Abstract: The Kalatag region in eastern Tianshan, NW China contains a number of economically important Cu deposits, including the HonghaiHuangtupo VMS-type Cu-Zn deposit hosted in the volcanicsedimentary rocks of the Late Ordovician to Early Silurian Daliugou Formation. The characteristic dualistic structure of the Cu-Zn deposit features  concordant massive sulfide and discordant vein-type ores in the footwall strata. The massive auriferous sulfide ores consist of pyritechalcopyrite, pyritechalcopyritesphalerite, pyritesphaleritechalcopyrite and sphalerite. Based on detailed mineragraphic analysis of various kinds of auriferous sulfide ores, and combined with scanning electron microscope and energy dispersive spectrometer hyphenated techniques (SEM/EDS), we clarified that the principle ore minerals are pyrite, chalcopyrite and sphalerite, while tetrahedrite, galena and pyrrhotite occur in minor quantities; gangue minerals are mainly quartz, sericite and barite with lesser chlorite, plagioclase and carbonate. Mineralization of the Honghai deposit can be divided into three periods: VMS mineralization, hydrothermal overlapping and supergene periods. The VMS mineralization period can be further subdivided into pyrite, sphaleritechalcopyrite-tetrahedritegalena and quartzbarite stages. Four grains of natural gold and silver metallic mineral were found in this deposit for the first time, their very different chemical contents inferred that the hydrothermal environment went through a transformation from intermediateacid to alkalescent, which benefited Au and Ag transport. Au and Ag were activated and re-enriched through metasomatism of minerals formed in the VMS mineralization period, by the late alkalescent hydrothermal solution. Through metasomatism, Au and Ag mineralization occurred not only in the intermediatehypothermal sphaleritechalcopyrite stage of the late VMS mineralization period, but also in the intermediatehyperthermal pyrite stage of the early VMS mineralization as well as the whole hydrothermal overlapping periods. In all mineral assemblages, except the four mineral grains, Au and Ag could not be observed under the electron microscope, which may illustrate that Au and Ag in this deposit mainly occur as constituents of the crystal lattice of host minerals.

Key words:  Kalatag region, VMS deposit, massive sulfide, metallogenic epoch, Au, Ag, occurrence