Open AccessHeat flow and thickness of the lithosphere in the Canadian Shield
Author(s) -
Jaupart C.,
Mareschal J. C.,
GuillouFrottier L.,
Davaille A.
Publication year - 1998
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/98jb01395
Subject(s) - mantle (geology) , lithosphere , mantle convection , earth's internal heat budget , geology , geophysics , radiogenic nuclide , crust , craton , creep , mantle wedge , heat flux , diffusion creep , shield , thermodynamics , mechanics , heat transfer , petrology , materials science , seismology , tectonics , physics , composite material , microstructure , grain boundary
Heat flow and radioactive heat production data were obtained in the Canadian Shield in order to estimate the crustal heat production and the mantle heat flow. Several methods have been used to determine radioactive heat production in the crust. The analysis yields values for the mantle heat flow in the craton that are consistently between 7 and 15 mW m −2 . Assuming that the lithosphere is in thermal equilibrium, we investigate the conditions for small‐scale convection to supply the required heat flux through its base. For a given creep law, the thickness of the lithosphere, the temperature at the base of the lithosphere, and the effective viscosity of the mantle are determined from the value of the mantle heat flow beneath the shield. The viscosity of the mantle depends on the creep mechanism and on the fluid content. Wet diffusion creep implies a viscosity between 10 20 and 10 21 Pa s, corresponding to a mantle temperature of 1620 K at a depth of 250 km. The other creep mechanisms can be ruled out because they imply values for viscosity and temperature inconsistent with geophysical data. For a given creep law, there is a minimum mantle temperature below which equilibrium cannot be reached. For wet diffusion creep, this minimum mantle temperature (1780 K at 280 km depth ) is close to that of the well‐mixed ( isentropic ) oceanic mantle at the same depth. For a thermally stable lithosphere, our model requires the mantle heat flow to be at least 13 mW m −2 and the compositional lithosphere to be less than 240 km.