Ultrasonic Velocity Measurements on Multiphase Agg

地球深部地幔的化学成分为地表的许多过程提供了重要信息，包括全球碳收支和水循环、地震和板块构造。由于没有来自超过12公里深度的样本可供直接实验室调查，该团队的方法是将候选岩石和矿物样本带回实验室仪器内的深部地幔压力和温度条件，然后进行现场实验，以了解这些矿物在地幔深处的物理和化学状态和性质。与以前的研究相比，这一项目标志着一项重大进步，它直接测量了合成岩石样品中的声速，这些样品与真实地球上的样品更相似。从技术和科学两个方面来说，这些技术进步都可以很容易地应用于非地球科学物质的研究，如那些对工业和能源科学以及新材料的设计和发现很重要的物质的研究。PIS建议使用超声干涉结合同步加速器X辐射直接测量热解岩成分和地幔矿物(KLb-1辉石；柯石英和辉钛矿)的多相聚集体上的纵波[P]和横波[S]波速和密度，直到下地幔顶部的P-T条件。这些直接测量的集料速度考虑了平衡样品中共存相(相分数、微量元素分配)之间的化学反应以及微量元素对弹性的影响，可以直接与地震速度-深度剖面进行比较。除了获得作为深度函数的热解成分模型的相平衡外，这些史无前例的结果还将为解释地震派生的速度和密度随深度变化的剖面提供关键数据，并对地球内部的矿物组成和动力学过程施加约束。

The chemical composition of the Earth's deep mantle holds important information for many processes at the surface, including the global carbon budget and water cycles, earthquakes, and plate tectonics. Since no samples from depths greater than 12 km are available for direct laboratory investigations, the team's approach is to bring candidate rock and mineral specimens back to the deep mantle pressure and temperature conditions inside a laboratory apparatus, and then conduct in-situ experiments to understand the physical and chemical states and properties of these minerals at mantle depths. In comparison with previous studies, this project marks a major advancement by measuring directly the sound velocities in synthetic rock samples which bear a closer resemblance to those in the real Earth. From both technological and scientific aspects, these technological advances can be readily applied to the study of non-geoscience substances, such as those important to industrial and energy sciences and for the designing and discovery of new materials.The PIs propose to conduct direct measurements of compressional [P] and shear [S] wave velocities and densities on multi-phase aggregates of pyrolitic composition and mantle constituent minerals (KLB-1 pyroxenes; coesite and stishovite) up to the P-T conditions of the top of the lower mantle using ultrasonic interferometry in conjunction with synchrotron X-radiation. These directly measured velocities of aggregates take into account the effects of chemical reactions among co-existing phases (phase fractions, minor element partitioning) in the equilibrated specimens as well as the effect of minor elements on elasticity and can be compared directly with seismic velocity-depth profiles. In addition to yielding phase equilibria for pyrolitic compositional model as a function of depth, these unprecedented results will provide critical data for the interpretation of seismically-derived velocity and density vs. depth profiles and place constraints on the mineralogical composition and dynamic processes of the Earth's interior.