The Gawler Craton covers approximately 440,000 square kilometres of central South Australia. Its

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

basement A basement or cellar is one or more Storey, floors of a building that are completely or partly below the storey, ground floor. It generally is used as a utility space for a building, where such items as the Furnace (house heating), furnace, ...

crustal block was

craton A craton (, , or ; from grc-gre, κράτος "strength") is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and ...

ised ca. 1550–1450 Ma. Prior to 1550 Ma the craton comprised a number of active

Proterozoic The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided i ...

orogenic Orogeny is a mountain building process. An orogeny is an event that takes place at a convergent plate margin when plate motion compresses the margin. An ''orogenic belt'' or ''orogen'' develops as the compressed plate crumples and is uplifted t ...

belts extending back in time to at least 2450 Ma. The Craton can be subdivided into a number of

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...

subdomains on the basis of structure and tectono

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostra ...

history. The south-central

Eyre Peninsula The Eyre Peninsula is a triangular peninsula in South Australia. It is bounded by the Spencer Gulf on the east, the Great Australian Bight on the west, and the Gawler Ranges to the north. Originally called Eyre’s Peninsula, it was named af ...

straddles the boundary between the Archaean to early

Palaeoproterozoic The Paleoproterozoic Era (;, also spelled Palaeoproterozoic), spanning the time period from (2.5–1.6 Ga), is the first of the three sub-divisions (eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's ...

Coulta Subdomain and the Cleve Subdomain, a Palaeoproterozoic orogenic belt ("mobile zone") probably representing a shelf or basinal depository for the Hutchison Group (ca. 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 Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...

acid In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a se ...

volcanic A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plat ...

s and

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand ...

s ranging from the Myola Volcanics and Moonta Porphyry to the Moonabie Formation and Wandearah Meta

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility.Blatt ''et al.'' 1980, ...

. Subsequent deformation on the craton has been largely epeirogenic forming shallow fault-bounded intracontinental depressions represented by

Cainozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configu ...

basins, the southern

continental margin A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margin ...

and

Spencer Gulf The Spencer Gulf is the westernmost and larger of two large inlets (the other being Gulf St Vincent) on the southern coast of Australia, in the state of South Australia, facing the Great Australian Bight. It spans from the Cape Catastrophe a ...

Physiography

The Gawler Craton, or Gawler Block, is a distinct physiographic province of the larger West Australian Shield division. It includes the smaller

Stuart Range Basin Stuart may refer to: Names *Stuart (name), a given name and surname (and list of people with the name) Automobile * Stuart (automobile) Places Australia Generally * Stuart Highway, connecting South Australia and the Northern Territory North ...

and

Pimba Platform Pimba is a Portuguese Portuguese may refer to: * anything of, from, or related to the country and nation of Portugal ** Portuguese cuisine, traditional foods ** Portuguese language, a Romance language *** Portuguese dialects, variants of the Po ...

physiographic sections.

Northwestern Fowler Domain

The Fowler Domain is a major tectonic zone on the north-western flank of the Gawler Craton comprising dense, magnetic, highly deformed, intermediate to

ultramafic Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed ...

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. These structures could have provided pathways for the intrusion of

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks in ...

-ultramafic bodies with potential for nickel sulfides, 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

clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks ...

s of the Corunna Conglomerate, the Gawler Range Volcanics (GRV), the Pandurra Formation, and thin platformal late Proterozoic and

Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago ...

sediments of the Stuart and Spencer Shelves. In and around the

Gawler Ranges The Gawler Ranges are a range of stoney hills in South Australia to the north of Eyre Peninsula. The Eyre Highway skirts the south of the ranges. The Gawler Ranges National Park is in the ranges north of Kimba and Wudinna. The ranges are cover ...

, the volcanics and older rocks were intruded by Hiltaba Suite granites (found in the

Hiltaba Nature Reserve Hiltaba Nature Reserve is located in the north of the Eyre Peninsula on the western edge of the Gawler Ranges, South Australia. It is situated on a former pastoral lease known as Hiltaba, or Hiltaba Station, that had operated as a sheep stati ...

) which are closely associated with formation of the giant Olympic Dam ore body of the Eastern Olympic Copper-Gold Province. 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 stabilisation 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 In geology, a shear zone is a thin zone within the Earth's crust or upper mantle that has been strongly deformed, due to the walls of rock on either side of the zone slipping past each other. In the upper crust, where rock is brittle, the she ...

, the Fowler Shear Zone, ca. 1600–1540 Ma.

Economic geology

Economically important deposits found in the craton include

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...

diamond Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, b ...

copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pink ...

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow t ...

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies un ...

iron ore Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the ...

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cut, ...

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

uranium Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when ...

, industrial minerals and

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, b ...

. The huge Olympic Dam copper-gold operation is located in the Eastern Olympic Copper-Gold Province at the cratons eastern edge. 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 centre 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 optimised open pit designed to 230 metres depth. 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 sulfides, 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 sulfide mineralisation. Ultramafic intrusive rock hosting nickel bearing sulfides (

pentlandite Pentlandite is an iron–nickel sulfide with the chemical formula . Pentlandite has a narrow variation range in Ni:Fe but it is usually described as having a Ni:Fe of 1:1. It also contains minor cobalt, usually at low levels as a fraction of wei ...

and

mackinawite Mackinawite is an iron nickel sulfide mineral with the chemical formula (where x = 0 to 0.11). The mineral crystallizes in the tetragonal crystal system and has been described as a distorted, close packed, cubic array of S atoms with some of t ...

) have returned values up to 0.49% nickel, 38 parts per billion (ppb) platinum and 58 ppb palladium. Previous explorations reported up to 0.74% nickel from samples obtained in shallow bedrock drilling. The

Thompson Belt The Thompson Belt, also referred to as the Thompson Nickel Belt, is an Archean and early Proterozoic geologic feature in Manitoba, Canada. It contains gneiss related to deformation of the Trans-Hudson orogeny The Trans-Hudson orogeny or Tra ...

in Canada has similar features and is considered by

Primary Industries and Regions SA Primary Industries and Regions SA (PIRSA), also known as Primary Industries and Regions South Australia, and the Department of Primary Industries and Regions SA, is an agency of the South Australian Government whose focus is the economic developme ...

(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. Drilling has confirmed significant widespread uranium mineralisation at the "Warrior" palaeochannel 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 Resources Limited. (2006
RCR Uranium Sector Review Report
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References

{{Physical geography topics Geology of South Australia Economic geology Cratons Structural geology Historical geology