Chen Yi-Wei, Colli Lorenzo, Bird Dale E, Wu Jonny, Zhu Hejun
Department of Earth and Atmospheric Science, University of Houston, Houston, USA.
Bird Geophysical, Houston, USA.
Nat Commun. 2021 Mar 11;12(1):1603. doi: 10.1038/s41467-021-21723-1.
The importance of a low-viscosity asthenosphere underlying mobile plates has been highlighted since the earliest days of the plate tectonics revolution. However, absolute asthenospheric viscosities are still poorly constrained, with estimates spanning up to 3 orders of magnitude. Here we follow a new approach using analytic solutions for Poiseuille-Couette channel flow to compute asthenospheric viscosities under the Caribbean. We estimate Caribbean dynamic topography and the associated pressure gradient, which, combined with flow velocities estimated from geologic markers and tomographic structure, yield our best-estimate asthenospheric viscosity of (3.0 ± 1.5)*10 Pa s. This value is consistent with independent estimates for non-cratonic and oceanic regions, and challenges the hypothesis that higher-viscosity asthenosphere inferred from postglacial rebound is globally-representative. The active flow driven by Galapagos plume overpressure shown here contradicts the traditional view that the asthenosphere is only a passive lubricating layer for Earth's tectonic plates.
自板块构造革命伊始，流动板块之下低粘度软流圈的重要性就已得到强调。然而，软流圈的绝对粘度仍受限于诸多因素，其估计范围跨度高达3个数量级。在此，我们采用一种新方法，利用泊肃叶 - 库埃特通道流的解析解来计算加勒比地区下方的软流圈粘度。我们估算了加勒比地区的动力学地形及相关压力梯度，再结合从地质标志和层析成像结构估算出的流速，得出软流圈粘度的最佳估计值为(3.0 ± 1.5)*10⁹帕·秒。该值与非克拉通和海洋区域的独立估计值一致，并对从冰后期回弹推断出的高粘度软流圈具有全球代表性这一假设提出了挑战。此处显示的由加拉帕戈斯地幔柱超压驱动的活跃流动，与软流圈仅是地球构造板块被动润滑层的传统观点相悖。
