Chemical Weathering Processes

Simple (congruent) Solution and PR

Dissolution of soluble minerals in H2O (direct solution) or in H20+CO2 (carbonation) to yield cations and anions in solution
PR: Highly soluble minerals (e.g. gypsum, halite), quartz and carbonate rocks

Hydrolysis (incongruent dissolution) and PR

Reaction between H+ and OH- ions of water and the ions of silicate minerals, yielding soluble cations, silicic acid, and clay minerals (if Al present)
PR: Silicate minerals

Oxidation and PR

Loss of an electron from an element (commonly Fe or Mn) in a mineral, resulting in the formation of oxides or hydroxides (if water present)
PR: Iron- and manganese- bearing silicate minerals, iron sulfides

Hydration and Dehydration) and PR

Gain (hydration) or loss (dehydration) of water molecules from a mineral, resulting in formation of a new mineral
PR: Ferric oxides and Evaporites

Ion Exchange and PR

Exchange of ions, principally cation, between solution and minerals
PR: Clay minerals and zeolites

Chelation

Bonding of metal ions to organic molecule having ring structures
PR: Silicate minerals