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 博士获得了 NSF EAR 博士后奖学金，在 Vera Schulte-Pelkum 博士的指导下在科罗拉多大学博尔德分校开展研究和教育活动。该项目的目标是改进对下地壳和地幔地震的解释。通过整合地球电阻率（大地电磁）测量和方向性的约束，在温度、压力、主要元素化学、水合和熔体分数方面出现异常。地震波速的依赖性（地震各向异性）是确定岩石圈流变和应力状态的基础，也是了解地震危险性的关键。大陆地壳和地幔的组成在地球历史上是如何演化的，这对于更好地了解自然资源的形成非常重要。Shinevar 博士的教育计划侧重于指导本科生。一个相关的研究项目，旨在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共宣传和 K-12 教育活动。岩石圈尺度上的地震波速度取决于(an) 存在的矿物的弹性模量以及存在的流体的分布和弹性模量主要取决于下地壳和地幔岩石的主要元素组成、含水量、压力和温度。最近使用了全岩石计算成分、热力学建模以及矿物模量和滞弹性的颗粒尺度实验观测的数据库，地震波速的解释是非唯一的，该项目将评估规模和震级。化学和热非均质性与最新的下地壳和上地幔地震层析模型相一致，从而量化了解释的不确定性。然而，并非这些层析模型的所有波速都可以用这些模型来解释。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限制地幔熔体分数或水合作用。限制条件下，层析成像模型将被编辑，以包括由于熔化或含水阶段而导致的异常区域的预期地震波速。地震延迟时间将被正向建模。验证这些计算。这一综合将增加我们对从太古宙到现在地幔岩石圈演化的理解，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。该奖项反映了 NSF 的法定使命。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，并被认为值得支持。

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