Mechanism of Weathering
The mechanism of weathering is visualized as a process whereby the hydrogen ions of crystalline water are base exchanged for the sodium ions of albite (which is used as a model). The structure of water is discussed. The water layers adsorbed on the feldspar exist as a crystalline network with a high degree of order. The small hydrogen ions from the water enter the albite and upset the electrical neutrality of the crystal. The crystal “attempts” to become neutral again by rejecting the sodium ion which is less strongly held than the invading hydrogen ion. This ion substitution causes the crystal to expand and the chemical reactivity of the system is increased which hastens the eventual collapse of the crystal. The residual products of decomposition are gels or “insoluble” silica depending on the Al/Si ratio existing in the system being considered. This mechanism is one in which the ions are interdiffusing between two phases in the solid state. This concept, if accepted, should have many direct applications to the problems of the role of “solutions” in other geological processes.