In situ geochemical analysis of multiple generations of sphalerite from the Weilasituo Sn-Li-Rb-Cu-Zn ore field (Inner Mongolia, northeastern China): Implication for critical metal enrichment and ore-forming process

Abstract

Weilasituo ore field is located in the southern part of Great Xing’an Range, Inner Mongolia of northeastern China with two main ore deposits, one is previously found Cu-Zn deposit and another is recently found Sn-Li-Rb deposit. Sphalerite occurs in both deposits with multiple generations from early magmatic to later hydrothermal origin, and five types (sph-I to sph-V) were distinguished in the Sn-Li-Rb deposit. A combination of electron microprobe and LA-ICP-MS analysis indicates that the Weilasituo sphalerite is rich in In, Cd, Sn, and poor in Fe, Ga and Ge. The ore-forming temperature of sphalerite ranges from 220 °C to 320 °C, indicating a medium-temperature environment for ore formation. Sphalerite from the Weilasituo Cu-Zn deposit shows high-Fe content, whereas the Fe content is low in the Sn-Li-Rb deposit. The difference in Fe content may not be solely related to the temperature, but also controlled by local deposition environments. It is proposed that in the Sn-Li-Rb deposit, the Fe in the host rock of biotite-plagioclase gneiss was extracted into the ore-forming fluid by greisenization to form zinnwaldite. Overall, the critical metals including Nb and Ta in columbite-group minerals, Li in zinnwaldite, Rb in feldspar and micas, and In and Cd in sphalerite, should be mined together for a comprehensive utilization of these associated elements in the Weilasituo mining area.