Regional geology of NSW orogens
Click on the area of interest to view some geological information.
Alternatively, you can click on one of the listed items below:
- Geology of the Lachlan Orogen
- Geology of the Thomson Orogen
- Geology of the Delamerian Orogen
- Geology of the New England Orogen
The Orogen underlies most of New South Wales, extending south into Victoria and eastern Tasmania. The oldest rocks are Ordovician continental margin, craton-derived turbidite packages, deposited on Cambrian oceanic crust, that are now separated from the Ordovician intra-oceanic Macquarie Arc by suture zones containing relics of Ordovician ocean crust.
The Macquarie Arc hosts world class porphyry Cu-Au deposits in the Cadia valley and Northparkes districts. Smaller deposits occur at Cargo and Copper Hill. Structurally controlled Au-Cu occurs at Cowal. Silurian volcanic-hosted, structurally controlled base metal deposits at Captains Flat, Woodlawn and Mineral Hill occur in volcanic-rich rifts. Sediment-hosted structurally controlled deposits in sediment rich basins include those in the Hill End Trough as well as three operating gold-base metal mines in the richly endowed Cobar Basin. There are excellent opportunities for further major discoveries under shallow cover.
The Thomson Orogen lies north of the Lachlan Orogen and extends north into central Queensland. The NSW portion of the orogen has potential for structurally controlled gold and base metal deposits in Cambrian to Ordovician oceanic crust and arc rocks, craton-derived turbidites, and Silurian-Devonian basins all within current exploration depths.
The Delamerian Orogen lies west of the Lachlan Orogen. Except for the Palaeoproterozoic-Neoproterozoic core around Broken Hill, most of the orogen is overlain by recent cover or by the Neogene Murray Basin. However, recently acquired geophysical data shows that mineralised rock packages such as the gold-rich Stawell Zone in the eastern part of the Delamerian Orogen in western Victoria extends north into New South Wales.
The Proterozoic Curnamona Craton, in western New South Wales, is represented by the Broken Hill and Euriowie Blocks, and is defined along its eastern margin by the unconformably overlying Koonenberry Belt. The cratonic units consist of strongly deformed and metamorphosed sedimentary and igneous rocks termed the Willyama Supergroup.
The Broken Hill deposit is arguably the worlds largest natural accumulation of base metals. An estimated 280 Mt of ore containing better than 30% combined metal existed prior to mining and the ore currently mined has grades ranging from 2.5 to 15% Pb, 20 to 300 g/t Ag and 5 to 20% Zn. The presence of the giant Broken Hill silver-lead-zinc deposit has led to a strong focus of modern exploration effort on this style of mineral deposit. Due to this quirk of history, exploration for other desirable commodities in this domain remains immature despite their proven high prospectivity.
Exploration targets include:
- Broken Hill type deposits (Pb, Zn, Ag)
- Platinum group metals
- Sediment-hosted Zn-Pb mineralisation (Mt Isa -type)
- Porphyry-skarn mineralisation (Cu, Au)
- Fe-oxide Cu-Au mineralisation (Olympic Dam -type, Tennant Creek -type)
New England Orogen
The New England Orogen is a significant mineral province in Eastern Australia with potential for large gold/silver systems. The Orogen comprises Devonian to Permian complexes. Devonian island arc assemblages accreted to the Australian continent late in the Devonian time. This was followed by repeated cycles of westward subduction and extension producing mineralised granites and volcanics from the Middle Devonian to Early Cretaceous.
Major deposits include gold at Hillgrove, Uralla, Nundle and Bingara. Significant gold resources have been recently discovered at Tooloom. New England Orogen deposit styles include mesothermal and epithermal gold, VMS, epithermal silver, and lateritic nickel. The Orogen also offers porphyry copper and gold opportunities. Other economically important commodities include tin, sapphires, diamonds, molybdenum, tungsten, magnesite, cobalt and antimony.