广西龙头山金矿床黄铁矿标型特征及其地质意义

Typomorphic features of pyrites from the Longtoushan gold deposit,Guangxi Province and the geological significance

广西龙头山金矿床是大瑶山成矿带内重要的金矿床,矿区发育大量不同类型的黄铁矿。根据黄铁矿的产出特征,将黄铁矿划分为5个世代,对应着5个成矿阶段:电气石-石英-硫化物阶段(Ⅰ)、石英-黄铁矿-黄铜矿阶段(Ⅱ)、石英-多金属硫化物阶段(Ⅲ)、石英-黄铁矿-闪锌矿阶段(Ⅳ)、石英-黄铁矿阶段(Ⅴ)。不同阶段黄铁矿晶形均以{100}为主,少见{210};金含量与{210}含量呈正相关。黄铁矿晶胞参数为5.411 86~5.415 52,变化幅度不大,与钴含量呈正相关,主成矿阶段受金含量影响而变大。形貌及砷含量变化特征表明,{210}和金含量随砷含量降低而升高,说明砷含量降低利于{210}的出现,且金与砷不存在正相关关系。形貌特征及微量元素特征均反映主成矿阶段温度应>220℃,且多集中于>300℃的范围;δFe—δS图解及矿床地质特征表明,成矿热液主要为岩浆热液。综合分析认为,龙头山金矿床为中-高温岩浆期后热液矿床。

The Longtoushan deposit is a very important gold deposit in the Dayaoshan metallogenic belt.Different types of pyrite are widespread in the study area.Based on occurrences the pyrites are divided into 5types corresponding to 5 mineralization stages：tourmaline-quartz-sulfide stage（Ⅰ）,quartz-pyritechalcopyrite stage（Ⅱ）,quartz-polymetallic sulfide stage（Ⅲ）,quartz-pyrite-sphalerite stage（Ⅳ）and quartz-pyrite stage（Ⅴ）.{100}pyrite is the main crystal form in all stages.There is also some{210}pyrite,and Au content is positively related to the content of{210}pyrite.The cell parameters of pyrite are in a narrow range 5.411 86-5.415 52 and positively related to the content of Co and the range gets bigger with change of the gold content in the main metallogenic stage.The morphology and the concentration change of As indicate that the contents of{210}pyrite and gold increase with the decrease of As.This suggests that there is no positive correlation between the contents of As and Au.The ore-forming temperature may be〉220℃and mainly concentrate in the range〉300℃according to morphology and trace elements.TheδFe—δS diagram and geological features of the deposit indicate that the ore-forming fluid is mainly magmatic hydrothermal fluid.We conclude that the Longtoushan deposit is a medium-high temperature post-magma hydrothermal type gold deposit.