桂北苗儿山中段向阳坪铀矿床热液脉体地球化学特征及指示意义  

Geochemical characteristics and indicative significance of hydrothermal vein in the Xiangyangping uranium ore deposit,middle segment of Miao’er Mountain,northern Guangxi

作　　者：陈琪[1] 高翔[1] 谭双 黄剑[1] CHEN Qi;GAO Xiang;TAN Shuang;HUANG Jian(Changsha Uranium Geology Research Institute,CNNC,Changsha 410007,China)

机构地区：[1]核工业二三〇研究所,湖南长沙410007

出　　处：《岩石矿物学杂志》2020年第6期795-807,共13页Acta Petrologica et Mineralogica

基　　金：中国核工业地质局地勘费项目(201917,202035-6)。

摘　　要：对向阳坪矿床硅质脉和方解石两种重要的脉石矿物进行了系统的稀土元素和碳氧同位素分析。结果表明,硅质脉、方解石与角砾岩矿石具有大体类似的轻稀土元素富集、负Eu异常明显的右倾海鸥型稀土元素配分模式,总体继承了豆乍山花岗岩地球化学特征,暗示了向阳坪矿床铀源主要来自赋矿围岩,硅质脉和硅质角砾在铀矿化过程伴随∑REE富集和HREE增加。方解石碳氧同位素组成指示成矿流体以地幔来源为主导,成矿期方解石具有明显低的δ13C值和高的δ18O值,暗示减压沸腾发生的CO2去气作用是导致晚期铀沉淀的主要因素。从成矿期到矿后期,方解石δ13C值升高,δ18O值呈降低趋势,同时硅质角砾具有弱的负Ce异常,均指示铀矿化晚期有大气降水参与,且受其淋滤改造,据此认为苗儿山中段花岗岩型铀矿多期成矿叠加和后期大气降水淋集改造是形成大矿体的主要成矿模式。In this paper,the authors studied quartz veins and calcite veins in the Xiangyangping uranium ore deposit located in the middle segment of Miao’er Mountain pluton.The research samples include quartz veins,calcite veins and breecia ores.They have similar REE patterns showing LREE-enrichment and strong negative Eu anomalies.This characteristic is the same as that of Douzhashan granite,suggesting that most of the uranium came from surrounding rocks.∑ REE and HREE from calcite veins and breecia ores grew with uranium-enrichment process.Carbon oxygen isotope analysis from calcite shows that most of the ore-forming fluid came from the mantle.The uranium-enrichment calcite shows lower δ13C value and high δ18O value,which indicates that CO2 degassing seems to have been the main factor in uranium mineral precipitation processing.From mineralization period to postmineralization period,δ13C value of calcite grew and δ18O value was reduced;besides,breecia ores had weak negative Ce anomalies.All of these data indicate that meteoric water took part in the process of post-mineralization.The authors built the uranium mineralization model for the middle segment of Miao’er Mountain pluton,and emphasized that multiple phases of mineralization and meteoric water seems to have been the critical factor of forming large orebody in this area.

关 键 词：硅质脉 方解石 稀土元素 碳氧同位素 向阳坪 苗儿山 

分 类 号：P619.14[天文地球—矿床学] P595[天文地球—地质学]