The Geochemistry of Acid Thermal Waters on Urup Island, Kuril Islands.

Kalacheva, E. G.; Taran, Yu. A.; Kotenko, T. A.; Voloshina, E. V.

The data acquired during the field work in 2017 were used to carry out a comprehensive geochemical study of thermal occurrences on Urup Island, which is part of the southern Kuril island arc. It was shown that the thermal waters of Berg Volcano concentrated in the caldera which is open westward at various distances from the extrusive dome are warm (Т up to 40°С), acid (рН 3.5–3.8) of the SO4–Cl–Ca type with mineral content reaching 2.5 g/L. The springs of Tri Sestry Volcano situated at its base near Cape Klyuchevoi have temperatures reaching 45°С, рН 4–Cl–Ca type with mineral content reaching 1.9 g/L. The isotope composition of water in these two groups of springs is close to that of local meteoric water. The ratios between the concentrations of main cations and the microcomponent composition are generally in agreement with the composition of the host rocks. We note that the Berg Volcano springs show a well-pronounced negative Eu anomaly in the distribution of rare earth elements. The anion composition, the isotope composition of sulfur in the dissolved sulfate (between 15.2 and 21.6‰), as well as the Cl/B and Cl/Br ratios, all indicate the involvement of magmatic volatiles in the formation of these waters. The total measured discharge of Сl and SO4 by the Berg springs is 9 ± 1.3 t/d and 23.3 ± 3.4 t/d, that for the springs on Cape Klyuchevoi is 0.5 ± 0.2 t/d and 2.3 ± 0.8 t/d, respectively. A preliminary estimate for the chemical erosion affecting the Berg Volcano edifice by thermal waters is 700–800 t/km2/yr.

KURIL Islands (Russia); GEOTHERMAL resources; GEOCHEMISTRY; RARE earth metals; ISLAND arcs; ISLANDS; BROMINE

Journal of Volcanology & Seismology, 2021, Vol 15, Issue 5, p349

0742-0463

Academic Journal

10.1134/S0742046321050031