What is the Real ΔGr Function of Albite Dissolution?

Abstract

One of the most significant environmental variables that affect albite dissolution rate is deviation from equilibrium (ΔG_r). Most of the studies that describe the effect of ΔG_r on albite dissolution rate were conducted under alkline pH (8.8-9.2), elvetad temperatures (80-300 °C) and for Amelia Courthouse (USA) albite. Comparison of the f(ΔG_r) derived from those studies to the only f(ΔG_r) from low temperature (25 °C), circum neutral pH and EVJE (Norway) albite leads to different ΔG_r functions. Yet, except for the study of¹, rate laws for silicate minerals dissolution, which are based on experiments conducted under ambient conditions, are lacking. Here we present new experimental results of single point batch experiments (SPBE) of albite dissolution in a isotopically spiked solution. The novel method that use Si isotopes² enables detecting rates that otherwise can’t be detected under ambient conditions. Albite dissolution rates were determined under neutral-acidic pH, temperatures of 3.6, 25 and 50 °C, and a wide range of undersaturation conditions. The dependency of the dissolution rate on deviation from equilibrium (f(ΔG_r)) was in agreement with the prediction of previous studies. However, the value of ΔG_crit was found to be significantly different, suggesting an effect of extrinsic properties of the environment.