德兴斑岩矿田辉钼矿中铼的分布特征及富集机制

Distribution characteristics and differential enrichment mechanism of rhenium in molybdenite in the Dexing copper ore field

世界上绝大部分Re赋存在斑岩型矿床的辉钼矿之中,且分布极不均匀。在矿床-矿石-矿物颗粒等不同尺度上,Re含量均存在较大差异,但造成这些差异的因素目前尚不清楚。本文以德兴矿田中富家坞和铜厂二个矿床的辉钼矿为研究对象,在细致的矿相学研究的基础上,对其开展了EPMA、LA-ICP-MS和XRD分析,同时结合前人研究资料,详细探讨了Re在这两个矿床辉钼矿中的分布规律及差异性富集机制。结果显示:富家坞和铜厂均普遍发育两种形态的辉钼矿(细粒集合体型和粗粒片状型),Re在两种辉钼矿中的分布均极为不均,但细粒集合体型相对更富Re,而同一形态辉钼矿铜厂矿床则具有更高的Re含量;同一矿床中辉钼矿结晶越晚,往往越富集Re;个别辉钼矿可见扭结现象,且扭结部位的Re含量更低,暗示后期构造变形可能导致了Re的丢失;两个矿床高Re辉钼矿和低Re辉钼矿的结构均为2H多型,表明Re含量与辉钼矿晶体结构无关。结合前人资料,本文认为成矿流体性质(如温度、盐度等)是导致铜厂和富家坞辉钼矿Re含量差异的主要因素。

Most of rhenium(Re)in the world is concentrated in molybdenite of porphyry deposits,but Re concentrations vary significantly on the scales of ore deposits,samples and even individual molybdenite.At present,the factors causing these variations are still unclear.This paper focused on the Fujiawu and Tongchang deposits at Dexing copper ore field.Distribution characteristics and enrichment mechanism of Re in molybdenite,by using EPMA,LA-ICP-MS,mapping and XRD,were systematically studied.The molybdenite,the main Re-bearing mineral at Dexing copper ore field,can be divided into two types,coarse-grained leaf-shaped molybdenite and fine-grained aggregate molybdenite.The results of LA-ICP-MS trace elements mapping showed that the distribution of Re in molybdenite is extremely uniform,the fine-grained aggregate molybdenite was more likely to have high value areas of Re.For molybdenite of the same form,the Tongchang deposit often has higher Re contents.For the same deposit,the later molybdenite generally has higher contents of Re than the earlier ones.The kink phenomenon was observed in some molybdenite,and the content of Re in the kink site is lower,suggesting that the late tectonic deformation may lead to the loss of Re.The results of XRD analysis showed that the samples of high Re-bearing and low Re-bearing molybdenite were all 2H polytypes in both the Fujiawu and the Tongchang deposits,which indicated that there was no obvious correlation between the Re contents of molybdenite and molybdenite polytypes.The temperature,salinity and pH were the dominant factors leading to the heterogeneous enrichment of rhenium in molybdenite in the Dexing copper ore field.