The Chinese research vessel Dayang Yihao (Ocean No. 1) returns to its base port after finishing a 215-day exploration of the Indian Ocean in Qingdao, east China's Shandong Province, June 18, 2015. During the 25,628-nautical mile voyage in China's 34th oceanic expedition mission, researchers on board the vessel explored the polymetallic sulfide resources on the sea bed. (Xinhua/Zhang Xudong)

The Chinese research vessel Dayang Yihao (Ocean No. 1) returns to its base port after finishing a 215-day exploration of the Indian Ocean in Qingdao, east China's Shandong Province, June 18, 2015. During the 25,628-nautical mile voyage in China's 34th oceanic expedition mission, researchers on board the vessel explored the polymetallic sulfide resources on the sea bed. (Xinhua/Zhang Xudong)

Photo taken on June 18, 2015 shows a basalt collected from Indian Ocean by researchers on board the Chinese research vessel Dayang Yihao (Ocean No. 1). During the 25,628-nautical mile voyage in China's 34th oceanic expedition mission, researchers on board the vessel explored the polymetallic sulfide resources on the sea bed. (Xinhua/Zhang Xudong)

Photo taken on June 18, 2015 shows volcanogenic massive sulfide collected from Indian Ocean by researchers on board the Chinese research vessel Dayang Yihao (Ocean No. 1). During the 25,628-nautical mile voyage in China's 34th oceanic expedition mission, researchers on board the vessel explored the polymetallic sulfide resources on the sea bed. (Xinhua/Zhang Xudong)