Unique СО2–saturated mineral waters of the Mukhen deposit (Khabarovsk Krai): Composition and genesis

The geochemistry of water and gas phases from high pCO2 sparkling springs within the northern Sikhote-Alin ridge region (Russian Far East)

“…The main factor controlling the formation of the Mukhen spa water is the strong input of CO2 along deep-seated faults in the subsurface aquifers. The isotopic data (δ 13 Cgas, 3 He/ 4 He, CO2/ 3 He) suggest that the CO2 in two boreholes at the spa has a common deep-seated (probably mantle) source. 3.…”

“…The source of CO2 gas in CO2-bearing cold spa waters in the Russian orient is still debatable. Therefore, we have investigated the genesis of CO2gas-free based upon CO2/ 3 He and 4 He/ 20 Ne ratios plus H-, He-, C-, and O-isotopic compositions [6,7]. Our data indicate that δ 13 C values for both dissolved and free gases are similar in the two boreholes studied, ranging from only -4.6 to -3.5‰ ( Table 1).…”

“…Ratios of 4 He/ 20 Ne vary from 0.63 to 4.03 ( Table 1). The positive correlation observed between 3 He/ 4 He and 4 He/ 20 Ne ratios indicates that noble gases in the spa waters are variable mixtures of deep-seated (mantle) and crustal components. It is possible that fluid derived from the mantle wedge (particularly CO2) penetrated into the groundwaters, such that the original volatiles become contaminated with atmospheric and crustal components during the migration process.…”

“…The large plate-like Oligocene-Miocene age dolerite and basalt bodies of 50 m thickness are overlain by bedrock. The study area contains many a fault zones, the largest being the Punchi fault zone which is approximately 150-200 m. Numerous gas seeps along these faults [3] extend from the western boundary of the region to the Mukhen River catchment beneath the volcanic and sedimentary rocks.…”

“…The comparison of δ 13 C values for the gas phase in the Mukhen spa correlates with those in the high-pCO2 spas in adjacent areas [5]. Measured 3 He/ 4 He ratios range from 2.85x10 -8 to 9.21x10 -8 , which again is similar to previous determinations for other spas of the region [5]. Ratios of 4 He/ 20 Ne vary from 0.63 to 4.03 ( Table 1).…”