Generation of mega-plumes from the core-mantle boundary in a compressible mantle with temperature-dependent viscosity

Details Generation of mega-plumes from the core-mantle boundary in a compressible mantle with temperature-dependent viscosity Generation of mega-plumes from the core-mantle boundary in a compressible mantle with temperature-dependent viscosity

Jun 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998georl..25.1999t&link_type=abstract

Geophysical Research Letters, Volume 25, Issue 11, p. 1999-2002

Physics

Geophysics

32

Tectonophysics: Dynamics, Convection Currents And Mantle Plumes, Tectonophysics: Dynamics Of Lithosphere And Mantle-General, Tectonophysics: Heat Generation And Transport, Mathematical Geophysics: Numerical Solutions

Scientific paper

We have investigated the development of axisymmetric mantle plumes in a compressible mantle with temperature-dependent viscosity, using two different values for the thermal activation energy. Thermodynamic parameters were based on realistic Earth values in the shallow mantle. We assumed a compressible mantle with a phase transition and a two layer viscosity structure (mantle 30 times more viscous beneath the phase change). A dramatic transition in plume dynamics occurred as the thermal activation energy was increased from 250 to 500 kJmol-1. A ``mega-plume'' was formed from the merging of small-scale instabilities swept into the plume's axis, rapidly flushing the entire contents of the hot thermal boundary layer into the upper mantle. Hot plume material with a temperature anomaly of 250 K reached the lithosphere for our assumed temperature drop of 500 K across the base of the mantle. Viscous heating over four orders of magnitude greater than chondritic radiogenic sources was observed during the initial plume-lithosphere-interaction.

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