The origin of salts in water bodies of the McMurdo Dry Valleys
Lithium distributions in lake and pond waters of the McMurdo Dry Valleys of southern Victoria Land, Antarctica were studied to elucidate the origin of dissolved salts and the evolutionary history of the lakes and ponds. The EfLi [(Li/Cl)sample/(Li/Cl)seawater] values of the bottom waters in Lakes Bonney and Fryxell were higher than unity (EfLi=4–7), indicating that the salts originated from sea salts (probably relict seawater) and have been subsequently modified by the contribution of meltwaters containing atmospheric fallout and/or rock and soil weathering products. In contrast, extremely high Li concentrations with high EfLi values in the Don Juan Pond water (EfLi = 180) and the bottom waters of Lake Vanda (EfLi = 40) suggest that the salts originated from deep groundwaters influenced mainly by saline water-rock interactions, as supported by the dissolution experiments of granite in NaCl solution. The low Li concentrations of pond waters with high EfLi values in the Labyrinth indicate that the salts are derived from atmospheric fallout. The decrease of the EfLi values with the increase of Cl concentrations can be explained by the repeated cycles of the migration of Li into the ice phase and subsequent ablation of surface ice, as indicated by seawater freezing experiments.(Received September 16 1997)
(Accepted April 8 1998)
Key Words: Antarctic lake; Li; McMurdo Dry Valleys; salt origin.