Gold mining history of South Australia in short bursts before big leap as north's Gawler Graton geo treasure tapped
The history of gold produced from South Australian mining shows short high bursts in the 19th and early 20th Century before the big leap towards the 21st Century with the discoveries in the northern Gawler Graton and its ancient geological legacy, tapped, firstly, by Olympic Dam mine along with copper and uranium.
Images courtesy South Australia government energy and mining department
Gold mining was spread over the history of South Australian European settlement soon after its start, with the metal a widespread legacy from the state’s ancient geology.
South Australia’s – and Australia’s – first authenticated gold find and mine was from 1846 at the Victoria mine, 18 kilometres northeast of Adelaide. Later discoveries brought short periods of high production that had significant effect on population movements during South Australia’s early development. But South Australia had to wait until the 21st Century for its gold potential to be revealed in a huge volume and not in a style previously imagined.
South Australia’s gold was found in most geological provinces as primary and/or secondary deposits. Primary deposits were of two types. Auriferous quartz veins, known as reefs or lodes, were typically along faults, shears, joints or bedding planes. It was generally associated with sulfide minerals, particularly pyrite but also pyrrhotite, chalcopyrite, arsenopyrite, sphalerite and galena. Base metal gold deposits also were obtained as a byproduct. Secondary deposits were from physical erosion or solution in groundwater from primary deposits and redeposited near the source as eluvial deposits in overlying soil and colluvium or further from the source as alluvial placer deposits. Many near-surface nuggets were formed by precipitation from groundwater.
In the early 21st Century, Archaean gold systems were an unknown concept in South Australia. The Gawler Craton in South Australia’s north revealed this gold deposit style with mined and contained resources surpassing one million ounces. The metavolcan-sedimentary complexes hosting these systems had the potential for significant greenfield gold resources.
Archaen rocks of the Gawler Craton were within the Mulgathing and Sleaford complexes. Sediment and volcanic effects within these complexes occurred between 2,570 million and 2,510 million years ago, with intrusives (igneous rocks that formed when magma cooled and solidified below the Earth's surface) clustering at 2,520 million years ago.
The Adelaide Geosyncline was ancient geological basin with gold-producing effect in South Australia. The very thick Neoproterozoic to Cambrian eras sedimentary succession in the Flinders and Mount Lofty Ranges was recognised by the state's pioneer geologists. Reg Sprigg, in 1952, first synthesised the sedimentary and tectonic history of this basin that he named Adelaide Geosyncline. The geosyncline accounted for\ 70% of the state’s total gold production prior to the Olympic Dam mine starting in 1988.
