Mineralogical characteristics of the Daping granite porphyry type Nb-Ta deposit, Fujian Province, China, and their implications for rare metal mineralization

다국어 초록 (Multilingual Abstract)

A newly discovered large-scale granite porphyry type Nb-rich Nb-Ta deposit in the Daping area, Fujian, China, is primarilyhosted by columbite minerals. Currently, there are limited reports on the enrichment mechanisms and metallogenicpotential of this new type of granite porphyry Nb-Ta deposit, and the factors controlling the differential enrichment of Nband Ta remain unclear. Based on petrographic observations, this study employs techniques such as EPMA and LA-ICP-MSto analyze the mineralogical textures and compositions of feldspar, mica, Nb-Ta minerals, and other accessory mineralsin the Daping granite porphyry. Integrating previous research findings, this work aims to investigate the enrichment anddifferentiation mechanisms of metallogenic elements in this new type of Nb-Ta deposit. The albite in the Daping graniteporphyry often forms “snowball texture” with quartz. Mica commonly exhibits a porous texture and displays an evolutionarysequence of muscovite-phengite-Li phengite-zinnwaldite-Li-Fe micas, indicating a progressive enrichment in Li.
Columbite exhibits zoning patterns, with Nb-rich cores and Ta-rich rims. The margins of the grains are subrounded toirregular, suggesting that the parental magma of the Daping granite porphyry underwent a highly fractionated evolutionprocess accompanied by hydrothermal alteration. The Nb-Ta mineralization is associated with an F- and Li-rich magmatichydrothermalsystem, although highly fractionated magmatic evolution is the dominant controlling factor. Furthermore,the vertical zonation of Nb and Ta in the study area may be related to the constitutional zone refining model process inthe F-Li-rich system. This model involves the formation of a low-viscosity, low-density boundary layer melt, enrichedin incompatible elements, which effectively separated from the remaining melt and crystal, and migrated upward to formthe ore deposit.