2014 Annual Science Report
Arizona State University Reporting | SEP 2013 – DEC 2014
Habitability of Water-Rich Environments - Task 1 - Improve and Test Codes to Model Water-Rock Interactions
Numerical codes have been developed to model chemical alteration of rocks by migrating fluids. One code is for alteration of permeable rocks by percolating fluids. Another code is for alteration of low-permeability rocks disrupted through hydro-fracturing by forming overpressured fluids. The codes could be used to model chemical weathering on Mars and Earth, and metasomatism on asteroids, moons, and planets.
Dr. Mironenko has developed a code to model alteration of permeable rocks by percolating water solutions. The code considers rates of fluid flow, pH-dependent kinetics of mineral dissolution, and chemical equilibration in aqueous solution including precipitating secondary minerals. The code is capable to constrain abundances of coexisting primary and secondary minerals during chemical alteration (e.g. weathering) in time and space. The code can be used to constrain chemical composition of subsurface mineralogy, aqueous solutions, and sources of free chemical energy to support life between water tables and planetary surfaces. The code was tested and calibrated with use of available data on weathering profiles on Hawaiian basalts. It can be applied to past and present near-surface aqueous environments on Earth and Mars.
Drs. Mironenko and Zolotov have developed a code to model transfer of fluids formed through water-rock interaction or/and dehydration of rocks in a temperature-pressure gradient field. The code’s algorithm assumes chemical equilibration and release of the fluid if fluid pressure exceeds lithostatic pressure by a value of rock’s tensile strength. For each rock layer, the calculated grain and fluid densities together with an adopted porosity are used to compute the rock’s density and the compressed layer’s new thickness. The fluid that did not fill the pore space is transferred to the overlaying layer and is allowed to react with the fresh rock. The calculations provide compositional profiles through the rock together with masses and volumes of all constituents (rocks, minerals, pore fluids, aqueous solutions, and gases). The code was applied for modeling of rock alteration and corresponding fluid transfer (metasomatism) during thermal evolution of Ceres.