Newtonian versus non-Newtonian upper mantle viscosity: Implications for subduction initiation
Newtonian versus non-Newtonian upper mantle viscosity: Implications for subduction initiation
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DOI：
10.1029/2005gl023457
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发表时间：
2005-10-08
影响因子：
5.2
通讯作者：
Hirth, G
中科院分区：
文献类型：
--
作者：
Billen, MI;Hirth, G
使用二维数值流模型分析了俯冲起始过程中流变学对板片尖端演化的影响。实验确定的流动定律具有很强的温度和应力依赖性，这会导致粘度的局部变化很大，从而直接影响俯冲起始。我们发现，由于流体动力应力将板片尖端拉向上方板块，具有牛顿粘度的模型会导致平坦或耦合俯冲。非牛顿流变学通过降低楔粘度和板片与楔角流的耦合来减少这些流体动力应力，使板片尖端的小负板片浮力足以在俯冲的早期阶段维持其倾角。
The effect of rheology on the evolution of the slab- tip during subduction initiation is analyzed using 2- D numerical flow models. Experimentally determined flow laws have both strong temperature- and stress- dependence, which leads to large local variations in viscosity with direct consequences for subduction initiation. We find that models with Newtonian viscosity lead to flat or coupled subduction due to hydrodynamic stresses that pull the slab- tip up towards the overriding plate. Non- Newtonian rheology reduces these hydrodynamic stresses by decreasing the wedge viscosity and the slab coupling to wedge- corner flow, rendering the small negative- slab buoyancy of the slab- tip sufficient to maintain its dip during the early stages of subduction.