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Basic geological regions of Australia, by age.
Basic geological regions of Australia, by age.

The Gawler Craton covers approximately 440,000 square kilometres of central South Australia. Its Precambrian crystalline basement crustal block was cratonised ca. The Precambrian ( Pre-Cambrian) is an informal name for the supereon comprising the eons of the Geologic timescale that came before the current In Materials science, a crystal is a Solid in which the constituent Atoms Molecules or Ions are packed in a regularly ordered repeating In Geology, the terms basement and crystalline basement are used to define the rocks below a sedimentary platform or cover or more generally A craton ( Greek kratos / κρἀτος ( neut. "strength" is an old and stable part of the Continental crust that has survived 1550-1450 Ma. Prior to 1550 Ma the craton comprised a number of active Proterozoic orogenic belts extending back in time to at least 2450 Ma. The Proterozoic (ˌproʊtərəˈzoʊɪk is a geological eon representing a period before the first abundant complex life on Earth. Orogeny (Greek for "mountain generating" is the process of natural Mountain building and may be studied as a tectonic structural event as a geographical event and

The Craton can be subdivided into a number of tectonic subdomains on the basis of structure and tectonostratigraphic history[1] The south-central Eyre Peninsula straddles the boundary between the Archaean to early Palaeoproterozoic Coulta Subdomain and the Cleve Subdomain, a Palaeoproterozoic orogenic belt ("mobile zone") probably representing a shelf or basinal depository for the Hutchison Group (ca. This article discusses the geologic usage for the philosophical or architectural usage see Architectonics ' Or see Plate tectonics. Stratigraphy, a branch of Geology, studies rock layers and layering ( stratification) The Paleoproterozoic (ˌpeɪlɪoʊˌproʊtərəˈzoʊɪk also spelled Palaeoproterozoic) is the first of the three sub-divisions ( eras) of the 1900-1845 Ma) prior to its deformation during the Kimban Orogeny (ca. 1845-1710 Ma). On northeastern Eyre Peninsula, the Cleve Subdomain is bounded by the slightly younger Moonta Subdomain which is characterised by less intensely deformed metamorphosed acid volcanics and sediments ranging from the Myola Volcanics and Moonta Porphyry to the Moonabie Formation and Wandearah Metasiltstone. Plate tectonics and hotspots Divergent plate boundaries At the Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of Siltstone is a Sedimentary rock which has a composition intermediate in grain size between the coarser Sandstones and the finer Mudstones and

Subsequent deformation on the craton has been largely epeirogenic forming shallow fault-bounded intracontinental depressions represented by Cainozoic basins, the southern continental margin and Spencer Gulf. The continental margin is the zone of the Ocean floor that separates the thin Oceanic crust from thick Continental crust.

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Physiography

The Gawler Craton, or Gawler Block, is a distinct physiographic province of the larger West Australian Shield division. Australian Shield, also called the Western Australian Shield or Western Plateau, occupies more than half of the continent of Australia. It includes the smaller Stuart Range Basin and Pimba Platform physiographic sections.

Northwestern Fowler Domain

Fowler Domain is a major tectonic zone on the north-western flank of the Gawler craton comprising dense, magnetic, highly deformed, intermediate to ultramafic intrusives overlain by thin Tertiary sands and recent sand dunes. Aeromagnetic surveys show the presence of a high concentration of crustal scale fractures and faults in this area. An aeromagnetic survey is a common type of Geophysical survey carried out using a Magnetometer aboard or towed behind an aircraft These structures could have provided pathways for the intrusion of mafic-ultramafic bodies with potential for nickel sulphides, chromite and platinoids.

Eastern Olympic Copper-Gold Province

The Olympic Copper-Gold Province is a 650 km long corridor along the eastern boundary of the craton.

Eastern and Central, Gawler Ranges

Palaeoproterozoic rocks of the eastern and central Gawler craton are overlain by relatively unmetamorphosed clastics of the Corunna Conglomerate, the Gawler Range Volcanics, the Pandurra Formation, and thin platformal late Proterozoic and Cambrian sediments of the Stuart and Spencer Shelves. Clastic rocks are composed of fragments or clasts, of pre-existing rock. The Gawler Ranges are a range of mountains in South Australia to the north of Eyre Peninsula. In and around the Gawler Ranges, the volcanics and older rocks were intruded by Hiltaba Suite granites which are closely associated with formation of the giant Olympic Dam orebody of the Eastern Olympic Copper-Gold Province. The Gawler Ranges are a range of mountains in South Australia to the north of Eyre Peninsula. Although relatively undeformed, the Gawler Range Volcanics, which extend from the centre of the craton to its eastern margin, represent a major period of crustal deformation ca. 1590 Ma which heralded the final consolidation and stabilization of the craton as it is seen today.

