粤北石土岭铀矿床同位素地球化学研究  

Isotopic geochemistry of Shituling uranium deposit,northern Guangdong Province,China

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

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]内生金属矿床成矿机制研究国家重点实验室 [3]核工业290研究所,广东韶关512026

出　　处：《矿床地质》2006年第1期71-82,共12页Mineral Deposits

基　　金：国家自然科学基金重点项目(40132010);高等学校博士学科点专项基金(20040284039);创新群体项目(40221301)的资助

摘　　要：石土岭铀矿床位于贵东岩体东南部与寒武纪浅变质岩接触带的内带,矿区内NWW向和NNE向基性岩脉十分发育。矿体主要赋存于帽峰岩体中,呈脉状产出,并受近EW向裂隙构造控制。沥青铀矿的U-Pb年龄(135Ma)与帽峰岩体的年龄(220Ma)相差明显,但与NWW向辉绿岩脉的年龄(143Ma)十分接近。矿石中黄铁矿的初始87Sr/86Sr值(0.71315~0.72579)介于成矿期间辉绿岩的值(0.70449~0.70632)与帽峰和下庄岩体演化至成矿时期(135Ma)的值(0.75058~0.99507)之间;黄铁矿的铅同位素组成呈线性分布,为基底变质岩铅与帽峰岩体铅及辉绿岩铅之间不同程度的混合。Sr、Pb同位素组成显示出成矿组分具多来源特征;成矿流体的δ18OH2O=2.0‰~8.1‰,δDH2O=-63‰^-51‰,反映出成矿流体主要由幔源流体组成;方解石的δ13C=-8.3‰,表明矿化剂∑CO2也来自地幔。因此,幔源流体在石土岭铀矿床的形成中具有十分重要的意义。The Shituling uranium deposit is located on the granitic side of the contact zone between the southeastern part of Guidong granite and the Precambrian low-grade metamorphic rocks. There occur many NWW- and NNE-striking basic veins in this area. The veinlike ore bodies mainly hosted in Maofeng granite are controlled by EW-trending fissure structures. The U-Pb age of uraninite （135 Ma） is obviously different from the formation age of Maofeng granite but close to the age of NWW-trending diabase veins. The initial ^87Sr/^86Sr values of pyrite （0. 71315～0. 72579） in the ore are between those of NWW-striking diabase（0. 70449～0. 70632）and Maofeng and Xiazhuang granites （0. 75058～0. 99507） at 135 Ma. The linear Pb isotope distribution of pyrite from the ore indicates that Pb in the ore was a mixture of Pb derived from the basement metamorphic rock, Maofeng granite and diabase. The Sr and Pb isotopes show multiple-source characteristics of the ore-forming components. The ore-forming fluids have δ^18OH2O of 2.0‰～8.1‰ and δDH2O of - 63‰～ - 51‰, suggesting that the ore-forming fluids were mainly composed of mantle fluids. The calcite δ^13C of - 8.3% suggests that the ∑CO2 in the fluids came from the mantle. Therefore, the mantle fluids might have played an important role in uranium mineralization of the Shituling uranium deposit.

关 键 词：地球化学 同位素 幔源流体 成矿物质来源 石土岭铀矿床 粤北 

分 类 号：P619.14[天文地球—矿床学] P597.2[天文地球—地质学]