Mineralization of sulfide mound at Wocan-1 hydrothermal field based on geological mapping, mineralogy and sulfur isotope studies, Carlsberg Ridge, Northwest Indian Ocean

The Wocan-1 hydrothermal field is distinct on the occurrence of an active sulfide mound, discovered on an axial volcanic ridge of the slow-spreading Carlsberg Ridge. The size of the mound is comparable to TAG active mound located in off-axis of Mid-Atlantic Ridge. In order to understand its formation and controlling factors, we did field geological mapping, mineralogical and geochemical analysis on the hydrothermal precipitates. Our results show the sulfide mound is ∼ 260 m in diameter and ∼ 50 m in height. The southern area of the mound is enriched in high-temperature Cu-rich sulfides, while the northern area is characterized by moderate-temperature Fe-rich sulfides and a talus of pyrite-anhydrite breccias and sands extending for > 200 m. The pyrite here exhibits recrystallization textures characterized by heavier δ34S compositions when compared to that in the southern area. It is considered that the normal faults extending into the northern area of the mound and the associated mass wasting facilitated the infiltration of seawater, which is responsible for the regional difference in mineralization of the mound. This study contributes to the understanding of the formation and controls of large sulfide mounds on the AVRs at the slow-spreading ridges.