Cryogenic Origin for Brine in the Subsurface of Antarctica

Frank, T.D., Gui, Z., and the ANDRILL SMS Science Team, 2010, Cryogenic origin for brine in the subsurface of southern McMurdo Sound, Antarctica: Geology, v.38, n.7, p.587–590.

The origin of hypersaline brine discovered in the subsurface of southern McMurdo Sound, Antarctica is caused by seawater freezing. Subsurface fluids from the AND-2A core are derived from seawater with little/no meltwater contamination, demonstrated by good correspondence of K/Cl, Na/Cl, Mg/Cl and Br/Cl ratios between southern McMurdo Sound seawater and subsurface water. Concentration experiments showed a distinctive pathway of the trends of Na-Br-Cl and SO4-Br-Cl, indicating the seawater freezing mode characterized by the precipitation of mirabilite at the beginning. This paper also explains that the depleted δO-18 observed is due to mirabilite precipitation and devitrification and zeolitization of the volcanic glass. A depositional model is proposed to reconcile cryogenic brine formation with stratigraphic evidence during glacial advance and retreat cycles since Oligocene.