The territory of the Russian Far East stretches from the Chukotka in the north to Vladivostok in the south, a distance of some 4000 km. Some areas (e.g. eastern Kamchatka and the Kurile Island) are characterized by modern volcanic activity and active hydrothermal systems. Other areas (e.g. Primorye and Sakhalin Island) were important volcanic centers during the Mesozoic and Cenozoic time. The geological history of these contrasting areas is of fundamental importance in determining the chemical and physical characteristics of the groundwaters. New data from the Primorye region and literature data for the other areas are used to highlight the differences in water type and composition.
The Koryak-Kamchatka area, comprising the southern part of the Koryak Upland and western Kamchatka, is characterized by waters with high HCO3 and SiO2, located in deep faults and fractures. In some areas, As and F bearing minerals occur. Artesian waters from depth greater than 200m are of HCO3-Cl type with high mineralization.
In the Kuril-Kamchatka area, there are abundant hot springs, geysers and fumaroles related to recent volcanic activity. The composition of these thermal waters and gases are rather variable. For example, within the Paratunka hydrothermal system there are the Northern, Nizhneparatunka, Sredneparatunka, and Karymshin hot springs. The Sredneparatunka hot springs are sulfate-bearing, Nizhneparatunka and Northern hot springs are chlorite- to carbonate- and sulfate-carbonate-bearing waters. The temperature of waters at the main water-bearing level is 70 to 90°C, only in a few wells of the Nizhneparatunka sector were the temperatures as high as 100 to 106°C recorded. The Uzon caldera contains a unique complete set of waters ranging from thigh-sodium waters. The Uzon chloride-sodium thermal waters have high metal contents.
The geology of Sakhalin Island is dominated by Mesozoic and Cenozoic rocks. A variety of groundwaters types exist to different terranes including Na-HCO3 waters with TDS up to 2-5g/l, SiO2-rich waters with TDS up to 2g/l, and Na-Cl waters with TDS up to 35g/l with high concentrations of As, I, Br, and B.
There are two main types of mineral waters in Primorye: thermal waters (up to 30°C) associated with the faulted margins of granite intrusions and high pCO2 waters closely related to deep fracture systems. The thermal waters are derived from meteoric waters heated by deep circulation along fault systems and their chemistry is controlled by water-rock interaction with granite, reaching equilibrium at relatively low temperature (C. 50°C). They are typical of thermal waters in granitic terranes with high pH, low mineralization, Na as the dominant cation and very low Mg. Several trace elements typically enriched in granitic rocks are also relatively high in these waters e.g. U, Mo, Ga, and Li. The high pCO2 waters are typically of Ca-HCO3 type with pCO2 up to 2.6 atm. Gas compositions are dominantly CO2 with minor N2. These waters are of meteoric origin but the gases (13C-6,9) are considered to be of deep, probably mantle, origin. These CO2-rich waters have been particularly aggressive and many contain high concentrations of immobile elements including Zr, Br, Al and the heavy REE's. The wide variation in solute geochemistry is primarily related to the variation in geology which varies widely in rock type age (Proterozoic to Pliocene).