Characteristics, distribution and implication of hydrothermal minerals in Tianxiu Hydrothermal Field, Carlsberg Ridge, northwest Indian Ocean

Hydrothermal minerals could originate from mass wasting of hydrothermal deposits or from the hydrothermal plume falling-out. The types and their spatial distribution of hydrothermal minerals are important indicators for constraining the location of hydrothermal field. The Tianxiu Hydrothermal Field (3°41′N,63°50′E) is an ultramafic-hosted field located on the Carlsberg Ridge, northwest Indian Ocean. In this paper, surface sediments collected from 4 stations near the active venting site of Tianxiu Hydrothermal Field and its surrounding regions were studied on hydrothermal minerals to understand their spatial variations on morphology, composition, abundance and particle size. Near the venting site (0 ~ 0.22 km) the hydrothermal minerals are dominated by Cu-Zn-Fe containing sulfide aggregates, in the size from gravel to sand, originated from the mass wasting of the sulfide deposits and precipitation from the hydrothermal fluid. For samples collected outside of the hydrothermal field (1.84 ~ 6.05 km away), the hydrothermal minerals are dominated by fine grain hydrothermal oxides and hydroxides derived from plume fallout. Our results suggest that the types and grain size of hydrothermal minerals and their spatial distribution can be served as a good indicator for tracking unknown active and inactive hydrothermal field and prospecting of the associated hydrothermal sulfide resources.