湖南板溪锑矿床的成矿地质特征

GEOLOGICAL CHARACTERISTICS OF THE FORMATION OF BANXI ANTIMONY DEPOSITS IN HUNAN

矿床位于雪峰古陆南部边缘，锡矿山北北东向锑矿带向北延伸与雪峰古陆东西向锑金矿带的交汇部位；板溪群五强溪组硅铝质板岩为主要赋矿围岩；燕山晚期东西向的石英斑岩脉群产于矿区北部，其含锑金较高，少数被合锑金石英脉穿插；矿床蚀变作用（毒砂化，黄铁矿化等）主要表现为热液扩散作用，蚀变矿物的生成途径包括热液带入成分的晶出和热液作用下原岩矿物解离，生成新的蚀变矿物；锑作为矿床成矿元素其迁方式以渗滤为主，扩散次之，在成矿演化过程中具有构造分异与亲断裂的特性；锑在成矿溶液中主要呈硫的络合物（ＮａｓｂＳ３）形式搬运，可溶性ＳｉＯ２是搬运锑的载体，表现为蚀变围岩明显的去硅去钠（带出）作用；变质作用与岩浆期后热液作用提供双热源，为成矿物质活化迁移的主要驱动因素。矿床属中低温热液充填辉锑矿－石英脉矿床。

Antimony deposits are situated on an intersection between the Xikuangshan NNE-striking extented toward the north antimony belt on the edge of the southern part of the Xuefeng oldland and the EW-striking antimony -gold belt within the Xuefeng oldland.Siliceous -aluminous slate of the Banxi Group Wuqiangxi Formation is the major ore-host rock.Late Yanshanian EW-striking quartz porphyry veins with higher antimony and gold occur in the north of the mining area, which are intersected in the minority by antimony-and gold-bearing quartz veins. Alteration of ore deposit(arsenopyritization,pyritization and so cu)is mainly displayed by hydrothermal diffusion process.The way ofthe formation of altered minerals includes decrystallization of hydrothermally introduced compositions and newly emerging altered minerals by means of dissociation of original minerals as a result of the hydrothermal process. Antimony, as an ore-forming element has a main migration pattern of percolation and a minor migration pattern of diffusion and possesses structure differential and fracturephile feature in the evolution process of metallogenesis. Antimony is migrated mainly as a sulfur complex(NaSbS3)in the ore-forming solution. Soluble SiO2 is a carrier of antimony migration, showing obviously and dealbitization of alteration rocks. Metamorphism and the postmagmatic hydrothermal process provided doublethermal source. It is a major drive factor of remobilizition migration of ore forming substances. Antimony deposits belong to the moderat-icw-temperature hydrothermal filliug stibnite-quartz vein type.