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Yilgarn Craton
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Yilgarn Craton
The Yilgarn Craton is a large craton that constitutes a major part of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts. Zircon grains in the Jack Hills, Narryer terrane have been dated at ~4.27 Ga, with one detrital zircon dated as old as 4.4 Ga.
The Murchison Province of the craton contains the over 2 billion year old Yarrabubba impact structure, previously regarded as the oldest dated meteorite impact crater, until the discovery of evidence such as shatter cones confirming the existence of the 3.47 billion year old North Pole Crater near Marble Bar in the Pilbara.
The Yilgarn Craton appears to have been assembled between ~2.94 and 2.63 Ga by the accretion of a multitude of formerly present blocks or terranes of existing continental crust, most of which formed between 3.2 Ga and 2.8 Ga.
This accretion event is recorded by widespread granite and granodiorite intrusions, which comprise over 70% of the Yilgarn craton; voluminous tholeiitic basalt and komatiite volcanism; regional metamorphism and deformation as well as the emplacement of the vast majority of the craton's endowment in gold mineralisation.
These accretion events occurred in several phases, probably by accretion of continental fragments separated by pauses in subduction, with renewed activity occurring episodically.
The craton is primarily composed of approximately 2.8 billion year old (~2.8 Ga) granite-gneiss metamorphic terrain (the Southwestern Province and Western Gneiss Belt), and three granite-greenstone terrains (the North-East Goldfields, the Southern Cross and the greenschist metamorphic Murchison Provinces). Some greenstone belts and granites are as old as 3.1-2.9 Ga, and some are younger, at ~2.75-2.65 Ga.
The craton is one of the distinct physiographic provinces of the West Australian Shield physiographic division, which comprises the Stirling-Mount Barren Block, Darling Hills, and Recherche Shelf sections.
The Western Gneiss terrane is a series of polydeformed high-grade early Archaean metamorphic belts, composed predominantly of feldspathic leucocratic granulite gneisses, which represent some of the oldest crustal fragments on Earth. The Western Gneiss terrane is distinct from the remainder of the Yilgarn Craton in that the latter has a predominance of metavolcanic rocks, both felsic and mafic, whereas the former consists of high-grade metasediments and gneisses of unknown protolith.
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Yilgarn Craton
The Yilgarn Craton is a large craton that constitutes a major part of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts. Zircon grains in the Jack Hills, Narryer terrane have been dated at ~4.27 Ga, with one detrital zircon dated as old as 4.4 Ga.
The Murchison Province of the craton contains the over 2 billion year old Yarrabubba impact structure, previously regarded as the oldest dated meteorite impact crater, until the discovery of evidence such as shatter cones confirming the existence of the 3.47 billion year old North Pole Crater near Marble Bar in the Pilbara.
The Yilgarn Craton appears to have been assembled between ~2.94 and 2.63 Ga by the accretion of a multitude of formerly present blocks or terranes of existing continental crust, most of which formed between 3.2 Ga and 2.8 Ga.
This accretion event is recorded by widespread granite and granodiorite intrusions, which comprise over 70% of the Yilgarn craton; voluminous tholeiitic basalt and komatiite volcanism; regional metamorphism and deformation as well as the emplacement of the vast majority of the craton's endowment in gold mineralisation.
These accretion events occurred in several phases, probably by accretion of continental fragments separated by pauses in subduction, with renewed activity occurring episodically.
The craton is primarily composed of approximately 2.8 billion year old (~2.8 Ga) granite-gneiss metamorphic terrain (the Southwestern Province and Western Gneiss Belt), and three granite-greenstone terrains (the North-East Goldfields, the Southern Cross and the greenschist metamorphic Murchison Provinces). Some greenstone belts and granites are as old as 3.1-2.9 Ga, and some are younger, at ~2.75-2.65 Ga.
The craton is one of the distinct physiographic provinces of the West Australian Shield physiographic division, which comprises the Stirling-Mount Barren Block, Darling Hills, and Recherche Shelf sections.
The Western Gneiss terrane is a series of polydeformed high-grade early Archaean metamorphic belts, composed predominantly of feldspathic leucocratic granulite gneisses, which represent some of the oldest crustal fragments on Earth. The Western Gneiss terrane is distinct from the remainder of the Yilgarn Craton in that the latter has a predominance of metavolcanic rocks, both felsic and mafic, whereas the former consists of high-grade metasediments and gneisses of unknown protolith.
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