Numerical Simulation-Based Analysis of Seafloor Hydrothermal Plumes: A Case Study of the Wocan-1 Hydrothermal Field, Carlsberg Ridge, Northwest Indian Ocean

Understanding the dynamics of deep-sea hydrothermal plumes and the depositional pattern of hydrothermal particles is essential for tracking the submarine hydrothermal venting site, prospecting polymetallic sulfide resources, as well as deciphering biogeochemistry cycling of marine elements. In this paper, a numerical model of the deep-sea hydrothermal plume is established based on the topography and long-term current monitoring data of the Wocan-1 hydrothermal field (WHF-1), Carlsberg Ridge, Northwest Indian Ocean. The model allows for a reconstruction of the hydrothermal plume in terms of its structure, velocity field, and temperature field. The relationships between the maximum height of the rising plume and the background current velocity, and between the height of the neutral-buoyancy layer and the background current velocity are established, respectively. The transport patterns of the hydrothermal particles and their controlling factors are revealed. Using hydrothermal particles with a density of similar to 5000 kg/m(3) (i.e., pyrite grains) as an example, it is found that pyrite larger than 1 mm can only be found near the venting site. Those in the size 0.3-0.5 mm can only be found within 137-240 m from the venting site, while those smaller than 0.2 mm can be transported over long distances of more than 1 km. Using the vertical temperature profiling data of WHF-1 obtained during the Jiaolong submersible diving cruise in March 2017, we reconstruct the past current velocity of 10 cm/s, similar to the current data retrieved from the observational mooring system. Our model and the findings contribute to a better understanding of the hydrothermal system of WHF-1, and provide useful information for tracing the hydrothermal vents, prospecting the submarine polymetallic sulfide resources, designing the long-term observation networks, and relevant studies on element cycling and energy budget.