高温高压下几种岩石熔融玻璃的弹性波速(英文)

Compressional and Shear Wave Velocities of Rock Glasses up to 2.0 GPa and 1000℃

利用超声波脉冲反射法和透射-反射联合法，测量了压力在0．4～2．0GPa条件下7种岩石熔融玻璃的纵波波速（us）和横波波速（us），并在恒压2．0GPa下，在0～1000℃和0～730℃温度范围内，分别测量了纵波波速和横波波速随温度的变化。结果显示，室温下随着压力的升高，大多数玻璃的V。和全部玻璃的us异常地降低。异常的波速-压力关系与玻璃中SiO2的含量密切相关，随着SiOz的质量分数从87％降低到52％，玻璃的纵波波速和横波波速对于压力的导数（δvp／δp和δvs／δP）分别从-0．159和-0．114扯m／（S·Pa）升高到0．050和-0．001弘m／（s·Pa）。分析认为，玻璃的波速随压力升高而降低的原因主要与玻璃中SiO2所具有的敞型结构有关。在2．0GPa压力下，玻璃的波速首先随温度升高而缓慢降低，当达到600～700℃后，开始快速下降，设此温度为玻璃的转变温度Tg。根据实验测得的玄武岩玻璃波速，结合上地幔二辉橄榄岩的弹性性质，推测若在上地幔岩石中存在体积分数大于20％的玄武岩质非晶质体，上地幔便可能形成地震波低速层。

Measurements of compressional and shear wave velocities （Vp and v~ ） under pressure from 0.4 to 2.0 GPa were performed on seven types of synthetic glasses, including basalt, andesite, dacite, amphibolite, py- roxenite, rhyolite and gneiss. At confining pressure of 2.0 GPa, the wave velocities were also measured as func- tions of temperature up to 1000 ℃ for compressional wave velocity （vp） and up to 730 ℃ for shear wave veloci- ty （v）. At room temperature, the wave velocities of the glasses decrease anomalously with pressure, as a result of the open structure of SiO2 in silica-rich glasses. With varying SiO2 mass fraction in the glasses from 87% to 52%,avp/ap increases from --0. 159 to 0. 050 μm/（s Pa）,and 9vs/ap increases from --0. 114 to --0. 001μm/（s Pa）. At 2.0 GPa,vp and v~ of the glasses decrease slowly first up to 600-700 ℃,indicating the glass transition temperatures （Tg）, and then decrease rapidly. Based on the elastic properties of basalt glass and mantle rocks,it is concluded that the basalt glass with volume fraction of about 20~ in matrix can cause the low velocity zone in upper mantle.