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| Gawler Range Volcanics | |
|---|---|
| Name | Gawler Range Volcanics |
| Type | Volcanic province |
| Age | Mesoproterozoic |
| Period | Statherian |
| Region | South Australia |
| Coordinates | 32°S 135°E |
| Namedfor | Gawler Ranges |
| Lithology | Rhyolite, rhyodacite, ignimbrite, volcaniclastic |
Gawler Range Volcanics are a Mesoproterozoic volcanic succession in South Australia associated with a major silicic large igneous province and a metallogenic province that influenced regional tectonics, crustal evolution, and mineralisation. The suite crops out principally in the Gawler Ranges and underlies parts of the Stuart Shelf and the Mulgathing Complex; it is temporally and spatially linked to tectono-magmatic events that involved the Yilgarn Craton, the Musgrave Province, the Curnamona Province, the Curnamona Basin, the Adelaide Rift Complex, and the Cretaceous exposures of Kangaroo Island.
The volcanics occur within the Gawler Craton and are spatially related to the Eyre Peninsula, the Spencer Gulf region, the Stuart Shelf, the Arkaroola Domain, and the Yarlbrinda Shear Zone; they are juxtaposed against units of the Curnamona Province, the Stuart Shelf Basin, the Warburton Basin, the Officer Basin, and the Mount Painter Inlier. Regional correlations have been proposed linking the province to crustal events recorded in the Musgrave Province, the Hamersley Basin, the Albany-Fraser Orogen, the Birksgate Complex, and the Mount Isa Inlier, and comparisons are often made with the volcanic assemblies of the Kimberley Basin, the Pilbara Craton, and the North China Craton.
Stratigraphically the package comprises thick successions of high-silica volcanics including extensive rhyolite and rhyodacite flows, ignimbrites, welded tuffs, and volcaniclastic sediments that overlie older Proterozoic basement such as the Coulta Complex, the Hiltaba Suite, the Curnamona Supersuite, and the Korabora Metamorphics. Lithologic members include crystal-rich rhyolites, devitrified dacitic breccias, ash-flow tuffs, and subvolcanic porphyries intruded by granophyric bodies comparable to the White Hill Granite, the Kalinjala Volcanics, and the Brougham Formation. Contacts with the underlying Mount Woods Inlier, the Yunta Inlier, and the Olympic Dam Domain record erosion surfaces and palaeotopography analogous to exposures in the Flinders Ranges, the Mount Isa Block, and the Curnamona Block.
Geochronological constraints use U–Pb zircon dating, Ar–Ar dating, and SHRIMP analyses that constrain emplacement to the Statherian (c. 1590–1580 Ma in some older literature, revised to c. 1595–1590 Ma in others) with high-precision ages derived from the Hiltaba Suite, the Ooldea Granite, the Gawler Range Complex, and coeval flows correlated to the Mount Isa event and the Warakurna Large Igneous Province. Radiometric results have been compared to dates from the Musgrave Block, the Curnamona Province, the Mawson Craton, the Capricorn Orogen, and the Eastern Ghats Belt to refine palaeocontinental reconstructions and to link magmatism with regional metamorphic pulses recorded in the Millicent Inlier, the Stuart Shelf, and the Coompana Complex.
Petrography shows high-silica, peraluminous to peralkaline rhyolitic textures with phenocrysts of quartz, sanidine, plagioclase, biotite, and rare amphibole similar to assemblages found in the Hiltaba Suite, the Gawler Range Granites, the Olympic Dam breccias, and the Tunkillia Assemblage. Whole-rock geochemistry displays enriched rare earth element patterns, negative Nb–Ta anomalies, high LILE/HFSE ratios, and isotopic signatures (Sr–Nd–Pb) that connect the volcanics to crustal melting and fractional crystallisation processes comparable to those invoked for the Archaean Greenstone Belts, the Lachlan Fold Belt, the Broken Hill Block, and the Lachlan Orogen. Trace element ratios and oxygen isotope data have been integrated with studies of the Mount Painter Inlier, the Mawson Craton, and the Woomera Proterozoic sequences to model magma sources and crust–mantle interaction.
Formation models invoke continental rifting, intracontinental extension, and large-scale felsic magmatism linked to mantle plume activity or lithospheric delamination with tectonic analogues in the North Atlantic Igneous Province, the Siberian Traps, the Deccan Province, and the Ferrar Large Igneous Province. Proposed mechanisms include crustal anatexis above a upwelling asthenosphere beneath the Gawler Craton, slab break-off scenarios referencing the Musgrave Orogeny, and transtensional regimes similar to those described for the Albany-Fraser Orogen, the Delamerian Orogen, the Lachlan Orogen, and the Arunta Inlier. Regional implications extend to basin development in the Officer Basin, the Eucla Basin, the Sturtian glaciations recorded in the Adelaide Geosyncline, and the assembly of Nuna/Columbia supercontinent reconstructions that incorporate the Kalahari Craton, the Laurentia Shield, and the North China Craton.
The volcanics are central to a metallogenic province hosting porphyry-style, epithermal, and iron-oxide-copper-gold (IOCG) mineralisation exemplified by nearby deposits such as Olympic Dam, Prominent Hill, and Carrapateena, and spatial associations with the Tarcoola, Challenger, and Hillside prospects. Mineralisation includes copper, uranium, gold, iron oxide, rare earth elements, and associated pathfinder elements shared with the Olympic IOCG system, the Hiltaba Suite-related mineral systems, the Mount Isa copper–lead–zinc–silver fields, and the Curnamona copper–gold occurrences. Exploration strategies reference structural corridors like the Yarlbrinda Fault, the Kimban Tectonic Zone, and the Mulgathing Shear Zone, and employ geophysical methods used in the Gawler Craton, the Woomera Prohibited Area, the Coober Pedy Basin, and the Stuart Shelf.
Exposures are prominent in the Gawler Ranges, near Mount Taylor, near Iron Knob, around Lake Gairdner, and in coastal sequences at Eyre Peninsula adjacent to Port Lincoln, Streaky Bay, and Coffin Bay; mapping efforts have involved the Geological Survey of South Australia, university teams from the University of Adelaide, the Australian National University, and international collaborators from the United States Geological Survey, the CSIRO, and the Geological Survey of Western Australia. Notable field localities include the Hiltaba Nature Reserve, the Yandanooka area, the Kingoonya region, the Wudinna Inlier, and the Umberatana Range where stratigraphy, structural relationships, and mineral occurrences are best displayed and correlated with geophysical datasets from magnetics, gravity, and seismic surveys conducted across the Eyre Peninsula, the Stuart Shelf, and the Mount Woods Inlier.
Category:Geology of South Australia