China's Haiyang Dizhi-6 completes 16th deep-sea expedition, discovers rare seabed minerals and tests world's first 10,000-metre ocean exploration system

For centuries, the deepest parts of the ocean remained beyond human reach, hidden beneath crushing pressure and perpetual darkness. Now, a Chinese research vessel has returned from one of its most ambitious missions yet, bringing back mineral samples from the seafloor and data gathered nearly eight kilometres beneath the Pacific Ocean's surface.

The research vessel Haiyang Dizhi-6 (Ocean Geology-6) has completed its 16th deep-sea geological survey expedition, marking another milestone in China's growing efforts to study the geology of the deep ocean and develop technologies capable of operating in some of Earth's most extreme environments.

The findings are expected to improve scientific understanding of deep-sea mineral resources, tectonic processes, and the largely unexplored ecosystems that exist in the ocean's deepest trenches.

Scientists recover mineral-rich nodules and 90 kilograms of basalt from the Pacific seabed

During the expedition, researchers used multiple geological survey techniques to investigate deep-ocean environments and collect samples from the Pacific Ocean floor. Among the materials recovered were polymetallic nodules, seabed rocks and near-bottom seawater samples.

Polymetallic nodules are among the most closely studied deep-sea mineral resources. These potato-sized deposits accumulate over millions of years and can contain economically significant concentrations of manganese, nickel, cobalt and copper. Similar nodules have been found scattered across abyssal plains at depths ranging from roughly 4,000 to 6,500 metres.

In a conversation with the China Global Television Network, Qin Pengbo of the Guangzhou Marine Geological Survey said the team identified an area containing high-abundance polymetallic nodules and recovered approximately 90 kilograms of basalt samples from the seafloor. He noted that these specimens could help scientists investigate mantle source characteristics beneath the region and improve understanding of Earth's deep geological evolution.

World's first full-ocean-depth electromagnetic survey system passes sea trials

The expedition was not limited to geological sampling. Researchers also carried out sea trials of what Chinese scientists describe as the world's first full-ocean-depth, 10,000-metre-class electromagnetic acquisition station and offshore operating system.

As reported by CCTV, the equipment was tested in an abyssal rift zone in the western Pacific at a depth of 7,737 metres, where it successfully collected high-quality electromagnetic data. Engineers reported that all performance indicators met the required standards during acceptance testing.

Electromagnetic surveys function somewhat like a medical scan of the Earth. By measuring naturally occurring electromagnetic signals, scientists can infer the structure, composition and physical properties of rocks hidden beneath the seafloor. Similar techniques were employed during the vessel's previous expeditions, where researchers described the resulting datasets as a form of geological CT scan of the ocean floor.

Why the deepest parts of the ocean matter to geologists

Marine geology is more than a search for mineral resources. The discipline investigates the structure and history of the ocean floor, helping researchers understand plate tectonics, volcanic activity, sediment transport and the evolution of Earth's crust. Because much of the deep ocean remains poorly mapped, each expedition contributes valuable information about one of the least explored regions of the planet.

The successful trial of the new electromagnetic system could support future research in the hadal zone, the deepest oceanic environment, and aid site selection for international ocean drilling projects. Such drilling programmes allow scientists to examine ancient sediments and rocks preserved beneath the seafloor, offering clues to Earth's geological history and changing climate.

As nations increasingly turn their attention towards the deep ocean, expeditions like that of Haiyang Dizhi-6 highlight how advances in robotics, geophysics and ocean engineering are opening regions that were once considered inaccessible. The vessel's latest voyage has added another set of observations from the ocean's depths, where many geological questions still remain unanswered.