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Indexed by:期刊论文

Date of Publication:2012-09-01

Journal:HIGH PRESSURE RESEARCH

Included Journals:SCIE、EI、Scopus

Volume:32

Issue:3

Page Number:385-395

ISSN No.:0895-7959

Key Words:wadsleyite; ringwoodite; elasticity; wave velocity; hydration; iron

Abstract:The elastic properties of hydrous iron-bearing wadsleyite (Mg1.75Fe0.125H0.25SiO4) and hydrous iron-bearing ringwoodite (Mg1.75Fe0.125H0.25SiO4) at high pressures are investigated using first-principles calculations. Hydration reduces the elastic moduli and wave velocities of wadsleyite and ringwoodite. Incorporation of 6.25 mol% iron insignificantly affects the bulk moduli, but reduces the shear moduli by 5.33 and 4.80 GPa in average for wadsleyite and ringwoodite, respectively. The compressional wave velocities of iron-bearing wadsleyite and iron-bearing ringwoodite decrease by an average 2.20% and 1.96% at pressures from 0 to 30 GPa, and the shear wave velocities decrease by an average 3.58% and 3.17%, respectively. Compared with the elastic moduli and wave velocities of dry, hydrous, and iron-bearing wadsleyite/ringwoodite, those of coexistence of iron and water decrease most. Adding simultaneously 6.7 mol% iron and 1.6 wt% water leads to decrease in the bulk(shear) modulus by 5.57%(7.80%) and 5.84%(4.77%) for wadsleyite and ringwoodite, and the compressional/shear wave velocities by 4.48%/6.11% and 4.77%/6.68%, respectively. These results demonstrate that the elasticities of wadsleyite and ringwoodite strongly depend on the chemical compositions, which has some implications on the origin of low velocity zones in the mantle transition zone.