Where has all the old crust gone?
Article Abstract:
Measurements of the lutetium/hafnium content of zircons in rocks from Greenland show that the Earth's mantle source was depleted by melt removal during the Hadean era. The rocks are almost 3.6 billion years old, and their neodymium isotopic content is due to metamorphic changes rather than the formation of a high amount of ancient crust. This indicates that the Earth was probably not covered by large amounts of thick crust during the Hadean era. The theory of the presence of a thick crust on early Earth is based on the isotopic composition of rocks, which may change due to metamorphosis.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1996
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Re-Os isotope evidence for the composition, formation and age of the lower continental crust
Article Abstract:
It has been established that apparent whole-rock Re-Os isochrons with no age significance may be produced during assimilation and fractional crystallization processes by depletion of Os through olivine-sulphide fractionation, linked with assimilation of radiogenic crust. Re-Os isotope data for two suites of lower-crustal xenoliths from North Queensland, Australia, show that the lower crust has between one and two times as much Os, around half as much Re and is less radiogenic than the upper continental crust.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1998
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The Earth's mantle remodelled
Article Abstract:
Sixty percent of the Earth's pyrolite upper mantle is composed of olivine which mediates whole-mantle convection. The upper mantle is also composed of pyroxene and garnet with Fe-enrichment in the higher phase of the transition zone. Analysis of seismic wave velocities and upper-mantle composition also indicated the presence of wadsleyite and garnet in the transition zone. Furthermore, perovskites with oxides were also detected in the lower mantle.
Publication Name: Nature
Subject: Zoology and wildlife conservation
ISSN: 0028-0836
Year: 1997
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