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Anomalous Sound Velocities of Antigorite at High Pressure and Implications for Detecting Serpentinization at Mantle Wedges
Author(s) -
Wang Duojun,
Liu Tao,
Chen Ting,
Qi Xintong,
Li Baosheng
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl082287
Subject(s) - geology , peridotite , mantle (geology) , mantle wedge , subduction , seismology , shear (geology) , geophysics , petrology , tectonics
Elastic properties of antigorite are important for interpretation of seismic mapping of serpentinization in the mantle wedge above subducting slabs. The compressional ( V P ) and shear ( V S ) wave velocities in pure antigorite aggregates were measured simultaneously up to 8.4 GPa by ultrasonic interferometry. We found that V P increases monotonically with pressure while V S increases with pressure up to about 3 GPa but undergoes a negative pressure dependence above 4 GPa. Compared to other mantle minerals, antigorite exhibits significantly lower P and S wave velocities as well as a higher V P / V S ratio at upper mantle pressures. We modeled velocity reductions manifesting through the formation of antigorite in mantle peridotite and provide compelling evidence that seismic anomalies with low‐velocity and high V P / V S ratios is caused by varying degrees of serpentinization in subduction zones.