Journal ArticleDOI
Genesis of Archean Peridotitic Magmas and Constraints on Archean Geothermal Gradients and Tectonics
TLDR
In this article, a model of peridotitic komatiite magma was developed in which selective removal of garnet during ascent produces CaO/Al 2 O 3 > 1 and heavy rare-earth element depletion in the resultant peridoteitic or mafic extrusions.Abstract:
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 resultant peridotitic or mafic extrusions. Magma genesis can be interpreted with a model of the Archean geotherm, lithosphere, and plate tectonics processes resembling the modern Earth, but this does not account for the distinctive preservation and character of Archean greenstone belts. A preferred model of a steeper Archean geotherm, thin lithosphere (≃50 km), and asthenosphere with approximately 5 percent melting does not allow eclogitization and subduction of basaltic oceanic crust, but it postulates scraping off of such crust against and between primitive sialic nucleii. This model may account for the distinctive characteristics of the Archean greenstone and “granite” terranes.read more
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Journal ArticleDOI
The primodial terrestrial magma ocean and its implication for stratification of the mantle
TL;DR: In this paper, the authors deduced fractional crystallization behavior of a magma ocean extending to lower mantle depths from estimations of melting relations for the deep mantle and the density relationships between ultrabasic liquid and mantle minerals.
Journal ArticleDOI
Basaltic Magmatism and the Bulk Composition of the Moon. II: Siderophile and Volatile Elements in Moon, Earth and Chondrites: Implications for Lunar Origin
A. E. Ringwood,S. E. Kesson +1 more
TL;DR: In this article, the relative abundances of siderophile and volatile elements in the Moon and in the Earth's mantle are obtained from a comparison of their abundances in terrestrial ocean-floor basalts and lunar low-Ti mare basalts.
Journal ArticleDOI
The evolution of Archaean greenstone terrains, Eastern Goldfields Province, Western Australia
TL;DR: In this article, the authors suggest that metamorphism and deformation of greenstone sequences and the evolution of intrusive granitoids in the Eastern Goldfields Province, Yilgarn Block, were related to a widespread and integrated tectonic event in the time interval 2700-2600 m.y.
Journal ArticleDOI
Komatiites and the structure of the Archaean mantle
Euan G. Nisbet,David Walker +1 more
TL;DR: The existence of komatiites with eruption temperatures greater than 1650°C requires that the mantle be vertically differentiated by the time of the Komatiite eruption as discussed by the authors.
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