High-pH waters from the new Gotthard rail base tunnel, Switzerland
Water samples collected from fractures, fissures and other water conducting features in crystalline rocks of the Central Alps exposed in the new Gotthard rail base tunnel currently under construction showed a marked variation of their chemical composition and their total load of dissolved solids. However, the general feature of the waters from all different host rocks in the tunnel is a high-alkaline pH value of up to 10.4. This feature distinguishes the runnel water from water found in other crystalline basement complexes. The source of solutes and the composition of the waters can be related to albite hydrolysis and deposition of zeolites on the fracture walls in conjunction with pH-controlling carbonate equilibria. Calcite dissolution and precipitation plays an important role in granites and gneisses. In sulfide-rich host rocks sulfide oxidation adds acid to the water along the migration path and results in Na-sulphate waters with high TDS. Locally the waters reached saturation with anhydrite and the mineral is found in fissures of fracture zones. Chloride is prominent in some waters and originates, together with an equivalent amount of Na, from crushed fluid inclusions. However, the contribution of water-rock interaction to the composition of the waters dominates over the passively added solids.
U.Seelig K.Bucher I.Stober
Institute of Mineralogy and Geochemistry, Albert-Ludwigs University, Freiburg, Germany Geological Survey of Baden-Württemberg, Freiburg, Germany
国际会议
第十二届水-岩相互作用国际研讨会(P0roceedings of the 12th International Symposium on Water-Rock Interaction)
昆明
英文
251-254
2007-07-31（万方平台首次上网日期，不代表论文的发表时间）