Processes Controling Isotopic Composition (δD and δ18O) of Thermal Waters of the Kuril Island Arc

Abstract

The edifices of many active volcanoes on the Kuril Islands contain hydrothermal systems whose surface manifestations include springs with diversity in their chemical compositions and in their physical and chemical parameters. Thermal waters of Kuril Islands were found to exhibit four main isotopic shifts relative to the local meteoric water line. The ultra-acid Cl–SO₄ (SO₄–Cl) waters show a mixing trend between the meteoric component and volcanic steam. Acid steam-heated SO₄ waters demonstrate trends indicating kinetic fractionation at temperatures near the boiling point. The isotope compositions for coastal springs plot at the line of mixing between meteoric and sea water. The oxygen isotope shift for the thermal waters that from geothermal wells is formed by isotope exchange with the host rock. The latitude effect detected in the isotope composition of meteoric water is also seen to varying degrees in the isotope composition of thermal water.