Columbite-tantalite minerals from Nanping granitic pegmatites, South China: compositional trends and genetic implications
Yang, Zhuming; Song, Renkui; Tao, Kejie; Zhang, Peishan
published: Aug 1, 2003
The No31 pegmatite group is the largest pegmatite cluster of the Nanping pegmatite field and represents one of the most important TaNb deposits in China. The columbitetantalite occurring in No31 pegmatites showed faint oscillatory zonation and complex patchy zonation patterns in back-scattered electron images. Microprobe analyses revealed that columbitetantalite in the pegmatites has a wide range of composition. Neither Mn/(Mn+Fe) nor Ta/(Ta+Nb) atomic ratio has obvious trend of compositional variation along the profile of a single pegmatite dike. However, in the quadrilateral diagrams the compositional trend in columbitetantalite varies from ferrocolumbite to tantocolumbite, then to manganotantalite. The features of zonation and composition in columbitetantalite imply that the formation of Nanping pegmatites underwent original differentiation stage and later metasomatism stage.