Occurrence and precipitation mechanism of silver in pyrite from chimney fragments in the Edmond hydrothermal field, Central Indian Ridge

•Texture, mineral assemblage, and micro-zone analysis of pyrites are the best indicators to judge the ore-forming process.•Decrease on the degree of fluid-seawater mixing as the temperature gradually increases during the growth of the chimneys.•Mixing of hydrothermal fluid with seawater is the main Ag precipitation mechanism.