摘要
张麻井铀钼矿床位于沽源-红山子铀成矿带西南段,是中国重要的与火山岩有关的热液铀矿床,其铀、钼储量均达到大型矿床的标准。铀-钼矿矿体主要分布于流纹斑岩岩体的内外接触带,钼矿化的分布范围略大于铀矿化,两者在空间上高度重叠。在铀-钼矿矿体外发育一层单钼矿体,与铀-钼矿矿体界限清晰,两者为截然分开的接触关系。为了研究该矿床铀成矿与钼成矿的关系,对张麻井的铀矿石、钼矿石进行主微量元素分析,采用质量平衡迁移计算方法,选择Yb 元素作为不活动组分,使用Grant 公式对其组分迁移定量计算。地球化学数据显示,铀矿石的平均w(U)、w(Mo)为1589×10^-6、3837×10^-6;钼矿石的平均w(U)、w(Mo)为493×10^-6、5706×10^-6,显示钼矿石具有更高的Mo 含量,更低的U 含量。计算结果显示铀矿石的Isocon 均小于以1(分别为0.48、0.58、0.46、0.53),相较流纹斑岩整体发生了组分带入,其中最明显的特点是带入大量SiO2,还带入Mo、U、Zn、Cu、Ni、V、Pb、Co 等成矿元素,K2O、Na2O、Rb、Cs 等碱金属,以及Ba、Sr 等大离子亲石元素,Cd、Bi、Sc、Eu 等组分也表现出较大程度的带入,仅碱金属Li,MnO 等少量组分显示带出;钼矿石的Isocon 均小于以1(分别为0.73、0.67、0.90、0.39),相较于流纹斑岩整体也发生了组分带入,带入的主要有成矿元素Mo、U、Ni、Zn、V、Co、Cu、Pb,碱金属K2O、Na2O、Rb、Li,大离子亲石元素Ba、Sr,以及TFeO、Cd、Bi、Sc 等组分,仅Cr、MnO 组分显示带出。质量平衡迁移计算之后,铀、钼矿石平均w(Mo)分别增加到7217×10^-6、7759×10^-6,显示两者增加的Mo 基本一致。铀、钼矿石平均w(U)分别增加到3131×10^-6、604×10^-6,显示前者增加的U 远远大于后者。在标准化Isocon 图解中,铀矿石和钼矿石的组分迁移具有一定相似性,但具体迁移特征也有一定的差异,整体上表现出相似而不相同的特点。结合矿石从铀-钼矿矿体到外侧的单钼矿体,U 含量迅速下降的地球化学特征,铀、钼矿体的空间分布特征以及其接触关系,文章认为两者极有可能是不同的成矿过程,而且可能是后期富铀成矿流体叠加在早期的钼矿之上。
Located in the southwestern part of the Guyuan-Hongshanzi uranium metallogenic belt, the Zhangmajing uranium-molybdenum deposit is an important volcanics-related hydrothermal uranium deposit in China, whose uranium and molybdenum reserves all meet the standards of large deposits. Uranium orebodies are mainly distributed in the inner and outer contact zones of the rhyolite porphyry body. The distribution of molybdenum ore is slightly larger than that of uranium ore, but they are highly superimposed upon each other in space. A layer of mono-molybdenum mineralization is developed outside the uranium deposit, and the boundary obviously shows completely separate contact relationship. In order to explore the relationship between the uranium mineralization and molybdenum mineralization of the deposit, the authors analyzed the main trace elements of the uranium ore and molybdenum ore in Zhangmajing with Yb as the inactive component to calculate component migration quantitatively by Grant formula. Geochemical data show that the average content of uranium and molybdenum in uranium ore is 1589×10^-6 and 3837×10^-6, whereas the average content of uranium and molybdenum in molybdenum ore is 493×10^-6 and 5706×10^-6, indicating that molybdenum ore has higher Mo content and lower U content. The calculation results show that the isocon of uranium ore is less than 1 (0.48, 0.58, 0.46 and 0.53, respectively), showing that the components was brought in on the whole. The most obvious feature is that a large amount of SiO2 was brought in. Besides, ore-forming elements such as Mo, U, Zn, Cu, Ni, V, Pb and Co, alkali metals such as K2O, Na2O, Rb and Cs, and large ion lithophile elements such as Ba and Sr, were all brought in. The components such as Cd, Bi, Sc, and Eu also exhibit a large degree of being brought in, only a small amount of alkali metal of Li and MnO were taken out. The isocon of molybdenum ore is less than 1 (0.73, 0.67, 0.90 and 0.39, respectively), and the components were also brought in on the whole. The main elements were brought in, which included ore-forming elements such as Mo, U, Ni, Zn, V, Co, Cu and Pb, alkali metals such as K2O, Na2O, Rb and Li, and large ion lithophile elements such as Ba, Sr, TFeO, TFeO, Cd, Bi and Sc. Only Cr and MnO components were taken out. The Mo content of uranium and molybdenum ore increased to 7217×10^-6 and 7759×10^-6, respectively, indicating that the increased Mo was almost coincided. The U content of uranium and molybdenum ore increased to 3131×10^-6 and 604×10^-6, respectively, indicating that the increase of U in the former was much larger than that in the latter. Uranium elements and molybdenum elements show some similarities in the migration of the components in the standardized Isocon diagram, but the specific migration characteristics also show some differences. They show some similarity but are not identical. The authors hold that uranium and molybdenum orebodies were formed by different mineralization processes, as shown by the combination of the spatial distribution characteristics with their contact relationships. It is probable that the later rich uranium ore-forming fluid was superimposed on the early molybdenum ore.
作者
宋凯
巫建华
郭恒飞
郭国林
SONG Kai;WU JianHua;GUO HengFei;GUO GuoLin(State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang 330013,Jiangxi,China;China Nonferrous Metals Geology and Mining Co.,Ltd.,Guilin 541004,Guangxi,China;No.243 Geological Party,CNNC,Chifeng 024000,Inner Mongolia,China)
出处
《矿床地质》
CAS
CSCD
北大核心
2019年第3期599-619,共21页
Mineral Deposits
基金
国家自然科学基金项目(编号:41372071)
中国核工业集团公司项目(编号:中核地计[2008]74号)的联合资助
关键词
地球化学
铀成矿
钼成矿
元素
组分迁移定量分析
张麻井铀钼矿床
geochemistry
uranium metallogenic
molybdenum metallogenic
element
quantitative analysis of component transfer
Zhangmajing uranium-molybdenum deposit
