Geoenvironmental characterisation of the King River Delta: A combined geophysical, geochemical and mineralogical approach

The Mount Lyell Mining and Railway company discharged nearly 95 Mt of tailings and 1.4 Mt of slag from its copper, gold and silver production into the Queen River from 1916 to 1994. Approximately 87.4 Mt of tailings has accumulated at the King River Delta. This research presents a geoenvironmental characterisation of the King River Delta that combines geophysical, geochemical and mineralogical data. Apparent resistivity and shear wave (Vs) profiles suggest the baseline of the tailings at 3-5 m depth. Low resistivity values (i.e. < 2 Ω·m) characterise the salt water intrusion, while resistivity values between roughly 5 to 12 Ω·m. below 15 m depth, suggests bedrock boundaries. Scanning electron microscope (SEM) analysis of sediments identifies pyrite, chalcopyrite. muscovite, quartz. chlorite. barite. and iron oxides in the tailings. Additionally, chemical analysis indicates high content of S and heavy metals (e.g., Fe, Cu, Co, Ni and Zn), which contribute to rapid acid formation and risk of metal leaching into the surrounded environment, confirmed by geochemical static tests.