| 云南北衙超大型金多金属矿床斑岩阶段成矿流体演化——来自流体包裹体并结合H-O同位素的约束 |
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| 引用本文：周向科,章西焕,王佳璇.2026.云南北衙超大型金多金属矿床斑岩阶段成矿流体演化——来自流体包裹体并结合H-O同位素的约束[J].地球学报,47(5):971-986. |
| DOI：10.3975/cagsb.2026.082501 |
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| 基金项目:本文由自然资源部科技创新发展项目(编号: 102121191130000009001)和自然资源科普与重大科技成果宣传项目(编号: 102121191130000009001)联合资助。 |
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| 中文摘要:北衙金多金属矿床是金沙江—红河富碱斑岩成矿带内典型的斑岩-矽卡岩复合型超大型矿床, 发育斑岩型Cu(-Mo)-Au、矽卡岩型Au-Cu-Fe及外围Pb-Zn-Ag等多类型矿化。已有研究多关注矽卡岩及复合热液阶段的流体演化, 而斑岩阶段不同脉体所记录的流体性质、相分离过程及Cu-Mo-Au沉淀机制仍缺乏系统约束。本文以斑岩阶段的A脉、B脉和D脉为研究对象, 开展流体包裹体岩相学和显微测温研究, 并结合已有H-O同位素资料, 探讨斑岩阶段成矿流体来源、演化及矿质沉淀过程。结果显示: A脉中发育VL相、LV相和LVH相三类包裹体, 均一温度为207~438 ℃, 盐度为3.33~47.66 wt. % NaCl equiv., 指示早期岩浆出溶热液具有明显的相态和盐度非均一性, 并引起钾长石化, 但硫化物沉淀较弱。B脉中VL相、LV相和LVH相包裹体共存, 均一温度和盐度范围较宽, 盐度呈低盐度与高盐度两组分布特征, 结合脉体中黄铜矿、黄铁矿和辉钼矿大量发育, 指示减压沸腾或流体相分离是Cu-Mo-Au卸载的重要机制。D脉以LV相包裹体为主, 均一温度和盐度整体降低, 并发育绢云母化和大量硫化物, 结合H-O同位素向大气降水线方向偏移, 表明晚阶段开放体系中大气降水混入促进了流体稀释、温度下降和金属络合物失稳。综合认为, 北衙斑岩阶段Cu-Mo-Au富集沉淀可能主要受早期岩浆流体出溶、B脉阶段减压沸腾/相分离及D脉阶段流体混合共同控制, 该流体演化过程为理解北衙斑岩-矽卡岩复合成矿系统提供了约束。 |
| 中文关键词:斑岩阶段脉体 流体包裹体测温 成矿流体演化 北衙金多金属矿床 |
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| Porphyry-stage Ore-forming Fluid Evolution in the Giant Beiya Au Polymetallic Deposit, Yunnan, China: Fluid Inclusion and H-O Isotopic Constraints |
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| Abstract:The Beiya Au polymetallic deposit, a giant porphyry–skarn system in the Jinshajiang–Red River alkali-rich porphyry metallogenic belt, is characterized by porphyry Cu(-Mo)-Au, skarn Au-Cu-Fe, and distal Pb-Zn-Ag mineralization. Previous studies have focused mainly on skarn-related and composite hydrothermal stages, whereas studies on fluid evolution recorded by porphyry-stage veins and its role in Cu-Mo-Au precipitation remain scarce. This study focuses on porphyry-stage A, B, and D veins, using fluid inclusion petrography and microthermometry, combined with published H-O isotopic data, to constrain the source, evolution, and metal precipitation processes of the ore-forming fluids. A veins contain VL, LV, and LVH inclusions with homogenization temperatures of 207–438 °C and salinities of 3.33–47.66 wt. % NaCl equiv., indicating an early magmatic–hydrothermal fluid with pronounced phase and salinity heterogeneity that caused potassic alteration with limited sulfide precipitation. B veins contain coexisting VL, LV, and LVH inclusions with broad temperature-salinity ranges and two salinity populations, are characterized by abundant chalcopyrite, pyrite, and molybdenite, suggesting that depressurization-related boiling or phase separation was a key trigger for Cu-Mo-Au deposition. D veins dominated by LV inclusions are associated with sericitization and abundant sulfides with generally lower temperatures and salinities. Combined with H-O isotopic compositions trending toward meteoric water, these features indicate that late-stage meteoric water input promoted fluid dilution, cooling, and destabilization of metal complexes. Overall, Cu-Mo-Au enrichment during the porphyry stage at Beiya may be controlled by early magmatic fluid exsolution, B-vein boiling/phase separation, and D-vein fluid mixing, providing constraints on the porphyry–skarn composite ore-forming system. |
| keywords:porphyry-stage veins microthermometry of fluid inclusions ore-forming fluid evolution Beiya gold polymetallic deposit |
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