Abstract

Plagioclase feldspar (Na[AlSi3O8] - Ca[Al2Si2O8) is the most abundant rock forming mineral in the Earth's crust. Its weathering behavior is one of the key factors that control the global CO2 cycle. Therefore, plagioclase dissolution kinetics has been studied experimentally and theoretically by a large number of investigators. However, the dissolution kinetics is still not well understood. This is especially true for Earth surface conditions, i.e., low temperatures, near neutral pH values and near equilibrium conditions.

Our research explores some current problems in feldspar dissolution, and has the potential to significantly improve our understanding of feldspar weathering. We use a powerful combination of experimental and theoretical techniques to study the dissolution kinetics of albite, anorthite and an intermediate plagioclase composition. This approach combines three different techniques: vertical scanning interferometry (VSI), (high temperature) atomic force microscopy (HAFM), and ab initio quantum mechanical calculations. Our results will be compared with existing data produced with mineral powders and single crystals in flow-through, batch and column experiments.

This work directly address four different problems: (1) the dissolution rates of plagioclase as a function of solid composition, temperature and pH; (2) a direct comparison of interferometric and atomic force microscopy data; (3) the link of such data to macroscopic (bulk) rates and ab initio calculations; and (4) the key relationship between reaction rate and mineral surface area in terms of total (BET) and reactive surface area.