滇西云县红豆山铜矿床流体地球化学和成矿年代学研究

The northern section of the south Lancangjiang metallogenic belt is an important part of Sanjiang tectonic magmatic belt in China, Yunxian Hongdoushan copper deposit is a newly discovered ore deposit in the northern section of the south Lancangjiang metallogenic belt.Copper ore bodies are vein and net vein, a small amount of disseminated and massive structure which are found in the Triassic in.the tectonic-alteration zone of Xiaodingxi group, The general distribution direction of the copper ore-body is nearly consistent with the direction of long axis of the deep porphyry vein , and higher grade and more thick ore bodies are in deep. Deep exploit engineering shows that granite porphyry side development radial tectonic - alteration mineralization belt, and is closely associated with the characteristics of porphyry spatial distribution . Above characteristics indicated tectonic - alteration mineralization belt controlled by concealed granite porphyry .Therefore, this study intended to be the Hongdoushan copper deposits as the main object，to the petrography of fluid inclusions as a breakthrough point, on the basis of the fine analysis of the ore deposits, by studing the fluid inclusions of copper-bearing quartz veins and calcite vein, chalcopyrite Re - Os isotope dating, the dating analysis of zircon U - Pb in granite porphyry , which expounds the source of ore-forming fluid of the deposit and the conditions of T - P - X of ore-forming, ore-forming material sources, determine the metallogenic epoch, reveals its metallogenic mechanism, to explain the metallogenic belt magmatic.hydrothermal mineralization for providing theoretical support and favorable basis.

南澜沧江成矿带北段是我国“三江”构造岩浆带的重要组成部分，云县红豆山铜矿床为该成矿带近年来新发现的矿床。铜矿体多呈脉状、网脉状，少量浸染状、块状产于上三叠统小定西组的构造-蚀变带中，总体展布方向与深部斑岩脉长轴方向近一致，向深部具增厚加富趋势；深部开拓工程显示花岗斑岩旁侧发育放射状构造-蚀变矿化带，且与斑岩空间展布特征关系密切。以上特征指示构造-蚀变矿化带受隐伏花岗斑岩控制。因此，拟以红豆山铜矿床为主要研究对象，流体包裹体岩相学研究为突破点，在矿床精细解剖的基础上，通过含铜石英脉、方解石脉的流体包裹体研究、黄铜矿Re-Os同位素测年、花岗斑岩中锆石U-Pb定年分析，阐明矿床的成矿流体来源及成矿T-P-X条件，成矿物质来源，厘定成矿时代，揭示其成矿机制，为解释该成矿带岩浆热液成矿作用提供理论支撑和有利依据。

云县红豆山铜矿是南澜沧江成矿带新发现的铜矿床，矿体主要分布在隐伏花岗斑岩顶部的长英质构造-蚀变带和石英脉中，成矿地质条件好。在构造-蚀变分带研究基础上，开展含铜脉体流体包裹体地球化学研究，结合C-O同位素特征、硫化物电子探针分析、深部揭露与成矿有关的斑岩锆石U-Pb定年、赋矿围岩（玄武质安山岩）锆石U-Pb定年，阐明成矿流体来源、成矿物质来源特征，厘定成矿时代，揭示其成矿机制，为南澜沧江成矿带岩浆热液矿床和斑岩铜矿床研究提供有利依据。.（1）红豆山铜矿床蚀变类型以硅化、钾长石化、绿泥石化、绿帘石化为主，其次为碳酸盐化、绢云母化、黄铁矿化等。蚀变受NE向F1和NWW向F3断裂控制明显。自断裂带至上盘围岩划分了4个蚀变分带：长英岩化-硅化带(Ⅰ)→长英岩化-碳酸盐化-绢云母化带(Ⅱ)→硅化-绿泥石化-绿帘石化带(Ⅲ)→弱长英岩化带（围岩）(Ⅳ)。深部揭露花岗斑岩脉中心至外围发育钾化带→绢云母化带→青磐岩化带。.（2）不同构造-蚀变带元素迁移特征表明：主量元素SiO2、K2O、Fe2O3在蚀变过程中的迁移量较大，与Cu成矿密切，微量元素Cu、Zn、Mo、Ag、U、K、P、Th在蚀变带中以迁入为主。.（3）流体包裹体研究表明，包裹体类型单一，仅发育纯液相和富液相气液两相包裹体两种，包裹体相对较小，类型相对单一。成矿流体温度变化于118.2-233.2℃之间，早阶段→晚阶段平均温度由163.7℃→为153.7℃；流体盐度（NaCleq）变化于6.88-21.33%之间;密度变化于0.94-1.08g·cm-3；流体包裹体中存在少量CO2成分，其水峰显示中低盐度流体特征。成矿流体为中-低温，中-低盐度的岩浆热液与大气降水混合流体。.（4）方解石δ13Cv-PDB/‰值介于-7.02‰～-6.13‰，平均值（-6.67‰）；δ13Ov-SMOW/‰值介于8.56‰～10.92‰，平均值9.66‰。说明C可能主要由岩浆热液作用提供。.综上，总结红豆山铜矿床成矿机制为：晚三叠世，由于碰撞转为伸展引张机制，富含铜元素的中酸性岩浆经多次上侵和分异演化，到晚期岩浆结晶阶段分异出富含挥发分和成矿元素的热液，并上侵入地表，在有利构造部位沉淀成矿。