China's deep-sea manned submersible Jiaolong has concluded a 120-day expedition in the southwest Indian Ocean, Yu Hongjun, mission commander, said Monday.

During the mission, the sub observed different hydrothermal areas, the characteristics of hydrothermal fluids and deep-sea biodiversity, gathering a huge amount of data and samples.

Jiaolong discovered new hydrothermal vents; deep-sea fissures emitting hot water. The finds could help research on the resources and environments of seafloor sulfide deposits that contain various metals.

The voyage also saw six trainee pilots, selected out of 130 candidates, complete their training "outstandingly", Yu said.

Jiaolong will embark on a new expedition to the northwest Pacific between June and August, followed by a journey to the Mariana Trench, where the sub reached a depth of 7,062 meters in June 2012, its deepest dive to date. (Xinhua)