Computer Simulation Investigations Of Plagioclase Dissolution

Feldspar weathering governs the temporal evolutions of many surface geochemical processes. Extensive studies investigating various aspects of feldspar dissolution processes have been carried out on both laboratory samples and field samples. A constant theme among these investigations concerns understanding the atomic-scale feldspar dissolution mechanisms. The objective of this study is to develop a general crystal dissolution kinetic model that could provide a comprehensive understanding of feldspar dissolution processes. Computer simulation investigations of two different dissolution mechanism hypotheses - leached layer hypothesis and surface-controlled hypothesis - were respectively tested on eight different feldspar compositions. The simulation results were systematically compared with previous studies: (1) the dependence of dissolution rates on the anorthite content; (2) the G dependence; (3) aluminum inhibition; (4) the presence of an altered layer; and (5) order-disorder perturbation on dissolution rates. It was confirmed that feldspar dissolution is surface-controlled and the corresponding dissolution model is applicable for all feldspar compositions.