•The basaltic ocean crust is replaced at Marine
Oceanic Ridges (MOR) by magma from shallow magma
chambers.
•A convection cell is set up where cool
ocean water descends into the fissured basaltic crust and the heated chemically altered hot water
ascends. “hydrothermal”
•A sulphidic plume (Fe, Zn, Pb, Cu)
issues forth from “black smokers” at 200 - 400oC.
•These hydrothermal
cellsaffect the
ion budgets of Mg, Si, K, Ca, Na and SO42-.