湘西雪峰弧形构造带大坪金矿地质特征、成矿流体性质与成矿机理研究

Research on the Geological Characteristics, Ore-Forming Fluid Properties, and Metallogenic Mechanism of the Daping Gold Deposit in the Xuefeng Arcuate Structural Belt, Western Hunan

摘要: 大坪金矿位于江南造山带西缘的雪峰弧形构造带南西段，是典型的韧脆性剪切带蚀变岩型中型金矿床。本文在系统整理矿区地质、地球化学和年代学资料的基础上，重点剖析了矿床的地质特征、矿体展布规律、矿石类型及围岩蚀变组合。通过同位素地球化学(H-O-S)和流体包裹体系统分析，限定了成矿流体的来源、性质及演化过程。研究表明，矿床受区域性F₈韧脆性剪切带及其配套NW向断裂的复合控制，赋矿地层为新元古界青白口系浅变质碎屑岩。成矿流体属中低温(165℃~299℃)、中低盐度(0.7%~24.3% NaCleqv)、中低压的H₂O-NaCl体系，成矿物质主要源于深部岩浆，并有地层物质的贡献。文章建立了“深部岩浆驱动、构造控矿、热液充填–交代”的成矿模式，指出NE向与NW向构造交汇部位及已知矿体深部是重要的找矿方向。

Abstract: The Daping gold deposit is located in the southwestern segment of the Xuefeng arc-shaped structural belt on the western margin of the Jiangnan Orogenic Belt. It is a typical medium-sized gold deposit of the type of altered rocks in ductile-brittle shear zones. Based on the systematic collection and analysis of geological, geochemical and chronological data of the mining area, this paper focuses on the geological characteristics, orebody distribution patterns, ore types and alteration assemblages of the deposit. Through the systematic analysis of fluid inclusions and isotopic geochemistry (H-O-S), the source, nature and evolution process of the ore-forming fluids were determined. The study indicates that the deposit is controlled by the regional F8 ductile-brittle shear zone and its associated NW-trending faults. The ore-bearing strata are the shallowly metamorphosed clastic rocks of the Neoproterozoic Qingbaikou System. The ore-forming fluids are of medium-low temperature (165˚C~299˚C), medium-low salinity (0.7%~24.3% NaCleqv), and medium-low pressure, belonging to the H₂O-NaCl system. The ore-forming materials mainly originated from deep magmas, with contributions from strata. A “deep magmatic driving, structural control, hydrothermal filling-replacement” ore-forming model was established, and it was pointed out that the intersection of NE-trending and NW-trending structures and the deep part of known orebodies are important exploration directions.