邦布造山型金矿床黄铁矿原位微量元素特征及其成矿意义

In Situ Trace Element Analysis of Pyrite from Bangbu Orogenic Gold Deposit and Its Metallogenic Significance

邦布金矿床是目前在雅江缝合带研究程度最高且唯一正在开采的大型造山型金矿床.为理解邦布金矿床中金的来源及迁移沉淀机制,运用原位微区分析技术对邦布矿床中不同世代含金黄铁矿的微量元素组成进行测定.结果显示,亲铁元素Co、Ni主要以类质同象的形式进入到黄铁矿的晶格中替代Fe,As和Se呈类质同象形式替换S,Au是以纳米颗粒的形式均匀或不均匀的分布于不同产状的黄铁矿之中.邦布金矿床中的含金石英脉中三个不同世代的黄铁矿的Co/Ni比值均小于1,保存了围岩中黄铁矿的信息,显示出一种沉积或沉积改造成因.Au与As和Se具有明显的正相关关系,As和Se对Au的迁移及富集具有重要的作用.

The Bangbu deposit is the only large orogenic gold deposit that is being exploited with the highest degree of research in the Yurlung-Zangbo suture zone. In order to understand the source, transportation and precipitation of Au in the Bangbu deposit,in situ microanalysis technique was used to obtain the trace elements compositions of Au-bearing pyrite from different generations.In situ trace elements results show that the siderophile elements Co and Ni mainly enter the lattice of pyrite to substitute Fe while As and Se substitute S in the form of isomorphism. Gold is distributed evenly in different generations of pyrite in the form of nanoparticles. The Co/Ni ratios of pyrite from three generations of Au -bearing quartz veins are all less than 1 which preserve the information of pyrite of the surrounding rocks indicating a kind of sedimentation or sedimentation-reformation origin. As and Se play important roles in the migration and accumulation of Au as Au has obvious positive correlation with As and Se.