Results 151 to 160 of about 11,453 (209)

Revisiting an Archean Impact Layer

Science, 2002
G. R. Byerly et al. 's report, “An archean impact layer from the Pilbara and Kaapvaal cratons” (23 Aug., p. [1325][1]), is an important addition to the growing literature on early Precambrian impact ejecta. Their zircon data provide compelling evidence that spherule layers in Australia and South Africa were formed simultaneously by a single impact ...
Bruce M, Simonson, Scott W, Hassler
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Rheological heterogeneity of Archean continental lithosphere: implications for Archean tectonics

7th SAGA Biennial Technical Meeting and Exhibition, 2001
In this contribution we discuss the rheology of the Archean continental lithosphere. Decoupling of the upper crust and mantle lithosphere may be a common situation in any tectonically active region and was probably the rule rather than the exception during the Archean. This has major implications for the style of Archean tectonism.
H.A. Jelsma, P.H.G.M. Dirks, M.J. de Wit
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Chemical discontinuities in Archean metavolcanic terrains and the development of Archean crust

Precambrian Research, 1980
Abstract Most large Archean greenstone belts ( ⋍ 2.7 Ga ), comprise thick (12–15 km) mafic to felsic metavolcanics sequences which exhibit consistent but discontinuous geochemical patterns resulting from mantle-crust processes. In a typical Archean metavolcanic sequence, thick (5–8 km) uniform tholeiitic basalt is followed by geochemically ...
A.M. Goodwin, I.E.M. Smith
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Was There Really an Archean Phosphate Crisis?

Science, 2007
During the Archean, massive amounts of iron were deposited in the form of banded iron formations. It has been suggested that sedimenting particles of ferric oxyhydroxide may have stripped dissolved phosphate from the oceans, causing a reduction in phytoplankton productivity.
Kurt O, Konhauser, Stefan V, Lalonde, Larry, Amskold, Heinrich D, Holland   +3 more
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Geochemistry of Precambrian carbonates: II. Archean greenstone belts and Archean sea water

Geochimica et Cosmochimica Acta, 1989
Carbonate rocks with geological attributes of marine sediments are a minor component of the Archean greenstone belts. Despite their relative scarcity, these rocks are important because they record chemical and isotopic properties of coeval oceans.
J, Veizer, J, Hoefs, D R, Lowe, P C, Thurston   +3 more
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Was There a Late Archean Biospheric Explosion?

Astrobiology, 2008
There is a growing body of evidence which suggests that the evolution of the planet drives the evolution of the biosphere. There have been 2 significant stages in Earth history when atmospheric oxygen levels rose rapidly, and both appear to be associated with supercontinent cycles.
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Archean ferropicrites and Early Archean deep mantle heterogeneity

Acta Petrologica Sinica, 2021
WANG Chao, SONG ShuGuang
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The Problematic Rise of Archean Oxygen

Science, 2002
In their intricate study, Catling et al . ([1][1]) attempted to explain the rise of atmospheric oxygen on the early Earth. The model they presented relies on a unique anaerobic ecosystem in which necessarily complex microbial fermentations interact closely with methanogens to decompose ...
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Is the Dongwanzi Complex an Archean Ophiolite?

Science, 2002
Zhao, G, Zhai, MG, Zhang, Q
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Genesis of Archean Peridotitic Magmas and Constraints on Archean Geothermal Gradients and Tectonics

Geology, 1975
The experimentally determined extrusion temperature (1650° ± 20°C) for Archean peridotitic komatiite magma implies diapirism of upper mantle peridotite from a depth of at least 200 km. Models of magma genesis are developed in which selective removal of garnet during ascent produces CaO/Al 2 O 3 > 1 and heavy rare-earth element depletion in the ...
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