Relation of mantle conductivity to physical conditions in the asthenosphere

Research output: Contribution to journalArticle

21 Citations (Scopus)

Abstract

Magnetotelluric soundings show that the conductivity increases in the asthenosphere. The depth of this conductivity zone decreases with an increase of the surface heat flow, i.e. in such cases the lithospheric plate is thinner. The depth of the velocity decrease of seismic shear wave (S waves) shows the same connection with the surface heat flow. The solidus of a mixed-volatile medium intersects the temperature curves belonging to different surface heat flows at depths where the conductivity increase and the velocity decrease appear. These connections point to partial melting in the asthenosphere, which can decrease the viscosity too, and help the movement of the lithospheric plates according to the ideas of global tectonics. The melt fraction of peridotite and pyrolite determined by Shankland and Waff from the effective conductivity of the asthenosphere is about 3-4% at 30 kbar and at o*=0.1 S m-1. In the upper mantle of old shields it is likely that there is no well-developed asthenosphere due to the low temperature. Over these so-called 'viscous anchors' the lithospheric plates do not move. It is supposed that the conductivity increases observed below crystalline shields at a depth of about 300 km indicate the phase transition of rocks. Thus in these areas the surface of the phase transition can be at a higher position than in the younger tectonic units.

Original languageEnglish
Pages (from-to)43-55
Number of pages13
JournalGeophysical Surveys
Volume4
Issue number1-2
DOIs
Publication statusPublished - Sep 1980

Fingerprint

asthenosphere
Earth mantle
conductivity
mantle
heat transmission
heat flow
Tectonics
Heat transfer
phase transition
Phase transitions
Magnetotellurics
tectonics
shield
Seismic waves
Shear waves
pyrolite
Anchors
solidus
peridotite
thin plates

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

Cite this

Relation of mantle conductivity to physical conditions in the asthenosphere. / Ádám, A.

In: Geophysical Surveys, Vol. 4, No. 1-2, 09.1980, p. 43-55.

Research output: Contribution to journalArticle

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AB - Magnetotelluric soundings show that the conductivity increases in the asthenosphere. The depth of this conductivity zone decreases with an increase of the surface heat flow, i.e. in such cases the lithospheric plate is thinner. The depth of the velocity decrease of seismic shear wave (S waves) shows the same connection with the surface heat flow. The solidus of a mixed-volatile medium intersects the temperature curves belonging to different surface heat flows at depths where the conductivity increase and the velocity decrease appear. These connections point to partial melting in the asthenosphere, which can decrease the viscosity too, and help the movement of the lithospheric plates according to the ideas of global tectonics. The melt fraction of peridotite and pyrolite determined by Shankland and Waff from the effective conductivity of the asthenosphere is about 3-4% at 30 kbar and at o*=0.1 S m-1. In the upper mantle of old shields it is likely that there is no well-developed asthenosphere due to the low temperature. Over these so-called 'viscous anchors' the lithospheric plates do not move. It is supposed that the conductivity increases observed below crystalline shields at a depth of about 300 km indicate the phase transition of rocks. Thus in these areas the surface of the phase transition can be at a higher position than in the younger tectonic units.

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