Geochemical study of Arima hot-spring waters, Hyogo, Japan, by means of tritium and deuterium.

Abstract

Tritium, deuterium and chloride concentrations in the Arima hot spring waters were measured as a clue to their origin and subsurface behavior. T-D-Cl relationships clearly indicate that the saline brine of deep origin (T=O TR, SD=-30%o and C1-=43 g/1) is mixed with young meteoric water having T=30 TR, SD= -50 %o and Cl-= Og/l in varying proportions to form a group of high chloride hot spring waters. The young meteoric water in a shallow aquifer is also mixed with the older meteoric water in a deeper aquifer characterized by high tritium concentration (^-100TR), forming another group of low chloride waters. The mixing ratio of the two meteoric waters varies with season.

Geochemical characteristics of Na-Ca-Cl-HCO3 type waters in Arima and its vicinity in the western Kinki district, Japan.

“…Based on the relationships between tritium (T) and Cl and between T and SD of the Arima brines collected in , Tanaka et al (1984 estimated the Cl and SD of the deep brine to be 43g/l and -30%o, respectively, in close agreement with Matsubaya et al (1973). Kozuki (1962), however, recorded the maximum Cl content of 54g/1 and tem perature of 124'C for a bottom water from the Gosho well (No.…”

“…Among these waters, those from Arima Spa have been noted for their high temperature and extremely high salinity (Ikeda, 1949(Ikeda, , 1955Miyake et al, 1954;Kozuki, 1962) and unique isotopic features Sakai and Matsubaya, 1974;Tanaka et al, 1984). Nakamura and Maeda (1961) studied that these brines are remains of the hydrothermal fluid that was associated with epithermal mineraliza tion observed in some drill cores from Ariake number 1 well.…”

“…Recently, Tanaka et al (1984) showed that the meteoric end-member of Arima brines is a shallow aquifer of tritium content (TR) of 30TU derived from the latest precipitation. They also proposed that the above aquifer is underlain by another older (over 8 years) meteoric circulation of TR = 100TU.…”

“…7, if the Ginsen water is considered to be a mixture of the meteoric end-member (F in Fig. 7) and surface water (D), the shallow aquifer of Tanaka et al (1984) should corre spond to F in Fig. 7.…”

Rare Earth Elements and Sr-Nd-Pb Isotopic Analyses of the Arima Hot Spring Waters, Southwest Japan: Implications for Origin of the Arima-type Brine

“…Within this context, the Arima-typebrine, which is a type of non-volcanic hot spring water with high chlorine content (~40000 ppm) and oxygenhydrogen isotopic ratios similar to magmatic/metamorphic thermal waters [20], has been argued to have originated from deep-seated brine [20][21][22]. The Arima-type brine may provide in valuable information concerning a slab-fluid in a fore-arc region where no magmatic information is available [23,24].…”