黔北务-正-道地区铝土矿中稀土元素的赋存状态及富集机理研究

The bauxite deposits in the Wuchuan-Zheng’an-Daozhen (WZD) area, northern Guizhou Province, are important components of the bauxite belt of the middle Guizhou and south Chongqing. In recent years, a major breakthrough has been achieved in ore prospecting including the proved two super large and eight large deposits with more than 7 tons of bauxite resources. It has been confirmed by us and other researchers that an obvious fractionation exists among different rare earth element (REE) across the profile through the WZD bauxite deposits and that the bottom zones of the ore bodies are enriched in REE with the total REE contents up to 6399 ppm. Furthermore, parisite and xenotime have also been found near the bottom of the profiles. However, researches on REE enrichment mechanism and comprehensive utilization of REE have been seriously restricted by the lack of system study on the occurrence of REE in the WZD bauxite deposits. This project focuses on three typical large- and super large-scale bauxite deposits in the WZD area. On the basis of detailed field investigations, systematic mineralogy and elemental geochemistry, and Tessier’s chemical sequential extraction experiment will be used to investigate the distribution, occurrences and enrichment mechanism of REE. This research will be helpful in improving both the mechanism of REE enrichment and comprehensive utilization of REE in the WZD bauxite deposits.

黔北务（川）-正（安）-道（真）地区铝土矿是黔中-渝南铝土矿成矿带的重要组成部分，近年来找矿取得重大突破，目前探明超大型矿床2个、大型矿床8个，控制各类别铝土矿资源量超过7亿吨。前人（包括申请者）已证实该区铝土矿剖面上稀土元素（REE）分异明显，且底部存在富REE层，REE总含量最高达6399ppm，并在其中发现氟菱钙铈矿和磷钇矿两种REE矿物，但有关该区REE的赋存状态尚未开展系统研究工作，严重制约了REE富集机理的深入探讨，同时也影响了该区铝土矿中REE的综合利用。本申请拟选取务-正-道地区3个代表性大型-超大型铝土矿床为研究对象，在详细的野外地质考察基础上，通过系统的矿物学以及元素地球化学分析，结合逐级化学提取实验，查明该区铝土矿中REE的赋存状态，揭示REE的迁移和富集机理。这对丰富和完善REE次生富集成矿理论，提高该区铝土矿的综合利用水平，均具有重要意义。

作为黔中-渝南铝土矿成矿带的重要组成部分，近年来黔北务（川）-正（安）-道（真）地区铝土矿在找矿方面已取得重大突破，已发现各类可控铝土矿资源量总计超过7亿吨。研究发现该区铝土矿剖面上稀土元素（REE）分异明显，且底部存在富REE层。但关于该区铝土矿中REE的赋存状态尚缺乏系统性研究，同时稀土元素的富集机理亦不明晰。本项目选取务-正-道地区具代表性的3个超大型铝土矿床为研究对象，通过详细的野外地质考察、系统的矿物学以及元素地球化学分析、单矿物LA-ICP-MS微量元素原位分析及逐级化学提取实验，查明了该区铝土矿中REE主要以独立矿物的形式存在，其中以氟碳钙铈矿、独居石和磷钇矿三种REE矿物为主。此外，少量REE则以离子吸附形式及类质同相形式存在。以后两种形式产出的稀土元素主要赋存于粘土矿物和铁矿物中，而重矿物及铝矿物不是其载体矿物。本项目以发现的上述三种稀土元素独立矿物为主要研究对象，通过对其形成过程的研究来揭示REE的迁移和富集机理。研究表明基底岩石类型以及风化过程中环境介质的pH值是影响该区REE富集的最主要因素。通过本项目的实施，对REE次生富集成矿理论的丰富和完善及该区铝土矿综合利用水平的提高，均具有重要意义。