Following the successful completion of the inaugural China–New Zealand collaborative dive expedition by the Institute of Deep-Sea Science and Engineering (IDSSE) of the Chinese Academy of Sciences (CAS) and the New Zealand National Institute of Water and Atmospheric Research (NIWA), both organizations have expressed their interest in conducting a second expedition to another hadal trench. After nearly a year of thoughtful discussion and meticulous preparation, we are delighted to announce the second China-New Zealand collaborative dive expedition to the Puysygur Trench, scheduled to take place from January to March of 2025. 

The Puysegur Trench is located in the southern part of the Tasman Sea, just off the southwestern coast of New Zealand. It is located a few hundred kilometers south of the South Island of New Zealand, and extends almost in a north-south direction. It is estimated that the deepest point of the Puysegur Trench reaches approximately 6,208 meters. It is a significant geological structure at the boundary of the Australian and Pacific plates. This subduction zone, an active geological process, involves the subduction of the Australian Plate beneath the Puysegur margin, which is the extended continental lithosphere of the Pacific Plate. This area has garnered significant interest from researchers across various disciplines, including geology, geophysics, oceanography, and biology, due to its unique geologic features and potential for scientific exploration.

According to the sampling of the trenches using full-ocean-depth Human Occupied Vehicle (HOV) Fendouzhe and other state-of-art deep-sea technologies, it is possible to reveal magmatic generations, regional geological evolution, and the processes of subduction initiation. The following questions are expected to be explored in this joint expedition:

• Explore sedimentary, magmatic, and geochemical responses to divergence, decollement, strike slip, and subduction initiation;
• Reveal when and how does subduction initiation start;
• Constrain the cycles of subducted materials;
• Discover hadal fluid activities (e.g., cold seeps, mud volcanoes, serpentinite-hosted…) and the associated ecosystems.

The scientific expedition is to be conducted by a multinational group of researchers, comprising scientists from seven countries: China, New Zealand, Denmark, Germany, France, Malaysia, and India. The participating scientists will represent a range of disciplines, including but not limited to biology, microbiology, oceanography, geophysics, geology, geochemistry, and environmental sciences.

Survey area of China-New Zealand collaborative dive expedition to the Puysygur Trench