This collaborative research explores the physico- chemical means by which sediments deposited at the earth's surface become lithified during burial. Solution-transfer creep is a possible mechanism, but the kinematics are not well defined. Experiments at Texas A&M University will monitor rates of pore-volume loss and water-rock interaction in sand-water mixtures under hydrostatic and nonhydrostatic conditions as a function of temperature, confining pressure, fluid pressure, grain size, clay content and aggregate volume strain. These will be performed in reactively inert pressure vessels that simulate temperature and pressure conditions typical of diagenesis. Experiments at University of Oklahoma will be conducted in a similar vessel, but with the added capabilities of triaxial loading and constant fluid flow. This effort will study compaction as a function of applied differential stress, study stress-related sand- water reaction kinetics, long-term constant flow conditions, and effects of solution undersaturation on compaction rates. data sets from both institutions will be interpreted in terms of constitutive "creep" laws for time-dependent volume strain, and together with reaction rate laws of mineral- water interaction under nonhydrostatic conditions (also experimentally determined), will be extrapolated to geological scenarios using numerical methods. The aim of this research is ultimately to quantify rates of pore-volume loss in sandstones during burial and to understand the thermodynamics kinetics of water-rock interaction under hydrostatic and nonhydrostatic conditions.
