Relationship in chemical composition between mother solution and allophane-like aluminosilicate precipitate through neutralization of acid hydrothermal water by seawater

摘要

A series of experiments on the formation of allophane-like aluminosilicate precipitates were carried out through neutralization of acid solutions in variety of relative proportions of Si, Fe and Al by seawater. The retrieval and decomposition procedures were available for precise determination of those components in the precipitates. Iron in the mother solutions was completely precipitated and Al was mostly precipitated, however, Si was partly co-precipitated with iron and aluminum. Iron and/or Al coexisting with Si caused a remarkable rise of the precipitated proportion of Si. This was ascribed to co-precipitation of these components on the formation of the precipitates. Difference in effect on the precipitated proportion of Si between Fe and Al was not noticeable. This result indicated equivalence of Fe to Al on the formation of the precipitates through neutralization. The correlations in the (Fe + Al)/Si and the Fe/Al molar ratios between the mother solution and the precipitates strongly designated that the relative proportions of Si, Fe and Al in hydrothermal water discharged from submarine volcanoes were able to be determined uniquely through chemical analysis of the precipitates causing discolored seawater.