CSEDI Collaborative Research: Chemistry and Dynamic Implications of Heterogeneous Fe and Si in the Deep Lower Mantle

CSEDI合作研究：下地幔深部异质铁和硅的化学和动力学意义

基本信息

批准号：
1664553
负责人：
Catherine Macris
金额：
$ 2.91万
依托单位：
Indiana University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-05-15 至 2020-04-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1664553&HistoricalAwards=false
关键词：
CSEDI Collaborative Research Chemistry Dynamic

项目摘要

The composition of Earth's rocky mantle is fundamentally linked to dynamic processes responsible for the composition and motion of tectonic plates on Earth's surface. Although the mantle is stirred by convection, it is not well-mixed: images of the mantle obtained from seismology reveal enigmatic regions of unknown composition and age. Progress towards identifying these regions and their role in the history of the Earth has been based on determining the range of compositions and physical properties consistent with remote geophysical observations. Physical properties of mantle minerals can be measured in experiments that mimic the high pressures and temperatures of the deep Earth. Effects of contrast in temperature, density, and viscosity on shapes and dynamics of mantle structures can be tested by simulations of convecting rock. The team combines complementary expertise in experimental mineralogy and computational geodynamics and will train students in both fields, resulting in not only new constraints on the compositions and origins of mantle heterogeneities, but also well-rounded, multidisciplinary young scientists.Attempts at explaining large low shear velocity provinces (LLSVPs) and ultralow velocity zones (ULVZs) identified by seismology at the base of the mantle involve various combinations of contrasting temperature and composition relative to the surrounding mantle. Possible mechanisms for generating compositional differences have dramatically different implications for the age of these regions, including subduction of modern basalt and segregation of iron-rich mantle during the formation of the planet. Towards understanding these provinces, the project will systematically investigate the effects of variable amounts of iron and silicon on observable properties of the lower mantle phase assemblage such as density and viscosity. A series of well-characterized samples with variable amounts of ferrous iron, ferric iron, and silicon will be compressed to lower mantle conditions to synthesize assemblages of bridgmanite, ferropericlase, and at the highest pressures, post-perovskite. Effects of iron and silicon content on mantle density will be obtained from equations of state. Effects of variable silicate fraction on strength and viscosity of the mantle will be evaluated from observed shear strain. Resulting constraints from experiments on density and viscosity will be incorporated in geodynamic simulations of effects of compositional differences between background mantle and heterogeneous provinces on resulting morphology of thermochemical piles. The results will be shared widely at conferences and on the web and will be of interest to a broad community of solid Earth geochemists and geophysicists.

地球岩石地幔的组成从根本上与负责地球表面构造板的组成和运动的动态过程有关。尽管地幔是通过对流搅动的，但并未充分混合：从地震学获得的地幔的图像揭示了未知组成和年龄的神秘区域。鉴定这些区域及其在地球历史中的作用的进展是基于确定与远程地球物理观测一致的组成和物理特性的范围。地幔矿物质的物理特性可以在模仿深地球的高压和温度的实验中测量。温度，密度和粘度对比度对地幔结构的形状和动力学的影响可以通过对流岩石的模拟来测试。该团队结合了实验性矿物学和计算地球动力学方面的补充专业知识，并将在这两个领域中培训学生，这不仅会对地幔异质性的组成和起源产生新的约束，而且还会构成和起源，而且在大型的低剪力范围内（通过大型低剪切速度范围）（lllsively Z）（Ulllsively Z）（Ulllsively）（ULLS）（ULLS）（ULLS）（ULLS）（ULS）进行了良好的多学科年轻科学家。地幔底部的地震学涉及相对于周围地幔的对比度和组成的各种组合。产生组成差异的可能机制对这些区域的年龄具有巨大的影响，包括现代玄武岩的俯冲和地球形成期间铁富铁的覆盖。为了理解这些省份，该项目将系统地研究铁和硅对较低地幔相的可观察性能（例如密度和粘度）的可观察性质的影响。一系列具有可变量的亚铁，铁铁和硅的特征良好的样品将被压缩至较低的地幔条件，以合成Bridgmanite，Ferropericlase的组合，并在最高的压力下，后晶壶。铁和硅含量对地幔密度的影响将从状态方程中获得。可变硅酸盐分数对地幔强度和粘度的影响将从观察到的剪切应变中评估。对密度和粘度实验的限制将融合到背景地幔与异质省对热化学桩形态的构图差异的影响中。结果将在会议和网络上广泛共享，并将对广阔的地球地球化学家和地球物理学家的广泛社区感兴趣。