鹿塩地域に湧出する塩水の季節変動とその要因について [in Japanese] Seasonal variation in chemical and isotopic compositions of Kashio brines and its interpretation [in Japanese]
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Kashio brines in the deep mountain area in the central Honshu have been noted for the high salinity, the non-meteoric δ<sup>18</sup>O and δ<sup>2</sup>H values of water, and its close relation to the Median Tectonic Line, the largest fault in Japan. Similar brines discharge in other localities along the fault. The Cl<sup>-</sup> content of the brine seasonally varied from 670 to 60 meq/l in harmony with the variations of δ<sup>18</sup>O from -2.4 to -8.7‰ and δ<sup>2</sup>H from -52 to -64‰. The stable isotopic and chemical data indicate that these variations are caused by dilution of ascending deep endmembers with two types of meteoric circulation. The first is a local meteoric circulation directly supplied from precipitation to the drainage basin of Kashio, having δ<sup>18</sup>O of -10.5 to -13‰ and δ<sup>2</sup>H of -72 to -86‰. The second is a circulation whose isotopic values are greater (δ<sup>18</sup>O: -9 to -10‰ and δ<sup>2</sup>H: -60 to -70‰) than the local meteoric water. The enrichment of heavy isotopes in the latter circulation may have resulted from ultra or ion-filtration of deep-circulating water during its passage through sedimentary rocks. A heavy precipitation in the drainage area increased after a few months the proportion of the first meteoric component and decreased that of the second.
Chikyukagaku 22(2), 149-156, 1988
The Geochemical Society of Japan