Fat Plumes May Reflect the Complex Rheology of the Lower Mantle
Fat Plumes May Reflect the Complex Rheology of the Lower Mantle
复制标题
脂肪羽可能反映了下地幔复杂的流变学
DOI：
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发表时间：
2018
影响因子：
5.2
通讯作者：
P. Cordier
中科院分区：
文献类型：
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作者：
A. Davaille;Phillippe Carrez;P. Cordier
最近对主要热点下的地幔进行的层析成像显示，向下延伸到核幔边界的地震速度很慢，证实了地幔热柱的存在。然而，这些羽流比之前想象的要厚得多。利用新的实验室实验和标度定律，我们证明了在粘塑性流体中发展的热羽的直径比在牛顿流体中发展的热羽的直径大得多。这种需要屈服应力的流变学与下地幔一致，主要是通过纯粹的位错攀升而变形。屈服应力值在1-10 Mpa之间，意味着位错密度在108m-1010m−2之间，将足以再现层析图像中观察到的羽状形貌。
Recent tomographic imaging of the mantle below major hot spots shows slow seismic velocities extending down to the core‐mantle boundary, confirming the existence of mantle plumes. However, these plumes are much thicker than previously thought. Using new laboratory experiments and scaling laws, we show that thermal plumes developing in a visco‐plastic fluid present much larger diameters than plumes developing in a Newtonian fluid. Such a rheology requiring a yield stress is consistent with a lower mantle predominantly deforming by pure dislocation climb. Yield stress values between 1 and 10 MPa, implying dislocation densities between 108 and 1010 m−2, would be sufficient to reproduce the plumes morphology observed in tomographic images.