Evolution of Nb–Ta Oxide Minerals and Their Relationship to the Magmatic-Hydrothermal Processes of the Nb–Ta Mineralized Syenitic Dikes in the Panxi Region, SW China

Previous geochemical and petrological studies have concluded that initially magmatic Nb–Ta mineralization is often modified by post-magmatic hydrothermal fluids; however, there still a lack of mineralogical evidence for the syenite-related deposit. From perspective minerals, pyrochlore supergroup minerals significance indicating fluid evolution alkaline rock or related carbonatite type deposits. The Panzhihua–Xichang (Panxi) region famous polymetallic metallogenic belt in southwestern China, abound with huge amount mineralized syenitic dikes. This study focuses on mineral textures chemical compositions main oxide (including columbite-(Fe), fersmite, fergusonite-(Y), especially group minerals) samples from Baicao Xiaoheiqing deposits, Huili area, Panxi region, to reveal magma process syenitic-dike-related oxides syenites are commonly characterized specific two-stage texture crystal scale, exhibiting complex metasomatic structure compositional zoning. Four types (pyrochlores I, II, III, IV) formed different stages were identified. euhedral pyrochlores I II fractional crystallization stage. Anhedral III linked activity magma-derived fluids at late evolution. IV fergusonite-(Y) tend be more concentrated areas undergone strong albitization, which typical phenomenon alteration. These phenomena provide evidences magmatic-hydrothermal transitional stage favored model explaining process. It also changes composition characteristics could serve as proxy processes.