9526762 Barnes The PI proposes to determine the rate constants and activation energies of the growth of pyrite from aqueous solutions. Measurements will be made at 100-300(C and pH from 2 below to neutrality. The flow-through method will be used where pressure vessels containing polysulfide or ferrous ammonium sulfate solutions, will be pumped into a reaction vessel containing pyrite seed grains about 1 mm in diameter. Reaction rate constants and activation energies will be measured as function of temperature, degree of supersaturation, polysulfide and other aqueous sulfur species, and pH. Applications of the resulting data are broad. They supply a quantitative basis for evaluating the flux of Fe and S into sediments, a major stage of their global cycles. The data also constrain the rates of formation of strongly magnetic greigite and of its reaction to form pyrite. From this information, the interpretation of paleomagnetic characteristics of sediments can be better understood where magnetite is absent to determine, for example, when the magnetic state was set and how it was preserved. An especially valuable application is to mineral exploration due to the high abundance of this mineral in ore-containing environments.
