Mechanism of leached layer formation during chemical weathering of silicate minerals
MetadataShow full item record
The dissolution of most common multicomponent silicate minerals and glasses is typically incongruent, as shown by the nonstoichiometric release of the solid phase components. This results in the formation of so-called surface leached layers. Due to the important effects these leached layers may have on mineral dissolution rates and secondary mineral formation, they have attracted a great deal of research. However, the mechanism of leached layer formation is a matter of vigorous debate. Here we report on an in situ atomic force microscopy (AFM) study of the dissolution of wollastonite, CaSiO 3, as an example of leached layer formation during dissolution. Our in situ AFM results provide, for the first time, clear direct experimental evidence that leached layers are formed in a tight interface-coupled two-step process: stoichiometric dissolution of the pristine mineral surfaces and subsequent precipitation of a secondary phase (most likely amorphous silica) from a supersaturated boundary layer of fluid in contact with the mineral surface. This occurs despite the fact that the bulk solution is undersaturated with respect to the secondary phase. Our results differ significantly from the concept of preferential leaching of cations, as postulated by most currently accepted incongruent dissolution models. This interface-coupled dissolution-precipitation model has important implications in understanding and evaluating dissolution kinetics of major rock-forming minerals. © 2012 Geological Society of America.
Showing items related by title, author, creator and subject.
An investigation into the leaching behaviour of copper oxide minerals in aqueous alkaline glycine solutionsTanda, B.; Eksteen, Jacques; Oraby, E. (2017)Copper oxide minerals are normally extracted by acidic leaching followed by copper recovery with solvent extraction and electrowinning. However, copper oxide deposits often containing large amounts of acid consumable ...
McGinnity, Justin (2001)Studies were conducted into the mechanism and kinetics of the dissolution of synthetic zinc sulfide and zinc concentrate in aqueous solutions containing sulfur dioxide.Experiments at ambient temperature established that ...
Control of silicate weathering by interface-coupled dissolutionprecipitation processes at the mineral-solution interfaceRuiz-Agudo, E.; King, H.; Patiño-López, L.; Putnis, C.; Geisler, T.; Rodriguez-Navarro, C.; Putnis, Andrew (2016)The mechanism of surface coating formation (the so-called surface altered layers [SALs] or leached layers) during weathering of silicate minerals is controversial and hinges on understanding the saturation state of the ...