Processes Responsible of Variations in the δ¹⁸O – δD values of Thermal Waters from the Kuril Islands (Russia)

Institute of Volcanology and Seismology, FEB RAS, Petropavlovsk-Kamchatsky 683006, Russia

^* Corresponding author: keg@kscnet.ru

Abstract

Many active and dormant volcanoes of the Kuril Islands host hydrothermal systems which discharge acid to ultra-acid SO₄-Cl (Cl-SO₄) and SO₄ waters. On some island, hot near-neutral Na-Cl waters can be found discharging in coastal hot springs. Four main different isotopic shifts relative to the local meteoric water line can be observed in the corresponding δD vs. δ¹⁸O diagram. For the acid Cl-SO₄ waters discharging within thermal fields on volcano slopes, there is a clear mixing trend between meteoric water and volcanic vapor. Steam-heated SO₄ waters demonstrate trends indicating kinetic fractionation at temperatures close to the boiling-point. For the coastal springs, the trend is apparently a mixing line between meteoric and seawater. The δ¹⁸O-shift for deep thermal waters is related to isotopic exchange with host rock but there is also a clear latitude effect in the isotopic composition of the meteoric endmember.