Central Yarlbrinda Shear Zone

In the central Craton, the Yarlbrinda Shear Zone was likely formed by the Kararan Orogeny and it is host to several major gold prospects including those in the Nuckulla Hill region (Sheoak, Myall and Bimba) and at Tunkillia.

Western Eyre Peninsula, Coulta Subdomain and Nuyts Subdomain

On western Eyre Peninsula, the Coulta Subdomain merges with the Nuyts Subdomain which is dominated by variably deformed ca. 1670-1610 Ma granitoids, mafics and felsic volcanics. Deformation is attributed to the Kalaran Orogeny which generated a major fold belt or shear zone, the Fowler Shear Zone, ca. 1600-1540 Ma.

Economic Geology

Minerals that have been found in the craton include gold, diamonds, copper, nickel, granite, iron ore, lead-zinc, uranium, coal, industrial minerals and arsenic. Gold (ˈɡoʊld is a Chemical element with the symbol Au (from its Latin name aurum) and Atomic number 79 In Mineralogy, diamond is the allotrope of carbon where the carbon atoms are arranged in Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Iron ores are rocks and Minerals from which Metallic Iron can be economically extracted Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly Zinc (ˈzɪŋk from Zink is a Metallic Chemical element with the symbol Zn and Atomic number 30 Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the Industrial minerals are geological materials which are mined for their commercial value which are not fuel (fuel minerals or Mineral fuels) and are not sources of metals ( Arsenic (ˈɑrsənɪk is a Chemical element that has the symbol As and Atomic number of 33

The huge Olympic Dam copper-gold operation is located in the Eastern Olympic Copper-Gold Province at the cratons eastern edge. Olympic Dam is a mining centre in South Australia located some 550 km NNW of Adelaide the capital city of South Australia. The Prominent Hill copper-gold mine is northwest of Olympic Dam and the Challenger Gold Mine is to the west of Prominent Hill located in the center of the craton. The 70 million tonne Kalkaroo Mine is to the south and contains approximately 320,000 tonnes of copper, 1 million ounces of gold and 8. 56 million kg of molybdenum in an optimized open pit designed to 230 metres depth (Havilah, 2006).

The Wynbring area, a large part of the western Fowler Domain, covers approximately 2,000 square kilometres and consists of fractures that may include intrusion of mafic-ultramafic bodies with potential for nickel sulphides, chromite and platinoids. Exploration and regional drilling near the northern end of the Fowler Domain and within the Harris Greenstone Belt has identified numerous large mafic and ultramafic bodies which have the potential to host nickel sulphide mineralization. Ultramafic intrusive rock hosting nickel bearing sulphides (pentlandite and mackinawite) has returned values up to 0. 49% nickel, 38 parts per billion "ppb" platinum and 58ppb palladium. Previous explorations reported up to 0. 74% nickel from samples obtained in shallow bedrock drilling (Mithrill Resources, 2005). The Thompson Nickel Belt in Canada has similar features and is considered by the Department of Primary Industry and Resources of South Australia (PIRSA) as a possible analogue of the Fowler Domain. The Thompson Nickel Belt hosts major nickel deposits which have been mined by Inco since the early 1960s. Previous explorations in the Wynbring area consisted of wide-spaced reconnaissance bedrock drilling by PIRSA that indicated the presence of a 30 kilometre-long zone of intermediate to ultramafic rocks adjacent to a major fault and geochemically anomalous in gold, nickel, chromium, platinum and palladium. (PlatSearch, 2004).

Drilling has confirmed significant widespread uranium mineralisation at the "Warrior" paleochannel in central Gawler just west of Prominent Hill and there is active uranium exploration over an extended portion of the Kingoonya Palaeochannel system within the southern Gawler Craton. "Warrior" is the most significant known uranium occurrence in the Gawler Craton. (Stellar, 2006).

See also

References

External links

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