Partial Melting and Melt Segregation in a Convecting Mantle
Partial Melting and Melt Segregation in a Convecting Mantle
复制标题
对流地幔中的部分熔融和熔融偏析
DOI：
10.1007/978-94-011-4016-4_5
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发表时间：
2000
影响因子：
2.8
通讯作者：
H. Schmeling
中科院分区：
文献类型：
--
作者：
H. Schmeling
地幔熔融的各种原因（减压、加热或水的释放）结合目前对上地幔温度和岩石圈应力状态的估计表明，在许多地区，软流圈可能部分熔融，但熔体可能并不总是能够上升到表面。讨论了变形介质中描述熔化、熔体偏析、压实和贫化的控制方程，着重讨论了所涉及的物理过程。为了将这些过程与对流上地幔流动相结合，引入了“压实Boussinesq近似”（CBA），并与已知的解决方案进行了测试。驱动力包括热浮力、熔融浮力、贫化浮力和富集浮力。体积粘度及其对孔隙率的依赖性对熔体流动有显着影响，甚至对于与压实长度相比大的距离。1D和2D孤立孔隙度波进行了讨论，特别强调一个变量的体积粘度，压实和膨胀的矩阵。在变粘度羽流头到达岩石圈底部的自洽模型中研究了熔融、分凝和凝固过程。结果表明，熔体浮力占主导地位的偏析速度。然而，一个可变的体积粘度可能仍然有一些影响的偏析速度，而动态压力可以忽略不计。在没有地幔柱的情况下，部分熔融的未耗尽的软流层可能会在热、熔融和耗尽浮力的驱动下产生熔融不稳定性。这种不稳定性横向传播的速度的顺序为几厘米/年，并有一个长度尺度约2倍的厚度的部分熔融的软流圈。与这种传播不稳定性相关的火山活动可能具有与热点轨迹相似的外观，这表明这种不稳定性可能是羽流假说的替代机制，至少对于某些火山链来说是这样。
Various causes for mantle melting (decompression, heating or release of water) combined with current estimates of upper mantle temperatures and the state of stress in the lithosphere suggest that in many regions the asthenosphere might be partially molten, but melts may not always be able to rise to the surface. The governing equations describing melting, melt segregation, compaction and depletion in a deforming medium are discussed with emphasis on the physical processes involved. To combine these processes with a convecting upper mantle flow, a “Compaction Boussinesq Approximation” (CBA) is introduced and tested with known solutions. Driving forces include thermal, melt, depletion and enrichment buoyancy. The bulk viscosity and its dependence on porosity has a significant effect on the melt flow even for distances large compared to the compaction length. 1D and 2D solitary porosity waves are discussed with particular emphasis on a variable bulk viscosity, compaction, and dilatation of the matrix. Melting, segregation and solidification processes are studied in a self-consistent model of a variable viscosity plume head arriving at the base of the lithosphere. It is shown that melt buoyancy dominates segregation velocities. However, a variable bulk viscosity may still have some influence on the segregation velocities, while dynamic pressures may be neglected. In the absence of a mantle plume a partially molten undepleted asthenosphere may develop melting instabilities, driven by thermal, melt and depletion buoyancy. This instability propagates laterally with velocities of the order of several cm/a and has a length scale of about 2 times the thickness of the partially molten asthenosphere. Volcanism associated with this propagating instability might have a similar appearance as hot spot tracks suggesting that this instability might be an alternative mechanism to the plume hypothesis at least for some volcanic chains.
1, 2-顺式氨基糖苷类的形成及生理活性物质的合成开发
DOI：
--
发表时间：
2010
期刊：
影响因子：
--
作者：
益山純英;飛田英里;三浦隆史;竹内英夫;眞鍋史乃
通讯作者：
眞鍋史乃
影响因子：
3.9
作者：
MCKENZIE, D;BICKLE, MJ
通讯作者：
BICKLE, MJ