Seismic Visibility of Eclogite in the Earth’s Upper Mantle—Implications From High Pressure‐Temperature Single‐Crystal Elastic Properties of Omphacite

Identifying and locating the geochemical geophysical heterogeneities in Earth’s interior is one of most important challenging tasks for deep Earth scientists. Subducted oceanic crust metamorphizes into dense eclogite upper mantle considered as a major cause Earth. In order to detect eclogitic materials inside Earth, precise measurements high pressure-temperature single-crystal elasticity minerals are thus exceedingly important. Omphacite, Na,Al-bearing clinopyroxene, constitutes up 75 vol% eclogite. present study, we performed first omphacite using Brillouin spectroscopy. Utilizing finite-strain approach, obtained following thermoelastic parameters omphacite: KS0’ = 4.5(1), G0’ 1.53(5), ∂KS0/∂T −0.029(5) GPa/K, ∂G0/∂T −0.013(5) with KS0 123(3) GPa, G0 74(2) ρ0 3.34(1) g/cm3. We found that seismic velocities undeformed similar pyrolite at depths 200–300 410–500 km, seismically invisible these depths. Combined lattice-preferred orientations naturally deformed eclogites, also modeled anisotropy various conditions. A 10 km thick subducted can result ∼0.2 s shear wave splitting mantle.