| 扬子西缘东炉房Cu-Mo矿床侵入岩年代学、地球化学特征及其成矿意义 |
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| 引用本文：段召艳,张有名,杨新强,杜斌,伍建兢,杨富成,江小均.2024.扬子西缘东炉房Cu-Mo矿床侵入岩年代学、地球化学特征及其成矿意义[J].地球学报,45(4):515-529. |
| DOI：10.3975/cagsb.2024.042401 |
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| 基金项目:云南省科技计划项目高层次科技人才及创新团队选拔专项(编号: 202305AT350004) |
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| 中文摘要:东炉房Cu-Mo矿床位于扬子陆块西缘, 矿床发育与石英二长斑岩相关的斑岩型Mo(-Cu)矿和接触带矽卡岩型Cu矿。前人开展的研究工作主要集中在斑岩Mo矿化的成因, 但是对矽卡岩型Cu矿化的研究较为薄弱。本文基于系统整理项目组对该矿床的勘查成果, 对矽卡岩型Cu矿化有关的石英闪长玢岩开展锆石U-Pb年代学和岩石地球化学分析。结果表明, 石英闪长玢岩锆石U-Pb加权平均年龄为82 Ma, 表明其形成于晚白垩世, 与格咱弧晚白垩世W-Mo(Cu)成矿作用时代一致。石英闪长玢岩具有高硅(SiO2=60.74%~ 63.36%)、富碱(Na2O+K2O=7.03%~9.29%)特征, 属准铝质(A/CNK=0.63~0.86)、钾玄岩系列I型花岗岩。岩石具有轻、重稀土分异明显(右倾型)和典型的埃达克质岩亲和性特征, 可能为幔源岩浆注入中-基性下地壳部分熔融的产物。岩浆岩源区性质、围岩类型等条件决定了东炉房矿床的矿化分带性, 深部石英二长斑岩的钾化带内发育斑岩型Mo(-Cu)矿化, 浅部石英闪长玢岩和碳酸盐岩接触带发育矽卡岩型Cu(-Mo)矿化, 外围大理岩局部发育脉状Pb-Zn-Au-Ag矿化。矿床由深到浅、由内到外构成了Mo(-Cu)→Cu(-Mo)→Pb、Zn、Au、Ag的斑岩成矿系统。通过区域综合对比认为格咱弧晚白垩世岩浆岩及相关成矿作用向南延伸至扬子陆块西缘, 形成于碰撞后伸展环境, 且由北往南岩浆分异程度逐渐降低, 幔源岩浆贡献逐渐增多, 导致成矿作用差异明显(休瓦促W-Mo→热林Mo-W→红山、铜厂沟Mo(-Cu)→东炉房Cu(-Mo))。 |
| 中文关键词:石英闪长玢岩 U-Pb年代学 地球化学 晚白垩世 东炉房 扬子西缘 |
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| Geochronology and Whole-rock Geochemistry of Intrusive Rocks from the Donglufang Cu-Mo Deposit in Western Margin of the Yangtze Block and Their Metallogenic Implications |
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| Abstract:The Donglufang Cu-Mo deposit is located in the western margin of the Yangtze Block. The deposit is characterized by porphyry Mo (-Cu) orebodies associated with quartz monzonite porphyry and skarn Cu orebodies. While previous research has mainly focused on the genesis of porphyry Mo mineralization, research on skarn Cu mineralization is relatively weak. In this paper, the zircon U-Pb geochronology and whole-rock geochemistry of Cu-mineralized quartz diorite porphyrite are studied on the basis of investigations of the exploration results of the deposit. The results show that the zircon U-Pb weighted average age of quartz diorite porphyrite is 82 Ma, indicating that it was formed in the Late Cretaceous, which is consistent with the W-Mo(Cu) mineralization age of the Late Cretaceous in the Geza arc. Quartz diorite porphyrite are high silica (SiO2=60.74%–63.36%), alkali-rich (Na2O+K2O=7.03%–9.29%), metaluminous (A/CNK=0.63–0.86), displaying shoshonitic I-type granite characteristics. The rare earth elements have obvious right-leaning patterns and typical adakite affinity characteristics, which can be interpreted as the product of partial melting of the intermediate-mafic lower crust mix with mantle-derived magma. The nature of the magmatic source and the type of wall rocks determine the mineralization zoning of the Donglufang Deposit, with porphyry Mo(-Cu) mineralization occurring in the potassic zone of the deep quartz monzogranite porphyry, skarn Cu(-Mo) mineralization occurring in the contact zone, and vein Pb-Zn-Au-Ag mineralization occurring in the peripheral marble. The deposit constitutes a porphyry mineralization system with Mo(-Cu), Cu(-Mo), and Pb-Zn-Au-Ag mineralization. Our comparative study shows that the Late Cretaceous magmatic rocks and related mineralization in Geza arc extend southward to the western margin of Yangze Block, formed in the post-collision extensional setting. The degree of magmatic differentiation gradually decreases from north to south, and the contribution of mantle-derived magma gradually increased, resulting in obvious different mineralization style from north to south, i.e., from northern Xiuwacu W-Mo, Relin Mo-W, Hongshan and Tongchanggou Mo(-Cu), to southernmost Donglufang Cu(-Mo). |
| keywords:quartz diorite porphyrite U-Pb geochronology geochemistry Late Cretaceous Donglufang the western margin of Yangtze Block |
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