Synonyms
Keywords
Geochronology, oldest rocks, zircon
Definition
The Acasta gneisses are the oldest known rocks on the surface of the Earth. They are exposed in northern Canada, north of Great Slave Lake, east of Great Bear Lake with the approximate position of 65° 10′ N and 115° 30′ W. They have a composition close to granitic and are interpreted to have formed, at least in part, from even older rocks that may be as old as 4.2 Ga.
Overview
The Acasta gneisses are the oldest dated rocks on Earth. They are exposed in northwestern Canada (65° 10′ N and 115° 30′ W) along the western margin of the Archean Slave craton (>2.5 Ga), in the core of a north-trending fold in the foreland of Wopmay orogen, a 2.02–1.84 Ga orogenic belt. The Acasta gneisses range in age from 4.03 Ga to ca. 3.6 Ga with distinct groupings at 4.03–3.94 Ga, 3.74–3.72 Ga, and 3.66–3.58 Ga. Rocks from these three distinct groups are compositionally diverse and range from graniteto quartz diorite to tonalite....
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References and Further Reading
Bowring SA, Housh TB (1995) The Earth’s early evolution. Science 269:1535–1540
Bowring SA, Housh TB, Isachsen CE (1990) The Acasta gneisses: remnant of Earth’s early crust. Origin of the Earth. Oxford University Press, New York
Bowring SA, Williams IS (1999) Priscoan (4.00–4.03 Ga) orthogneisses from northwestern Canada. Contrib Mineralog Petrol 134:3–16
Iizuka T, Horie K, Komiya T, Maruyama S, Hirata T, Hidaka T, Windley BF (2006) 4.2 Ga zircon xenocryst in an Acasta gniess from northwestern Canada: evidence for early continental crust. Geology 34:245–248
Iizuka T, Komiya T, Ueno Y, Katayama I, Uehara Y, Matuyama S, Hirata T, Johnson SP, Dunkley DJ (2007) Geology and zircon geochronology of the Acasta Gneiss Complex, northwestern Canada: new constraints on its tectonothermal history. Precambrian Res 153:179–208
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© 2011 Springer-Verlag Berlin Heidelberg
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Bowring, S.A. (2011). Acasta Gneiss. In: Gargaud, M., et al. Encyclopedia of Astrobiology. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-11274-4_11
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DOI: https://doi.org/10.1007/978-3-642-11274-4_11
Publisher Name: Springer, Berlin, Heidelberg
Print ISBN: 978-3-642-11271-3
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