不整合面型铀矿床蚀变特征及其意义--以北澳大利亚鳄鱼河谷矿集区为例  

Alteration Characteristics and Significance of Unconformityrelated Uranium Deposits: The Alligator River Uranium Field,Northern Australia

作　　者：裴柳宁 郭春影[2] PEI Liuning;GUO Chunying(Researeh Institute No.203,CNNC,Xi'an,Shaanxi 710086,China;CNNC Key Laboratory of Uranium Resource Exploration and Evaluation Technology,Beijing Research Institute of Uranium Geology,Beijing 100029,China)

机构地区：[1]核工业二O三研究所,陕西西安710086 [2]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

出　　处：《世界核地质科学》2022年第4期660-674,共15页World Nuclear Geoscience

基　　金：中国核工业地质局地勘费科研项目“华北陆块北缘不整合面有关的铀矿成矿条件分析及远景评价”(编号:地D1802);铀矿地质科研项目“华北陆块元古宇富大铀矿成矿环境研究”(编号:202204-3)联合资助。

摘　　要：澳大利亚北部鳄鱼河谷铀矿集区(ARUF),产出多个世界级不整合面型铀矿床。这些铀矿床多位于古元古界氧化盖层(Kombolgie亚群)与新太古界—古元古界变质基底(Nanambu杂岩)之间的不整合面附近。矿体受断裂构造控制,呈似层状、透镜状、板状、半球状等。铀矿物以沥青铀矿和晶质铀矿为主。与铀成矿相关的蚀变大致有两个阶段,约1 800 Ma的Shoobridge构造期的矿前热液蚀变阶段,以(富Fe)绿泥石+白云母+独居石热液蚀变组合为主,控制了之后剪切带的活化及铀矿床的形成位置;约1 680~1 640 Ma的主成矿阶段,以(富Mg)绿泥石+绢云母+赤铁矿±石英/燧石±伊利石±菱镁矿蚀变组合为主,是铀矿带内最常见蚀变。蚀变在矿床尺度上也有基本一致的空间分带性,即靠近矿体主要有镁绿泥石化、绢云母化、赤铁矿化、硅化及伊利石化蚀变带,向外至远离矿带主要是铁绿泥石化、绢云母化、碳酸盐化、白云母化及石墨化蚀变带。绿泥石从内到外的成分变化(从富Mg至富Fe)及蚀变带范围,指示了矿体的品位变化及矿体的边界。厘定ARUF不整合面型铀矿床的蚀变特征,有利于深入理解铀成矿的物理化学条件、物质来源及控矿条件等因素,以期为ARUF地区将来扩大铀资源量提供参考资料。Alligator Rivers Uranium Field(ARUF) is located in Northern Australia, there are several world-class unconformity-related uranium deposits. Most of uranium deposits are located near the unconformity between the Paleoproterozoic oxide cover(Kombolgie subgroup) and the Neoarchean-Paleoproterozoic metamorphic basement(Nanambu complex). The orebody is controlled by fault structure and in the shape of stratoid,lentoid,plate and hemispherical forms.Uranium minerals are mainly pitchblende and uraninite. The alteration associated with uranium mineralization can be divided into two stages. The Pre-ore hydrothermal alteration stage of Shoobridge tectonics at about 1 800 Ma, is mainly composed of ferrochlorite+muscovite+monazite and control the activation of the shear zone and the formation of uranium deposit. The main oreforming stage of 1 680~1 640 Ma,is dominated by the alteration combination of amesite+sericite+hematite±quartz/chert±illite±magnesite,which are the most common alteration in the uranium ore belt. The alteration also has the same spatial zoning on the scale of the deposit, the alteration zones of magnesium-rich chloritization, sericitization, hematitization, silicitization and illitization are mainly near the ore body, and the alteration zones of ferrochloritization,sericitization, carbonation, muscovitrification and graphitization are usually far away from the orebody. From inside to outside, the variation of chlorite components(From Magnesium-rich to iron-rich) and the scale of alteration zone will indicate the grade and boundary of orebody,respectively. Therefore, the determination of the alteration characteristics in the ARUF unconformity-related uranium deposits is conducive to understand the physical and chemical conditions, material sources and ore-controlling conditions of uranium mineralization which can provide reference for the future expansion of uranium resources in ARUF.

关 键 词：鳄鱼河谷铀矿集区 不整合面型铀矿床 断裂控矿 两阶段蚀变 蚀变分带 

分 类 号：P612[天文地球—矿床学]