Seafloor Massive Sulfides
When two plates drift apart, hot magma rises to the surface as it decompresses. Meanwhile, the seawater above is drawn down to the subsurface. This water rises upon heating and cycles back up through the Stockwork Zone. The flow of these hot, concentrated fluids leads to the alteration of the shallow crust below the surface. This is because the power of these rising fluids fractures the old, cooled pillow lavas, stripping them of their elements via dissolution and re-precipitating these metals elsewhere in the system, creating a vein-like structure, often rich in iron ores.
This seawater continues to rise upon heating and erupts as a “dusty” material as contact with the cooler seawater triggers the precipitation of dissolved minerals. Commonly known as “Black Smokers”, these deposits settle onto the seafloor and form ore bodies that are often rich in Cu, Au, Zu and Ag.