粤北302铀矿床同位素地球化学研究  

Study on isotope geochemistry of uranium deposit 302 in northern Guangdong province

作　　者：沈渭洲[1] 凌洪飞[1] 邓平[2,3] 朱捌 黄国龙 谭正中 

机构地区：[1]南京大学地球科学与工程学院内生金属矿床成矿机制研究国家重点实验室,江苏南京210093 [2]核工业290研究所,广东韶关512026 [3]中国地质科学院地质研究所,北京100037

出　　处：《铀矿地质》2010年第2期80-87,共8页Uranium Geology

基　　金：核工业地质局科研项目(南京大学);核工业地质局生产中科研项目(290研究所);教育部科学研究重大项目(项目编号:306007)资助

摘　　要：位于粤北诸广山岩体东南部的302铀矿床是我国规模较大、埋藏较深的花岗岩型铀矿床之一。该矿床产于印支期油洞岩体和燕山早期长江岩体的断裂蚀变带内,矿区内NWW向基性岩脉十分发育,矿体呈似脉状、扁豆状或透镜状。同位素研究表明,矿石的沥青铀矿Sm-Nd和U-Pb等时线年龄(70 Ma)与油洞岩体(232 Ma)、长江岩体(160 Ma)的年龄相差巨大;主成矿期成矿流体的δDH2O值为-65‰～-82‰(平均为-75‰),δ18OH2O值为6.8‰～0.6‰(平均为3.9‰),反映出成矿流体主要由地幔流体组成;方解石的δ13C值为-8.4‰～-5.3‰,表明矿化剂ΣCO2也来自地幔;矿区内辉绿岩的(87Sr/86Sr)i值为0.70861～0.70882,花岗岩的(87Sr/86Sr)i值为0.73519～0.77152,萤石的(87Sr/86Sr)i值为0.71474～0.71697,表明成矿组分Sr可能来源于基性脉岩(幔源)与赋矿花岗岩体(壳源),并呈不同程度的混合,而主成矿组分铀主要来源于赋矿花岗岩体。Located at the southeastern part of the Zhuguangshan granite composite in northern Guangdong province,uranium deposit 302 is one of the largest and most deeply buried granite-type uranium deposits in China.In the deposit area there are many NNW striking mafic dikes which intrude into the granite.The ore bodies appear in shape of vein-like,flat beanpod-like and lens-like within the hydrothermally altered fault zones in the Indosinian Youdong granite and early Yanshanian Changjiang granite.The formation age of the pitchblendes in ores（70 Ma） dated with Sm-Nd and U-Pb isochron methods is evidently different from that of the host Youdong granite（232 Ma） and Changjiang granite（160 Ma） dated with zircon U-Pb methods.Study of oxygen and hydrogen isotopes at main metallogenic epoch reveals that the δDH2O value of ore-forming fluid ranges from-65‰ to-82‰ with the average value of-75‰ and δ18OH2O ranges from 6.8‰ to 0.6‰ with the average of 3.9‰ which indicate that the ore-forming fluids were mainly composed of mantle-derived fluids.Calcites in the ore veins have δ13C values between-8.4‰ and-5.4‰ which indicate that the ΣCO2 were also originated from the mantle,while the diabase dikes and granites in the deposit area have initial（87Sr/86Sr）i ratios of 0.70861—0.70882 and 0.73519—0.77152 respectively and the fluorites have initial（87Sr/86Sr）i ratios of 0.71474—0.71697 which implicate that the Sr in the ore-forming fluids may have been a mixture of Sr from mafic dikes and granites.The uranium of the deposit may have been from the granites.

关 键 词：同位素 地幔流体 成矿物质来源 粤北302铀矿床 

分 类 号：P611[天文地球—矿床学]