风化淋积过程中矿物演化对稀土元素富集-分异的制约:以梅州仁居稀土矿床为例

Constraints on the REE Enrichment-fractionation in Weathering Crust by the Mineral Evolution in the Weathering and Leaching Processes:A Case Study of the Renju REE Deposit in the Meizhou Area,Guangdong,China

我国南方的离子吸附型稀土矿床是世界上最主要的中重稀土来源,研究这类矿床的禀赋特征和成矿机制,可为中重稀土储量的增加和稀土资源的高效利用提供理论支撑。本文对梅州仁居离子吸附型稀土矿的风化壳及基岩进行了矿物学和元素地球化学分析,探究风化过程中矿物演化对稀土元素富集-分异的制约机制。结果显示,仁居风化壳及其基岩相对富集轻稀土,自基岩至稀土富集层,离子交换态稀土含量呈增加趋势,富轻稀土副矿物榍石和磷灰石等在全风化层中消失。榍石是仁居风化壳中稀土元素的主要来源,风化壳中的离子交换态稀土主要被高岭石和埃洛石吸附。铁锰氧化物可能是轻-重稀土元素分异以及Ce与其他稀土元素分异的原因之一。

The ion-adsorption REE deposits in South China are the main sources of MREE and HREE in the world.Understanding the mineralization mechanism and REE speciation of the ion-adsorption REE deposit may shed lights on the efficient prospecting and utilization of such type of REE resources.In order to explore the constraint mechanism on the enrichment and fractionation of REEs in weathering crust by the mineral evolution in the weathering process,in this paper,we have conducted mineralogical and geochemical studies of the bedrock and regolith of the Renju ion-adsorption REE deposit in the Meizhou area,Guangdong,China.The results show that the regolith and its bedrock of the Renju deposit are relatively enriched with LREE.From the bedrock towards the REE-enriched horizon,the contents of ion-exchangeable REEs are gradually increased.LREE-rich minerals including titanite,apatite and others are disappeared in the completely weathered horizon.Titanite was the main source of REEs in weathered crust,and its released REEs by weathering were mainly adsorbed by kaolinite and halloysite in form of ion-exchangeable REEs.The Fe-Mn oxide could be one of factors resulted in the fractionation of LREE and HREE and of Ce and other REEs among various horizons in the deposit.