Abstract
This study re-evaluates the adiabatic temperature profile of the Earth’s
mantle. The global average temperature at the 410-km discontinuity is
estimated to be 1805(18) K by comparing the globally averaged depths of
the 410-km discontinuity with the previously determined phase diagram of
the olivine-wadsleyite transition in the system
(Mg,Fe)2SiO4 at two temperatures. The
temperature at the 410-km discontinuity is extrapolated to shallower and
deeper regions using the adiabatic temperature gradient, which is
estimated from the pressure-volume-temperature relations and heat
capacities of the major mantle minerals, namely, olivine, wadselyite,
ringwoodite, and bridgmanite. The experimental temperatures and
pressures in the original studies used in these evaluations are
re-calculated using the recently proposed pressure correction on EMF of
the W97Re3-W75Re25 thermocouple. The uncertainties are evaluated by the
Monte Carlo simulation. The temperatures on the adiabatic geotherm are
found to be 1617(16), 1959(19), 1925(19), and 2530(30) K, respectively,
at a 50-km depth, just above the 660-km discontinuity, just below the
660-km discontinuity, and a 2800-km depth. These temperatures are higher
than those given by Katsura et al. [2010]. The 50-km depth
temperature is slightly higher but generally agrees to that estimated
from the melting of depleted peridotite.
