The steep temperature gradient near the bottom of the mantle is known to generate a negative correlation between the shear wave velocity(VS)and the depth in most regions of the D00 layer,as detected by seismological o...The steep temperature gradient near the bottom of the mantle is known to generate a negative correlation between the shear wave velocity(VS)and the depth in most regions of the D00 layer,as detected by seismological observations.However,increasing VSwith depth is observed at the D00 layer beneath Central America,where the Farallon slab sinks,and the origin of this anomaly has not beenwell constrained.Here,we calculate the thermoelastic constants and obtain the elastic wave velocities of hydrous phase H with various Al contents and cation configurations,which may act as a water carrier to the D00 layer.We find its VS to be substantially lower than the post-perovskite-type bridgmanite.The dehydration of Al-enriched phase H and the redistribution of Al from the hydrous component to dry silicates would gradually raise the VS below the top of the D00 layer.The presence of 3.5 wt%water is sufficient to compensate for the thermal effects to match the seismic anomaly at the bottomof themantle beneath Central America.The positive slope of VS versus depth in the D00 layer may fingerprint deep water recycling.展开更多
基金supported by the National Natural Science Foundation of Chinawith grant nos.T2425016,42394114,42192535,and 42150101.
文摘The steep temperature gradient near the bottom of the mantle is known to generate a negative correlation between the shear wave velocity(VS)and the depth in most regions of the D00 layer,as detected by seismological observations.However,increasing VSwith depth is observed at the D00 layer beneath Central America,where the Farallon slab sinks,and the origin of this anomaly has not beenwell constrained.Here,we calculate the thermoelastic constants and obtain the elastic wave velocities of hydrous phase H with various Al contents and cation configurations,which may act as a water carrier to the D00 layer.We find its VS to be substantially lower than the post-perovskite-type bridgmanite.The dehydration of Al-enriched phase H and the redistribution of Al from the hydrous component to dry silicates would gradually raise the VS below the top of the D00 layer.The presence of 3.5 wt%water is sufficient to compensate for the thermal effects to match the seismic anomaly at the bottomof themantle beneath Central America.The positive slope of VS versus depth in the D00 layer may fingerprint deep water recycling.
