spreading has occurred for hundreds of million of years. At the fresh resurgence of new floor we have magma, hydrothermal solutions from the deep crust with all

spreading has occurred for hundreds of million of years. At the fresh resurgence of new floor we have magma, hydrothermal solutions from the deep crust with all the gasses/water/metals and compounds are forced up from the magma(which holds them under HUGE pressure as dissolved species) as pressure drops, they become discrete fluid streams as the varying pressure/temperature/solubility product reveal. These are the 'black smokers' - they form the nodules etc., we have read about. All manner of oxidation states, many reduction/oxidation pathways and a number of organisms employ these to live on - bacteria/worms/crabs - a whole strange ecosystem. As the spreading widens, the fluid ceases, the bacteria die, the ecology migrates and collapses, with new colonization at the active zone. Much of earth mineral came this way, some via volcanos and several by meteors(Sudbury Nickel). The important aspect is:- far from the active zone there are dead zones, some a 1000KM wide, all packed with the same minerals - but covered by sediments of varying thickness. Deep ocean mining should go in this dead zone = kills nothing. All they need to do is rake up the nodules and use a filter to grab the loosened sediment, compress to bricks and drop to the floor, minimizing drifting sediments. So we can have cake and eat it - just the right rules are needed.