多宝山矿田铜山斑岩铜矿床地质特征与蚀变分带:对热液-矿化中心及深部勘查的启示

Geological characteristics and alteration zonation of Tongshan porphyry copper deposit within Duobaoshan orefield,Heilongjiang:Implications for hydrothermal-mineralization center and further exploration

大兴安岭铜山斑岩铜矿床位于中亚成矿域东段多宝山矿集区的东南部。前人对其进行了一些研究工作,但是针对其作为斑岩铜矿类型本身最重要标志的斑岩并未报道,且缺乏对该矿床基础矿床地质特征的详细研究。笔者在详细的野外工作、岩相学和矿相学工作的基础上,首次发现了该矿床的矿化斑岩,并将矿区的蚀变、矿化、脉系,划分出热液期和表生期:热液期包括以磁铁矿-钾长石-黄铁矿(Ⅰ)-黄铜矿-绿帘石-绿泥石为特征的热液活动早阶段,以石英-辉钼矿-黄铜矿-黄铁矿(Ⅱ)-少量闪锌矿-方铅矿及痕量斑铜矿为特征的主成矿阶段,以石英-方解石-黄铁矿(Ⅲ)为特征的热液活动晚阶段以及孔雀石-蓝铜矿及少量蓝辉铜矿为特征的表生期。根据镜下156个薄片中的蚀变矿物鉴定及含量统计,划分出1064勘探线剖面的蚀变矿物组合及分带;根据铜山断层上、下盘蚀变带的类型、组合、强度对比分析,推测热液蚀变成矿中心与斑岩体顶部大致位于ZK1064-2钻孔正下方1400 m深处,这为下一步深部找矿勘探提供了指导方向。

The Tongshan porphyry copper deposit is located in the Duobaoshan orefield of the Da Hinggan Mountains belt, belonging to the east section of Central Asia Metallogenic Domain. Some research work has been done on the Tongshan copper deposit. As a porphyry deposit, however, porphyry intrusion, one of the most typical symbols for all the porphyry deposits, has not been identified. Based on detailed field work, petrography and mineralogy, the authors first found the mineralized porphyry in the Tongshan copper deposit. Systematic work was done upon mineralization, veins systems, and alteration and, on such a basis, the authors divided the epoch of hydrothermal activity in Tongshan into two episodes, with three stages in the hydrothermal period： the early-hydrothermal stage characterized by magnetite, potash feldspar, pyrite（ Ⅰ）, chalcopyrite, epidote and chlorite; the ore-forming stage characterized by molybdenite, chalcopyrite, pyrite（ Ⅱ）, minor sphalerite and galena as well as trace bornite; the late hydrothermal stage characterized by quartz, calcite and pyrite（ Ⅲ）; the supergene period characterized by malachite,azurite and digenite. Through estimation of the amounts of the alteration minerals in 156 thin sections from geological section along No. 1064 prospecting line, the authors established alteration zoning of Tongshan deposit. Based on the contrastive analysis of alteration types, assemblage, intensity of two fault walls, the authors hold that the top of the porphyry intrusion and the center of hydrothermal alteration mineralization are approximately located at the depth of about 1400 m just under drill hole ZK1064-2, and this results offer guiding orientation for further prospecting and exploration.