EAR-PF: Water in the Lower Mantle: Gaining Insight through Melt Generation and Deformation Textures

Cara Vennari博士获得了NSF EAR博士后奖学金，在芝加哥大学和犹他大学开展研究和教育计划。水在上地幔中得到了广泛的研究，它被证明降低了地幔岩石的熔融温度并削弱了它；然而，对下地幔中的水的系统研究较少。在实验室实验中，她将利用钻石砧腔产生高压，研究不同含水率的下地幔岩石的熔融温度和强度，以增进我们对含水硅酸盐熔体的理解，并解释下地幔的局部各向异性区域。这项工作的更广泛影响包括将其直接应用于其他地球科学学科(地球动力学、岩石学、地球物理学、行星科学和地球化学)、对年轻学生的指导，以及通过外联计划提供志愿服务。这个项目的总体目标是了解下地幔中水的影响。第一种是合成热解石的高压熔融，目的是确定(水含量范围内)熔融温度，探索稳定相，并探索熔融和再结晶产物的阳离子和水合分布。含水熔体和矿物学被认为影响下地幔性质的流变性，然而，没有实验证据支持这一点，因此第二类实验将是在低地幔压力下的轴向应力实验，以研究含水橄榄岩的变形。用于熔化测量的技术包括原位粉末衍射和非原位扫描电子显微镜分析。下地幔水化阶段的强度测量将使用径向几何的X射线衍射进行调查。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Dr. Cara Vennari has been granted an NSF EAR postdoctoral fellowship to carry out research and education plans at the University of Chicago and the University of Utah. Water has been studied extensively in the upper mantle, where it has been shown to lower the melting temperature of mantle rock and weaken it; however, there has been less systematic study of water in the lower mantle. Using diamond anvil cells to generate high pressures during laboratory experiments, she will investigate the melting temperature and strength of lower mantle rock with a variety of water content to advance our understanding of hydrous silicate melts and explain local anisotropic regions of the lower mantle. Broader impacts of this work include its direct application to other Earth science disciplines (geodynamics, petrology, geophysics, planetary sciences and geochemistry), mentorship of younger students, and volunteering through outreach programs. The overall goal of this project is to understand the effect of water in the lower mantle. The first is high pressure melting of synthetic pyrolite composition, with the goals being to determine (with a range of water content) the melting temperature, explore the stable phases, and probe the melt and recrystallized products for the cation and hydrous distribution. Hydrous melts and mineralogy have been assumed to affect the rheologic character of the lower mantle properties; however, there have been no experimental evidence to support this, so the second type of experiment will be an axial stress experiment at lower mantle pressures to investigate the deformation of hydrous peridotite. Techniques used for the melting measurements include in situ powder diffraction coupled with ex situ SEM analysis. Strength measurements of hydrated lower mantle phases will be investigated using X-ray diffraction with radial geometry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.