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: 0752166
• 负责人: Colleen Dalton
• 金额: $ 5.76万
• 依托单位: Trustees of Boston 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 2012-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0752166&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).

智力优势：该项目将研究地球内部的一个基本性质——地幔位温、地震速度和衰减与洋中脊玄武岩（MORBs）岩石学之间的关系。特别是，我们将测试一个假设，即地幔位温的变化存在于全球洋中脊系统的轴线上，最高可达200摄氏度。如果这是真的，这种热变化应该产生可观察到的地震特征，因为温度升高导致剪切波速度减慢和剪切波衰减增大。洋中脊标志着板块之间的边界，板块在此分离，在此之下，地幔经历融化和上升流。原则上，岩石学对脊顶下地幔内部温度的估计应该与地震学对温度的估计一致。两种方法的一致将验证MORB钠和铁含量是地幔位温大变化的结果的解释，并将提供更清晰的岩石学和地震数据的正确解释，这些数据可以应用于山脊系统以外的地震数据，并通过时间利用来自更古老岩石的数据。这将为地球科学家最基本的两种工具——地震学和海底岩石样品的岩石学分析——的数据解释提供更大的信心。建议的工作包括对地震学和岩石学资料集的单独和联合检查。几个全球地震横波速度模型将用于约束沿整个洋中脊系统波速的三维变化。考虑不同小组使用一系列地震数据和不同技术开发的速度模型，将有助于区分稳健和可重复的特征与那些只有弱约束的特征。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。在实验室测量剪切速度和衰减方面的最新进展，将允许对地震观测到的温度和成分的数量作出比以前可能的更严格的解释。由于全球PetDB数据库的存在，以及过去几年收集的大量新数据集，岩石学分析将相对于以前的工作得到加强，这将大大提高全球覆盖范围。新的和改进的程序将用于纠正这些数据的化学分馏和实验室间的偏差。由此产生的数据集可以用来估计每个脊段的温度，并评估潜在的成分变化。岩石学和地震学数据集的综合分析包括对两组数据的比较，以寻找相关性和有趣的模式。一种新颖的方法也将用于检查这些数据集在频域内，以调查在各种长度尺度的相关性的可能性。更广泛的影响：该项目本质上是跨学科的，并利用了地震学和岩石学数据推断的自然交叉点。不管结果如何，这项工作的意义是深远的。现今整个地球的温度和成分分布与地幔流动和地球表面可观察到的构造过程密切相关。了解温度、成分和岩石学之间的关系，将有助于反演地球的热历史。此外，将在解决围绕岩石学和地震学资料正确解释的突出争议方面取得进展。该项目为一名研究生提供支持，该研究生将在其职业生涯的早期阶段参与跨学科项目。波士顿大学本科生的参与将为潜在的未来研究生引入研究环境。该项目为一名早期职业女性科学家（道尔顿）提供资金，以获得与研究生和另一学科的知名科学家（朗缪尔）合作的经验。