Modeling Mantle Circulation, Temperatures and Melting Processes Beneath Back-Arc Spreading Centers

摘要：地球内部是一个对流引擎，它产生了我们的大陆、海洋和大气，并随着时间的推移不断重塑它们。板块分开的伸展脊和板块汇聚的俯冲带，代表了地球内部与海洋和大气之间能量和化学物质交换的主要场所。俯冲带尤其重要，因为它们发生在大陆边缘附近，而地球人口中有很大一部分居住在那里，而且还在不断增长。在有记录的历史中，俯冲带还产生了所有的大地震，以及各种由俯冲引起的危险，包括熔岩流；火山碎屑流;还有毁灭性的海啸。这项研究验证了一个假设，即在俯冲板块之上存在一个扩张中心，就地幔流动（和应力场）、温度、熔体和新地壳的产生等方面，极大地改变了这个系统。本文采用二维（2-D）数值模型和一种新颖的三维（3-D）实验室模拟装置进行弧后扩张俯冲。结果将描述地幔环流模式、地幔温度以及这些复杂系统中产生和提取的熔体类型和体积的可变性之间的关系。将生成数值模型，以显示在全球弧系统中观测到的不同俯冲参数如何在二维意义上影响地幔过程和地壳生长。这些结果将用于计算离开地幔的熔体的特征，并通过与现有化学数据的比较，将使重点放在实际系统可能出现的情景上。实验室模型是由美国国家科学基金资助开发的，可以很好地扩展到地幔，将用于表征地幔流动、应力、温度和熔融生产的三维时空模式，这些模式在俯冲和板块扩张过程相互作用的复杂区域。实验室模型的3-D方面允许与现有数据集进行有效的比较，超越了2-D计算机模型的可能性。更广泛的影响

ABSTRACT (Kincaid - 0453656) The Earth's interior represents a convective engine that generated our continents, oceans and atmosphere and continues to reshape them over time. Spreading ridges, where plates move apart, and subduction zones where plates converge, represent the dominant sites for energy and chemical exchange between Earth's interior and our oceans and atmosphere. Subduction zones, in particular, are important because they occur near continental margins where a large and growing percentage of Earth's population resides. Subduction zones have also produced all of the great earthquakes in recorded history, along with a variety of subduction-induced hazards including lava flows; pyroclastic flows; and devastating tsunamis. This research tests the hypothesis that the presence of a spreading center above a subducting plate dramatically modifies the system in terms of mantle flow (and stress fields), temperatures, and the production of melt and new crust. Two-dimensional (2-D) numerical models and a novel apparatus for three-dimensional (3-D) laboratory analog models of subduction with back-arc spreading are used. Results will characterize relationships between mantle circulation patterns, mantle temperatures, and variability in the types and volumes of melt that are produced and extracted from within these complex systems. Numerical models will be generated to show how different subduction parameters observed in the global arc system influence mantle processes and crustal growth in a 2-D sense. These results will be used to calculate the characteristics of melt leaving the mantle and, through comparisons with available chemical data, will allow focus to be brought on scenarios that are possible for the actual system. Laboratory models, developed with prior NSF funding that scale well to the mantle, will be used to characterize the 3-D spatial and temporal patterns in mantle flow, stress, temperature, and melt production in complex regions where subduction and plate spreading processes interact. The 3-D aspects of the laboratory models allow for effective comparisons with existing data sets, going beyond what is possible with 2-D computer models. Broader Impacts