地幔转换带条件下岩石矿物波速测量方法:超声波与多面砧技术的结合

Sound Velocity Measurement of Minerals and Rocks at Mantle Transition Zone Conditions Using Ultrasonic and Multianvil Techniques

地幔矿物的波速测量研究是认识地球深部物质组成和性质的重要方法.国际上在大压机中利用超声波技术对地幔矿物材料开展了广泛的波速测量研究,实验温压范围达到地幔转换带条件,而国内大压机超声波波速测量局限于6GPa压力以内.在中国地质大学(武汉)地球深部研究实验室1 000tWalker型多面砧大压机上,利用超声波技术,建立了一套高压波速测量系统,对地幔转换带矿物Mg_2SiO_4瓦兹利石多晶样品在18GPa压力范围内的弹性波速进行了测量,测量结果与前人超声波波速测量结果相比总体吻合程度良好.利用多面砧大压机和超声波技术,在国内首次实现了地幔转换带高压条件下的波速测量,缩短了我国高压波速测量水平与国外先进水平的差距,同时可以为中国及周边地区地球物理观测资料的解析提供矿物物理方面的实验约束,为国内岩石矿物和固体材料的弹性研究提供实验技术支持.

Experimental studies of the sound velocity of minerals of the mantle are crucial for understanding the compositions and properties of the Earth＇s deep interiors. The ultrasonic technique has been globally used in the multianvil press for velocity measurements of various mantle minerals at relevant P-T conditions of the mantle transition zone. However, the ultrasonic ve- locity measurements in multianvil in China have been limited to 〈6 GPa conditions in the past. Recently, we developed a new ultrasonic velocity measurement system in a 1 000 t Walker type multianvil press installed in China University of Geosciences （Wuhan） and measured the velocities of an Mg2 SiO4 wadsleyite polycrystalline sample up to 18 GPa. The results are compara- ble with those of previous ultrasonic studies. For the first time in China, the sound velocity measurement was taken at high pressure conditions of the mantle transition zone in a multianvil with ultrasonic techniques, bridging the gap between the do- mestic and the international advanced level. The technique would provide not only experimental constraints on the interpretation of the geophysical observation beneath China and surrounding regions, but also experimental supports for the studies on the elastic properties of minerals/rocks and condensed materials in China.