Water in the mantle: Results from electrical conductivity beneath the French Alps

Pascal Tarits (1) , Sophie Hautot (2) , F Perrier (3)

1 LDO - Domaines Océaniques
2 School of Geosciences
3 Service Radioanalyses, Chimie, Environnement, CEA, Bruyères-le-Châtel

A deep magnetotelluric sounding in the French Alps provided a vertical electrical conductivity profile between ~200–1000 km. Two prominent features are observed. First, the conductivity in the depth range 400– 800 km is smaller than the conductivity of a pyrolite mantle obtained from laboratory results for a normal geotherm. Second, the data do not require the conductivity to change throughout the transition zone (410– 660 km). In this part of the mantle, a temperature of 350– 450 C less than normal explains the magnetotelluric conductivity profile. At 200 – 400 km, our model favors a cold mantle with 1000 – 1500 ppm of water dissolved in olivine. If correct, this model suggests that the subducted slab is dehydrated before reaching the transition zone.

Domaines: Planète et Univers [physics]

Pascal Tarits, Sophie Hautot, F Perrier. Water in the mantle: Results from electrical conductivity beneath the French Alps. Geophysical Research Letters, 2004, 31 (6), pp.L06612. ⟨10.1029/2003GL019277⟩. ⟨insu-01298769⟩