Abstract
Recently, the Tertiary sedimentary rock has been being watched as a host rock of the space utilization for the deep underground. In order to estimate a geochemical feature of the underground water in the rock mass, an extraction and analysis of the pore water in the rock is very important method. From this view point, we produced a new apparatus for extracting the pore water in the soft rock, and we applied it to extract the pore water of the core sample which was taken from a deep drill hole.
Before analyzing the pore water, the evaluation of the drilling water effect to the core sample was performed, and its effect was estimated 2 to 12% in sandy rocks at the upper depth, and 0% in mudstone at the lower depth. From the analytical results of the pore water of each depth, it is recognized that the deep seated underground water is rich in sodium and bicarbonate, and the deeper water is lighter in oxygen isotope. It is supposed that the pore water chemistry results from the calcite dissolution and ion exchange of the clay minerals, and the oxygen and hydrogen isotopes in the pore water can be explained as a result of the fractionation during the alteration of plagioclase to kaolinite.
