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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 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.
Archean tectonic history of the Barberton Greenstone Belt [ edit ] The Barberton Greenstone Belt is located on the Kaapvaal craton , which covers much of the southeastern part of Africa, and was formed by the emplacement of granitoid batholiths . [ 7 ]
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.
The Isua Greenstone Belt is an Archean greenstone belt in southwestern Greenland, aged between 3.7 and 3.8 billion years. [2] The belt contains variably metamorphosed mafic volcanic and sedimentary rocks, and is the largest exposure of Eoarchaean supracrustal rocks on Earth. [3]
Being one of the few most well-preserved Archean portions of the crust, with Archean felsic volcanic rocks, the BGB is well studied. It provides present geologic evidence of Earth during the Archean (pre-3.0 Ga). Despite the BGB being a well studied area, its tectonic evolution has been the cause of much debate. Map of South Africa.
Archean anorthosites represent the second largest anorthosite deposits on Earth. Most have been dated between 3,200 and 2,800 Ma, and commonly associated with basalts and/or greenstone belts. [1] Archean anorthosites are distinct texturally and mineralogically from Proterozoic anorthosite bodies.
The Abitibi greenstone belt is a 2,800-to-2,600-million-year-old greenstone belt that spans across the Ontario–Quebec border in Canada. [1] It is mostly made of volcanic rocks, but also includes ultramafic rocks, mafic intrusions, granitoid rocks, and early and middle Precambrian sediments.