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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Book ChapterDOI
Chapter 18 Earth Tectonics and Thermal History: Review And a Hot-Spot Model for the Archaean
TL;DR: A variety of geophysical, petrological, and geochemical models for the earth are reviewed in this paper, which deal with either the initial or present states of the earth and do not attempt a comprehensive theory.
Book ChapterDOI
Melting Phase Relations of Mantle Peridotite up to 25 GPa: Speculations on the Origin and Evolution of the Earth’s Mantle
Eiichi Takahashi,Eiji Ito +1 more
Journal ArticleDOI
An evolutionary system of mineralogy, Part VI: Earth’s earliest Hadean crust (>4370 Ma)
TL;DR: In this article , a catalog of the earliest Hadean species includes 80 primary phases associated with ultramafic and mafic igneous rocks, as well as more than 80 minerals deposited from immiscible S-rich fluids and late-stage Si-rich residual melts.
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