Metal partitioning in acid hypersaline sediments: Lake Tyrrell, Victoria, Australia

Oxic, metal-rich, low-pH groundwater enters a playa lake system at Lake Tyrrell. Partitioning of metals in the playa sediments was studied to determine the fate of the dissolved metals. Analysis of leachates from sequential extractions of sediment within the top 70 cm of the lake floor indicates that most of the Cu, Pb, Zn, Fe and Mn are adsorbed onto Feoxides. Cu, and to a lesser extent Mn, are bound to organics or sulfides in discrete, thin layers, while Pb is deposited on exchangeable sites in upper layers, possibly as sulfates. Metal concentrations are not enriched in the sediments, which may be due to low pH's and/or limited sulfate reduction in the system. The Lake Tyrrell system may represent an ore-forming system before extensive precipitation of metal sulfides.