川滇黔交界地区铅锌矿床含矿角砾岩特征及其构造意义

川滇黔交界地区的铅锌矿床中普遍发育含矿角砾岩。文章综述了角砾岩的成因分类,在重点矿床野外地质调查的基础之上,对川滇黔交界地区的铅锌矿床含矿角砾岩进行了详细研究。结果表明:大部分含矿角砾岩显示张性角砾岩的特点,仅个别矿床同时出现挤压角砾岩。综合区域地质构造演化特征和典型铅锌矿床的同位素测年数据,可大致推断出,从中二叠世茅口期以来该铅锌成矿区伸展构造至少有2期:一期发生在铅锌矿化之前或同时,即早二叠世/晚二叠世的升降运动(东吴运动)与晚二叠世峨眉山玄武岩喷发期间,此次伸展作用形成的角砾岩为成矿流体提供了大量的容矿空间,并最终导致成矿流体沿断裂运移并充填沉淀而形成角砾状或网脉状-脉状构造的矿石;另一期发生在铅锌矿化之后,即白垩纪—古近纪,发育一系列正断层,并有可能破坏了铅锌矿体的连续性。

Feature of ore-bearing breccias of lead-zinc deposits in Sichuan-Yunnan- Guizhou border area and its tectonic significance

Ore-bearing breccias commonly exist in lead-zinc deposits in the Sichuan-Yuanan-Guizhou border area. On the basis of a comprehensive study of the genetic classification of breccias and the field geological investigation in key deposits, the authors studied the features of ore-bearing breccias in lead-zinc deposits in the Sichuan-Yuanan-Guizhou border area. The results demonstrate that most of the ore-bearing breccias show features of extensional breccias, with compressional breccias seen in a few deposits. Through combining geological evolution of this area with the metallogenic epochs of the existing typical lead-zinc deposits based on isotope dating data, the authors roughly infer that there have existed at least two extensional tectonic events in this lead-zinc ore district since the middle Permian Maokou period: one extension occurred before or simultaneously with the mineralization, i.e., the early Permian/late Permian uplift and subsidence movement (Dongwu movement) and the Late Permian Emeishan basalt eruption period. The breccias formed by this extension provided extensive space for ore-forming fluids, which subsequently moved along the fault, filled the space and precipitated, forming breccia or stockwork ores. The other extension occurred after the mineralization, i.e. from Cretaceous to Paleogene, during which a series of normal faults was formed, which destroyed the continuity of the lead-zinc body.