Hydrothermal signature in the axial-sediments from the Carlsberg Ridge in the northwest Indian Ocean

30 sediments grabbed from 24 sites between the equator and 10°N along the Carlsberg Ridge (CR) in the northwest Indian Ocean has been analyzed for bulk chemical compositions. Hydrothermal components in the sediments are identified and characterized. They mainly occur at 6.3°N as sulfide debris and at 3.6°N as both sulfide and high temperature water-rock interaction products. The enrichment of chalcophile elements such as Zn, Cu, Pb and the depletion of alkalis metals such as K and Rb are the typical features of hydrothermal components. High U/Fe, low (Nd/Yb)N and negative Ce anomaly infer the uptake of seawater in the hydrothermal deposits by oxidizing after deposition. However, the general enrichment of Mn in hydrothermal plumed-derived materials is not found in the sediments, which may indicate the limited diffusion of fluids or plumes, at least in the direction along the Carlsberg spreading center. The hydrothermal components show their similarity to the hydrothermal deposits from the Indian Ocean Ridge. At 3.6°N ultramafic rocks or gabbroic intrusions, may be involved in the hydrothermal system.