Premium
The old continental shields stability related to mantle convection
Author(s) -
Mimouni Ali,
Rabinowicz Michel
Publication year - 1988
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl015i001p00068
Subject(s) - downwelling , thermal conductivity , geophysics , lithosphere , geology , mantle (geology) , convection , mantle convection , rayleigh number , petrology , mechanics , materials science , natural convection , tectonics , upwelling , composite material , physics , seismology , oceanography
Two dimensional thermal convection of a fluid layer overlayed by a conductive lid is studied. Lateral thermal conductivity variation is assumed within the rigid lid, in order to see how an increase of the thermal conductivity within the lithosphere can stabilize a downwelling plume beneath it. Calculations are performed for a constant viscosity fluid with Rayleigh numbers (Ra) up to 4 × 10 5 . Different lid thicknesses (δ) and thermal conductivity (k) values are considered. The numerical results reveal a coupling between the zone of high thermal conductivity and the downwelling plumes. The adjustment time of the convective circulation decreases when the values of parameters (Ra, δ, k) increase. The lowest value for the adjustment time (500 My), is obtained for Ra = 4 × 10 5 . The calculations suggest that an increase of the effective thermal conductivity causes the anchoring of downwelling mantle jets below primitive continental nuclei. The presence of such sinking plumes attached to the cratonic lithosphere may protect them against disruption by mantle flow. The increase in the effective thermal conductivity of the cratonic lithosphere is attribued to thermal conductivity anisotropy of olivine crystal. Such a mechanism can explain the stability of old continental shields.