EAR-PF:Quantifying Scale of Lower Crust and Mantle Heterogeneities Beneath the Continental United States: Bridging Seismology, Mineral Physics, Petrology, and Magnetotellurics

EAR-PF：美国大陆下方地壳和地幔异质性的量化尺度：连接地震学、矿物物理学、岩石学和大地电磁学

• 批准号: 1952642
• 负责人: William Shinevar
• 金额: $ 17.4万
• 依托单位: Shinevar, William J
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-02-01 至 2023-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1952642&HistoricalAwards=false
• 关键词: EAR; PF; Quantifying; Scale; Lower

Dr. William Shinevar has been granted an NSF EAR Postdoctoral Fellowship to carry out research and education activities at University of Colorado Boulder under the mentorship of Dr. Vera Schulte-Pelkum. The goal of this project is to improve interpretations of lower crustal and mantle seismic anomalies in terms of temperature, pressure, major element chemistry, hydration, and melt fraction by integrating constraints from the measurement of Earth’s electrical resistivity (magnetotellurics), and the directional dependence of the seismic wavespeeds (seismic anisotropy). Constraining the scale of lower crustal and mantle thermal and chemical heterogeneities is fundamental to determining the rheology and stress state of the lithosphere. This, in turn, is crucial to understanding seismic hazard, as well as how the continental crust and mantle compositionally evolved over Earth’s history, which is important to better understand the formation of natural resources. Dr. Shinevar’s education plan focuses on mentoring an undergraduate student on a research project associated in order to introduce a student to interdisciplinary approaches for understanding Earth processes. In addition, he will participate in public outreach and K-12 education activities in the Boulder area.Seismic wave speed on the lithospheric-scale is dependent on the (an)elastic moduli of the minerals present as well as the distribution and elastic moduli of fluids if present. The minerals present mainly depend on major element composition, water content, pressure, and temperature. Seismic wavespeeds of lower crustal and mantle rocks have been recently calculated using databases of whole-rock compositions, thermodynamic modelling, and grain-scale experimental observations of mineral moduli and anelasticity. The interpretation of seismic wavespeeds is non-unique. Applying these new calculations, this project will assess the scale and magnitude of chemical and thermal heterogeneities compatible with the most current seismic tomographic models of the lower crust and upper mantle, thus quantifying interpretation uncertainty. However, not all wavespeeds from these tomographic models can be interpreted using these calculations. For these anomalous regions, two other datasets will be used: seismic anisotropy can estimate uncertainty in isotropic tomographic models, and magnetotelluric measurements, which are highly sensitive to fluids and silicate melts, can better constrain mantle melt fraction or hydration. With these independent constraints, tomographic models will be edited to include expected seismic wavespeeds in anomalous regions due to melt or hydrous phases. Seismic delay times will be forward modeled to validate these calculations. This synthesis will increase our understanding of the evolution of mantle lithosphere from the Archean to the present as well as allow for a direct link between large-scale geophysical observations and small-scale laboratory measurements.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.

William Shinevar博士已获得NSF博士后奖学金，在Vera Schulte Pelkum博士的指导下在科罗拉多博尔德大学开展研究和教育活动。该项目的目标是通过整合地球电阻率测量（大地电磁法）和地震波速度（地震各向异性）的方向依赖性的约束，改善对温度、压力、主要元素化学、水合作用和熔融分数方面的下地壳和地幔地震异常的解释。制约下地壳和地幔热化学非均匀性的尺度是确定岩石圈流变学和应力状态的基础。反过来，这对于理解地震危险性以及大陆地壳和地幔在地球历史上的成分演变至关重要，这对于更好地理解自然资源的形成至关重要。Shinevar博士的教育计划侧重于指导一名本科生进行相关的研究项目，以便向学生介绍了解地球过程的跨学科方法。此外，他还将参加博尔德地区的公众宣传和K-12教育活动。岩石圈尺度上的地震波速度取决于存在的矿物的弹性模量以及流体的分布和弹性模量（如果存在的话）。矿物的存在主要取决于主量元素组成、含水量、压力和温度。下地壳和地幔岩石的地震波速度最近已经计算使用数据库的全岩成分，热力学模型，矿物模量和滞弹性的颗粒尺度实验观察。地震波速度的解释是不唯一的。应用这些新的计算，该项目将评估与最新的下地壳和上地幔地震层析成像模型兼容的化学和热不均匀性的规模和幅度，从而量化解释的不确定性。然而，并不是所有的波速从这些层析模型可以解释使用这些计算。对于这些异常区域，将使用另外两个数据集：地震各向异性可以估计各向同性层析成像模型的不确定性，而对流体和硅酸盐熔体高度敏感的大地电磁测量可以更好地约束地幔熔体分数或水合作用。有了这些独立的约束条件，层析成像模型将被编辑，以包括预期的地震波速异常地区，由于熔融或含水相。将对地震延迟时间进行正演模拟，以验证这些计算。这一综合将增加我们对地幔岩石圈从太古代到现在的演化的理解，并允许大规模地球物理观测和小规模实验室测量之间的直接联系。这一奖项反映了NSF的法定使命，并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

Mantle thermochemical variations beneath the continental United States through petrologic interpretation of seismic tomography

通过地震层析成像的岩石学解释美国大陆下方的地幔热化学变化

• 发表时间: 2023
• 期刊: Earth and planetary science letters
• 影响因子: 5.3
• 作者: Shinevar, William J.;Golos, Eva M.;Jagoutz, Oliver;Behn, Mark D.;Van der Hilst, Robert D.
• 通讯作者: Van der Hilst, Robert D.

Geophysical‐Geochemical Modeling of Deep Crustal Compositions: Examples of Continental Crust in Typical Tectonic Settings and North China Craton

• DOI: 10.1029/2022jb025536
• 发表时间: 2023-05
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: D. Cui;Jing‐Liang Guo;William J. Shinevar;Liang Guo;Wangchun Xu;Hongfei Zhang;Zhenyi Jin