Mineralization of the ion adsorption-type REE deposits in the central part of the Lincang granites in western Yunnan

The Late Triassic biotite monzogranites in the central part of the Lincang granites in western Yunnan are considered as the naturally mineralized parent rocks of the ion adsorption-type REE deposits. The hot and humid climatic conditions in this area are responsible for the formation of the tremendous granite weathering crust, and the preservation in the flat terrains, moderate mountains, moderate mountains-hills and intermontane basins in the moderate mountains. The granite weathering crust may be divided, according to the intensity of weathering from the surface to the bedrock, into the humus layer, loam layer, completely weathering layer, locally weathering layer, slightly weathering layer and fresh bedrock. The completely weathering layers occur as the main pay streaks of the ion adsorption-type REE deposits. Geochemically, the weathering processes gave rise to the fractionation and concentration of the rare earth elements, with the stress on the mineralization of light rare earth elements such as La and Ce. Three types of mineralization model for the ion adsorption-type REE deposits are presented here according to the geomorphological types. The majority of the REE ore bodies reside in the gently moderate mountains and moderate mountains-hills in the study area.