The deposit, also known as seafloor massive sulphides, forms when mineral-rich magma of 400 C erupts from hydrothermal vents on to the seabed. It was discovered in 1977 and is known to contain copper, lead, zinc, silver and gold, barium and nickel. It is present in all oceans. The vents are estimated to occur at every 100 km along the 60,000 km along mid-oceanic ridge encircling earth. Only 350 vents have been discovered so far.