Physicochemical Model of Silver Behavior in a Weathering Profile

— A weathering profile of phyllite shales with an original Ag concentration of 10 –5 wt % (the average Ag concentration in the Earth’s crust is 7 × 10 –6 wt %) was numerically simulated with the SELECTOR program package. Under oxidizing conditions, Ag occurs in the solutions dominantly in the form of the cation and a few percent of the anion , at a total Ag concentration of ×10 –6.4 mol/L. Under reduced conditions, the dominant ion is , whose concentration is 10 –8.19 mol/L. The mineral form of Ag throughout the whole vertical section is native silver.