HR: 0800h
AN: MR31A-0128 [Abstracts]
TI: Effect of Phase Transition of Intermediate Plagioclase on Elastic Wave Velocity
AU: * Kono, Y
EM: d03ta007@ynu.ac.jp
AF: Yokohana National University, 79-7, Tokiwadai, Hodogaya-ku, Yokohama, 240-8501
Japan
AU: Ishikawa, M
EM: ishikawa@ed.ynu.ac.jp
AF: Yokohana National University, 79-7, Tokiwadai, Hodogaya-ku, Yokohama, 240-8501
Japan
AU: Arima, M
EM: arima@server2.edhs.ynu.ac.jp
AF: Yokohana National University, 79-7, Tokiwadai, Hodogaya-ku, Yokohama, 240-8501
Japan
AB:
We measured compressional (Vp) and shear (Vs) wave velocities of plagioclases with albite, labradorite, and bytownite
composition up to 700°C at 1 GPa with a piston cylinder high-pressure apparatus. The Vp and Vs measurements were
conducted with the pulse reflection method. Simultaneous Vp and Vs measurements were carried out using 10°Y-cut
LiNbO3 transducer. The discontinuous change in temperature derivative of Vp and Vs at 400°C is observed in the
labradorite while the albite and bytownite show linear Vp and Vs change with elevating temperature up to 700°C. The
temperature derivative of Vp (dVp/dT) and Vs (dVs/dT) is -0.9x10-4 km s-1 °C-1 and -1.2x10-4 km
s-1 °C-1 in the albite, respectively. In the bytownite dVp/dT is -1.2x10-4 km s-1 °C-1
and dVs/dT is -0.9x10-4 km s-1 °C-1. The dVp/dT and dVs/dT in the labradorite is -0.7x10-4 and
-1.2x10-4 km s-1 °C-1 below 400°C, respectively. Above 400°C dVp/dT and dVs/dT increase to
-3.0x10-4 and -3.3x10-4 km s-1 °C-1, respectively. The XRD analyses of the labradorite before and
after high P-T measurements show that the discontinuous change in temperature derivative of Vp and Vs in the labradorite
would be the result of phase transition of plagioclase. The present data suggest that Vp and Vs of intermediate plagioclase
above 400°C could not be evaluated by the simple mixing theory using the low temperature Vp and Vs values of end-member
plagioclases (albite and anorthite).
DE: 3909 Elasticity and anelasticity
DE: 3924 High-pressure behavior
DE: 3954 X-ray, neutron, and electron spectroscopy and diffraction
DE: 8124 Earth's interior: composition and state (1212, 7207, 7208, 8105)
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005