Dissolution/precipitation reactions involving calcite and plagioclase can have an enormous impact on the porosity and permeability of sedimentary rocks during diagenesis. Such reactions are also known to be important controls on the vent fluid chemistry in geothermal systems. It is thus important to understand the factors influencing the rates of these mineral reactions, since their timing relative to the production of oil or gas can be crucial to the development of major hydrocarbon reserves, or alternatively their timing may strongly influence the locus or extent of mineralization in hydrothermal ore deposits. This project will initiate a series of hydrothermal experiments which quantitatively evaluate the influence of fluid chemistry, grain size (surface area), temperature and pressure on reaction rates for mineral reactions involving calcite and plagioclase feldspar, phases which have been shown to significantly affect the porosity inventory of petroleum reservoirs, and are demonstrably important to the chemistry of geothermal fluids. The use of isotopic tracers to measure kinetic and thermodynamic parameters is a new experimental approach which is especially well suited to the study of sediment diagenesis and hydrothermal alteration processes, where reactions often proceed very close to equilibrium.
