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These sinking greenstones forced the granitic partial melts sideways and upwards, emplacing them into the margins of the belt and later folding them. The greenstone cover allows the granitic layer to remobilize and form the dome structure. This two stage event is dated between 3.26 and 3.22 Ga. [10]
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 Kaapvaal craton was once part of a supercontinent geologists term Vaalbara that also included the Pilbara craton of western Australia. [ 7 ]
The Barberton Greenstone Belt records impact events in 8 layers containing spherules (tiny spheres which form from condensed vapour created by the impact) dubbed S1 through S8, spanning from about 3.5 to 3.2 billion years ago, [3] which likely represent at least 4 but perhaps as many as 8 or more impact events. [4]
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
Lopian orogeny – Archean orogeny – Formation of two different types of terrain compatible with plate tectonic concepts. One is a belt of high-grade gneisses formed in a regime of strong mobility, while the other is a region of granitoid intrusions and greenstone belts surrounded by the remnants of a Saamian substratum, (2.9–2.6 Ga)
[8]: 158 It is the earliest datable orogeny in North America [9]: 1 and brought the Archean Eon to a close. [8]: 152 The end of the Archean Eon marks a major change in the development of the Earth's crust: the crust was essentially formed and achieved thicknesses of about 40 km (25 mi) under the continents. [8]: 158
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The Leonean Orogeny 3.5 to 2.9 billion years ago and the Liberian Orogeny 2.9 to 2.5 billion years ago both influenced the Archean rocks.. Greenstone belts, sequences of metamorphic and volcanic rocks associated with cratons and used by geologists to study early tectonics are found in south-central Liberia, dating to 2.1 billion years ago.