Compaction–dissolution waves in an upwelling mantle column
Compaction–dissolution waves in an upwelling mantle column
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上涌地幔柱中的压实-溶解波
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
E. Parmentier
中科院分区：
文献类型：
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作者：
M. Hesse;A. Schiemenz;Yan Liang;E. Parmentier
摘要在熔体流动的数值模拟中，孔隙度和熔体压力的压缩-溶解波是自发形成的，熔体在上升流、粘性压缩的多孔柱体中的迁移是在溶解度梯度下进行的。斜方辉石在熔体中的溶解度被假定为随高度线性增加，并诱导梯度反应，假定为在局部平衡。近似的垂直，1-D，稳态的解决方案，假设可以忽略不计的抗压实。稳态解的线性稳定性的特点是复杂的特征值和振荡的不稳定性与强大的波数选择。这种不稳定性导致了在非线性数值模拟中观察到的棋盘形溶解波的形成。这些波的相速度大于固体速度，但小于熔体速度。振荡不稳定性实现了在一定范围内的参数和波动特性的变化进行了探讨。幂律体积粘度公式，η = η/φ m，示出以指数m线性地降低生长速率。对于小扰动，增长率和相速度从高分辨率的数值模拟测量预测的线性理论，以及在非线性政权的主导波数。我们提出了一个regime图的反应infiltration不稳定性在viscouslycompacting porousmedium和showthatemission-dissolutionwaves are favored通过增加固体上涌和小溶解度梯度相对于高孔隙度通道。流型图表明，沉积-溶解波的形成是洋中脊下熔体输运的一种可行的新物理机制。
SUMMARY Compaction–dissolution waves in porosity and melt pressure form spontaneously in numerical simulations of melt migration in an upwelling, viscously compacting, porous column in a solubilitygradient.Themeltfractionisassumedtobesmallandthesolidcomprisesolivineand orthopyroxene. The solubility of orthopyroxene in the melt is assumed to increase linearly with height and induces a gradient reaction, assumed to be at local equilibrium. Approximations for the vertical, 1-D, steady-state solutions are derived assuming negligible resistance to compaction. The linear stability of the steady-state solutions is characterized by complex eigenvalues and an oscillatory instability with strong wavenumber selection. This instability leads to the formation of checkerboard compaction–dissolution waves observed in the nonlinear numerical simulations. The phase velocity of these waves is larger than the solid velocity but smaller than the melt velocity. The oscillatory instability is realized over a range of parameters and the variation in wave properties is explored. A power-law bulk-viscosity formulation, ξ = η/φ m , is shown to decrease growth rates linearly in the exponent, m. For small perturbations, the growth rates and phase velocities measured from high-resolution numerical simulations are predicted by the linear theory as well as the dominant wavenumber in the non-linear regime. We present a regime diagram for reaction infiltration instabilities in viscouslycompacting porousmediaandshowthatcompaction–dissolutionwaves arefavoured by increasing solid upwelling and small solubility gradients relative to high-porosity channels. The regime diagram suggests that the formation of compaction–dissolution waves is a feasible new physical mechanism for melt transport beneath mid-ocean ridges.