In the field: South Australian rocks, mines, and sampling for secondary prospectivity
On a recent morning in the frosty mid of May, it came time to venture into the South Australian outback.
I spent many undergraduate field days up there, immersed in the sedimentary rocks of the Adelaide Superbasin and among the stratigraphies of Snowball Earth, Ediacaran fauna, and Gondwanaland. So much of my geological brain – my curiosity, skills, and ways of thinking – evolved among these rocks. So as I departed for my first MIWATCH fieldwork in partnership with the Geological Society of South Australia, it actually felt like I was returning home.
The global issue of mine waste is intense and fascinating. I spent my University of Adelaide Honours degree characterising the Prominent Hill tailings deposit, and during my time at OZ Minerals and BHP, I was deeply motivated by reimagining yesterday’s mine waste as tomorrow’s opportunity. After all, the consequences of metal mining is nothing less than the biggest industrial waste problem on the planet. The fundamental pulse of my passion with MIWATCH is the thought of designing opportunities that remedy mine waste footprints while enacting circular resource recovery. In our exponentially high-technology material world, and nature dependant economies, it’s never been more important to balance both these outcomes.
South Australia is geologically blessed. We house an incredible diversity of critical minerals with tonnes on tonnes to spare. Our resources future will be rich, and our old mines are worthy of exploration to this end. MIWATCH recently partnered with the Geological Survey of South Australia (GSSA) to assess the secondary prospectivity of mine waste across the state. For the last fieldwork of this collaboration, myself and fellow MIWATCH-er Francesco were welcomed and facilitated by Daniel Orr, SA Department of Energy and Mining, and together we set out to sample two historic mine sites set in the Olary Province, South Australia.
We spent our first few days sinking holes into tailings dams at an abandoned gold mine called Alma and Victoria. Alma and Victoria is peppered with over 100 years of mining and reprocessing history – and we really did feel that history. The mine overlooked a crumbling heritage-listed pub that would’ve poured many a beer for this once bustling outback community. Today’s residents don’t care about the gold yet have somehow made the mine their home – kangaroos, wallabies, and emu’s all wonder through the breeze-blown slopes of the Alma and Victoria shafts, adits and tailings dams. Nestled in Alma and Victoria’s tails and waste rock, we think we’ll find some of the critical metals that, while concentrated with gold, were ‘thrown out’ as waste materials during historic mining and processing.
Paratoo Mine, meanwhile, hides globally unique minerals and vividly coloured copper among its waste rock piles. At its peak in the late 1800s, the rocks mined at Paratoo likely contained grades of over 25% copper. And, even more exciting than this, strange secondary rare earth minerals like decrespignyite-(Y), paratooite-(La) were discovered here nearly a century later. In the way of secondary prospectivity, Paratoo is a fascinating site to reflect on geological reality of precious metal mineralisation: it’s manifold! Yesterday’s copper waste still contains the mineralogical fingerprints of a chemically diverse earth. And for now, I feel lucky to call this unique exploration my job!
