Content and isotope ratios of noble gases in congelation ice of lake Vostok

Isotope ratios of noble gases (He, Ne, Ar) were studied in samples collected by degassing of cores of water frozen over a glacier of Lake Vostok. The gases were collected into glass retorts during three days of degassing of cores, which have just been extracted from the borehole. Within the error, the isotope $^{3}$He/$^{4}$He ratios of 0.28 $\pm$ 0.08 $R_A$ ($R_A$ = 1.38 $\times$ 10$^{-6}$ is the ratio for air) correspond to those from [1]. The $^{4}$Не/$^{20}$Ne and $^{40}$Ar/$^{36}$Ar ratios (12.4 $\pm$ 4.6 $R_A$ and 1.0074 $\pm$ 0.0023 $R_A$, respectively) exceed their contents in air ($^{4}$Не/$^{20}$Ne$_{A}$ = 0.29; $^{40}$Ar/$^{36}$Ar$_{A}$ = 298.6) and may indicate some contribution of terrigenous gas to the gaseous balance of the lake, as well as the high content of ancient ground waters in the lake. The $^{3}$He/$^{4}$He ratio of 0.28 $R_A$ means low mantle $^{3}$He flux typical of continental platforms far from active rift zones.