Mineral Systems of Victoria
Uncovering Victoria's mineral prospectivity
The Geological Survey of Victoria has implemented a 'systems' approach to classifying Neoproterozoic – Paleozoic-age metallogeny in Victoria, characterising several major overlapping mineral exploration fairways within the State's geology. This helps define prospectivity and greatly improves ground-selection and exploration efficiencies.
All Neoproterozoic-Paleozoic mineral exploration fairways are deeply buried and inaccessible beneath Cretaceous-Cenozoic cover of the Otway and Gippsland Basins in southern Victoria, and so their configurations are not depicted there. The fairways that lie beneath thin Murray Basin cover in northern and north-western Victoria are all potentially explorable.
The fairways have been defined as follows:
Stavely Arc base-metals/gold fairway
A newly-recognised continental margin volcanic arc setting for a Cambrian magmatic succession. The arc has Cambrian age mineralisation with porphyry and VMS plays (copper, molybdenum, gold).
VMS plays such as the McRaes/Eclipse prospect are contained within Cambrian calc-alkaline mafic-intermediate volcanic arc successions (e.g. the Mount Stavely Volcanic Complex). Magmatic-hydrothermal base metals (+/- gold) are associated with Cambrian intermediate-felsic porphyry intrusions (e.g. ’ Thursdays Gossan’ Cu, Mo) that variously intrude the deformed volcanic successions, the overlying deformed metasedimentary rocks (Glenthompson Sandstone), and other intermediate-felsic intrusions (e.g. within the Buckeran Diorite).
Delamerian mafic-ultramafic nickel fairway
This fairway has Neo-Proterozoic –Early Cambrian age mineralisation. It contains nickel, Platinum Group Elements (PGE’s) and nickel-enriched Precambrian-Cambrian ultramafic (e.g. Hummocks Serpentinite, Williamson Road Serpentinite) and mafic (e.g. Dimboola Igneous Complex) igneous rocks, uplifted to near-surface along faults developed within the eastern Delamerian Fold Belt. The Delamerian fairway contains the possibility of remobilised hydrothermal nickel adjacent to younger granites (e.g. Avebury, western Tasmania) or supergene nickel in overlying laterite ( such as within the Dundas Tableland).
Stawell-style orogenic gold fairway (greenstone (+/- VMS) – gold association).
Ordovician to Devonian age mineralisation hosted by Cambrian metaigneous rocks +/- VHMS; multi-million ounce plays. Includes Cambrian VMS as fault-slices within shear zones (e.g. Mount Ararat Copper prospect) and potential strata- form Cambrian VMS within coherent mafic metavolcanic rock packages exposed adjacent to faults elsewhere in Victoria. Includes Ordovician (Magdala mine, Stawell; Moyston; Pitfield Plains) and Devonian (Wonga mine, Stawell) orogenic gold hosted by shear zones developed within, and especially adjacent to, Cambrian mafic metavolcanic (greenstone) rock packages.
Kanmantoo-Strathalbyn SEDEX base-metals fairway
This fairway is a newly recognised opportunity extending from southeast South Australia. It has Cambrian age mineralisation (zinc, copper, lead, silver). Stratiform base metals of probable sea-floor (back-arc) volcanic exhalative origin are now hosted by Cambrian siliciclastic deep marine sediments (e.g. Steep Bank Greywacke Member) that are direct correlates of stratigraphy hosting proven economic base-metal concentrations in southeast South Australia (e.g. the Angas Zn mine).
Macquarie Arc Derivatives base metals (gold) fairway
This fairway is a newly recognised context for several play types in rocks which are inferred to overlay deeply buried metalliferous Macquarie Arc material, with metals reworked towards surface during subsequent magmatic events (lead, zinc, copper, molybdenum, gold and iron).
