δ-(Al,Fe)OOH is considered to be one of the most important hydrous phases on Earth,remaining stable under the extreme conditions throughout the mantle.The behavior ofδ-(Al,Fe)OOH at high pressure is essential to und...δ-(Al,Fe)OOH is considered to be one of the most important hydrous phases on Earth,remaining stable under the extreme conditions throughout the mantle.The behavior ofδ-(Al,Fe)OOH at high pressure is essential to understanding the deep water cycle.δ-(Al_(0.956)Fe_(0.044))OOH crystals synthesized at 21 GPa and 1473 K were investigated by high-pressure Brillouin light scattering spectroscopy and synchrotron X-ray diffraction up to 135.4 GPa in diamond anvil cells.The incorporation of 5 mol%FeOOH increases the unit-cell volume ofδ-AlOOH by~1%and decreases the shear-wave velocity(VS)by~5%at 20–135 GPa.In particular,the compressional(V_(P))and shear(VS)wave velocities ofδ-(Al_(0.956)Fe_(0.044))OOH are 7%–16%and 10%–24%greater than all the major minerals in the mantle transition zone including wadsleyite,ringwoodite,and majorite.The distinctly high sound velocities ofδ-(Al_(0.956)Fe_(0.044))OOH at 20–25 GPa may contribute to the seismic anomalies observed at~560–680 km depths in the cold and stagnant slab beneath Izu-Bonin and/or Korea.Furthermore,the VS ofδ-(Al_(0.956)Fe_(0.044))OOH is about 10%and 4%–12%lower than iron-bearing bridgmanite Mg_(0.96)Fe_(0.05)Si_(0.99O3)and ferropericlase(Mg_(0.92)Fe_(0.08))O,respectively,under the lowermost mantle conditions,which might partially contribute to the large low-shear-velocity provinces and ultralow velocity zones at the bottom of the lower mantle.展开更多
基金the National Key Research and Development Program of China(2019YFA0708502)the National Natural Science Foundation of China(Grant No.U1930401)+3 种基金BL14U1 of the Shanghai Synchrotron Radiation Facility for beamtime access based on proposal 2019-SSRF-PT-011035 and Geo-SoilEnviroCARS(Sector 13-BMC and 13-BMD)at the Advanced Photon Source,Argonne National Laboratory,USAthe National Science Foundation Earth Sciences(Grant No.EAR1128799)the Department of Energy-GeoSciences(Grant No.DEFG02-94ER14466)The Advanced Photon Source is a U.S.Department of Energy(DOE)Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DE-AC02-06CH11357.
文摘δ-(Al,Fe)OOH is considered to be one of the most important hydrous phases on Earth,remaining stable under the extreme conditions throughout the mantle.The behavior ofδ-(Al,Fe)OOH at high pressure is essential to understanding the deep water cycle.δ-(Al_(0.956)Fe_(0.044))OOH crystals synthesized at 21 GPa and 1473 K were investigated by high-pressure Brillouin light scattering spectroscopy and synchrotron X-ray diffraction up to 135.4 GPa in diamond anvil cells.The incorporation of 5 mol%FeOOH increases the unit-cell volume ofδ-AlOOH by~1%and decreases the shear-wave velocity(VS)by~5%at 20–135 GPa.In particular,the compressional(V_(P))and shear(VS)wave velocities ofδ-(Al_(0.956)Fe_(0.044))OOH are 7%–16%and 10%–24%greater than all the major minerals in the mantle transition zone including wadsleyite,ringwoodite,and majorite.The distinctly high sound velocities ofδ-(Al_(0.956)Fe_(0.044))OOH at 20–25 GPa may contribute to the seismic anomalies observed at~560–680 km depths in the cold and stagnant slab beneath Izu-Bonin and/or Korea.Furthermore,the VS ofδ-(Al_(0.956)Fe_(0.044))OOH is about 10%and 4%–12%lower than iron-bearing bridgmanite Mg_(0.96)Fe_(0.05)Si_(0.99O3)and ferropericlase(Mg_(0.92)Fe_(0.08))O,respectively,under the lowermost mantle conditions,which might partially contribute to the large low-shear-velocity provinces and ultralow velocity zones at the bottom of the lower mantle.
