Calcium in Bridgmanite in the Deep Mantle

火山活动，例如今天在夏威夷和最近在黄石公园看到的火山活动，与来自地球内部深处的热量有关。尽管地震研究已经在地幔深处发现了一些大型候选结构，这些结构可能代表了这些大型火山中心的热量或物质来源，但人们对这些结构的起源和性质知之甚少。在这个项目中，该团队将调查地球深层地幔中主要矿物可能的成分变化，以便更好地了解深层地幔中全球尺度结构的性质，这些结构可能会影响我们星球不断变化的表面。预计在这个项目中进行的实验将促进我们对深根火山作用的形成及其演化的认识。这些知识在一系列主题中都很重要，包括评估某些类型的自然灾害和提供对导致地球形成为行星的过程的见解。该项目将支持亚利桑那州立大学的本科生研究，为对地球科学感兴趣的学生提供实验室研究机会。初步实验表明，在深部地幔的压力-温度条件下，Ca（钙）溶解于桥菱石（下地幔主要矿物）中。在本项目中，计划测量Ca进入桥菱石晶体结构的压力-温度条件。研究的另一个目标是测量含钙桥菱岩的物理性质，以与地震识别的大型地幔结构（如大低剪切速度省）的性质进行比较。提出的实验包括高压-高温下的原位x射线测量和利用电子显微镜对回收样品进行化学分析。由于含钙矿物在下地幔对产热元素的储存能力中起着重要作用，本研究项目有望弥补我们对深部地幔不同地球化学结构中产热元素分布的认识空白。

Volcanic activity, such as that seen in Hawaii today and Yellowstone in the recent past, are linked to heat coming from deep in the Earth's interior. Although seismic studies have identified a few large scale candidate structures in the deep mantle that could represent the source of heat or material to feeds these large volcanic centers, little is known about the origin and nature of those structures. In this project, the team will investigate probable compositional changes in the dominant mineral in the Earth's deep mantle, in order to better understand the nature of the global-scale structures in the deep mantle that could affect our planet's changing surface. It is expected that the experiments to be conducted in this project will result in advancing our knowledge of the formation of deeply rooted volcanism and their evolution. Such knowledge is important in a range of topics that include assessing some types of natural hazard and providing insights into the processes that led to the formation of the Earth as a planet. The project will support undergraduate research at Arizona State University, providing laboratory research opportunities for students interested in the geosciences. Preliminary experiments suggest that Ca, Calcium, dissolves into bridgmanite (the dominant lower mantle mineral) at the pressure-temperature conditions of the deep mantle. In this project, it is planned to measure the pressure-temperature conditions where Ca enters into the crystal structure of bridgmanite. An additional goal of the study will be to measure the physical properties of Ca-bearing bridgmanite to compare with the properties of the seismically identified large scale mantle structures, such as Large Low Shear Velocity Provinces. The proposed experiments include in situ X-ray measurements at high pressure-temperature and chemical analysis of the recovered samples using electron microscopy. Because Ca-bearing minerals play an important role in the storage capacity of the lower mantle for heat producing elements, this research project is expected to close a gap in our knowledge of how heat producing elements are distributed among different geochemical structures in the deep mantle.