粤北长江铀矿田基性岩脉年代学、地球化学特征及其地质意义  

Geochronological and Geochemical Characteristics and Geological Significances of Mafic Dykes From Changjiang Uranium Ore Field in Northern Guangdong

作　　者：庞雅庆[1] 高飞[1] 孟晓庆[2] 范洪海 王勇剑[1] 何德宝[1] PANG Yaqing;GAO Fei;MENG Xiaoqing;FAN Honghai;WANG Yongjian;HE Debao(CNNC Key Laboratory of Uranium Resources Exploration and Evaluation Technology,Beijing Research Institute of Uranium Geology,Beijing 100029,China;China University of Geosciences,Beijing 100083,China)

机构地区：[1]核工业北京地质研究院、中核集团铀资源勘查与评价技术重点实验室,北京100029 [2]中国地质大学(北京),北京100083

出　　处：《铀矿地质》2023年第2期251-264,共14页Uranium Geology

基　　金：中国核工业地质局项目“广西摩天岭地区铀矿成矿规律与远景预测”(编号:202238-10);“华南富大铀矿空间定位条件与远景预测研究”(编号:202035-6、202138-10)联合资助。

摘　　要：粤北长江铀矿田位于诸广山复式岩体中南部,发育不同类型和期次基性岩脉。文章通过开展系统的岩石学、Ar-Ar年代学和地球化学分析,探究了基性岩脉类型、成岩年龄、构造背景、岩浆来源以及与铀成矿的关系。岩石学和年代学研究表明,该地区基性岩脉类型主要为辉绿岩、辉绿玢岩、闪斜煌岩及辉石煌斑岩等,基性岩脉至少分为三期:136.8 Ma、120.7 Ma、113.8~110.1 Ma,与华南中生代主要的地壳拉张活动时间相一致。地球化学研究结果表明,基性岩脉中大离子亲石元素Rb、Ba、K、Sr富集,高场元素Nb、Ta、Zr、Hf、Ti相对亏损,各类元素参数特征显示其具有拉张裂谷带玄武岩地球化学特征,可能为俯冲交代作用形成的富集地幔部分熔融形成。综合分析认为,该地区铀成矿作用是基性岩脉侵位后的地质事件,基性岩脉与铀成矿时空关系密切,受控于华南岩石圈伸展的动力学背景。The Changjiang uranium ore field is located in south central Zhuguangshan complex pluton.Mafic dykes of different types and stages have been found in this area.By petrological,Ar-Ar geochronological and geochemical research,this paper discussed the types,ages,tectonic settings,magma sources of the mafic dyke and their relations to uranium mineralization.Petrology and Ar-Ar dating results showed that the four types of mafic dykes including diabase,diabase-porphyrite,diorite amphibolite,pyroxene lamprophyre were recognized in the study area.Mafic dykes can be classified into three phases at least:136.8 Ma,120.7 Ma,113.8~110.1 Ma,which are coincident with the major episodes of crustal extensional activities in southern China.Geochemical characteristics indicate that mafic dykes are rich in large ion lithophile elements(Rb,Ba,K,Sr),and dupleted in high field intensity elements(Nb,Ta,Zr,Hf,Ti),and their parameters are with the characteristic of basalt in tension rift zone.Mafic dykes were formed from partial melting of enriched mantle due to subduction metasomatism.Based on the aforementioned analyses,the uranium metallogenesis was believed the geological event after mafic dykes intrusion.The mafic dykes is closely related to uranium mineralization in space-time,which are controlled by geodynamic setting of lithospheric extension.

关 键 词：地球化学 AR-AR年代学 富集地幔 基性岩脉 长江铀矿田 

分 类 号：P597[天文地球—地球化学] P595[天文地球—地质学]