Collaborative Research: Investigations of the relationship between seismological and petrological constraints on upper-mantle temperature and composition

合作研究：地震学和岩石学约束对上地幔温度和成分之间关系的研究

• 批准号: 0752281
• 负责人: Charles Langmuir
• 金额: $ 14.31万
• 依托单位: Harvard University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-04-01 至 2011-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0752281&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigations; relationship; between

OCE-0752166Intellectual Merit: This project will investigate a fundamental property of the Earth's interior - the relationship between mantle potential temperature, seismic velocity and attenuation, and the petrology of mid-ocean ridge basalts (MORBs). In particular, we will test a hypothesis that variations in mantle potential temperature exist along the axis of the global mid-ocean ridge system, of up to 200 C. If this is true, such thermal variations should produce an observable seismic signature, as increased temperature leads to slower shear-wave velocities and to higher shear-wave attenuation. The mid-ocean ridge marks the boundary between tectonic plates at which the plates are separating, and beneath which the Earth's mantle undergoes melting and upwelling. In principal, petrological estimates of temperature within the mantle beneath the ridge crests should agree with seismological estimates of temperature. Agreement of the two approaches will test the interpretation that MORB sodium and iron content is the result of large variations in mantle potential temperature, and will provide greater clarity concerning the proper interpretation of both petrological and seismic data that can be applied beyond the ridge system using the seismic data, and through time making use of data from older rocks. This will provide greater confidence for the interpretation of data from two of the most fundamental tools for Earth scientists, seismology and petrological analysis of seafloor rock samples.The proposed work consists of separate and joint examinations of seismological and petrological datasets. Several global seismic shear-wave velocity models will be used to constrain three-dimensional variations in wave speed along the entire mid-ocean ridge system. Consideration of velocity models developed by different groups using a range of seismic data and diverse techniques will help distinguish robust and reproducible features from those that are only weakly constrained. Global attenuation models will be used to assist the interpretation of the velocity anomalies, as the sensitivity of attenuation to factors such as temperature and composition complements the sensitivity of velocity. Recent progress in laboratory measurements of shear velocity and attenuation will permit a more rigorous interpretation of the seismologically observed quantities in terms of temperature and composition than has previously been possible. The petrological analysis will be enhanced relative to previous work by the existence of the global PetDB database, and extensive new datasets collected over the past several years that will substantially enhance the global coverage. New and improved procedures will be used to correct these data for chemical fractionation and inter-laboratory bias. The resulting dataset can then be used to estimate temperature along each ridge segment and to evaluate potential compositional variations. The combined analysis of the petrological and seismological datasets involves comparison of the two sets of data to look for correlations and intriguing patterns. A novel approach will be used also examine these datasets within the frequency domain to investigate the possibility of correlations at various length scales.Broader Impacts: This project is inherently cross-disciplinary and takes advantage of a natural intersection in the inferences that can be made from seismological and petrological data. Regardless of the result, the implications of this work are far-reaching. The present-day distribution of temperature and composition throughout the Earth is strongly coupled to mantle flow and the tectonic processes that are observable at theEarth's surface. Understanding the relationship between temperature, composition, and petrology will allow back-projections of the Earth's thermal history. In addition, progress will be made toward resolving outstanding controversies surrounding the proper interpretation of petrological and seismological data. This project provides support for one graduate student who will benefit from involvement in an interdisciplinary project at an early stage in her career. Involvement of an undergraduate at Boston University will introduce a potential future graduate student to the research environment. The project provides funding for an early-career female scientist (Dalton) to gain experience working with both the graduate student and an established scientist from another discipline (Langmuir).

OCE-0752166Intlectual Fure：该项目将研究地球内部的基本特性 - 地幔潜在温度，地震速度和衰减之间的关系，以及中元山脊玄武岩（MORBS）的岩石学。特别是，我们将检验一个假设，即沿全球中山脊系统轴的地幔电势温度的变化存在，最高为200C。如果这是正确的，则这种热变化应产生可观察到的地震签名，因为温度的增加会导致较慢的剪切波速度和更高的剪切波动率。海山脊标志着板隔开的构造板之间的边界，地球的地幔在地球上经历了融化和上升流。在本金中，山脊波峰下地幔中温度的岩石学估计值应与温度的地震学估计值一致。这两种方法的一致性将测试以下解释：MORB钠和铁含量是地幔潜在温度差异很大的结果，并且将提供更明显的清晰度，即可以使用地震数据以及从旧岩石中使用时间来使用山脊系统以外的岩石学和地震数据的正确解释。这将为解释地球科学家的两个最基本工具的数据提供更大的信心，对海底岩石样品的地震学和岩石学分析。拟议的工作包括对地震和岩石学数据集的单独和共同检查。几种全球地震剪切波速度模型将用于沿整个海洋中部山脊系统的波速限制三维变化。使用一系列地震数据和多种技术的不同组开发的速度模型的考虑将有助于区分仅弱约束的稳健和可再现特征。全球衰减模型将用于帮助解释速度异常，因为衰减对温度和成分等因素的敏感性补充了速度的敏感性。剪切速度和衰减实验室测量的最新进展将使对地震学观察到的数量在温度和组成方面进行更严格的解释。相对于以前的工作，通过存在全球PETDB数据库，并且在过去几年中收集的广泛的新数据集将大大增强全球覆盖范围。新的和改进的程序将用于纠正这些数据，以实现化学分馏和实验室间偏差。然后，所得数据集可用于估算每个山脊段的温度并评估潜在的组成变化。岩石学和地震学数据集的组合分析涉及两组数据的比较，以寻找相关性和有趣的模式。将使用一种新颖的方法检查频域内的这些数据集，以研究各个长度尺度上相关性的可能性。Boader的影响：该项目本质上是跨学科的，并利用了可以从地震和质学数据制成的推论中的自然交集。无论结果如何，这项工作的含义是深远的。当前的温度和成分在整个地球上的分布与地幔流以及可在Theearth表面可观察到的构造过程密切相结合。了解温度，成分和岩石学之间的关系将允许对地球的热史进行重新投影。此外，将在解决岩石学和地震学数据的适当解释方面解决杰出争议方面的进展。该项目为一名研究生提供了支持，该研究生将受益于她职业生涯的早期跨学科项目。在波士顿大学的本科生的参与将向研究环境介绍潜在的未来研究生。该项目为早期职业女科学家（道尔顿）提供资金，以获得与研究生和一位既定学科（Langmuir）的知名科学家一起工作的经验。