江西邹家山铀矿床中的重稀土富集成矿机制研究

The great majority ore-deposits of rare earth elements (REE) are the type enriched with light rare earth elements (LREE), and rare are with heavy rare earth elements (HREE). Our preliminary research has found that there is high grade HREE in uranium ore-body of deeper Zoujiashan ore-deposit, even some ore-bodies have reached industrial grade of HREE. These ore-bodies are a rare samples for the genesis study of HREE ore-deposit. To identify the geological factors controlling HREE enrichment and explore HREE metallogenic mechanism, mainly in Zoujiashan uranium ore-deposit, this project will research in detail the field geological and petrographic characteristics of HREE-rich uranium ore-bodies. By means of chemical composition analysis, electron probe microanalysis (EPMA), mineral liberation analysis (MLA) and X-ray diffraction analysis et al., the project will investigate the occurrence characteristics of HREE in different types of uranium ores, altered rocks and minerals, and summarize the spatio-temporal variations of their characteristics. Using the chemistry partial extraction method, under different physico-chemical conditions, the study will carry out leaching experiment with HREE-rich uranium ore, and understand the REE phase compositions. Based on the above work, compared with the characteristics of ore-bodies without enrichment HREE, and combined with the previous research results on REE fractionation, the project will study the enrichment mechanism of HREE, and the significance and position of HREE mineralization in polymetallic metallogenic evolution series of Xiangshan ore-field.

国内外稀土矿床绝大部分是轻稀土富集型，重稀土富集型矿床罕见。在邹家山等矿床的深部，申请人发现多条铀矿体中伴生高含量重稀土、部分已达工业品位,是难得的研究样本。为查明控制重稀土富集的地质因素，探索其成矿机理，本项目以邹家山矿床为主要研究对象，详细研究富重稀土矿体的野外地质及岩相学特征；采用化学成分分析、电子探针、MLA和X衍射等方法，查明富重稀土矿石、蚀变围岩及单矿物中稀土组成及时空上的变化规律；应用偏提取等方法，在不同物理化学条件下研究矿石中稀土的相态组成。并与重稀土不富集的矿体特征比较，结合前人稀土分馏研究成果，探讨重稀土的富集成矿机制，分析重稀土富集成矿作用在相山矿田多金属成矿演化系列中的地位和意义。

国内外稀土矿床绝大部分是轻稀土富集型，但本项目组发现在邹家山矿床深部伴生高含量重稀土。本项目以此为对象，采用成分分析、电子探针、MLA、浸出和吸附实验等方法，查明重稀土富集的主要地质特征，探索成矿机理。主要认识有：.（1）铀矿石明显富集HREE。HREE与CaO、TiO2、P2O5、U、Th、Mo、LREE、Pb、Sr、Nb、Ta、W、F、Cl等呈显著正相关。富U矿石（U>0.3%）中∑REE+Y变化于380.16×10-6~9679.5×10-6，平均值为3220.55×10-6（是背景值的276.82×10-6的11.6倍），矿石中U与REE非线正相关；富U矿石的LREE/HREE平均仅为0.60、远低于围岩的9.65；富铀矿石中轻稀土总量与围岩相近，而HREE明显高于围岩。.铀矿石中独居石、氟碳钙铈矿、磷灰石、钾长石为轻稀土富集型。磷钇矿、沥青铀矿、钛铀矿、铀钍石、铀石、钍石、锆石为重稀土富集型。萤石轻、重稀土富集型两类都有。而伊利石、黄铁矿的轻重稀土无明显相对富集。.稀土矿物相几乎全为重稀土矿物磷钇矿。少量离子吸附相REE，不超过稀土总量的15%。.（2）在酸及氧化剂条件下，铀矿石中轻、重稀土元素的浸出行为明显不同。HREE浸出率是LREE的２倍左右。随原子序数的增加，LREE(La~Eu)的浸出率较明显增加，而HREE(Gd~Lu~Y)的浸出率则小幅度递减；REE中Gd的浸出率最高，La的浸出率最低。在硫酸浓度为30g/L和100mL中2mL30%过氧化氢时，REE浸出率最高、达60%左右。.（3）HREE成矿经历3个阶段：第一阶段（145~132Ma）岩浆的充分演化，为早期HREE富集提供物质基础。第二阶段（120Ma±）以高温、碱性、富Na的岩浆残余热液为主的成矿热液，形成轻稀土富集的钠交代型铀矿石。第三阶段（100~65 Ma）以富K的红盆卤水为主的成矿热液，形成重稀土富集的水云母-萤石型铀矿石。