A Hybrid Mechanism for Enhanced Core‐Mantle Boundary Chemical Interaction
A Hybrid Mechanism for Enhanced Core‐Mantle Boundary Chemical Interaction
复制标题
增强核幔边界化学相互作用的混合机制
DOI：
10.1029/2021gl094456
复制
发表时间：
2021
影响因子：
5.2
通讯作者：
Hernlund John W.
中科院分区：
文献类型：
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作者：
Lim Kang Wei;Bonati Irene;Hernlund John W.
检测地核-地幔边界（CMB）的化学特征可以让我们前所未有地了解地球的深处内部和远古的过去。洋岛玄武岩（OIB）中的几种同位素和元素异常已被提议作为核心示踪剂。然而，将地核的特定化学特征传递到地幔的过程仍然不确定。在这里，我们提出了一种混合机制，该机制是由动态地形、液态金属多孔渗透到水下岩石中、弱化金属硅酸盐糊状物的重力塌陷以及诱导的小规模地幔环流中来自上方的额外岩石的下拉之间的协同反馈产生的。使用与薄层重力扩散耦合的地幔对流模型，我们发现，当糊状层的粘度降低到比上覆地幔小 105 倍的值时，由于该层的重力塌陷而引起的地幔循环变得与浮力驱动的地幔流相当。
Detection of chemical signatures from the core‐mantle boundary (CMB) could provide an unprecedented glimpse into our planet's deep interior and ancient past. Several isotopic and elemental anomalies in ocean island basalts (OIBs) have been proposed as core tracers. However, the process(es) by which particular chemical signatures from the core are conveyed into the mantle remain uncertain. Here, we propose a hybrid mechanism that results from a collaborative feedback between dynamic topography, porous infiltration of liquid metal into submerged rock, gravitational collapse of weakened metal‐silicate mush, and draw‐down of additional rocks from above in the induced small‐scale mantle circulation. Using a mantle convection model coupled to gravitational spreading of a thin layer, we show that induced mantle circulation due to the gravitational collapse of the layer becomes comparable to buoyancy‐driven mantle flow when the viscosity of the mushy layer is reduced to values ∼105times smaller than the overlying mantle.