THE TRACE-METAL GEOCHEMISTRY OF THE LAKE TYRRELL SYSTEM BRINES (VICTORIA, AUSTRALIA)

We have analyzed the waters of the Lake Tyrrell system for the trace metals, Fe, Mn, Pb, Cu and Zn. In a number of samples both dissolved Fe(T) and Fe2+ were also determined. Great care was exercised to minimize any contamination of the samples. Not surprisingly the highest metal concentrations occur in the low-pH, high-Eh regional groundwaters, with much lower values observed in the reflux brines and the neutral Wahpool-Timboram waters. It is thought that the source of these metals to the groundwaters is the dissolution of a suite of heavy minerals within the aquifer, the Pliocene Parilla Sand. As the acid groundwaters flow toward the lake some metals are removed near lake edge at depth. The metal concentrations in the spring zone region indicate an extremely dynamic system, where at different times of the year due to changes in the hydrologic regime metals can be either removed or solubilized.