Characteristics of alteration and mineralization of the Shaxi porphyry copper deposit, Luzong area, Anhui Province
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摘要:
沙溪斑岩铜矿是长江中下游成矿带中部庐枞火山岩盆地外围的一个大型铜矿床。本文在前人工作基础上, 基于详细的野外观察和系统的岩相学、矿相学工作, 详细研究了矿床的蚀变特征及分带。结果表明, 矿床的蚀变类型有钾硅酸盐化、青磐岩化、长石分解蚀变和高岭土化, 从深到浅依次发育有钾硅酸盐化、长石分解蚀变叠加钾硅酸盐化、长石分解蚀变和高岭土化等蚀变。确定了矿化特征、矿物生成顺序并划分了成矿阶段, 即：钾硅酸盐阶段、石英硫化物阶段和石英碳酸盐阶段, 其中, 石英硫化物阶段又可进一步分为石英硫化物亚阶段和绿帘石-绿泥石亚阶段。基于蚀变及矿化特征认为, 沙溪铜矿床的矿化始于钾硅酸盐阶段的晚期, 石英硫化物亚阶段是黄铜矿主要的沉淀阶段, 石英碳酸盐阶段也对成矿贡献了部分铜质。与世界上不同构造环境的典型斑岩铜矿床对比认为, 沙溪矿床总体上与这些矿床的蚀变、矿化特征类似；与陆缘弧、岛弧、陆内碰撞造山后伸展环境矿床在矿体产出位置、蚀变分带方面相似；而由于围岩性质的差异, 与板内环境的德兴矿床在矿体位置、蚀变分带方面存在差异, 但是二者在脉体类型特别是与矿化关系密切的脉体特征上较为一致。因此, 对于斑岩型矿床而言, 构造背景可能控制了其岩浆的形成、演化以及含矿性, 而岩浆岩最终定位的深度、围岩等条件则控制了其蚀变、矿化特征。
Abstract:Shaxi is a large porphyry copper deposit located outside the Luzong volcanic basin in the Middle and Lower Reaches of the Yangtze River metallogenic belt. Before this study, geological investigations of wall rock alteration and mineralization characteristics of the deposit were minor, restricting application of these guides to exploration and to further study of the metallogenesis of the region. On the basis of previous work plus our detailed field observations and petrographic and mineralogical studies, we have characterized the magmatic rocks and their sequence of intrusion, the mineralogy of alteration (alteration type: potassic alteration, propylitization, feldspar-destructive alteration and kaolinization) and its zoning (from deep to shallow: potassic alteration, feldspar-destructive alteration and kaolinization), the characteristics of mineralization, the sequence of mineral deposition and the ore-forming stages (potassium silicate stage, quartz sulfide stage and quartz carbonate stage; the quartz sulfide stage can be further divided into quartz sulfide sub-stage and epidote-chlorite sub-stage). Based on the characteristics of alteration and mineralization at Shaxi, we find that the chalcopyrite began to precipitate in the late stage of the potassium silicate alteration, and reached a peak during the quartz sulfide sub-stage. The quartz carbonate stage also contributed some copper to the ore. The alteration and mineralization characteristics of Shaxi porphyry copper deposit are generally similar to porphyry deposits in different tectonic environments. The alteration zoning in Shaxi deposit is similar to that in deposits in continental marginal arcs and island arcs, and intracontinental collision post-orogenic extension environments, but the alteration at Shaxi is different from that at Dexing deposit, which occurs in an intraplate setting, but the ore types and mineralization are similar. Consequently, the tectonic setting may control the formation and evolution and the ore-bearing potential of magma, but the final emplacement depth of the magmatic rocks and the nature of their wall rocks control the alteration and mineralization characteristics of porphyry deposits.
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Key words:
- Alteration /
- Mineralization /
- Ore-forming stage /
- Shaxi porphyry copper deposit
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图 2
沙溪斑岩型铜矿床中主要岩浆岩特征
Figure 2.
Characteristics of the major magmatic rock in Shaxi porphyry deposit
图 3
沙溪斑岩型铜矿床13号勘探线蚀变带及脉体分布图
Figure 3.
Alteration zone and veins map of 13 prospecting line in Shaxi porphyry deposit
图 4
沙溪斑岩型铜矿床不同类型的蚀变特征
Figure 4.
Different types of alteration features in Shaxi porphyry deposit
图 5
沙溪斑岩型铜矿床各种脉体特征及相互关系
Figure 5.
Characteristics of the various veins and the relationship between them in Shaxi porphyry deposit
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