The results of REE leached by some organic acids with various concentrations and water/rock ratios for different durations from a mixed sample of the weathering crust of a granite in Gonghe, Guangdong, China, showed that: 1) the contents of REE leached increase with increasing concentrations of the organic acids; 2) the contents of REE leached by 0.01mol/L organic acids increase with increasing water/rock ratio; 3) the interaction between the organic acids and the samples enhances the pH value of the medium and the contents of REE leached tend to increase with decreasing pH value; and 4) compared with those leached by ammonia sulfate, the REE leached by the organic acids are characterized by a weaker negative Ce anomaly, a stronger negative Eu anomaly, and lower (La/Sm) N and ( Gd/Yb) N ratios, indicating that the organic acids have made contributions to the fractionation of REE in the weathering crust.

Microorganisms in the lateritic profiles of the Lianxian gold deposit in Guangdong were cultured, isolated and identified. The microorganisms include bacteria such as Bacillus, Enterobacter, Pseudom onas, Lactobacillus, Actinetobacter, Aeromona, Listeria, Agrobacterium, Corynebacterium, and Morax- ella, fungi such as Penicillium, A lternaria, Cladosporium, Saccharcom yces, M ucor, and the chemoautotrophic Thiobacillus. It is shown in a leaching experiment that the microorganisms can accelerate the leaching of Cu, Cd, Zn, and that the G- bacteria are most efficient for leaching Cu, Zn and the G+ bacteria are better for leaching Cd.

Microbes were cultured from the samples at various depths in a weathering profile of RE-bearing granite in Gonghe RE mine, Guangdong Province. The cultured microbes, existing at a depth of 0.2～12m and being more plentiful within 3m in the profile,include bacteria (Bacillus, Enterobacter, Escherichia, Alkaligenes, Neisseria, Staphylococcus and anaerobic bacteria such as Clostridium), fungi (Aspergillus niger, Aspergillus f lavus, Penicillium, Mucor and Saccharomycete) and actinomyces. Experiments were made under room temperature by using solutions of the cultured microbes and their metabolites, compared with distilled water and the culture solution without microbes, to leach RE from the sample of the weathering crust. The results are shown by the experiments: (1) The mixed microbes cultured from the profile and their metabolites increase the quantity of RE leached from the sample and reduce the pH of the solutions. (2) The ability to leach RE from the sample varies with various microbes, decreasing in a sequence of fungi (Mucor, saccharomycete, Aspegillus and Penicillium), zymotic bacilli (Enterobacter, Escherichia etc.), Staphylococcus, zymotic Bacillus, actinomyces and Alkaligenes. (3) The RE leached with bacteria is mainly related to the pH value of the solutions influenced by the metabolites of the bacteria; whereas that leached with fungi is mainly related to the adsorption and imbibition of RE by the fungi and the complexing of RE with their metabolites. (4) Compared with that leached with ammonium sulfate, the fractionation of the RE leached with microbes is characterized by higher δCe, lower δEu and lower ratios of NLa/Sm and N Gd/ Yb. The result of the fractionation of RE accords with the distribution of RE in the various layers of a profile of weathering crust of granite in South China. The experimental results indicate that microbes and their metabolites should play a positive role in the mobilization, migration and fractionation of RE in the weathering crust in South China.

对华南风化壳剖面中稀土元素分布的研究结果，稀土元素的总量在各剖面的垂向上多呈抛物线型分布。轻稀土与重稀土之间、Ce和Eu与其它稀土元素之间在剖面中出现明显的分异作用。重稀土自上往下迁移的能力较强，在剖面的中下部相对富集。轻稀土在风化壳中比重稀土更加富集或更加贫化。Ce异常（δCe）在垂向上的变化规律与稀土总量相反，在风化壳表层出现明显的正异常，而在全风化层中亏损。Eu异常（δEu）在风化壳中自下而上有逐渐增大的趋势。影响风化壳中稀土元素的活动性和分异作用的因素有原岩的稀土分布及风化壳的矿物组合、Ph值、氧化还原条件、雨水和地下水以及有机质和微生物等。

以竹细塘和神背岩体为例，研究燕山晚期黑云母花岗岩的风化壳及其稀土成矿特征。结果表明：风化壳剖面发育层状结构，自下而上，碎屑矿物减少，粘土矿物含量增加，活动组分（K2O，Na2O，CaO）减少，稳定组分（Al2O3，Fe2O3，TiO2）增加。风化壳中稀土分布总体上保持原岩特征，但各风化壳层中铈负异常均增加，铕和铒负异常消失乃至出现正异常；全风化壳的中下部稀土最为富集，稀土分布型式也变化最大；在全风化和半风化壳层中稀土含量与粘土矿物呈明显的正相关关系。非矿物相稀土在风化壳中主要以活性态存在，此外还以铁铝共沉淀态和有机结合态形式赋存。