An Experimental Study on the Strength of the Lithosphere: Large-strain shear deformation experiments of olivine + orthopyroxene aggregates

岩石圈强度的实验研究：橄榄石斜方辉石聚集体大应变剪切变形实验

• 批准号: 1214861
• 负责人: Shun-ichiro Karato
• 金额: $ 32万
• 依托单位: Yale University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-15 至 2014-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1214861&HistoricalAwards=false
• 关键词: Experimental; Study; Strength; Lithosphere; Large

Although plate tectonics is well documented on Earth, the reason why plate tectonics works on Earth but not on other terrestrial planets such as Venus, Mars is not well understood. In fact, plate tectonics is not an obvious mode of tectonics on Earth-like planets. On Earth-like planets, the near-surface layer is strong because of low temperature and the most 'natural' mode of tectonics is the so-called 'stagnant-lid' convection where the surface layer is rigid and does not deform (this is a case for Mars and most of other planets). In fact, if one uses a standard model of the strength of the lithosphere, the oceanic lithosphere on Earth will be too strong for plate tectonics to operate. Consequently, some weakening processes need to be invoked in order to understand why plate tectonics operates on Earth. After reviewing various new observations on the strength of Earth materials, we believe that the reduction in the strength in the deep lithosphere is a key to the operation of plate tectonics, and focus our attention to this issue.Based on our previous studies, we hypothesize that the presence of a secondary phase mineral orthopyroxene (the primary one being olivine) might have a key influence on the weakening. Consequently, we will conduct systematic experimental studies on deformation of a mixture of olivine and orthopyroxene for various ratios with a range of water contents. Rheological behavior (i.e., the stress-strain relationship) and the micro-structural evolution will be investigated. The results will then be interpreted by a model of weakening, and applied to Earth and other terrestrial planets. The results of this study will shed some lights on the reason for the operation of plate tectonics on Earth but not on other terrestrial planets.

尽管板块构造在地球上有充分的文献记载，但板块构造在地球上起作用而不是在金星等其他陆地行星上起作用的原因，火星尚不清楚。实际上，板块构造并不是地球状行星上构造的一种明显的模式。在类似地球的行星上，由于低温和最“自然”的构造模式，近地面层是强大的火星和大多数其他行星的案例）。实际上，如果人们使用岩石圈强度的标准模型，那么地球上的海洋岩石圈将太强，无法进行板块构造。因此，需要调用一些弱化的过程，以了解板块构造为何在地球上运行。在回顾了有关地球材料强度的各种新观察之后，我们认为，深层岩石圈强度的降低是板块构造运行的关键，并将注意力集中在这一问题上。基于我们以前的研究，我们假设次级矿物邻苯二烯（主要是橄榄石）的存在可能会对弱化产生关键影响。因此，我们将针对各种比率与一系列水含量的各种比率进行系统的实验研究。将研究流变行为（即应力 - 应变关系）和微结构演化。然后，结果将通过弱化的模型来解释，并应用于地球和其他陆地行星。这项研究的结果将为地球上板块构造运行而不是在其他陆地行星上运行的原因。