BACKGROUND In Shandong Province, northwest of the Jiaodong area is the most important gold metallogenic area. The Xinli gold deposit is not only an important deposit in the Sanshandao-Xinli metallogenic belt, but also one of the most typical gold deposits in this area. Research on the Xinli gold mine has been carried out for years and has achieved many fruitful results, however, the mineralogical characteristics and mineral typomorphic characteristics of gold minerals and gold-bearing minerals still need to be studied further.

OBJECTIVES To investigate the mineralogical characteristics and geological significance of gold minerals and gold-bearing pyrites from the Xinli gold deposit.

METHODS Polarized light microscope identification and electron probe microanalysis were the main methods in the research of gold minerals and gold-bearing minerals. The geological significance was explored through mineral typological characteristics.

RESULTS The results show that most of the gold minerals in the Xinli gold deposit are electrum, a small amount of native gold and kustelite. The gold fineness ranges from 336.2 to 834.9, with an average of 699.8. The content of S in gold-bearing pyrite is 51.69%-53.78%, with an average of 53.19%; Fe content is 45.69%-47.62%, with an average of 46.52%; The S/Fe value is 1.99, and sulfur is depleted slightly.

CONCLUSIONS The morphological typomorphism of gold-bearing pyrites shows an evolutionary trend from coarse-grained cubic shape to medium- and fine- grained pentagonal-dodecahedral shape and then to fine-grained cubic shape, which reflects the gradual reduction of hydrothermal fluid temperature in different metallogenic stages. The compositional typomorphic characteristics indicate that the ore-forming hydrothermal solution has typical characteristics of medium hypabyssal and medium-low temperature. Therefore, it is considered that there are three stages of mineralization in the hydrothermal alteration period of the Xinli gold deposit, of which the third stage is the main mineralization period.