Experimental study of the flow behavior of garnet at high pressures: implications for the rheology of subducted lithosphere

高压下石榴石流动行为的实验研究：对俯冲岩石圈流变学的影响

• 批准号: 1045832
• 负责人: Shenghua Mei
• 金额: $ 30.24万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-01-15 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1045832&HistoricalAwards=false
• 关键词: Experimental; study; flow; behavior; garnet

This proposal focuses on investigating the strength of earth materials at extreme pressure-temperature conditions in order to provide the solid basis that is necessary to model geodynamic activities associated with plate tectonics. The results of this proposed study are important not only to a broad spectrum of the geophysics community but also to energy sciences since, in the latter, understanding geophysical properties and processes is critical to managing improved production of Earth's energy resources and safe disposal of energy related waste. Furthermore, this research will establish new experimental techniques, and the results will be integrated into the academic curriculum and will provide an important learning experience for students.Specifically, this proposed study is designed to develop a fundamental understanding of the mechanical properties of garnet at high pressures. Since garnet is an important mineral in Earth's subducting plates and the transition zone, the strength of garnet plays an important role in governing the dynamics of such tectonically active regions. Despite its importance, to date the mechanical properties of garnet have been poorly constrained, mainly because the working pressure for conventional apparatuses is too low to reach the stability field for garnet at high temperatures. This shortcoming limits enormously the advance of our understanding of the dynamic behavior of the subducted lithosphere. This proposed study describes research that utilizes a new generation of high-pressure equipment, the deformation-DIA apparatus, an advanced mechanical testing system capable of deforming geo-materials at much higher pressures and temperatures than previously possible. With this apparatus, it is now achievable to investigate the physical properties of garnet at the high pressure-temperature conditions appropriate to subduction zones. Three specific tasks are proposed to be undertaken. First, we will quantify the effect of pressure on the high-temperature strength of garnet. Second, we will investigate the influence of chemical environment (e.g., water) on the flow behavior of garnet at high temperatures and pressures. Third, we will determine the difference in strength between olivine and garnet, the two of the most abundant minerals in Earth's upper mantle. In general, the results of this research will contribute to the solution of geodynamic problems by providing a foundation of scientific understanding of earth materials at extreme conditions.

该提案的重点是研究地球材料在极端压力-温度条件下的强度，以便为模拟与板块构造相关的地球动力学活动提供必要的坚实基础。这项研究的结果不仅对地球物理学界很重要，而且对能源科学也很重要，因为在能源科学中，了解地球物理特性和过程对于管理提高地球能源资源的生产和安全处置与能源相关的废物至关重要。此外，这项研究将建立新的实验技术，其结果将融入学术课程，并为学生提供重要的学习经验。具体来说，这项研究旨在对石榴石在高压下的机械性能有一个基本的了解。由于石榴石是地球俯冲板块和过渡带的重要矿物，因此石榴石的强度在控制此类构造活动区域的动力学方面发挥着重要作用。尽管石榴石很重要，但迄今为止，石榴石的机械性能受到的限制很少，主要是因为传统设备的工作压力太低，无法达到石榴石在高温下的稳定场。这一缺点极大地限制了我们对俯冲岩石圈动态行为的理解的进展。 这项拟议的研究描述了利用新一代高压设备、变形 DIA 装置的研究，这是一种先进的机械测试系统，能够在比以前更高的压力和温度下使地质材料变形。 利用该设备，现在可以在适合俯冲带的高压-温度条件下研究石榴石的物理性质。提出三项具体任务。首先，我们将量化压力对石榴石高温强度的影响。其次，我们将研究化学环境（例如水）对石榴石在高温高压下的流动行为的影响。第三，我们将确定地球上地幔中最丰富的两种矿物橄榄石和石榴石之间的强度差异。总的来说，这项研究的结果将有助于地球动力学问题的解决，为极端条件下地球材料的科学理解奠定基础。