投稿时间：2024-06-11
修订日期：2024-12-27
网络发布日期：2025-03-10
中文摘要:老挝Sepon地区是东南亚Truongson褶皱带中重要的铜金钼矿集区，区内出露Thengkham、Khanong和Padan等多个英安斑岩岩体。以往针对Thengkham和Khanong两个成矿岩体开展了系统研究和找矿勘查评价，基本厘定了成矿时代、蚀变类型、岩石地球化学组成和成矿特征。Padan是矿集区内同一构造带中出露的又一个重要的英安斑岩岩体，但其成岩时代、蚀变特征以及岩浆岩属性还不清楚，制约了找矿勘查的部署。文章针对目前尚未获得找矿突破的Padan英安斑岩开展了年代学和岩石地球化学分析，获得了锆石LA-ICP-MS U-Pb谐和年龄为(283.1±1.7) Ma (MSWD=0.006，n=10)，代表了其结晶年龄。Padan英安斑岩的w(SiO2)为69.4%~74.0%，w(K2O)为5.02%~5.46%，w(MgO)为0.45%~0.81%，具有高硅、富钾、低镁的特征。英安斑岩的A/CNK ＞ 1.1，为过铝质岩石；富集Rb、K、Ba、Th和U等大离子亲石元素，而亏损Nb、Sr、P、Ti等高场强元素；稀土元素总量低、轻稀土元素相对重稀土元素富集，δEu的变化范围在0.53~0.94，平均值为0.78。岩石地球化学特征表明，Padan英安斑岩为钾玄岩系列至高钾钙碱性系列的I型岛弧花岗岩，母岩为受上地壳物质混染的地幔楔部分熔融的产物，并经历了较高程度的岩浆结晶分异作用。基于Padan岩体与区内其他成矿岩体具有相似的成岩年龄、矿化蚀变组合、物质组成以及构造演化历史，文章认为Padan岩体具有良好的斑岩型矿床成矿潜力。
中文关键词:英安斑岩 锆石U-Pb年代学 岩石地球化学 Sepon铜金矿集区 老挝
Abstract:The Sepon district in the Truongson fold belt is an important Cu-Au-Mo ore cluster in Laos, where several rhyodacite porphyritic intrusions, including the Thengkham, Khanong and Padan, are exposed within the area. Previous scientific studies and exploration evaluations focusing on the mineralization associated-Thengkham and Khanong intrusions have revealed their magma ages, alteration assemblages and host rock geochemical compositions. The Padan rhyodacite is another intrusion in Sepon district but underwent limited study, which hinder further evaluation on its mineralization potential. This study focuses on the Padan rhyodacite porphyry, which is spatially close to the mineralized rhyodacite porphyritic intrusions but has yet to be discovered for significant resources, for geochronology and bulk geochemical composition analysis. Zircon LA-ICP-MS U-Pb dating yielded a concordia age of (283.1±1.7) Ma (MSWD=0.006, n=10), representing the crystallization age of the rhyodacite porphyry. The Padan intrusion is characterized by elevated w(SiO2) and w(K2O) but depleted w(MgO) compositions, varying from 69.4% to 74.0%, 5.02% to 5.46%, and 0.45% to 0.81%, respectively. The rhyodacite porphyry have A/CNK ratios greater than 1.1, showing the characteristics of peraluminous rocks. In addition, the rhyodacite porphyry is enriched in large-ion-lithophile-elements (e.g., Rb, K, Ba, Th, and U) but depleted in high-field-strength elements (e.g., Nb, Sr, P, and Ti). Total rare earth element compositions are low, with δEu anomalies varying from 0.53 to 0.94 with an average of 0.78. The chondrite-normalized REE distribution patterns show enrichment of LREE compared to the HREE. In summary, geochemical compositions suggest that the Padan rhyodacite porphyry is I-type granite belonging to the shoshonite series or high-K calc-alkaline series. Magma was derived from the partial melting of UCC-involved mantle wedge and subjected to a high degree of crystallization differentiation. Based on the similarities in mineralization age, alteration assemblage, bulk geochemical composition, and magma evolution history between the Padan intrusion and other ore-bearing intrusions in the area, we infer that the Padan intrusion has good potential for economic porphyry type mineralization.
keywords:rhyodacite porphyry zircon U-Pb geochronology bulk rock geochemistry Sepon porphyry Cu-Au-Mo ore cluster Laos
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引用文本：
赵光辉,徐林刚,宋彦博,Meng LEE.2025.老挝Sepon斑岩型铜金钼矿集区Padan岩体锆石U-Pb年代学、岩石地球化学及其地质意义[J].矿床地质,44(1):231~247ZHAO GuangHui,XU LinGang,SONG YanBo,Meng LEE.2025.Zircon U-Pb age, geochemical compositions of Padan pluton in Sepon porphyritic Cu-Au-Mo district, Laos, and their geological significance[J].Mineral Deposits44(1):231~247
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