Role of strain-dependent weakening memory on the style of mantle convection and plate boundary stability
Role of strain-dependent weakening memory on the style of mantle convection and plate boundary stability
复制标题
应变相关的弱化记忆对地幔对流类型和板块边界稳定性的作用
DOI：
10.1093/gji/ggz167
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发表时间：
2019
影响因子：
2.8
通讯作者：
Becker, Thorsten W
中科院分区：
文献类型：
--
作者：
Fuchs, Lukas;Becker, Thorsten W
板块构造表面运动与对流地幔的关系仍然是地球科学的主要问题之一。特别是，尽管应变记忆，即在地质时期保存和重新激活构造继承的能力，似乎是板块构造的一个关键特征，但板块边界应变局部化的原因和后果仍然存在争议。在这里，我们分析了参数化损伤弱化流变学（应变相关弱化）如何影响板块边界形成的时间依赖性、移动盖和静止盖之间的过渡以及二维对流模型中板块的重组。我们的模型中与应变相关的弱化允许岩石圈弱区的自洽形成和保存，这些弱区是由于海沟区域的大规模压缩变形而形成的俯冲带残余物。这种遗传性薄弱带可以被重新激活为板内俯冲带、邻近俯冲带的山脊或本身作为扩张中心。由于沿板块边界的弱化、继承的弱区以及部分沿扩展中心的累积应变，削弱了岩石圈的浅部，移动盖对流的寿命增加。应变相关的弱化还增强了沿会聚板边界的应变局部化，从而提高了其稳定性和寿命。因此，构造继承对于理解板块重组的时间依赖性具有重要贡献。如果弱区完全穿透岩石圈并且相对弱化至少 20%，则应变相关的弱化会导致移动-静止盖过渡转变为更高的有效屈服应力。
How plate tectonic surface motions relate to the convecting mantle remains one of the major problems in geosciences. In particular, the cause and consequence of strain localization at plate boundaries remains debated, even though strain memory, that is, the ability to preserve and reactivate tectonic inheritance over geological time, appears to be a critical feature in plate tectonics. Here, we analyse how a parametrized damage weakening rheology, strain-dependent weakening, affects the time-dependence of plate boundary formation, the transition between mobile and stagnant-lid and the reorganization of plates in 2-D convection models. The strain-dependent weakening within our models allows for a self-consistent formation and preservation of lithospheric weak zones, which are formed as remnants of subduction zones due to large-scale compressional deformation in the trench region. Such inherited weak zones can be reactivated as intraplate subduction zones, ridge adjacent subduction or as spreading centres themselves. Due to the weakening along plate boundaries, the inherited weak zones, and partly the accumulated strain along spreading centres, which weakens the shallow parts of the lithosphere, the longevity of mobile-lid convection increases. Strain-dependent weakening also enhances strain localization along convergent plate boundaries which increases their stability and longevity. As a consequence, tectonic inheritance is an important contribution to understanding the time-dependence of plate reorganization. Strain-dependent weakening results in a shift of the mobile-stagnant lid transition to higher effective yield stresses, if the weak zones fully penetrate the lithosphere and are relatively weakened by at least 20 per cent.
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