A novel mining approach for seafloor massive sulfide deposits

Abstract

Sulfidic polymetallic ore deposits, known as seafloor massive sulfides (SMS) occur on the seabed as precipitation products from hot hydrothermal solutions as a result of mixing with cold seawater and are usually found at depths between 1,500 and 4,100 m. These deposits are formed basically in tectonically active spreading zones of oceans (mid-ocean ridges and "back-arc" spreading systems) and are the result of the global heat transfer from the mantle above the oceanic crust into the water column. In these SMS deposits, metals such as copper (Cu), zinc (Zn) and lead (Pb) as well as trace elements of silver (Ag), gold (Au) and rare antimony (Sb), cadmium (Cd), gallium (Ga), germanium (Ge), and indium (In) are present. This paper describes a novel technology for mining SMS deposits based on the vertical cutting approach developed by a joint research between BAUER Maschinen GmbH and Technip. A hyperbaric mathematical cutting model has been used to calculate the forces needed to excavate SMS deposits in water depth up to 2,000m. The model shows that in hyperbaric conditions, what influences the cutting energy is the water column rather than the geomechanical properties of the rock. Based on the mathematical model a preliminary cutting tool design is shown.