Abstract We show slab-parallel advection and Rayleigh-Taylor instability (RTI) as two competing gravity-driven flow mechanisms in the melt-rich layer atop a subducting slab. Scaled laboratory model results, supported by CFD simulations, indicate a transition of the RTI to advection mechanism at a threshold slab-dip angle (α) between 20° and 30°. The advection mechanism results in updip flow, forming a single plume at the upper edge of the melt-rich layer. Based on lubrication approximation, we present an analytical solution of the linear stability problem to perform a criticality analysis of α for the transition between RTI and advection, as observed in the experiments. The solution indicates this transition to occur at α⁎ = 28°, in favorable agreement with the experimental values. The article finally highlights the implications of this criticality analysis in interpreting the spatial distributions of subduction volcanism.

中文翻译：

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俯冲带富熔层中板条平行平流与瑞利-泰勒不稳定性的关系：临界性分析

摘要 我们将板坯平行平流和瑞利-泰勒不稳定性 (RTI) 展示为俯冲板坯顶部富熔层中两种相互竞争的重力驱动流动机制。由 CFD 模拟支持的按比例缩放的实验室模型结果表明，在 20° 和 30° 之间的阈值平板倾角 (α) 下，RTI 向平流机制过渡。平流机制导致上倾流，在富含熔体的层的上边缘形成单个羽流。根据润滑近似，我们提出了线性稳定性问题的解析解，以对 RTI 和对流之间的过渡进行临界分析，如实验中所观察到的。解表明这种转变发生在 α⁎ = 28°，与实验值一致。