shear event during the Late Caledonian led to the deformation of low-metamorphic rocks and the activation, transport and enrichment of gold. Thus, the veined gold deposits in southwestern Hunan should be classified as the meso-epithermal type associated with the shear zone.