Clays geochemistry

Marumo, K. and Hattori, K.H. (1997) Seafloor hydrothermal clay alteration at Jade in the back-arc Okinawa Trough Mineralogy, geochemistry and isotope characteri.stics. Geochim. Cosmochim. Acta, 63, 2785-2804. 

The ion exchange model is most commonly applied in geochemistry to describe the interaction of major cationic species with clay minerals, or the clay mineral fraction of a sediment it has also been applied to zeolites and other minerals, and to ions besides the major cations (e.g., Viani and Bruton, 1992). As the name suggests, the model treats not the sorption and desorption of a species on the surface and in the interlayers of the clay, but the replacement of one ion there by another. 

Novel geochemical methods that can indicate the presence and composition of deep seated mineralization are therefore essential. In this study, the multi-element geochemistry of soils and their clay-sized fractions are compared for the deeply buried Talbot VMS Cu-Zn prospect, northern Manitoba, Canada. 

Millot, G. (1970). Geology of Clays Weathering, Sedimentology, Geochemistry. Chapman and Hall, London. 

An understanding of much of aqueous geochemistry requires an accurate description of the water-mineral interface. Water molecules in contact with> or close to, the silicate surface are in a different environment than molecules in bulk water, and it is generally agreed that these adsorbed water molecules have different properties than bulk water. Because this interfacial contact is so important, the adsorbed water has been extensively studied. Specifically, two major questions have been examined 1) how do the properties of surface adsorbed water differ from bulk water, and 2) to what distance is water perturbed by the silicate surface These are difficult questions to answer because the interfacial region normally is a very small portion of the water-mineral system. To increase the proportion of surface to bulk, the expanding clay minerals, with their large specific surface areas, have proved to be useful experimental materials. 

Another type of reaction that responds to WD cycles is the fixation of K and NH4 ions by smectite (3-7). The fixation of K in smectite has been studied extensively by soil scientists because of its effect on the availability of plant nutrients. The reaction also decreases smectite s ability to swell, decreases its cation exchange capacity (CEC), and modifies its BrjSnsted acidity. Therefore, an understanding of this phenomenon is applicable to many fields of study that are concerned with swelling clays, fields such as soil fertility, soil mechanics, waste disposal, clay catalysis, and the geochemistry of ground and surface waters. 

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