The Mt Isa Zn-Pb-Ag Deposits, QLD

CSIRO Mineral Resources have been using the new Maia Mapper technology to better understand the formation of major sediment-hosted Zn-Pb deposits such as those in the in the McArthur Basin of the Northern Territory (McArthur River, Teena), the Cloncurry district of Queensland (Cannington) and in the Red Dog region of Alaska. The Maia Mapper system allows researchers to not only assess the distribution of metals at unprecedented resolution on large slab and drill core samples, but it offers an unparalleled ability to quantitatively map trace elements that were previously impossible to detect using X-ray methods due to their low abundance or overlaps in X-ray spectral peaks. This has enabled CSIRO researchers to map deleterious and toxic trace elements such as thallium (Tl) in these ore deposits which allows mining companies to effectively process ores with control measures on these trace elements. Furthermore, understanding the macro-distribution of these trace elements (e.g. Tl) has led to significant advances in the understanding of the formation mechanisms of the ore deposits by allowing data-driven targeting for more detailed petrographic studies on the micro and nano-scale. Ultimately these findings have contributed to new models of ore formation which build on previous carbonate-replacement models (Spinks et al., 2019; 2020).

The capabilities of the Maia Mapper also allow CSIRO researchers to map the distribution of (trace) elements that are classed as Critical Metals, such as germanium (Ge). The massive Zn-Pb deposits of the McArthur and Isa basins are thought to be important sources of Critical Metals but their concentration and deportment in these deposits is critically understudied. The generally low concentrations of Critical Metals pose analytical challenges in understanding their distribution using traditional petrographic techniques. However, the Maia Mapper can map the distribution of some Critical Metals (e.g. Ge) in ore samples.

We have a good understanding of the Zn-Pb deposits in the McArthur Basin and as such we have a good understanding of their formation mechanisms and trace element/critical element endowment. However, we have no analyses from the Isa Basin (other than the Cannington deposit) which hosts a far greater number of deposits, with additional Cu-Au overprint. In order to gain a greater understanding of these deposits which make up the world’s most important zinc belt we propose a Maia Mapper and targeted petrography project whereby we analyse a number of large (up to 50 cm) orezone samples from Zn-Pb-Cu deposits such as George Fisher, Mount Isa, Dugald River, Lady Loretta, Century. This will further the understanding of the formation mechanisms of these mineral systems, aiding future exploration, and provide high quality open-file datasets on these globally important ore deposits.