Strategic mine waste planning has only been actively pursued in the past decades, with historical mining operations having used inappropriate disposal methods by today’s environmental standards. This can result in environmental degradation to downstream catchments. One such example is the King River delta/Macquarie Harbour, western Tasmania, and is the focus of this project. Approximately 100 Mt of mine tailings and slag materials have been discharged into the Queen and King rivers from the Mount Lyell copper mine, Queenstown, since the 1890s. Furthermore, the 2.5 km² King River delta contains approximately 10 Mt of mine tailings, with a further 10 Mt of fine tailings deposited beyond it. Whilst the tailings properties and the geochemistry of Macquarie Harbour have been documented, the sulfide chemistry of individual minerals (i.e., pyrite) has yet to be detailed at the micro-scale. This research project aims to mineralogically and geochemically characterise tailings and slag materials in the riverine and deltaic systems and establish if reprocessing of these materials is an environmentally and economically viable rehabilitation option.

PhD student Sibele Nascimento has spent 2019 characterising in detail the mineralogical and geochemical properties of the King River delta tailings. Preliminary results indicate that substantial cobalt and minor copper are present in pyrite and chalcopyrite phases and are likely target metals for metals recovery. At the recent SGA 2019 conference in Glasgow, Scotland, Sibele was awarded a best student talk prize for her presentation detailing preliminary results from the integrated analysis of mineralogical, geochemical and geophysical observations across the delta. In 2020 Sibele will finalise her mineralogical analysis of collected samples and will commence flotation and bio-oxidation test work to determine the best methodology to recover cobalt and other metals.

Strategic mine waste planning has only been actively pursued in the past decades, with historic mining operations having used inappropriate disposal methods by today’s environmental standards. This can result in environmental degradation to downstream catchments. One such example is the King River delta/Macquarie Harbour, western Tasmania, and is the focus of this project. Approximately 100 Mt of mine tailings and slag materials have been discharged into the Queen and King rivers from the Mount Lyell copper mine, Queenstown, since the 1890s. Furthermore, the 2.5 km2 King River delta contains approximately 10 Mt of mine tailings, with a further 10 Mt of fine tailings deposited beyond it. Whilst the tailings properties and the geochemistry of Macquarie Harbour have been documented, the sulfide chemistry of individual minerals (i.e., pyrite) has yet to be detailed at the micro-scale. This research project aims to mineralogically and geochemically characterise tailings and slag materials in the riverine and deltaic systems and establish if reprocessing of these materials is an environmentally and economically viable rehabilitation option.

PhD student Sibele Nascimento and her supervisors completed three site visits in 2018, collecting sediment samples across the site and conducted geophysical surveys (EM, seismic and IP). As part of this work, Sibele and the team trialled a new method of imaging trenches in 3D to support field observations as when working in such sites, slumping of trenches is potentially likely which can be prohibitive to logging. In 2019 Sibele will continue to characterise these materials in the geochemical laboratory but has already identified that pyrite contains high concentrations of cobalt. In 2019 Sibele will commence flotation and biooxidation test work to determine the best methodology to recover cobalt and other metals.

Strategic mine waste planning has only been actively pursued in the past decades, with historic mining operations having used inappropriate disposal methods by today’s environmental standards. This can result in environmental degradation to downstream catchments. One such example is the King River delta/Macquarie Harbour, western Tasmania, and is the focus of this project. Approximately 100 Mt of mine tailings and slag materials have been discharged into the Queen and King rivers from the Mount Lyell copper mine, Queenstown, since the 1890s. Furthermore, the 2.5 km2 King River delta contains approximately 10 Mt of mine tailings, with a further 10 Mt of fine tailings deposited beyond it. Whilst the tailings properties and the geochemistry of Macquarie Harbour have been documented, the sulfide chemistry of individual minerals (i.e., pyrite) has yet to be detailed at the micro-scale. This research project aims to mineralogically and geochemically characterise tailings and slag materials in the riverine and deltaic systems, and establish if reprocessing of these materials is an environmentally and economically viable rehabilitation option.

PhD student Sibele Nascimento commenced in October, with her first fieldwork being conducted in December. Geophysical surveying as well as water and sediment sampling were performed.