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The Archean Eon (IPA: / ɑːr ˈ k iː ə n / ar-KEE-ən, also spelled Archaean or Archæan), in older sources sometimes called the Archaeozoic, is the second of the four geologic eons of Earth's history, preceded by the Hadean Eon and followed by the Proterozoic. The Archean represents the time period from (million years
The oldest dated rocks formed on Earth, as an aggregate of minerals that have not been subsequently broken down by erosion or melted, are more than 4 billion years old, formed during the Hadean Eon of Earth's geological history, and mark the start of the Archean Eon, which is defined to start with the formation of the oldest intact rocks on Earth.
Morton gneiss, also known as rainbow gneiss, is an Archean-age gneiss found in the Minnesota River Valley of southwestern Minnesota, United States. It is one of the oldest stones on Earth, at about 3.5 billion years old. Along with the nearby Montevideo Gneiss, it is the oldest intact continental crust rock in the United States. [1]
Archaean or Archean, a geologic eon between Hadean and Proterozoic; Something related to Archaea, a domain of single-celled microorganisms
A large number of geological and geochemical methods have been applied to the rocks of the Isua Greenstone Belt. These include subdivision of the various lithologies and units within the belt using a combination of geological mapping and U-Pb zircon dating, typically using sensitive high-resolution ion microprobe (SHRIMP), analyses; [3] major and trace element chemistry; [11] [12] structural ...
The West African early Proterozoic greenstone belts are similar to the Archean greenstone belts. These similarities include a decrease in the amount of ultramafic and mafic rocks as you move up the stratigraphic column, in addition to an increase in pyroclastics, felsic and/or andesite rocks.
The Canadian Shield is a collage of Archean plates and accreted juvenile arc terranes and sedimentary basins of the Proterozoic Eon that were progressively amalgamated during the interval 2.45–1.24 Ga, with the most substantial growth period occurring during the Trans-Hudson orogeny, between c. 1.90–1.80 Ga. [5] The Canadian Shield was the ...
However, other authors doubt the existence of Archean subduction by pointing out the absence of major plate tectonic indicators during most of the Archean Eon. [13] It is also noted that Archean TTGs were intrusive rocks while the modern adakite is extrusive in nature, thus their magma should differ in composition, especially in water content. [14]