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The Yilgarn Craton is a large craton that constitutes the bulk 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.〔Earlier known as ''Yilgarn Block'' - section 'Yilgarn Block by I.R. Williams page 33 -81〕 == Geology == 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;〔Chen, She Fa, John E.Greenfield, David R. Nelson, Angela Riganti, and Steven Wyche. (2003) "Lithostratigraphy and tectonic evolution of contrasting greenstone successions in the central Yilgarn Craton, Western Australia." Precambrian Research, Vol. 127, Issues 1-3 , 10 November, pp. 249-266.〕 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. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Yilgarn Craton」の詳細全文を読む スポンサード リンク
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