湖南常宁新盟山英安玢岩岩石成因及其与矿化关系研究  

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

作　　者：赵增霞 冯佐海[1,2] 刘磊[1,2] 肖阳 ZHAO Zengxia;FENG Zuohai;LIU Lei;XIAO Yang(Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Guilin University of Technology,Guilin 541004,China;Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources,Guilin University of Technology,Guilin 541004,China)

机构地区：[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　　处：《高校地质学报》2022年第2期153-164,共12页Geological Journal of China Universities

基　　金：国家自然科学基金(41903041);广西科技计划项目(2021GXNSFBA220063,桂科AD19110099,2019GXNSFDA245009);桂林理工大学科研启动费(GLUTQD2017059)联合资助。

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n(;Pb)/n(;U)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。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;Pb/;U 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.

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 

分 类 号：P588.14[天文地球—岩石学]