攀枝花大田505铀矿床晶质铀矿的构造岩浆演化条件——来自新元古代花岗岩的制约  

Tectonic magmatic evolution conditions of uraninite in Datian 505 uranium deposit,Panzhihua:Constraints from Neoproterozoic granites

作　　者：艾月兵 程军 纪德宝 王伟 Ai Yuebing;Cheng Jun;Ji Debao;Wang Wei(Sichuan Geological and Mineral Survey Institute,Sichuan Geological and Mineral Resources Group Co.,Ltd.,Chengdu 610031,China)

机构地区：[1]四川省地质矿产集团有限公司地质矿产调查所,四川成都610031

出　　处：《资源环境与工程》2025年第2期145-154,共10页Resources Environment & Engineering

摘　　要：攀枝花大田505铀矿床是康滇地轴典型的前寒武纪铀矿床,以往学者们对该矿床进行了广泛的研究,主要集中于晶质铀矿本身及其伴生矿物,对于晶质铀矿与区域构造岩浆演化的关系研究不足。为了揭示晶质铀矿形成时的构造岩浆演化条件,在大田505铀矿床北部富铀Ⅰ号带附近采集了花岗岩样品,对其进行岩相学、U-Pb年代学和岩石地球化学研究。结果表明,花岗岩锆石U-Pb年龄为(774.45±4.92)Ma,与晶质铀矿电子探针年龄(780 Ma)较一致;花岗岩具有富Si(SiO_(2)含量为70.72%~76.68%)、富K(K_(2)O含量为3.06%~5.42%)、富碱(Na_(2)O+K_(2)O含量为7.26%~9.14%)的特征,微量和稀土元素地球化学特征表明其为准铝质A 2型花岗岩;花岗岩可能形成于英云闪长岩—花岗闪长岩的部分熔融,为高温低压环境,其构造背景为弧后扩张造成的伸展环境。综合分析认为,大田505铀矿床的花岗岩的形成条件与晶质铀矿一致,推测该矿床晶质铀矿的形成与海洋沉积物及蚀变洋壳改造的地幔关系密切,改造的富集型地幔在弧后稳定裂谷期部分熔融,使得U缓慢富集结晶形成大颗粒晶质铀矿。The Datian 505 uranium deposit in Panzhihua is a typical Precambrian uranium deposit in the Kangdian axis,and has been extensively studied by scholars.However,these studies have focused on the uraninite and its associated minerals,and the relationship between uraninite and tectonic magmatic evolution is insufficient.In order to reveal the conditions of tectonic magmatic evolution during the formation of uranium deposits,granite samples were collected near the uranium-rich zone I in the northern part of this uranium deposit,and the petrography,U-Pb geochronology and petrogeochemistry were studied.The results show that the zircon U-Pb age of granite is(774.45±4.92)Ma,which is consistent with the electron probe age of uraninite(780 Ma).The granite is rich in silicon(SiO_(2)content is 70.72%-76.68%),potassium(K_(2)O content is 3.06%-5.42%)and alkali(Na_(2)O+K_(2)O content is 7.26%-9.14%).The geochemical characteristics of trace and rare earth elements indicate that it is a quasi-aluminous A 2-type granite.The granite was formed by partial melting of tonalite-granodiorite,which is a high temperature and low pressure environment,and its tectonic background is an extensional environment caused by back-arc expansion.According to the comprehensive analysis,the formation conditions of granite are consistent with that of uraninite.It is speculated that the formation of uraninite in Datian 505 uranium deposit is closely related to the marine sediments and the mantle modified by the altered oceanic crust.The modified enriched mantle was partially melted in the back-arc stable rift period,which made U slowly enrich and crystallize to form large granular uraninite.

关 键 词：晶质铀矿 花岗岩 构造岩浆演化 大田505铀矿床 康滇地轴 

分 类 号：P619.14[天文地球—矿床学]