%0 Journal Article %T Anomalous elastic properties of coesite at high pressure and implications for the upper mantle X-discontinuity %+ Institut de Physique du Globe de Paris (IPGP) %A Chen, Ting %A Gwanmesia, Gabriel D. %A Wang, Xuebing %A Zou, Yongtao %A Liebermann, Robert C. %A Michaut, Chloé %A Li, Baosheng %< avec comité de lecture %@ 0012-821X %J Earth and Planetary Science Letters %I Elsevier %V 412 %P 42-51 %8 2015 %D 2015 %Z 2015E&PSL.412...42C %R 10.1016/j.epsl.2014.12.025 %K coesite %K elastic properties %K ultrasonic interferometry %K high pressure %K X-discontinuity %Z Sciences of the Universe [physics]Journal articles %X Compressional and shear wave velocities of coesite have been measured using ultrasonic interferometry in a multi-anvil apparatus up to 12.6 GPa at room temperature for the first time. While the P wave velocity increases continuously with pressure, the S wave exhibits an anomalous softening and the velocity decreases continuously with pressure. Finite strain analysis of the data yielded KS0 = 103.6 (4) GPa, G0 = 61.6 (2) GPa and K0 = 2.9 (1), G0 = 0.3 (1) for the bulk and shear moduli and their pressure derivatives, respectively. The anomalous elastic behavior of coesite results in large velocity and impedance contrasts across the coesite-stishovite transition, reaching ∼39% and ∼48% for P and S wave velocity contrasts, and ∼70% and 78% for P and S wave impedance contrasts, respectively, at pressure ∼8 GPa, with P and S wave velocity perturbations showing no apparent dependence on depths (i.e., dln ⁡V (P or S) / dh ∼ 0) within 8-12 GPa. These unusually large contrasts and depth independent characteristics render the transition between the two silica polymorphs one of the most plausible candidates for the cause of the seismically observed X-discontinuity. The current P and S wave velocity perturbation dependences on the SiO2 content, d (ln ⁡VP) / d (SiO2) ∼ 0.43 (wt%)-1 and d (ln ⁡VS) / d (SiO2) ∼ 0.60 (wt%)-1, can serve as a geophysical probe to track ancient subducted eclogite materials to gain insights on the geodynamics of the mantle. %G English %L insu-03580030 %U https://insu.hal.science/insu-03580030 %~ INSU %~ UNIV-PARIS7 %~ AFRIQ %~ CNRS %~ IPGP %~ SORBONNE-UNIVERSITE %~ UNIV-PARIS %~ SU-TI %~ ALLIANCE-SU %~ TEST3-HALCNRS