| 张晓鹏,陈向平,王建青,王纪昆,董帅,曲为贵,张有军,王倩.昌都—芒康盆地西北缘始新世煌斑岩岩石成因及其对构造环境的指示——岩石地球化学和锆石U-Pb年代学约束[J].矿产勘查,2023,14(7):1011-1025 |
| 昌都—芒康盆地西北缘始新世煌斑岩岩石成因及其对构造环境的指示——岩石地球化学和锆石U-Pb年代学约束 |
| Genesis of Eocene lamprophyres at the northwest of the Changdu—Mangkang Basin and its indicative significance for tectonic environment——constraints of petrogeochemistry and zircon U-Pb geochronology |
| 投稿时间：2023-04-17 修订日期：2023-05-22 |
| DOI：10.20008/j.kckc.202307002 |
| 中文关键词: 煌斑岩脉 LA-ICP-MS 锆石U-Pb年龄 地球化学 构造环境 昌都—芒康盆地西北缘 |
| 英文关键词: lamprophyres LA-ICP-MS zircon U-Pb dating geochemistry tectonic environment northwest margin of Changdu-Mangkang Basin. |
| 基金项目:本文受中国地质调查局项目（DD20160016-02）及天津华北地质勘查局科研项目（HK2022-B3）联合资助。 |
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| 中文摘要: |
| 煌斑岩是反映深部构造-岩浆作用和源区地球化学性质的良好地质体。本文对昌都—芒康盆地西北缘出露的煌斑岩脉进行系统研究，煌斑岩中锆石U-Pb同位素年龄通过LA-ICP-MS测定，得到其206Pb/238U加权平均年龄分别为（36.05±0.29）Ma、（35.89±0.32）Ma、（37.67±0.16）Ma，该年龄值基本代表岩体的岩浆结晶时代，据此将研究区煌斑岩脉体形成时代归属为始新世。地球化学分析表明，煌斑岩属于钙碱性弱钾质—钾质系列，具有大离子亲石元素和轻稀土元素富集，高场强元素和稀土元素亏损的成分特征。综合分析表明煌斑岩具有俯冲带幔源岩石的成分特征，属于“俯冲-隆升”模式下新生代构造岩浆演化碰撞晚期构造环境的岛弧岩浆岩。在始新世（35~37 Ma）澜沧江构造带与金沙江结合带之间的走滑深大断裂构造带发生的大规模水平错移，导致局部区域发生俯冲，上涌的软流圈亏损地幔加热了地壳物质，导致其部分熔融，形成煌斑岩。 |
| 英文摘要: |
| Lamprophyres are good geological proxy for the deep tectonic magmatism and geochemical properties of the source region. In this paper， the lamprophyre veins exposed in the northwestern margin of Changdu - Mangkang Basin were systematically studied. Zircon U-Pb isotopes of the lamprophyre were determined by LA-ICP-MS， and the 206Pb/238U ages of the lamprophyres were （36.05±0.29） Ma， （35.89±0.32） Ma， and （37.67±0.16） Ma， respectively. These ages essentially represented the magmatic crystallization age of rock body， therefore， the formation age of lamprophyre vein body in the survey area was attributed to the Eocene. Geochemical analysis showed that lamprophyre belonged to the calc-alkali weak-potassic series， with compositional features of enrichment of large ion lithophile elements and light rare earth elements， and depletion of heavy high field strength elements and rare earth elements. Comprehensive analysis indicated that the lamprophyre had the composition characteristics of mantle source rocks in the subduction zone， and belonged to island arc magmatic rocks in the late tectonic environment of Cenozoic tectono magmatic evolution and collision under the "subduction uplift" model. The large-scale horizontal displacement of the strike slip deep fault structural belt between the Lancang River tectonic belt and the Jinsha River junction belt in the Eocene （about 35-37 Ma） led to local subduction， and the upwelling Asthenosphere depleted mantle heated the crustal material， leading to partial melting， forming the lamprophyre. |
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