外生稀土矿床的分布、类型和成因概述

The Overview of the Distribution,Type and Genesis of the Exogenetic Rare Earth Elements( REE) Deposits

稀土是当今危机资源,勘探和研究稀土矿床是世界热点。外生矿床是重要的稀土来源之一。本文综述了残-坡积、(河流)冲积和海滨砂矿,碳酸盐岩风化壳型,花岗岩风化壳型等稀土矿床地质特征和成因认识。风化壳型稀土矿床是由富稀土的原岩经过地表机械和化学风化作用形成,母岩稀土的最初富集是形成风化壳型稀土矿床的前提,风化壳继承了母岩的稀土特征。目前世界对重稀土的需求最为突出,中国南岭花岗岩风化壳型重稀土矿床为世界之最。风化是后期稀土提炼富集过程,成矿关键在于花岗岩岩浆阶段重稀土矿物的形成。然而,何种因素形成南岭地区具有稀土成矿潜力的花岗岩,富稀土花岗岩表现出的轻重稀土分异是由于源区性质的差异还是源于岩浆演化过程中的分异作用,以及重稀土矿物的形成机制仍有待于研究。

Rare earth elements （REE） are critical metals in the world. Exploration and study of the REE deposits become a hot issue. Exogenetic deposits are one of REE resource. The paper briefly overview geological features and origin of REE deposits from residual-diluvial, fluvial and beach placer, carbonatite and granitoid weathering crust. The weathering type REE deposits are formed by the chemical weathering processes of the REE-rich parent rocks. The initial REE-enrichment of the parent rocks is the premise for the formation of this type deposit, and the weathering crusts have inherited the REE distribution patterns of the primary rocks to a great extend. World presently has great demand for heavy REE （ HREE）. Granitoid weathering HREE deposits in Nanling region of South China are rare and attract many geologists. Weathering process is secondary extraction and enrichment. Primary HREE mineral formation is a key. However, the questions why the granites having potential to generate rare earth mineralization within weathering crusts mainly occurred and concentrated in Nanling region, and whether the LREE/HREE fractionation of the REE-rich granite is due to the discrepancy of their magma source or the differentiation of the magma during evolution, and how the HREE mineral formed, are still not clear and need more study.