| This thesis explores and discusses the artificial and natural oxidation and hydrolysis of hydrothermal sulfide upon interaction with normal seawater.;The oxidation of sulfide occurs in many seafloor spreading areas, such as 21(DEGREES)N on the East Pacific Ridge. In these areas the old surfaces of the sulfide chimneys are found to be covered by an orange stain, and sediment near the base of the nonactive vents is also found to consist of what has been referred to as amorphous iron oxide and hydroxide. Examination of this iron oxyhydroxide shows that it contains substantial amounts of (delta)-(Fe,Zn)OOH, often associated with some unoxidized sulfide. This finding, for the first time, and in accord with the earlier prediction from laboratory experiments, establishes that the slow oxidation of sulfide minerals on the seafloor gives rise to a mineral with the (delta)-FeOOH structure (Moammar. 1981). The x-ray diffractogram of natural (delta)-(Fe,Zn)OOH shows 12 diffraction lines, most of them strong and sharp in comparison to the synthetic (delta)-FeOOH, which is usually characterized by weak and broad diffraction lines.;This thesis also discusses the exceedingly low solubility of zinc in seawater, from (delta)-(Fe,Zn)OOH and the analogous phase (zinc-ferrihydroxide) and the zinc exchange minerals, 10-(ANGSTROM) manganate and montmorillonite. The concentrations of all four are of the same magnitude (16, 36. 4. and 12 nM. respectively) as the zinc concentration in deep ocean water ((TURN) 10 nM), which suggests that manganates and montmorillonite with iron oxyhydroxides control zinc concentration in the deep ocean, as originally suggested by Krauskopf (1956).;Synthetic and natural ferrosphalerite particles used in kinetic oxidation and hydrolysis studies in seawater develop dense, crystalline coatings consisting of ordered and ferrimagnetic (delta)- (Fe, Zn)OOH. Due to the formation of this reactive diffusion barrier, the release of Zn into solution decreases rapidly, and sulfide oxidation is reduced to a low rate determined by the diffusion of oxygen through the oxyhydroxide film. This also acts as an efficient solvent for ions such as Zn('2+), Ca('2+), and possibly Cd('2+), which contribute to the stabilization of the (delta)-FeOOH structure. |
