ANALYSIS MEANS FOR MIGRATION AND ENRICHMENT OF ORE-FORMING ELEMENTS IN GRANITE: Mineralization and Weathering Process of Datongshan REE Orefield in Southwestern Yunnan

The study area is located in the middle-southern part of Lincang granite in southwestern Yunnan. To verify the coexistence condition of non-ferrous and rare metals in the rare earth element (REE) orebody, 30 chemical samples are collected from the drilled orebody to analyze elements including W, Sn, Nb, Ta, Rb and Cs. The following methods and steps are adopted to study the migration and enrichment of ore-forming elements in granite: First, the analysis values of each element are arranged in order from large to small and divided into 6 groups, with 5 data in each group. Observation shows that, of the samples, 21 have no mineralization, 4 have Sn mineralization, 4 have Rb mineralization, and one has Sn and Rb mineralization. Then, among the unmineralized samples, the element contents (in mass fraction) of weathered crust are compared with those of unweathered rocks to quantitatively evaluate the migration and enrichment degree of elements during weathering. Compared with the bedrocks in the area, the contents of W, Sn, Nb and Ta have increased (showing enrichment), while the contents of Rb and Cs have decreased (showing migration). Finally, the average values of Sn and Rb mineralized samples are compared with those of non-mineralized samples to quantitatively evaluate the mineralization degree of rocks. According to the average value of mineralized samples, Sn mineralization is accompanied by weak W and Ta mineralization, Rb mineralization by obvious W, Ta and Cs mineralization, and Sn-Rb mineralization by obvious W, Ta and Cs mineralization.