摘要
粤北佛冈岩体中的琶江铀矿区位于桃山-诸广铀成矿带南段,区内发育有典型的花岗岩型铀矿床及铀矿化点,其赋矿岩石主要为二云母花岗岩。为精确厘定这些赋矿二云母花岗岩的形成时代,深入探讨其成岩条件与岩浆演化特征,并揭示岩石成因及其与铀成矿的关系,对矿区内二云母花岗岩开展LA-ICP-MS锆石U-Pb定年和微量元素分析,以及全岩主量和微量元素地球化学研究。锆石U-Pb定年结果表明,二云母花岗岩的形成年龄为162.4±1.9 Ma和159.3±2.3 Ma,与佛冈岩体主体花岗岩的形成时代一致,均为燕山早期岩浆活动的产物。二云母花岗岩具有高硅、高碱、富铝的特征,A/CNK值为1.20~1.33,表现出强过铝质特性;其U含量为4.52~12.2μg/g,高于中国东部上地壳的平均U含量(2.7μg/g)。结合前人研究成果,认为琶江铀矿区二云母花岗岩属于高分异I型花岗岩,其岩浆温度为743~764℃,氧逸度为ΔFMQ-2.5。在岩浆演化过程中,经历了磷灰石、榍石、斜长石、黑云母等矿物的强烈分离结晶作用,并混入了大量富U的沉积物质,最终演化形成富铀的强过铝质岩浆体系,该岩浆体系为后期铀成矿作用提供重要铀源。本研究表明,在低氧逸度条件下, I型花岗岩岩浆经大量富U沉积物质混染并经历强烈分离结晶演化后,同样能够形成富铀花岗岩,并在有利地质条件下作为铀源岩参与成矿作用。
The Pajiang uranium ore district,located within the Fogang batholith in Northern Guangdong Province,is situated in the southern part of the Taoshan-Zhuguang uranium metallogenic belt.This ore district hosts several typical granite-related U deposits and uranium mineralization occurrences,with the ore bodies predominantly occurring within the two-mica granite.To precisely determine the age of the two-mica granite,investigate the physicochemical conditions and magmatic evolution processes,and provide critical insights into its petrogenesis and relationship to uranium mineralization,LA-ICP-MS zircon U-Pb dating,trace element analysis,and whole-rock major and trace element geochemical analysis were conducted.Zircon U-Pb dating results indicate that the two-mica granite formed at 162.4±1.9 Ma and 159.3±2.3 Ma,contemporaneous with the main plutons of the Fogang complex,corresponding to the early Yanshanian magmatic activity.The two-mica granite exhibits high silica,alkali,and aluminum contents,with A/CNK values ranging from 1.20 to 1.33(average 1.25),indicating a strongly peraluminous nature.Additionally,its U concentrations ranging from 4.52μg/g to 12.2μg/g,with an average of 8.23μg/g,exceed the average upper crust value in eastern China.Integrating geochronological,geochemical,and zircon trace element data with previous studies,we suggest that the two-mica granite in the Pajiang uranium ore district is highly fractionated I-type granite,with magmatic temperatures of 743-764℃and oxygen fugacity ofΔFMQ-2.5.Furthermore,the magmatic evolution involved extensive fractional crystallization of minerals such as apatite,titanite,plagioclase,and biotite,accompanied by the assimilation of U-rich sedimentary materials into the magma.This process led to the development of a U-rich,strongly peraluminous magmatic system,which eventually solidified into the U-rich two-mica granite,serving as an important uranium source for mineralization.Our findings suggest that I-type granitic magma can generate U-rich granite when it is subjected to significant assimilation of U-rich sedimentary material and extensive fractional crystallization under low oxygen fugacity conditions.Subsequently,this U-rich granite may serve as an uranium source and facilitate mineralization in favorable geological environments.
作者
陶继华
杨跃贵
徐志添
冷成彪
冯凡斌
吴海辉
华天宇
李杰
周栋文
冀石磊
TAO Jihua;YANG Yuegui;XU Zhitian;LENG Chengbiao;FENG Fanbin;WU Haihui;HUA Tianyu;LI Jie;ZHOU Dongwen;JI Shilei(National Key Laboratory of Uranium Resources Exploration-Mining and Nuclear Remote Sensing,East China University of Technology,Nanchang 330013,Jiangxi,China;School of Earth and Planetary Sciences,East China University of Technology,Nanchang 330013,Jiangxi,China;Guangdong Institute of Mineral Resources Exploration(Guangdong Institute of Nuclear Geological Exploration Research),Guangzhou 510000,Guangdong,China;Observation and Research Station of Granite-type U Deposit in South China,Ministry of Natural Resources,Shaoguan 512600,Guangdong,China)
出处
《大地构造与成矿学》
北大核心
2025年第4期844-860,I0009-I0013,共22页
Geotectonica et Metallogenia
基金
国家自然科学基金项目(42473044、41963002、42063001)
铀资源探采与核遥感全国重点实验室(东华理工大学)自主部署项目(2024QZ-TD-01)
东华理工大学-中国铀业有限公司联合基金(2022NRE-LH-19)
广东省核工业地质局二九三大队科研发展基金项目(科研202302)联合资助。
关键词
琶江铀矿区
二云母花岗岩
佛冈岩体
岩石成因
铀成矿作用
Pajiang uranium ore district
two-mica granite
Fogang batholith
petrogenesis
uranium mineralization
