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: 1361325
• 负责人: Nicholas Schmerr
• 金额: $ 26万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1361325&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.

地球大陆是通过在地质时间上的土地质量合并而组装的，最终形成了稳定的大陆室内体，相关的构造活性和变形通常分离到大陆的外围。随着时间的流逝，连续的变形发作以延伸，压缩，岩浆，积聚和裂纹的形式形式，使次大陆上地幔具有复杂的热和化学变异性标志。许多古老的大陆区域已经通过相对较新的动态过程进行了修改，例如大陆边缘的活跃火山，裂谷和俯冲造成了复杂的次大陆地幔。特别令人感兴趣的是熔融，融化产生，融化的迁移和在次大陆上地幔中的熔融存储的历史和影响，因为它为过去和现在的动态过程（包括大陆的形成）提供了一个窗口。这个多学科的项目将对次大陆上地幔中工作中的动力学，化学和热过程及其与地球内过去和现在的融化之间的关系进行系统的，化学和热过程的研究。研究小组将主要的本科机构与研究机构联系起来，包括通过在线和面对面的研究合作进行博士后研究人员，本科研究人员的培训。这些联系将通过长期的跨机构研究经验以及与研究人员合作开发课程活动，描述高中和本科教室的地球结构的课程活动来加强这些联系。这个为期两年的项目将开发并应用融化，材料矿物学和流变型的岩石物理模型，以互补的地震方法提供，从而对次大陆上层地幔内的速度和密度结构进行了全面的特征。该团队将调查以下假设：次大陆上地幔内的地震特征与部分熔化的过去或当前发作相关，并且它们带有由对流运动和地下室流动的过去和现在带来的热，化学和动力学过程的指纹。他们将通过以下方式通过：1）使用四个对绝对剪切和压缩波敏感的地震工具，它们的相对变化以及阻抗对比，不连续性的清晰度和各向异性结构，2）通过地球动体动力学建模，以量化融合的融合（或Re re rez）是否存在，或者是否存在融合（或Rez）的存在，或者是恢复性的。 3）将推论模型与地幔流变学，电导率，温度和组成的预测以及这些参数中的变化与构造演化和动态设置的关系进行比较。