Lasaga 9526794 It is proposed to continue the studies of the experimental determination of the dissolution and precipitation kinetics of silicates and aluminosilicates as functions of pH, temperature, ionic strength, catalysis/inhibition and the Gibbs Free energy of reaction. We will examine the surfaces of the reacted minerals using surface analytical techniques (XPS, AES, SEM, AFM in particular), which when combined with rates determined from solution shemistry using flow-through and column reactors will provide information on surface reaction mechanisms. In situ observations of reaacting mineral surfaces, using the AFM at lower temperature and new optical interferometric techniques at hydrothermal temperatures, will provide a bridge between the conventional kinetics experiments and ex-situ surface analysis. The new experimental findings on the kinetics of mineral-fluid interactions will be coupled with extensive molecular physics studies done in our group to ascertain the atomic dynamics governing geochemical processes. Our experimental work continues to lead the way in describing both dissolution and precipitation rates of major rock-forming silicates and aluminosilicates as a function of G, as well as being the first to measure precipitation rates in phases more complex than quartz. The non-trivial full rate laws that have been developed in our prior work are proving to be very important in successfully applying experimental rate data to model field cases, such as the Pijiguaos, bauxite deposit in Venezuela using accurate two-dimensional hydrodynamic fluid flow models. With the continuing work proposed here, the coupling of experiment, theory and models should result in the first completely quantitative physical and chemical model of water-rock interactions from the atomic level to the field setting under a wide set of geological environments including diagenesis in a dynamic sedimentary basin or the chemical evolution in a major bauxite deposit.
