ELASTIC WAVE VELOCITY OF ROCKS AT HIGH PRESSURE AND TEMPERATURE AND PETROLOGICAL MODEL OF CRUSTAL STRUCTURES

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In order to better constrain the interpretation of the seismic structures, experimental measurements at high pressure (up to 1000 Mpa) and temperature (up to 1000□) of the compressional wave velocity (Vp) and shear wave velocity (Vs) on rock samples representative of deep crustal lithologies from the Mount Tanzawa (central Japan), Ichinomegata (NE Japan), Kohistan paleo-crustal section (northern Pakistan), Lutzow-Holm Bay and Enderby Land (East Antarctica) have been performed.The main results are :(1) Vp of the garnet clinopyroxenite decreases linearly from room temperature to 800 ℃, and decreases rapidly at temperatures higher than 800 ℃. Vp of the dunite decreases linearly from room temperature to 1000 ℃. Vp of the garnet clinopyroxenite is 7.74 km/s at room temperature, 7.70 km/s at 400 ℃, 7.66 km/s at 700 ℃, and 7.45 km/s at 1000 ℃. Vp of the dunite is 8.49 km/s at room temperature, 8.30 km/s at 400 ℃, 8.12 km/s at 700 ℃, and 7.90 km/s at 1000 ℃. Temperature derivative of Vp is-1.24 10-4 km/s℃ for the garnet clinopyroxenite and -6.06 10-4 km/s℃ for the dunite.(2) At constant pressure of 1.0 Gpa, the Vp of hornblende gabbro gradually decreased from 7.21 km/s at 25 ℃ to 6.91 km/s at 700 ℃. Similarly the Vp values of the pyroxene-hornblende gabbros reduces from 7.06 km/s at 25 ℃ to 6.73 km/s 800 ℃. Also the Vp value of the hornblendite lowers from 7.11 km/s (25 ℃) to 6.45 km/s (800 ℃).