Elena Kalacheva

The hydrothermal system of Mendeleev Volcano, Kunashir Island, Kuril Islands: The geochemistry and the transport of magmatic components

This paper reports a detailed geochemical study of thermal occurrences as observed in the edifice and on the flanks of Mendeleev Volcano, Kunashir Island in August and September 2015. We showed that three main types of thermal water are discharged there (neutral chloride sodium, acid chloride sulfate, and acid sulfate types); these waters exhibit a zonality that is typical of volcano-hydrothermal island arc systems. Spontaneous and solfataric gases have relatively low 3He/4He ratios, ranging between 5.4Ra and 5.6Ra, and δ13C-CO2 between –4.8‰ and –3.1‰, and contain a light isotope of carbon in methane (δ13C ≈ –40‰). Gas and isotope geothermometers yield relatively low temperatures around 200°C. The isotope compositions in all types of water are similar to that of local meteoric water. The distribution of microcomponents varies among different types. The isotope composition of dissolved Sr varies considerably, from 0.7034 as observed in Kunashir rocks on an average to 0.7052 in coastal springs, which may have resulted from admixtures of seawater. The total hydrothermal transport rates of magmatic Cl and SO4, as observed for Mendeleev Volcano, are 7.8 t/d and 11.6 t/d, respectively. The natural outward transport of heat by the volcano’s hydrothermal system is estimated as 21 MW.

The geochemistry of steam hydrothermal occurrences in the Koshelev volcanic massif, southern Kamchatka

New data are presented on the geochemistry of thermal waters in the Koshelev volcanic massif in southern Kamchatka. We discuss the conditions for the generation of thermal waters, possible variants of thermal and deep-seated material supply for the Koshelev hydrothermal system, and propose a conceptual model for the system.

Geochemistry of Thermal Waters of Ketoi Island, Kuril Island Arc

The data obtained during the fieldworks in July 2016 were used for the geochemical description of thermal manifestations of Ketoi and Pallas Peak volcanoes on Ketoi Island in the middle of the Kuril Island arc. It is shown that the older edifice of Ketoi Volcano hosts a high temperature hydrothermal system whose surface manifestations are concentrated in the eroded crater of the volcano. Two main types of thermal water are discharged there: the acid and low-acid waters of the Ca–SO4 composition in thermal pools that are diluted to varying degrees with meteoric water, and boron-rich neutral boiling water of the Na–Ca–SO4 composition. The isotopic composition of both water types is similar to that of the local meteoric waters. Calculation of mineral saturation indices for hydrothermal minerals, as well as the behavior of boron, suggest that the waters of the first type are formed nearer the surface, while the boiling sulfate waters are most likely derived from steam condensates formed at depth at a temperature of approximately 200°С. The thermal springs related to Pallas Peak Volcano discharge acid sulfate chloride water. The total measured hydrothermal output of Cl and SO4 from Ketoi and Pallas Peak volcanoes is 8.5 t/day and 30 t/day, respectively.

The geochemistry of thermal waters and fumarolic gases on Shiashkotan I., Kuril Islands

Based on geochemical studies we have updated our knowledge of the generation conditions and discharge of thermal waters on Shiashkotan Island. The thermal springs, which are abundant on the island, are surface expressions of the North Shiashkotan and Kuntomintar hydrothermal systems. The North Shiashkotan hydrothermal system shows the classical hydrochemical zonality. The discharge of the Kuntomintar hydrothermal system is confined within two thermal fields that are situated in the central and northeastern craters of the eponymous volcano. The high temperature of the gases that are issuing from Kuntomintar Volcano to the ground surface and the higher predictive ratios S/Cl, S/C, and CO2/H2 in its composition provide evidence of a possible renewal of its fumarole activity.