兵庫県南東部の温泉の化学組成と粘土鉱物の産状

抄録

The mode of occurrence of clay minerals and the interaction between hot waters and wall rocks in Arima and Takarazuka have been investigated by X-ray powder diffraction, microscopic observation and chemical analysis. The alteration halo can be divided into three zones, such as, zone I (chlorite-mica zone), zone II (silica zone) and zone III (mica-kaolinite zone). Low, medium and high-temperature waters are mainly located in zone I, II and III respectively. Calcite veinlets are present in drilling cores of zone I and II. The pH values of hot waters in zone II calculated on the basis of the calcite-brine equilibrium equations are higher than those in zone I. Partial CO₂ pressure of hot waters are almost constant, indicating a 3.8 atmospheric pressure in zone I, and a 4.9 atmospheric pressure in zone II. The most important factor controlling the chemical composition of hot waters seems to be the calcite-brine equilibrium in wall rocks.