Mineralization of ion-adsorption type rare earth deposits in Western Yunnan, China

With the widespread application of heavy rare earth elements (HREEs) in high-tech fields, ion-adsorption type rare earth element (iREE) deposits have attracted much attention as the main output deposit type of HREE metals. In recent years in western Yunnan, southwest China, iREE deposits have made some large discoveries and received a high degree of attention. In this article, we summarize the metallogenic background, distribution, and metallogenic characteristics of iREE deposits in the Tengchong and the Lincang Granite Belt in western Yunnan, and analyzes the roles of ore-forming parent rock, regional metamorphism and alteration, epigenesis, and granite regolith composition in the metallogenesis of the iREE deposit in western Yunnan. It is believed that the high REE content granite parent rocks, metamorphic or magmatic-hydrothermal alteration, hot and humid climate, gentle topography, large and thick granite regolith are all favorable factors for iREE deposit formation. The long-term and multi-stage magmatic evolution formed high REE content granite parent rocks. Strong magmatic-hydrothermal activity and strong metamorphism associated with regional slip movement have contributed to the enrichment of REE elements and the formation of easily dissociated REE-bearing minerals, laying the ma-terial foundation for iREE deposits. The humid, hot and rainy climate and the vegetation-rich surface environ-ment are conducive to weathering, which contributes to the formation of granite regolith and clay minerals, and the dissociation of REE-bearing minerals. Favorable topographical areas help to retain large-scale and thicker granite regolith, in which the clay minerals continue to adsorb the REE ions which have been infiltrated and migrated by the aqueous solution downward, leading to the gradual enrichment of REE elements and the for-mation of iREE deposits.