Abstract:The Tiegelongnan deposit yields the largest porphyry-high sulfidation Cu (Au, Ag) mineralization system in the Bangong-Nujiang metallogenic belt of Tibet. For the advanced argillic alteration was widely imposed on the phyllic zone, which results in a complex mineralization process and metallogenic system that impedes the construction of an accurate metallogenic model. Based on the previous exploration and research works of the Tiegelongnan deposit, we mainly focus on the typical alteration mineral (sericite) to study its mineralogical characteristics by scanning electron microscope and electron microscope, and uncover the mineralogical characteristics and genesis of sericite which produced in different conditions and locations, which aimed to study the metallogenic mechanism of the Tiegelongnan deposit. Finally the significance of the mineralization mechanism was discussed through all the geochemical analyses. It is proved that the sericite of the Tiegelongnan deposit are composed of muscovite, illite and celadonite endmembers as well as minor paragonite endmembers. In the ore-body sericite and copper minerals have a close paragenetic link. In the early-stage water-rock interactions in deep levels, high Si and low Al sericite-chalcopyrite was produced in porphyries, while high Al and low Si sericite-chalcopyrite was yielded in sandstone. With the progression of hydrothermal evolution towards shallower levels, the sulfides graded to bornite and covellite and the sericite with high Al and low Si content was produced. Besides, sericites from the altered sandstones are also enriched in Fetot, Fe3+, Na+ compared to those present in intrusions. Fe2+-rich sericite in porphyries indicates a reduced hydrothermal condition, while Fe3+-rich sericite in sandstone implies a relative oxidized hydrothermal condition. In the mediate-shallow level of the phyllic alteration zone of the Tiegelongnan deposit, sericites frequently occurring with a certain amount of kaolinite as well as bornite and covellite, which reflects that the SO2 enrichment, temperature decreasing and acid increasing resulted in a stronger water-rock interaction and copper precipitation. All in all, different mineral assemblages concerning with sericite and the distinct sericite geochemical characteristics have some important implications for the hydrothermal conditions and the exploration prospecting.