Nature and origin of an aluminous vermiculitic weathering product in acid soils from upland catchments in Scotland

Abstract

A B S T R A C T:Vermiculitization of mica is one of the main weathering processes in soils from three upland catchments receiving various levels of acid deposition. Usually this process is manifested by the presence of interstratified mica-vermiculite with the interlayer space in the vermiculite often partially filled with polymeric hydroxyaluminium species. In one peaty podzol, regularly interstratified mica-vermiculite clearly develops at the expense of mica and is the dominant mineral in the Eh horizon. It was concentrated by chemical treatments to remove organic matter, free iron oxides, and any AI species in the interlayer, and the structural formula calculated from chemical analysis confirmed the dioctahedral character of both vermiculite and mica components, and indicated that the vermiculitic weathering product was formed from a dioctahedral mica. The degree of interlayering in the interstratified phases seemed to he pH-dependent with resultant implications for soil and freshwater acidification.

Pedogenic processes and clay transformations in bisequal soils of the Southern Taiga zone

“…In both profiles, the pH of the Alfisol sequa favours Al immobilisation and Al-hydroxomonomers may have been incorporated in the interlayer of vermiculite, as found by Bain et al (1990) in some acid soils of Scotland. The Al intercalation was present in the Bt of both profiles, as the collapse to 1.0 nm was obtained only after heating, but the profiles were different below the discontinuity.…”

Rates and nonstoichiometry of vermiculite dissolution at 22°C

“…The formation of vermiculite is generally attributed to alteration of a precursor mica by low temperature weathering processes (Fanning et al, 1989). This type of transformation has been described in soils where formation of interstratified mica-vermiculite and hydroxyinterlayered vermiculite has been found to be important mineral weathering/alteration processes (April et al, 1986;Wilson, 1986;Harris et al, 1988;Olson, 1988;Bain et al, 1990). Acker and Bricker (1992) reported on biotite dissolution rates and their pH dependence in open system experiments.…”

Clay minerals: Precise markers of the spatial and temporal variability of the biogeochemical soil environment

“…From the degree of collapse of 2:1 phyllosilicates saturated by K, with and without Na-citrate treatment, in comparison with the amount of Al-hydroxides extracted by Na-citrate, the concept of degree of interlayering of vermiculite developed by Bain et al (1990) is thus specified in both of the following notions: the quantity of hydroxyl-Al (collapse after K-saturation without Na-citrate treatment) and quality of fixation (collapse after K-saturation with Na-citrate treatment).…”