诸广中部鹿井铀矿田辉绿岩磷灰石U-Pb年龄、地球化学特征及其与铀成矿关系  

Geochronology and geochemistry of dolerite in the Lujing uranium ore field of central Zhuguangshan complex,and its relationshipwith uranium mineralization

作　　者：钟福军 夏菲[1,2] 王玲[1,2] 刘国奇 潘家永[1,2] 刘颖[2] 李志鹏[2,3] ZHONG Fujun;XIA Fei;WANG Ling;LIU Guoqi;PAN Jiayong;LIU Ying;LI Zhipeng(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang,Jiangzi 330013,China;School of Geoscience,East China University of Technology,Nanchang,Jiangi 330013,China;No.270 Research Institute of Nuclear Industry,CNNC,Nanchang,Jiangzi 330200,China)

机构地区：[1]东华理工大学核资源与环境国家重点实验室,江西南昌330013 [2]东华理工大学地球科学学院,江西南昌330013 [3]核工业二七○研究所,江西南昌330200

出　　处：《地质学报》2023年第8期2593-2608,共16页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号42002095,42172098,41962007,42162013);核资源与环境国家重点实验室自主基金(编号2020Z08);东华理工大学-中国铀业有限公司联合基金(编号NRE2021-05,NER2021-09)联合资助的成果。

摘　　要：辉绿岩脉与热液型铀矿化关系十分密切。本文以鹿井矿田辉绿岩为研究对象,通过野外地质调查、磷灰石U-Pb年代学和地球化学研究,旨在探究其形成时代、岩石成因、构造背景及其与铀成矿关系,为探讨区域铀成矿机制提供依据。辉绿岩中磷灰石的U-Pb定年指示,辉绿岩形成年龄为~200 Ma,是诸广—贵东地区200~190 Ma基性岩浆活动的重要组成。辉绿岩地球化学组成类似于洋岛玄武岩(OIB)特征,形成于早侏罗世—晚三叠世之交的岩石圈伸展构造背景下,岩浆起源于亏损地幔源区且被流体交代,岩浆形成过程经历了一定程度的分离结晶和地壳混染作用。鹿井矿田主要铀矿床的成矿年龄为128~51 Ma,明显晚于区内辉绿岩的形成时代(~200 Ma),因此,由~200 Ma的基性岩浆活动直接提供成矿所需的矿化剂ΣCO_(2)的可能性较小。辉绿岩在鹿井矿田“交点”型矿化的形成过程中,不仅提供了有利的氧化—还原界面,而且基性岩浆侵位时所形成的次级构造裂隙还为成矿提供了有利的空间。There is close relationship between dolerite and hydrothermal U mineralization.In this paper,dolerite in the Lujing U ore field of the Zhuguangshan complex was investigated by petrography,LA-ICP-MS apatite U-Pb dating and whole rock geochemical analysis.The aims were focused on the geochronology,petrogenesis and its implication for U mineralization.The analysis result indicated that the dolerite formed at ca.200 Ma,suggesting an Early Jurassic-Late Triassic age and a vital role of basic magma(200~190 Ma)in the Zhuguang-Guidong region.This age corresponds to an Early Jurassic-Late Triassic geodynamic setting which is characterized by lithospheric extension in South China.The geochemical composition of the dolerite in the Lujing U ore field is similar to the oceanic island basalt(OIB).Dolerite was the product of 5%~10%partial melting of the pyroperidotite,and the parental magma derived from mantle changed by metasomatism fluids.The diagenetic process of dolerite has undergone a variational degree crustal contamination and fractional crystallization.The previous studies suggested that the U mineraliztion in the Lujing ore field formed during the period 128~51 Ma and is much younger than the emplacement age of dolerite(ca.200 Ma).Therefore,we speculate that the necessary mineralizerΣCO_(2) for U mineralization did not directly come from the ca.200 Ma basic magma,but,for intersection of U mineralization,the the dolerite provided the favorable reductive environment for UO_(2) precipitation from U-rich oxidized fluid.Additionally,the secondary tectonic fissure caused by the invasion of basic magma offered a suitable space for fluid migration and U mineralization.

关 键 词：热液铀矿 辉绿岩 磷灰石U-Pb定年 岩石圈伸展 鹿井矿田 

分 类 号：P619.14[天文地球—矿床学]