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Abnormal acoustic wave velocities in basaltic and (Fe,Al)‐bearing silicate glasses at high pressures
Author(s) -
Liu Jin,
Lin JungFu
Publication year - 2014
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 - 10.1002/2014gl062053
Subject(s) - silicate , basalt , softening , geology , mantle (geology) , mineralogy , materials science , aluminosilicate , composite material , geochemistry , chemistry , biochemistry , organic chemistry , catalysis
We have measured acoustic V P and V S velocities of (Fe,Al)‐bearing MgSiO 3 silicate glasses and an Icelandic basalt glass up to 25 GPa. The velocity profiles of the (Fe,Al)‐bearing and basaltic silicate glasses display decreased V P and V S with minima at approximately 5 and 2 GPa, respectively, which could be explained by the mode softening in the aluminosilicate networks. Our results represent the first observation of such velocity softening extending into the chemically complex basaltic glass at a relatively low transition pressure, which is likely due to its degree of polymerization, while the Fe and Al substitutions reduce sound velocities in MgSiO 3 glass. If the velocity softening in the basaltic and silicate glasses can be used as analogs for understanding melts in Earth's interior, these observations suggest that the melt fraction needed to account for the velocity reduction in the upper mantle low‐velocity zone may be smaller than previously thought.