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高校地质学报 ›› 2022, Vol. 28 ›› Issue (2): 153-164.DOI: 10.16108/j.issn1006-7493.2021029

• 华南构造演化专栏 • 上一篇    下一篇

湖南常宁新盟山英安玢岩岩石成因及其与矿化关系研究

赵增霞1, 2,冯佐海1,2*,刘 磊1, 2,肖 阳1, 2   

  1. 1. 桂林理工大学 广西隐伏金属矿产勘查重点实验室,桂林 541004;
    2. 桂林理工大学 有色金属矿产勘查与资源高效利用协同创新中心,桂林 541004
  • 出版日期:2022-04-20 发布日期:2022-04-26

Petrogenesis of Xinmengshan Dacite Porthyry in Changning, Hunan Province: Implications for Relationship of Magmatism and Mineralization

ZHAO Zengxia1,2,FENG Zuohai1,2*,LIU Lei1,2,XIAO Yang1,2   

  1. 1. Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, Guilin University of Technology, Guilin 541004, China;
    2. Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources, Guilin University of Technology, Guilin 541004, China
  • Online:2022-04-20 Published:2022-04-26

摘要: 通过对湖南省常宁市新盟山英安玢岩进行岩石地球化学、锆石U-Pb定年以及绿泥石矿物化学等综合研究,结合前人研究成果,探讨其岩石地球化学性质、形成时代、物质来源及其与成矿作用的关系。LA-ICP-MS锆石U-Pb定年结果显示,新盟山英安玢岩的(206Pb)/n(238U)加权平均年龄为152.9±1.2 Ma,属于晚侏罗世产物,与矿田内成矿作用时间一致。岩石富集轻稀土和Rb、Th、U、La、Pb、Nd、Zr、Hf等元素,亏损重稀土和Nb、Ta、Ba、Sr、P等元素,表明新盟山英安玢岩主要起源于地壳,可能混有少量地幔物质。绿泥石主要为斜绿泥石,形成温度大约为280℃,与矿田内的铜钼矿化作用温度一致。晚侏罗世时研究区处于拉张—伸展的构造背景,岩石圈拉张减薄,地壳物质部分熔融(可能混有少量地幔物质)形成新盟山英安玢岩。岩浆结晶晚期,热液流体在铜钼矿化的同时不断交代新盟山英安玢岩,引起广泛的绿泥石化。

关键词: 岩石地球化学, 成岩年龄, 绿泥石温度计, 新盟山, 英安玢岩

Abstract: Based on detailed geological investigation, this paper investigated the whole-rock element geochemistry, zircon U-Pb dating and chlorite mineral chemistry of Xinmegnshan dacite porphyry in Changning City, Hunan Province. With reference to previous research, we discussed petrochemical characteristics, magmatic age, magma sources, as well as relationship with mineralization in Shuikoushan orefield. LA-ICP-MS zircon U-Pb isotopic analyses showed that Xinmegnshan dacite porphyry erupted during the Late Jurassic, with a weighted mean 206Pb/238U age of 152.9±1.2 Ma (MSWD=0.27, 2σ, N=17). Xinmegnshan dacite porphyry was rich in Light Rare Earth Elements (LREEs) and Rb, Th, U, La, Pb, Nd, Zr, Hf, while depleted in Heavy Rare Earth Elements (HREEs) and Nb, Ta, Ba, Sr, P, showing crust-derived affinities, and might be contaminated by mantle material. Chlorite was mainly clinochlore with alteration temperature of 280℃ , which was similar to that of the Cu-Mo mineralization in this orefield. During Late Jurassic, the tectonic extension and thinning of the continental lithosphere in the study area induced partial melting of the crust, and produced granitic magma, which might mix with a small amount of mantle material. The magma then invaded along deep faults and formed Xinmegnshan dacite porphyry. At the late stage of magma crystallization, as Cu-Mo precipitation, the hydrothermal fluid replaced the dacite porphyry continuously and resulted in widespread chloritization.

Key words: petrochemistry, diagenetic age, chlorite thermometer, Xinmegnshan, dacite porphyry

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