CSEDI Collaborative Research: Investigating the Nature of the Subcontinental Upper Mantle

CSEDI 合作研究：调查次大陆上地幔的性质

• 批准号: 1458184
• 负责人: Anna Courtier
• 金额: $ 7万
• 依托单位: University of Wisconsin-Whitewater
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-07-23 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1458184&HistoricalAwards=false
• 关键词: CSEDI; Collaborative; Research; Investigating; Nature

Earth's continents have been assembled via amalgamation of land masses over geologic time, eventually forming stable continental interiors, with associated tectonic activity and deformation typically isolated to the periphery of the continent. Over time, successive episodes of deformation in the form of extension, compression, magmatism, accretion, and rifting have left the sub-continental upper mantle with a complex signature of thermal and chemical variability. Many ancient continental areas have been modified by relatively recent dynamic processes, for example active volcanism, rifting, and subduction at continental edges contribute to a complex sub-continental mantle. Of particular interest is the history and influence of melting, melt production, melt migration, and melt storage in sub-continental upper mantle, as it provides a window into past and present dynamical processes, including the formation of continents. This multi-disciplinary project will provide a systematic and geographically-detailed investigation of the dynamical, chemical, and thermal processes at work within the sub-continental upper mantle and their relationships to past and present melting within the Earth. The research team links a primarily undergraduate institution with a research institution and will include training of a postdoctoral researcher, undergraduate researchers through online and face-to-face research collaborations. These connections will be strengthened through long-term cross-institutional research experiences and the inclusion of a pre-service teacher working with the researchers to develop curricular activities describing Earth structure for high school and undergraduate classrooms. This two-year project will develop and apply rock physics models of melt, material mineralogies, and rheologies against observables provided by complementary seismic approaches, providing a comprehensive characterization of the velocity and density structure within the sub-continental upper mantle. The team will investigate the hypothesis that seismic signatures within the sub-continental upper mantle are relatable to past or current episodes of partial melting, and that they bear the fingerprints of thermal, chemical, and dynamical processes brought about by convective motions and mantle flow, both past and present. They will decipher these signals by: 1) using four seismic tools sensitive to absolute shear and compressional wavespeeds, their relative variations, as well as impedance contrasts, discontinuity sharpness, and anisotropic structure, 2) through geodynamic modeling of the seismic observables to quantify whether the presence of melt (or remnant, frozen-in melt) is consistent with the observed seismic structures, and 3) comparison of the inferred models to predictions for mantle rheology, electrical conductivity, temperatures, and composition, and the relationship of variations in these parameters to tectonic evolution and dynamical settings.

在地质时期，地球上的大陆通过陆地块的合并而聚集在一起，最终形成稳定的大陆内部，伴随着相关的构造活动和变形，这些活动和变形通常孤立于大陆的外围。随着时间的推移，伸展、挤压、岩浆活动、增生和裂谷等形式的连续变形事件使次大陆上地幔具有复杂的热变化和化学变化特征。许多古老的大陆地区已经被相对较新的动力学过程所改变，例如大陆边缘的活火山作用、裂谷作用和俯冲作用，形成了复杂的陆下地幔。特别感兴趣的是熔融，熔体生产，熔体迁移和熔体储存在次大陆上地幔的历史和影响，因为它提供了一个窗口，过去和现在的动力学过程，包括大陆的形成。这个多学科的项目将提供一个系统的和地理上详细的调查动力，化学和热过程在工作中的次大陆上地幔和它们的关系，过去和现在在地球内的熔融。该研究团队将一个主要的本科院校与一个研究机构联系起来，并将包括通过在线和面对面的研究合作培训博士后研究人员和本科研究人员。这些连接将通过长期的跨机构的研究经验，并纳入一个职前教师与研究人员合作，以开发课程活动，描述地球结构的高中和本科生的教室得到加强。这个为期两年的项目将开发和应用岩石物理模型的熔体，材料矿物学和流变学对观测提供的补充地震方法，提供一个全面的表征速度和密度结构内的次大陆上地幔。该小组将调查这样一种假设，即次大陆上地幔内的地震特征与过去或当前的部分熔融事件有关，并且它们具有过去和现在的对流运动和地幔流动所带来的热、化学和动力学过程的指纹。他们将通过以下方式破译这些信号：1）使用对绝对剪切和压缩波速度、它们的相对变化以及阻抗对比、不连续性锐度和各向异性结构敏感的四种地震工具，2）通过地震观测值的地球动力学建模来量化是否存在熔融（或残余物，冻结在熔体中）与观测到的地震结构一致，以及3）将推断的模型与地幔流变学，电导率，温度和成分的预测进行比较，以及这些参数的变化与构造演化和动力学背景的关系。