Study on typomorphic characteristics of muscovites in Lailishan tin deposit of Yunnan Province

Lailishan tin deposit is one of the most famous tin polymetallic deposits in western Yunnan. To investigate its ore genesis and provide scientific basis for exploration and prospecting, the authors studied typomorphic characteristics of muscovites in the mining area. The results show that muscovite is one of the most dominant minerals in this mining area, which is mainly distributed in the first and second mineralization stage and the adjacent wall rocks. The authors found that the muscovites of mineralization stages are mostly spatulate or flabellate (stellated) aggregation under optical microscope. And the muscovites of the wall rocks are mostly subhedral-euhedral and have clear cleavage. The EPMA data indicate that muscovites of different mineralization stages have different compositions, which show that the genesis of the muscovites is affected by the metallogenic hydrothermal evolution. The muscovites of the wall rocks are typically phengite. The Na-Mg diagram indicates that the wall rocks were mostly formed in medium-low temperature and medium-high pressure. The metasandstones were formed in high pressure, and the hornstones were formed in medium-high pressure. The results of this study have a guiding significance for further prospecting in this area.