高温高压下蛇纹岩脱水的弹性特征及其意义

为了了解蛇纹石在脱水过程中的弹性性质 ,在 1 0GPa和同时加热条件下 ,利用脉冲透射法对采自云南双沟街的蛇纹岩进行了超声测量 .实验发现 ,当温度升高至 640℃时 ,蛇纹岩的超声波纵波速度随温度的升高而急剧下降 .温度继续升高 （70 0℃以上 ） ,样品在高压腔中爆炸 .通过对超声波速下降时和样品发生爆炸前的超声波波形的比较发现 ,随温度升高超声波振幅有了明显的增大 .实验产物的鉴定并与前人相关实验结果比较表明 ,蛇纹岩在高压高温下波速的突然下降和振幅增大与样品中蛇纹石发生脱水反应有关 .目前还不能准确解释超声波振幅增大的原因 ,但上述现象的发现为探讨深部地质灾害的成因并对其进行监测提供了一个新的线索 .

THE ELASTIC CHARACTERISTICS OF SERPENTINITE DEHYDRATION AT HIGH TEMPERATURE-HIGH PRESSURE AND ITS SIGNIFICANCE

To understand the elastic characteristics of serpentinite dehydration, the ultrasonic velocities of serpentinite from Shuanggoujie, Yunnan province, southwest China, were measured at 1.0 GPa and high temperature by the pulse transmission method. Meanwhile the wave forms were observed. The ultrasonic velocities of the serpentinite decreased sharply with increasing temperature as it is higher than 640℃. At temperature higher than 700℃, the experimental sample exploded in the chamber. The amplitude of the ultrasonic wave recorded as the ultrasonic velocity began to decrease was smaller than that obtained before the sample explode. Comparing the present experiment with the previous ones, we believe that the drop of the ultrasonic velocity and the increase of its amplitude is related with the dehydration of the serpentine in the rock. The phenomenon of the amplitude’s increase could not be explained exactly at present. Nevertheless, the new discovery may provide a clue for elucidating and predicting the disaster in the earth’s interior.