南岭东段上窑铀矿床花岗斑岩脉岩石成因及构造意义  

Petrogenesis and Tectonic Implications of Granite Porphyry Veins in the Shangjiao Uranium Deposit,Eastern Nanling Range

作　　者：赖静 刘文泉 钟福军 LAI Jing;LIU Wenquan;ZHONG Fujun(Research Institute No.290,CNNC,Shaoguan,Guangdong 512029,China;Guangdong Provincial Key Laboratory of Environmental Protection and Nuclear Radiation Tracking Research,Shaoguan,Guangdong 512029,China;Guangdong Provincial Engineering Technology Research Center of Radioactive Eco-Environmental Protection,Shaoguan,Guangdong 512029,China;State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang,Jiangxi 330013,China)

机构地区：[1]核工业二九○研究所,广东韶关512029 [2]广东省环境保护核辐射追踪研究重点实验室,广东韶关512029 [3]广东省放射性生态环境保护工程技术研究中心,广东韶关512029 [4]东华理工大学核资源与环境国家重点实验室,江西南昌300013

出　　处：《现代地质》2025年第2期277-293,共17页Geoscience

基　　金：广东省青嶂山矿集区铀-多金属矿产资源调查评价与勘查项目(202240);广东省贵东岩体东部地区铀矿资源调查评价与勘查项目(202239);国家自然科学青年基金项目“粤北棉花坑铀矿床成矿流体性质与演化:来自沥青铀矿微区原位分析证据”(42002095)。

摘　　要：为进一步揭示华南中生代的地球动力学背景及其构造演化过程,本文对南岭东段上窖铀矿床花岗斑岩的锆石U-Pb年代学、Hf同位素和地球化学特征开展研究。结果显示,岩浆锆石^(206)Pb/^(238)U加权平均年龄为(190.6±2.2)Ma和(190.6±1.3)Ma,表明花岗斑岩侵位于早侏罗世。岩石具有高硅(68.97%~69.56%),富碱(N_(2)O+K_(2)O为9.12%~9.28%),贫钙(0.50%~1.22%)、镁(0.09%~0.11%)和低磷(0.05%)的特征,属高钾钙碱性(里特曼指数σ为3.16~3.27)、准铝质-弱过铝质(A/CNK为0.98~1.09)系列。大离子亲石元素Rb、Th和U相对富集,高场强元素Zr、Hf、Nb、Ta、Ti相对亏损;富集轻稀土元素,亏损重稀土元素,呈负Eu异常。岩石地球化学特征综合指示上窑铀矿床的花岗斑岩为A型花岗岩。锆石ε_(Hf)(t)值为+5.39~+9.07,平均+6.91,对应的地壳模式年龄(T_(DM2))为887~652 Ma,指示其主要物源为新元古代的新生镁铁质地壳。花岗斑岩形成于古太平洋俯冲构造背景下局部板内伸展构造环境,龙源坝岩体是古特提斯和古太平洋两大构造域的转换的地质体的证据展示。结合区域岩浆岩年代学特征和华南构造背景,认为古特提斯和古太平洋两大构造域的转换可能开始于190 Ma之前。To further constrain the Mesozoic geodynamic background and tectonic evolution of South China,this study investigates zircon U-Pb geochronology,Hf isotopes,and geochemical characteristics of granite porphyry from the Shangjiao Uranium Deposit in the Longyuanba pluton.Zircon U-Pb dating yields weighted mean ~(206)Pb/~(238)U ages of(190.6±2.2) Ma(MSWD=0.11) and(190.6±1.3) Ma,indicating Early Jurassic emplacement.Bulk-rock analyses reveal the granite porphyry is characterized by high silica(SiO_2=68.97%-69.56%),alkali enrichment(Na_2O+K_2O=9.12%-9.28%),and depletion in calcium(CaO=0.50%-1.22%),magnesium(MgO=0.09%-0.11%),and phosphorus(P_2O_5=0.05%),classifying as high-K calc-alkaline(σ=3.16-3.27) metaluminous to weakly peraluminous rocks(A/CNK=0.98-1.09).Geochemically,the rocks show enrichment in large-ion lithophile elements(Rb,Th,U),depletion in high-field-strength elements(Zr,Hf,Nb,Ta,Ti),light rare earth element enrichment with negative Eu anomalies,and heavy rare earth element depletion,collectively indicating an A-type granite affinity.Zircon ε_(Hf)(t) values range from+5.39 to+9.07(average+6.91),corresponding to two-stage model ages(T_(DM2)) of 652-887 Ma,suggesting derivation primarily from Neoproterozoic juvenile mafic crust formed through mantle magma differentiation.The granite porphyry formed in an intraplate extensional setting during Paleo-Pacific Plate subduction,with the Longyuanba pluton serving as critical evidence for the tectonic transition between the Paleo-Tethyan and Paleo-Pacific regimes.Combined with the chronological characteristics of regional magmatic rocks and the tectonic setting of South China,it was concluded that the transition from the Tethyan orogenic regime to the Paleo-Pacific tectonic regime already started before 190 Ma.

关 键 词：锆石U-PB年代学 HF同位素 地球化学特征 构造背景 花岗斑岩 上窖铀矿床 

分 类 号：P581[天文地球—岩石学] P588.12[天文地球—地质学] P597