AL,SI ORDER IN ALBITE AND ITS EFFECT ON ALBITE DISSOLUTION PROCESSES: A MONTE CARLO STUDY

Abstract

The role of (Al,Si) disorder in the kinetics of albite dissolution is explored through parameterized Monte Carlo methods. Two dissolution mechanisms - multilayer leaching and single-layer retreat - were tested on 48 albite test configurations. In simulations involving multilayer leaching, dissolution rates increased with decreasing long-range order (LRO). We observed a fivefold maximum increase in dissolution rate tied to (Al,Si) disordering, roughly equivalent to that accompanying a decrease of 1.4 pH units at pH 1-5. This increase in rate due to disordering in albite is similar to that observed from compositional variation in plagioclase feldspars (An47 vs. An0) at low pH. In contrast, (Al,Si) disordering had no discernible effect during the simulations involving the single-layer retreat mechanism. These results suggest that the effect of (Al,Si) disorder on albite dissolution rate is mechanism-dependent.