CHEMICAL WEATHERING IN GRANITIC ENVIRONMENTS

Abstract

Factors controlling chemical weathering in granitic environments are deduced using an extensive database from the literature. Based on a transition state theory model, we evaluated the effects on chemical weathering of runoff, temperature and pH. The dependence between temperature and runoff, and chemical weathering is complicated by other factors such as the presence/depth of soil cover. Soil cover favors chemical weathering when it is thin and rich in weatherable minerals. In contrast, it reduces chemical weathering when is thick and poor in primary minerals. Processes that increase the contact time and the surface of the water-rock interactions such as physical denudation, increase chemical weathering rates in granitic environments. The effect of temperature can be quantified assuming an apparent activation energy value of 48.7 kJ/mol to describe chemical weathering of silica in granitic crystalline environment under high runoff conditions.