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The Earth's Lower MantleGeneral Physical and Chemical Models of the Earth’s Lower Mantle

The Earth's Lower Mantle: General Physical and Chemical Models of the Earth’s Lower Mantle [The most popular model of the lower mantle is the Preliminary Reference Earth Model (PREM)Preliminary Reference Earth Model (PREM), derived from seismic observations assuming the pyrolitic composition of the lower mantle. The uppermost part of the lower mantle (~660–770 km deep) has a steep velocity gradient, reflecting the mineral structure transformation from ringwoodite to bridgmaniteBridgmanite and ferropericlaseFerropericlase, after which gradual increase in both the compressional velocity (Vp) and shear velocity (Vs) reflects the near adiabatic compression of mineral phases. The adiabatic geothermal gradient within the upper mantle decreases with increasing depth without phase transitions. Subducting lithospheric slabs may significantly cool temperature profiles, particularly in the upper part of the lower mantle. However, results of experiments on the densityDensity of natural peridotite, performed within the range of entire lower-mantle pressures along the geothermGeotherm, demonstrated their significant mismatch with the PREM density model. This implies that the upper and the lower mantle must have different chemical compositions, i.e. the mantle is chemically stratified, with the inference of a non-pyrolitic composition of the lower mantle. The diapason of oxygen fugacity within the entire sequence of lower-mantle region may reach ten logarithmic units, varying from below the IW buffer to the FMQ buffer values.] http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png

The Earth's Lower MantleGeneral Physical and Chemical Models of the Earth’s Lower Mantle

Part of the Springer Geology Book Series
Kaminsky, Felix V.
The Earth's Lower Mantle — May 23, 2017
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17 pages

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Publisher
Springer International Publishing
Copyright
© Springer International Publishing AG 2017
ISBN
978-3-319-55683-3
Pages
5 –22
DOI
10.1007/978-3-319-55684-0_2
Publisher site
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Abstract

[The most popular model of the lower mantle is the Preliminary Reference Earth Model (PREM)Preliminary Reference Earth Model (PREM), derived from seismic observations assuming the pyrolitic composition of the lower mantle. The uppermost part of the lower mantle (~660–770 km deep) has a steep velocity gradient, reflecting the mineral structure transformation from ringwoodite to bridgmaniteBridgmanite and ferropericlaseFerropericlase, after which gradual increase in both the compressional velocity (Vp) and shear velocity (Vs) reflects the near adiabatic compression of mineral phases. The adiabatic geothermal gradient within the upper mantle decreases with increasing depth without phase transitions. Subducting lithospheric slabs may significantly cool temperature profiles, particularly in the upper part of the lower mantle. However, results of experiments on the densityDensity of natural peridotite, performed within the range of entire lower-mantle pressures along the geothermGeotherm, demonstrated their significant mismatch with the PREM density model. This implies that the upper and the lower mantle must have different chemical compositions, i.e. the mantle is chemically stratified, with the inference of a non-pyrolitic composition of the lower mantle. The diapason of oxygen fugacity within the entire sequence of lower-mantle region may reach ten logarithmic units, varying from below the IW buffer to the FMQ buffer values.]

Published: May 23, 2017

Keywords: Shear Wave Velocity; Oxygen Fugacity; Lower Mantle; Logarithmic Unit; PREMPreliminary Reference Earth Model

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