德兴铜厂斑岩铜矿脉体类型、分布规律及其对成矿的指示意义

德兴铜矿是中国东部重要的大型斑岩铜矿,由朱砂红、铜厂和富家坞等3个矿床组成。在详细的野外脉体填图基础上,文章把德兴铜厂斑岩铜矿的成矿脉体划分为A脉、B脉、D脉和H脉等4种类型。研究发现,A脉的形成与钾化蚀变有关,脉体不规则且不连续,以粒状石英±钾长石±黑云母±磁铁矿±少量黄铁矿±少量黄铜矿的矿物组合为特征;B脉的形成与钾质硅酸盐水解有关,脉体较规则且连续,以石英±辉钼矿±黄铜矿±黄铁矿的矿物组合为特征,石英颗粒呈典型的梳状或长柱状对称于脉壁生长;D脉的形成与石英-绢云母化蚀变有关,以黄铁矿±石英±黄铜矿的矿物组合为特征,脉壁发育绢云母晕;H脉的形成与碳酸盐化有关,以方解石±赤铁矿±黄铁矿±黄铜矿的矿物组合为特征。这4种脉体分别记录了成矿流体演化至不同阶段,热液蚀变作用的特点及其与Cu-Mo硫化物沉淀的关系。脉体的宽度-间距定量统计分析表明,脉体宽度(T)服从于幂次分布定律;脉体间距(S)服从于负指数分布或介于对数正态分布与负指数分布之间。脉体宽度分维值D值(0.91~1.35)普遍>1,反映脉体系统的连通性较差,矿化程度较弱。脉体间距变差系数Cν值(0.49~0.92)均<1,说明脉体簇生聚集程度较低,矿化程度较弱;处于脉体聚集中心的脉体,代表着热液流体运移的通道,制约着其他脉体的展布。

Types and distribution of veins in Tongchang porphyry copper deposit, Dexing, Jiangxi Province

The Dexing copper ore district is composed of Zhushahong, Tongchang and Fujiawu ore deposits. Based on systematic field observation of veins, the authors divided the veins in the Tongchang porphyry copper deposit into four types:A, B, D and H, which have recorded the evolution of ore fluids. The A-type veins related to primarily K-feldspathization are irregular and slighly mineralized, characterized by quartz±K-feldspar±biotite±magnetite with minor pyrite and chalcopyrite; the B-type veins whose symmetrical pectinate quartz is vertical to the vein wall are enriched in chalcopyrite and molybdenite, related to hydrolysis of potassium silicate and characterized by quartz±molybdenite±chalcopyrite±pyrite; the D-type veins related to sericitization are enriched in pyrite with sericite halos; the latest hypothermal H-type veins related to carbonatization are characterized by calcite±hematite±pyrite±chalcopyrite. A statistical analysis of the thickness distribution of veins in the Tongchang porphyry copper deposit indicates that vein thickness data conform to the power-law distribution whereas the spatial distribution of veins follows a negative exponential law or a law between the negative exponential and log-normal. The fractal dimension D relative to the linkage of vein systems reflects the mineralization rate. The fractal dimension D (0.91~1.35) is high, which indicates poorly-connected systems and weak mineralization. The C_v coefficient (0.49~0.92) is low, which indicates a bad clustered organization of the veins and weak mineralization. The veins located in the clustering center as the function of channel ways for ore fluids are thicker and control the development of vein systems.