This paper reports the first rare earth element (REE) concentrations in accreted ice refrozen from sub-glacial Lake Vostok(East Antarctica). REE were determined in various sections of the Vostok ice core in order to geochemically characterize itsimpurities. Samples were obtained from accreted ice and, for comparison, from the upper glacier ice of atmospheric origin(undisturbed, disturbed and glacial flour ice). REE concentrations ranged between 0.8-56 pg g-1 for Ce and 0.0035-0.24 pg g-1 for Lu in glacier ice, and between <0.1-24 pg g-1 for Ce and <0.0004-0.02 pg g-1for Lu in accreted ice. Inter-estingly, the REE concentrations in the upper accreted ice (AC1; characterized by visible aggregates containing a mixtureof very fine terrigenous particles) and in the deeper accreted ice (AC2; characterized by transparent ice) are lower than thosein fresh water and seawater, respectively. We suggest that such ultra-low concentrations are unlikely to be representative ofthe real REE content in Lake Vostok, but instead may reflect phase exclusion processes occurring at the ice/water interfaceduring refreezing. In particular, the uneven spatial distribution (on the order of a few cm) and the large range of REE con-centrations observed in AC1 are consistent with the occurrence/absence of the aggregates in adjacent ice, and point to thepresence of solid-phase concentration/exclusion processes occurring within separate pockets of frazil ice during AC1 forma-tion. Interestingly, if the LREE enrichment found in AC1 was not produced by chemical fractionation occurring in Lake Vos-tok water, this may reflect a contribution of bedrock material, possibly in combination with aeolian dust released into the lakeby melting of the glacier ice. Collectively, this valuable information provides new insight into the accreted ice formation pro-cesses, the bedrock geology of East Antarctica as well as the water chemistry and circulation of Lake Vostok.
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