InSAR Measurements and Theoretical Modeling of Deformation due to Large Mid-crustal Magma Bodies: Investigation of the Dynamics and Timescales of Crustal Anatexis

InSAR 测量和大型中地壳岩浆体变形的理论建模：研究地壳深熔的动力学和时间尺度

• 批准号: 0208165
• 负责人: Yuri Fialko
• 金额: $ 20.18万
• 依托单位: University of California-San Diego Scripps Inst of Oceanography
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2006-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0208165&HistoricalAwards=false
• 关键词: InSAR; Measurements; Theoretical; Modeling; Deformation

FialkoEAR-0208165The proposed models regarding characteristic spatiotemporal scales of formation of parental silicic magma bodies in the continental crust range from partial melting of the tectonically thickened fluid-rich lower crust to magmatic underplating, whereby the heat required to produce crustal melting is advected by intrusions of mafic sills (presumably, from the mantle source). These models predict very different time scales for the production of granitic magma. The pertologically-based model of slow equilibrium melting of the lower crust implies that granites are generated on "orogenic'' time scales of the order of millions of years. In contrast, theoretical models of magmatic underplating predict that anatectic melts are produced on quite short timescales of the order of the crystallization time of typical mafic underplates (e.g., 100-1000 years for sill intrusions that are a few tens to a few hundred meters thick). In principle, the intrusion of mafic underplates, the volume changes associated with in situ melting, and the subsequent evacuation of the resulting granitoid magmas can each generate geodetically observable deformation. Geodetic measurements in areas of contemporaneous large active magma bodies may therefore provide critical constraints on the timescales and dynamics of crustal anatexis. This project uses Interferometric Synthetic Aperture Radar (InSAR) observations in regions of the ongoing crustal magmatism to constrain typical rates of the large-scale melt generation and/or migration, and to test the proposed models of the granitic melt production. The primary targets include large mid-crustal magma bodies imaged by seismic studies, in particular, the Socorro (New Mexico, USA), the Altiplano-Puna (South America), and the Southern Tibet (Asia) magma bodies. The observed spatial patterns and average rates of magma-induced deformation are combined with theoretical modeling that explicitly includes thermodynamics of melting/freezing, realistic variations in the mechanical properties of the host rocks, and inelastic deformation, to develop a detailed quantitative understanding of the dynamics of crustal anatexis. Independent observables that are brought to bear on the model results include constraints on the lateral extent and thickness of the mid-crustal magma bodies from seismic imaging, inferences about the duration and total amplitude of the magma-induced uplift from geomorphologic studies, and structural and geochemical signatures of the exhumed ancient magma bodies. Results of this work are relevant to interpretations of seismic observations of "bright spots'' in the mid-to-lower continental crust, field and theoretical studies of the crustal magmatism, and origin and evolution of the continental crust.

FialkoeAR-0208165关于特征的模型，关于特征的时空尺度的形成了代壳中的硅质岩浆体形成的范围从构造富含构造的富含流体的下皮到岩浆的部分熔化到碎屑，从而产生了cormulation的碎屑，从而产生了cormumation的碎屑，从而产生了由介绍的介绍（co）。这些模型预测了花岗岩岩浆生产的时间尺度非常不同。基于特学的较低地壳的缓慢平衡融化模型意味着花岗岩是在“造山学”的时间尺度上产生的数百万年的时间尺度。相反，相反，岩浆降低的理论模型预测，摩擦式融化预测，在典型的含量（E.G）的典型含量（E.G）的时间很短的时间内，就会在很短的时间内产生。在原理上，几个米的厚度正在进行的地壳岩浆岩层区域中的干涉合成孔径（INSAR）观察，以限制大规模融化产生和/或迁移的典型速率，并测试花岗质熔体生产的拟议模型。主要目标包括大型的中壳岩浆体，尤其是地震研究成像的大型岩浆体，尤其是Socorro（美国新墨西哥州），Altiplano-Puna（南美）和南部西藏（亚洲）Magma Bodies。 观察到的空间模式和岩浆诱导的变形的平均速率与理论建模相结合，这些模型明确地包括融化/冷冻，宿主岩石机械性能的现实变化的热力学，以及无弹性变形，以详细的定量理解，对Croustal Anatexis的动力学有详细的定量理解。在模型结果上带来的独立可观察物包括对地震成像中近腐蚀岩浆体的横向范围和厚度的限制，从地震成像的推断，对岩浆诱导的地质学研究的持续时间和总幅度的推论，以及从结构性和地球化学的质地，以及在刺激的古代岩浆身体的结构和地球化学签名中。这项工作的结果与对地壳岩浆岩岩中的大陆地壳，田间和理论研究的“明亮斑点”的地震观察的解释有关，以及大陆地壳的起源和进化。