Mineral inclusions in the accretion ice above Lake Vostok

The paper is based on additional studies of mineral inclusions in the accretion ice sampled by deep drilling at Vostok Station in central Antarctica. The studies include X-ray microtomography of two mineral inclusions with identification of their mineral composition; analysis of clay minerals in the soft aggregate of the largest inclusion; and geochronological study of zircon grains. X-ray microtomography shows intact morphology of the inclusions in the ice core and their internal texture. The soft aggregate of the largest inclusion is characterized by the dominance of illite, intermediate concentrations of chlorite and small amounts of kaolinite. A notable feature is the absence of mixed-layer minerals typical of Antarctic coastal areas. The most valuable information is derived from new geochronological data and their integration with previous dating data. The detrital zircon U-Pb ages show strong probability peaks between 900 and 1100 Ma, while the detrital monazite ages are clustered between 1250 and 1450 Ma. Both of these age intervals correspond to the Rayner Orogeny.