High Pressure-Temperature Single-Crystal Elasticity of the Lower-Mantle Bridgmanite

下地幔布里奇曼石的高压-高温单晶弹性

• 批准号: 1916941
• 负责人: Jung-Fu Lin
• 金额: $ 41.53万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-06-01 至 2023-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1916941&HistoricalAwards=false
• 关键词: Pressure; Temperature; Single; Crystal; Elasticity

Earth's lower mantle extends from 670 km depth down to the core-mantle boundary, 2900 km deep. There, pressure and temperature exceed 1.3 million atm and 3500 K (5840 degree Fahrenheit). Understanding its properties is critical to constrain the planet dynamics. The lower mantle conducts heat away from the outer core. This contributes to power the Earth's magnetic field which shields us from the solar wind. Furthermore, thermal convection in the mantle drives plate tectonics and associated hazards, such as earthquakes and volcanic eruptions. Seismology, the study of seismic (elastic) waves, allows to observe directly the lower-mantle structures. But their interpretation requires knowledge of the elastic properties of the constitutive minerals. Bridgmanite accounts for more than 3/4th of the volume of the lower mantle, making it the most abundant mineral in the Earth. It is also of crucial interest when investigating lower-mantle properties. Here, the team quantifies experimentally the elastic properties of bridgmanite at the extreme conditions of the deep Earth. Coupling high pressure devices and state-of-the-art analytical techniques, they provide data allowing the interpretation of lower-mantle structures; notably that of large enigmatic provinces showing low seismic shear velocities. The project has strong implications in Seismology and broad impacts in Geodynamics. It also provides support and training in Mineral Physics for several graduate and undergraduate students, as well as educational outreach toward local elementary and middle schools. In this study, the team synthesize large single crystals of (Al,Fe)-bearing bridgmanite in the laboratory. Crystal properties are investigated at extreme conditions of pressure and temperature in the diamond-anvil cell. This apparatus generates high pressures at the tip of two opposing diamonds. The high temperatures are obtained by external heating or using focused laser beams. Crystal elastic properties are measured in situ using a combination of laboratory Brillouin and impulsive stimulated light scattering, as well as X-ray diffraction at national synchrotron facilities. This is achievable because the team is developing new technology in time-resolved impulsive laser spectroscopy. These new techniques will be shared with the community for future studies of material properties at extreme conditions. The researchers use the obtained data to constrain bridgmanite full elastic moduli as a function of pressure, temperature and of its contents in iron and aluminum. Extrapolation of the results to conditions relevant to the lower mantle, as well as modeling, allows interpreting seismological observations. The project outcomes further the understanding of seismic velocities, temperature profiles and chemical compositions in the deep Earth.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.

地球的下地幔从670公里深处延伸到2900公里深处的核幔边界。在那里，压力和温度超过130万大气压和3500 K（5840华氏度）。了解它的性质对于约束行星动力学至关重要。下地幔将热量从外核传导出去。这有助于为地球磁场提供动力，使我们免受太阳风的影响。此外，地幔中的热对流驱动板块构造和相关的灾害，如地震和火山爆发。地震学，研究地震（弹性）波，可以直接观察下地幔结构。但它们的解释需要了解构成矿物的弹性性质。Bridgmanite占下地幔体积的3/4以上，使其成为地球上最丰富的矿物。在研究下地幔性质时，它也是至关重要的。在这里，该团队通过实验量化了布里奇曼石在地球深部极端条件下的弹性特性。结合高压设备和最先进的分析技术，它们提供的数据可以解释下地幔结构，特别是显示低地震剪切速度的大型神秘省份。该项目在地震学和地球动力学的广泛影响有很大的影响。它还为一些研究生和本科生提供矿物物理学方面的支持和培训，以及对当地小学和中学的教育推广。在这项研究中，该团队在实验室中合成了含（Al，Fe）的bridgmanite的大单晶。在金刚石压砧单元中，在极端的压力和温度条件下研究晶体性质。该装置在两个相对的金刚石的尖端处产生高压。通过外部加热或使用聚焦激光束获得高温。晶体的弹性性能测量原位使用实验室布里渊和脉冲受激光散射，以及X射线衍射在国家同步加速器设施的组合。这是可以实现的，因为该团队正在开发时间分辨脉冲激光光谱学的新技术。这些新技术将与社区共享，用于未来极端条件下材料特性的研究。研究人员利用获得的数据来约束作为压力、温度及其在铁和铝中含量的函数的桥镁石全弹性模量。将结果外推到与下地幔相关的条件，以及建模，可以解释地震观测。该项目的成果进一步了解地震速度，温度分布和地球深部的化学成分。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

项目成果

Nonlinear effects of hydration on high-pressure sound velocities of rhyolitic glasses

水合作用对流纹岩玻璃高压声速的非线性影响

• DOI: 10.2138/am-2021-7597
• 发表时间: 2021
• 期刊: American Mineralogist
• 影响因子: 3.1
• 作者: Gu, Jesse T.;Fu, Suyu;Gardner, James E.;Yamashita, Shigeru;Okuchi, Takuo;Lin, Jung-Fu
• 通讯作者: Lin, Jung-Fu

Atomistic insight into the ferroelastic post-stishovite transition by high-pressure single-crystal X-ray diffraction

• DOI: 10.2138/am-2022-8458
• 发表时间: 2022-07
• 期刊: American Mineralogist
• 影响因子: 3.1
• 作者: Yanyao Zhang;S. Chariton;Jiaming He;S. Fu;Fang Xu;V. Prakapenka;Jung‐Fu Lin