TY - JOUR
T1 - Single-crystal elastic properties of lawsonite and theirvariation with temperature
AU - Schilling, Frank R.
AU - Sinogeikin, Stanislav V.
AU - Bass, Jay D.
N1 - Funding Information:
We thank I. Daniel and G. Fiquet for providing the sample. We are grateful to G.A. Abers, M. Carpenter, A. Kalinichev, J. Parise and B. Wunder for helpful comments. The constructive reviews by Q. Williams and an anonymous reviewer substantially improved the manuscript. This research was supported by the German Science foundation (DFG–Heisenberg grant) and the National Science Foundation (grant EAR 0003383).
Copyright:
Copyright 2017 Elsevier B.V., All rights reserved.
PY - 2003/4/15
Y1 - 2003/4/15
N2 - We have measured the elastic wave velocities and single-crystal elastic moduli of lawsonite (CaAl2(Si2 O7)(OH)2·H2O) by Brillouin spectroscopy at high temperatures to 450 °C and at room pressure. Lawsonite is generally characterized by high longitudinal (vP) and shear (vS) elastic wave velocities. A number of the elastic properties increase with increasing temperature, including the shear modulus, G (∂G /∂T=+2.01 GPa/100 K), and the aggregate velocities vP and vS. These anomalous properties are likely related to a displacive phase transition at ∼0 °C. This is supported by the small value of the elastic modulus c 66 (18(1) GPa at room temperature), and the fact that c 66 softens as temperature is decreased approaching the ∼0 °C phase transition. The anomalous behavior in c 66 leads to a decrease in vP/vS and Poisson's ratio with increasing temperature at 1 atm pressure. Our results show that the aggregate bulk modulus (KS=125(2) GPa at 21 °C) decreases monotonically with increasing temperature ( ∂K S / ∂ T =-1.8 GPa/100 K), in contrast to the results of Daneil et al. (1999) who observed a minimum in the bulk modulus at ∼230 °C. In general, the aggregate elastic wave velocities of lawsonite under high P - T conditions of a subducted slab are expected to remain comparable to those of anhydrous mafic silicates. This observation reinforces the notion that other hydrous minerals persist in subducted oceanic crust to considerable depth (∼250 km), in order to explain the low velocity layers observed in some subduction zones (e.g. Helffrich, 1996; Abers, 2000).
AB - We have measured the elastic wave velocities and single-crystal elastic moduli of lawsonite (CaAl2(Si2 O7)(OH)2·H2O) by Brillouin spectroscopy at high temperatures to 450 °C and at room pressure. Lawsonite is generally characterized by high longitudinal (vP) and shear (vS) elastic wave velocities. A number of the elastic properties increase with increasing temperature, including the shear modulus, G (∂G /∂T=+2.01 GPa/100 K), and the aggregate velocities vP and vS. These anomalous properties are likely related to a displacive phase transition at ∼0 °C. This is supported by the small value of the elastic modulus c 66 (18(1) GPa at room temperature), and the fact that c 66 softens as temperature is decreased approaching the ∼0 °C phase transition. The anomalous behavior in c 66 leads to a decrease in vP/vS and Poisson's ratio with increasing temperature at 1 atm pressure. Our results show that the aggregate bulk modulus (KS=125(2) GPa at 21 °C) decreases monotonically with increasing temperature ( ∂K S / ∂ T =-1.8 GPa/100 K), in contrast to the results of Daneil et al. (1999) who observed a minimum in the bulk modulus at ∼230 °C. In general, the aggregate elastic wave velocities of lawsonite under high P - T conditions of a subducted slab are expected to remain comparable to those of anhydrous mafic silicates. This observation reinforces the notion that other hydrous minerals persist in subducted oceanic crust to considerable depth (∼250 km), in order to explain the low velocity layers observed in some subduction zones (e.g. Helffrich, 1996; Abers, 2000).
KW - Elastic properties
KW - High temperature
KW - Hydrous minerals
KW - Lawsonite
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U2 - 10.1016/S0031-9201(03)00024-4
DO - 10.1016/S0031-9201(03)00024-4
M3 - Article
AN - SCOPUS:0037869239
SN - 0031-9201
VL - 136
SP - 107
EP - 118
JO - Physics of the Earth and Planetary Interiors
JF - Physics of the Earth and Planetary Interiors
IS - 1-2
ER -