New Zealand and Japanese scientists are hoping to discover strategic mineral deposits and new forms of life in a joint exploration of some of the world's deepest waters in the southwest Pacific.

Scientists from New Zealand's National Institute for Water and Atmospheric Research (NIWA) and Institute of Geological and Nuclear Sciences (GNS Science) are to join the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) on Japanese research vessel Yokosuka in Tonga this week.

Together they are to explore ecosystems in underwater mountains and volcanoes of the Louisville Seamount Chain and northern Kermadec Arc, about 1,000 kilometers northeast of New Zealand, using one of the world's most advanced deep diving manned submarines, which is capable of going to 6.5 km below the ocean surface.

"You never know what to expect in the deep sea, animal life on the seamounts could be sparse, or there could be rich diversity and abundant new communities," NIWA fisheries scientist Dr Malcolm Clark said in a statement Tuesday.

The scientists would also look at the role seamounts played in the distribution of life in the deep sea.

It was thought that some animals used the seamounts as " stepping stones" across the ocean by establishing communities on one before moving to the next, he said.

The other focus of the expedition would volcanoes along the northern part of the Kermadec Arc, where they would dive to hydrothermal systems (seafloor hot springs) to sample the hot water being discharged from vents on the seafloor together with any mineralization and animals.

"These hydrothermal systems are likely to host significant minerals deposits, in keeping with those discovered in the southern part of the Kermadec Arc," GNS principal scientist Dr Cornel de Ronde said in the statement.

"Confirmation of their existence will have strategic importance for New Zealand considering the number of volcanoes along the 1, 300-km length of Kermadec Arc that sits within New Zealand's territorial waters."

Habitats located at the vent sites often hosted unique animals adapted to survive in extreme temperature and chemical conditions that were hostile to most life forms.