云南大红山铁铜矿床钠质赋矿岩系成因及其成矿意义

Although has been researched for decades, the metallogenesis of the Dahongshan Fe-Cu deposit in Yunnan Province is still unsolved due to the lack of a clear understanding to the genesis of the Proterozoic sodic ore-hosting strata “Manganghe Formation-Hongshan Formation” of the Dahongshan Group. Our previous study discovered some surgary albites in the strata, which is the typical texture of metasomatism. Thus, this project proposal decide to focus the study on the genesis of the albite in the strata, to understand the exact origin of the deposit. Optical Microscope Cathode Luminescence (OM-CL) and Scanning Electron Microscope Cathode Luminescence (SEM-CL) analyses will be used to observe the microstructure of the albite; In-situ elemental analyses will be performed in the way of Electro-Probe Microanalyzer (EPMA) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS); Microscopic temperature measurement and component analysis on the Primary fluid inclusions in the albite will be used to confirm the characteristics of the fluid. According to the features above, we can affirm the genesis of the albite and the sodic ore-hosting strata of the “Manganghe -Hongshan Formation”. Associate with the precise dating such as zircon SHRIMP U-Pb, Molybdenite/Chalcopyrite Re-Os, Fluorite Sm-Nd, elemental geochemistry and isotopic analyses, we will contract the geochronology and other characteristics of the strata and the ores to know the essence of the “Hongshan Formation” and its construction to the mineralization. Thus, the metallogenesis of the Dahongshan deposit will be revealed, to further elucidate the Proterozoic geodynamic scenario of the central Yunnan region.

云南大红山铁铜矿床成因长期以来未达成共识（喷流沉积/岩浆-火山-气液交代），争议集中于区内元古代大红山群曼岗河组-红山组钠质赋矿围岩是同生钠质角斑岩还是后生钠质交代岩。本次研究以在该岩系中发现交代糖粒状钠长石为契机，以钠长石成因为主要研究对象，通过光学显微镜阴极发光和扫描电镜-阴极发光，精细观察其显微结构；通过电子探针、元素扫描、LA-ICP-MS，测定其原位元素组成及分布；对钠长石中原生流体包裹体进行显微测温及包裹体成分分析，确定流体性质；总结对比上述特征，确认钠长石成因类型，进而确认曼岗河组-红山组钠质赋矿围岩成因。结合锆石SHRIMP U-Pb、辉钼矿/黄铜矿Re-Os、萤石Sm-Nd年龄、元素地球化学和同位素特征，对比各地层/地质体和矿床时代和性质，确定原“红山组”真正成因及成矿贡献。结合最新矿床学研究资料，确定大红山铁铜矿床成因，进而对理解滇中地区元古代动力学演化和成矿做出贡献。

云南大红山铁铜矿床成因长期以来未达成共识（喷流沉积亦或岩浆-火山-气液交代），争议集中于区内元古代大红山群曼岗河组-红山组钠质赋矿围岩是同生钠质角斑岩还是后生钠质交代岩。本项目以云南嘎洒大红山矿区曼岗河组-红山组一、二段钠质赋矿围岩中不同类型钠长石的性质和成因、红山组第三段熔岩的年代和成因为重点研究对象，针对不同成因的钠长石样品展开岩矿鉴定、显微镜+阴极发光电子成像分析（OM-CL）、高分辨率扫描电镜+阴极发光电子成像分析（SEM-CL）、电子探针（EPMA）/激光剥蚀电感耦合等离子体质谱仪（LA-ICP-MS）原位成分测定，对比国内外已有研究资料，确认钠长石成因类型，并在此基础上对曼岗河组钠质赋矿围岩的成因做出判断；通过对红山组第三段熔岩和第一段火山岩进行精细的锆石SHRIMP U-Pb同位素测年工作以对比其形成时代；对矿床进行详细的地质考察，重点观察其产出特征，岩矿组构，围岩蚀变，构造特征，成矿期次等。全面搜集总结前人已有矿床地球化学、同位素数据，着重讨论物质来源、流体性质和成矿机制三个方面的问题。结合上述系统研究，建立大红山矿床成矿模式，为区域成矿规律研究和下一步找矿预测提供依据。