顽火辉石的高温高压同步辐射研究

 采用同步辐射能量色散X射线衍射技术、激光加热技术和金刚石对顶砧（DAC）高压装置，在温度为2 000 K和压力为23 GPa的范围内，对采自地幔二辉橄榄岩中的顽火斜方辉石，进行了原位的高温高压能量色散X射线衍射（EDXRD）测量。实验结果表明：当压力为15.3 GPa、温度为1 600 K时（相当于地球内部410 km处的地震波不连续界面的温压环境），顽火斜方辉石转变为橄榄石的β相——瓦兹利石（Wadsleyite）相；继续加温加压至2 000 K、23 GPa时（相当于地球内部670 km处的地震波不连续界面的温压环境），顽火斜方辉石相变为钛铁矿（Ilmenite）结构和钙钛矿（Perovskite）结构的混和相。实验结果进一步证明，在地幔中存在的两个地震波不连续界面是由橄榄石、顽火斜方辉石等矿物的相变引起的。

Synchrotron Radiation Diffraction of Enstatite under High Temperature and High Pressure

In-situ energy dispersive X-ray diffraction measurements of enstatite have been studied by using diamond anvil cell (DAC) with synchrotron radiation and laser heating in the range of 0~23 GPa and 293~2 000 K. We have found that enstatite transform to wadsleyite phase at 15.3 GPa and 1 600 K. At temperatures up to 2 000 K and pressure up to 23 GPa we have observed mixed phase of ilmenite and perovskite structure. The experiment further demonstrates that the density and seismic-wave velocity jumps are attributed to the phase transition of olivine and enstatite minerals.