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张龙,陈振宇,李胜荣,黄国龙. 2018. 粤北棉花坑(302)铀矿床围岩蚀变分带的铀矿物研究. 岩石学报, 34(9): 2657-2670
粤北棉花坑(302)铀矿床围岩蚀变分带的铀矿物研究
作者单位E-mail
张龙 中国科学院地质与地球物理研究所, 中国科学院矿产资源研究院重点实验室, 北京 100029
中国科学院大学, 北京 100049
中国地质科学院矿产资源研究所, 自然资源部成矿作用与资源评价重点实验室, 北京 100037 
 
陈振宇 中国地质科学院矿产资源研究所, 自然资源部成矿作用与资源评价重点实验室, 北京 100037 czy7803@126.com 
李胜荣 中国地质大学地球科学与资源学院, 北京 100083  
黄国龙 核工业290研究所, 韶关 512026  
基金项目:本文受国家自然科学基金项目(41741010)和中国地质大调查项目(12120113090500)联合资助.
摘要:
      粤北棉花坑(302)铀矿床是华南最大的花岗岩型铀矿床。本文以该铀矿床的一个代表性钻孔岩心为研究对象,利用电子探针对该钻孔中的铀矿物进行系统研究。该钻孔岩心具有明显的垂直围岩蚀变分带现象:从上到下可分为四个带,分别为:正常花岗岩或弱蚀变带(Ⅰ带);高岭石化、绢云母化带(Ⅱ带);强绢云母化、绿泥石化带(Ⅲ带);矿化带(Ⅳ带)。铀矿物类型也具有分带现象:Ⅰ带、Ⅱ带、Ⅲ带的铀矿物主要是晶质铀矿和铀钍石;矿化带Ⅳ带的铀矿物主要有沥青铀矿、铀石、钛铀矿、铀钍石四种类型。运用电子探针测年方法对不同蚀变带的晶质铀矿和沥青铀矿进行定年,获得晶质铀矿的化学年龄为165±3.1Ma,代表长江岩体的形成年龄;沥青铀矿的化学年龄可分为四组:~120Ma、~102Ma、~92Ma和~68Ma,代表矿区多期次的热液活动时间,也可代表粤北地区多期次铀成矿作用年龄,前三组可能代表早期铀成矿事件,第四组为主成矿期。广泛发育的热液蚀变促使U发生活化、转移,进而在有利空间富集成矿。对典型铀矿床作深入细致的蚀变分带研究工作,有助于提高对成岩成矿过程的认识。
英文摘要:
      The Mianhuakeng uranium deposit (No.302) is the largest granite-hosted uranium deposit in South China. Here, we conduct detailed studies upon wall-rock alteration zones and chemical dating of uranium minerals of a representative drill hole from this deposit by electron probe microanalyzer (EPMA). This deposit shows obvious vertical wall-rock alteration zones, which can be mainly divided into four zones, namely, the fresh granite or weak alteration zone, the kaolinization and sericitization zone, the strong sericitization and the chloritization zone, and the mineralization zone. Uranium minerals also show vertical alteration zoning, where the main uranium minerals of the Ⅰ, Ⅱ, and Ⅲ zones are uraninite and uranothorite, whereas the dominant uranium minerals of the Ⅳ zone are pitchblende, coffinite, uranothorite, and brannerite. EPMA dating upon the uranium minerals of different alteration zones shows that the chemical ages of the uraninites only has one group age of 165±3.1Ma, which represents the formation age of the Changjiang granite; while the chemical ages of the pitchblendes have four groups of ages, i.e.,~120Ma,~102Ma,~92Ma, and~68Ma, respectively, which represent multiple episodes of hydrothermal events that are responsible for the precipitation of U ores in the deposit. The first three groups of ages may represent the early stages of uranium mineralization, and the last one is the main metallogenic epoch of the No.302 deposit. Extensive hydrothermal alteration could mobilize U from the magmatic U-bearing accessory minerals such as uraninite. Detailed research on the alteration zones of the typical uranium deposit is helpful to improve the prospecting effect of concealed deposits.
关键词:铀矿物  围岩蚀变分带  电子探针  棉花坑铀矿床  粤北
投稿时间:2017-10-08  修订日期:2018-06-04
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主办单位:中国矿物岩石地球化学学会
印刷版(Print): ISSN 1000-0569 网络版(Online): ISSN 2095-8927
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