Natural Weathering Rates of Silicate Minerals

This chapter presents 1) the development of rates that quantitatively describe silicate mineral and rock weathering, 2) a summary of the available literature rate data for the weathering of several common silicate minerals, and 3) a discussion of the chemical, physical and hydrologic processes that control silicate mineral weathering at the Earth’s surface. Quantitative rates of weathering are important in understanding reaction mechanisms and in addressing a number of economic and environmental issues. Mass change, defined in terms of elements, isotopes or mineral abundances is determined from either solid state (soil, regolith, rock) or solute (pore water, groundwater, surface water) compositions. Solid-state mass differences reflect weathering over geologic time scales while solute compositions reflect the residence time of the water. These mass losses or gains are normalized to surface area defined on a geographic, volumetric or mineral-specific basis. The advantages of this approach are that such rates are related to reaction mechanisms and can be used as predictive tools in estimating how weathering will behave under various environmental conditions.