Abstract: Au-As paragenesis and separation mechanism is analyzed from the perspective of distributing characteristic, migration forms and precipitation mechanism.The research results show that,the content of Au and As grows and declines simultaneously in early stage while grows and declines respectively in later stage. Besides that, they are not overlap in space.Temperature, pressure, pH as well as the similarity of crystal chemistry and geochemistry properties decide that Au and As are able to form clathrate of ［AuAs］^2-、［Au(AsS₂)］0、［Au(AsS₃)］^2- to migrate.In the main metallogenic period, due to the abundant selenium and scarce sulfur in ore-forming hydrothermal and the change of physical and chemical conditions, Au and As mineralize in earth crust by separating and precipitating.Au and As experience three stages of symbiosis separation and concentration in early stage、main stage and later stage of mineralization, which explains the origin of DaShui gold ore to some extent, puts forward the possibility mechanism of lacking sulfur from the angle of As and provides new idea for exploring similar ore deposit and finding new As ore deposit.

Key words: Au-As paragenesis and separation, Distribution characteristics, Migration mode, Precipitation mechanism