Column infiltration experiments

Column Infiltration Experiments. Six infiltration experiments, each at a different flow, were performed with one column of glauconite. The apparatus used in the infiltration experiments consisted of a mineral column contained in a stainless-steel tube connected to a sample-injection valve and a solution-metering pump. Glauconite [a hydrous silicate, nominally (K,Na) (Al,Fe ... 

In the column infiltration experiments with strontium, the model predictions closely resemble the experimental curves for the four flow rates compared. The input parameters to the ARDISC model were derived from experimental data obtained in infiltration experiments. The model predictions were based on the assumptions that the rate for adsorption and the rate for desorption were equal and that the sorption reactions were both first order. 

Figure 24 Chondrite-normalized abundances of REEs in a wall-rock harzburgite from Lherz (dotted lines— whole-rock analyses), compared with numerical experiments of ID porous melt flow, after Bodinier et al. (1990). The harzburgite samples were collected at 25-65 cm from an amphibole-pyroxenite dike. In contrast with the 0-25 cm wall-rock adjacent to the dike, they are devoid of amphibole but contain minute amounts of apatite (Woodland et al., 1996). The strong REE fractionation observed in these samples is explained by chromatographic fractionation due to diffusional exchange of the elements between peridotite minerals and advective interstitial melt (Navon and Stolper, 1987 Vasseur et al, 1991). The results are shown in (a) for variable t t ratio, where t is the duration of the infiltration process and t the time it takes for the melt to percolate throughout the percolation column (Navon and Stolper, 1987). This parameter is proportional to the average melt/rock ratio in the percolation column. In (b), the results are shown for constant f/fc but variable proportion of clinopyroxene at the scale of the studied peridotite slices (<5 cm). All model parameters may be found in Bodinier et al. (1990). As discussed in the text, this model was criticized by Nielson and Wilshire (1993). An improved version taking into account the gradual solidiflcation of melt down the wall-rock thermal gradient and the isotopic variations was recently proposed by Bodinier et al. (2003).

If the excess pressure is ascribed to the hydrostatic load of infiltrating water, then ANe should be a measure of the amplitude of water table fluctuations. A verification of a direct link between water table fluctuations and ANe or q under field conditions is still missing. Experiments with sand columns (Holocher et al. 2002) support the correlation of q with the amplitude of water level changes. 

However, laboratory and field studies under defined conditions are needed to firmly establish the relationships between excess air parameters and environmental conditions during infiltration. Early laboratory experiments with sand columns designed to create and study excess air used somewhat artificial constructions to increase the hydrostatic pressure in the column and facilitate the dissolution of bubbles (Groning 1989 Osenbriick 1991). More recent laboratory studies have demonstrated that excess air can... 

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