The Macquarie Arc Derivatives fairway includes Silurian continental back-arc/rift VMS (e.g. Benambra Zn/Cu (Ag), Devonian porphyry (e.g. Mount Unicorn Mo/Cu), Devonian intrusion-related gold (e.g. Grant/Dargo), Siluro-Devonian shear-hosted gold (e.g. Omeo, Cassilis) and skarn magnetite/hematite (Nowa Nowa).
Macquarie Arc Base Metals (gold) fairway
The Macquarie Arc is a newly recognised copper- gold opportunity extending south from New South Wales into the Deddick Zone (Ordovician age mineralisation). There is potential for porphyry and VMS plays, and (beneath younger cover) for equivalents to NSW Ordovician Cu-Au porphyry mineralisation (e.g. Cadia, Parkes) and Ordovician VMS.
Selwyn Block base-metals (gold) fairway
The Selwyn Block is a recently recognised opportunity extending from western Tasmania into Central Victoria (Mt Read Volcanics and Avebury-Ni play types; Cambrian age mineralisation). Although mostly deeply buried beneath younger rocks (Melbourne Zone), t he Selwyn Block crops out in several places, where VMS and porphyry-style mineralisation within Cambrian calc-alkaline rocks (e.g. Hill 800, Jamieson), and nickel, chromite and PGE-enriched Precambrian-Cambrian ultramafic rocks (e.g. Theile Igneous Complex, Dolodrook, along with unnamed ultramafic rocks at Cape Liptrap extending inland beneath shallow cover) occur. Adjacent opportunities to explore under shallow cover remain untested.
Wagga-Omeo Zone tin – tantalum fairway
The Wagga-Omeo Zone has plays in Koetong Supersuite igneous rocks (Silurian age mineralisation). The Wagga-Omeo Zone contains pegmatite and greisen dyke -hosted tin-tantalum-niobium mineralisation (e.g. Walwa, Mitta Mitta) and lode-tin (Burrowye, Mount Alfred, Walwa).
Bendigo-style orogenic gold (+/- antimony) fairway (slate belt gold association)
The Bendigo-style fairway is of Ordovician-Devonian age mineralisation. Multiple multi-million ounce nuggetty gold and disseminated gold-antimony plays are proven.
The fairway includes Ordovician high-grade ‘nuggetty’ gold- in -quartz -vein plays and Siluro-Devonian disseminated gold +/-antimony plays. The ‘nuggetty’ plays are developed within deformed Cambro-Ordovician siliciclastic marine sediments associated with folds and faults (e.g. Bendigo, Ballarat, St Arnaud), within Siluro-Devonian siliciclastic marine sediments (e.g. Walhalla), and in quartz vein arrays developed within Devonian igneous rocks (e.g. Woods Point Dyke Swarm). Disseminated gold-antimony plays are developed within Ordovician-Devonian siliciclastic marine sediments and are associated with fault and fracture networks (e.g. Fosterville, Costerfield, Chiltern).
Devonian magmatic-hydrothermal metals
A mostly state-wide magmatic province (excludes far western Victoria where no Devonian age magmatism is known). Mineralisation is closely associated with highly fractionated Devonian igneous rocks and includes molybdenum, copper, gold, tungsten and Rare Earth Elements (REE’s). It overlaps in concept with the Macquarie Arc Derivatives fairway.
There are a range of known and possible play-types (porphyry, stockwork, sheeted vein and greisen) depending on chemistry, degree-of-fractionation and depth of erosion. Many shallowly buried intrusions remain untested.
The province includes:
- porphyry-style base metals (Mafeking - Au, Mo; Mt Moliagul - Mo, Au; Monkey Gully - W, Mo; Everton – Mo ; Thologolong/Womobi Mine - W, Mo; Benambra/Mt Murphy - W; Wangarabell – Mo)
- stockworks (Woods Point Dyke Swarm - see also the Bendigo-style fairway)
- sheeted veins (e.g. Mount Unicorn Mo - see also Macquarie Arc Derivatives base metals )