Magma Dynamics with the Enthalpy Method: Benchmark Solutions and Magmatic Focusing at Mid-ocean Ridges
Magma Dynamics with the Enthalpy Method: Benchmark Solutions and Magmatic Focusing at Mid-ocean Ridges
复制标题
采用热函法的岩浆动力学：大洋中脊的基准解决方案和岩浆聚焦
DOI：
10.1093/petrology/egn058
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发表时间：
2008
影响因子：
3.9
通讯作者：
R. Katz
中科院分区：
文献类型：
--
作者：
R. Katz
岩浆的发生和运输将地幔对流与地表火山活动联系起来，从而与地球的长期化学和形态演化联系起来；地壳。然而，构造背景下岩浆-地幔相互作用的动力学建模仍然是一个挑战，因为在一个可渗透、致密和主动变形的地幔基质中，多组分热力学和熔体分离的复杂性。在这里，我描述了一种灵活的方法来制定这种基于焓法模型的热化学，这是一种通常用于合金凝固模拟的技术。这种方法允许根据熟悉的二元相图进行融化和冻结，与能量守恒和两相压实和流动相一致。我将焓法扩展到两个以上的热力学分量。一维上升流和熔融柱的模拟为该方法提供了基准。向快速扩张的洋中脊输送岩浆的熔融区域的二维模拟证明了焓法的实用性。这些计算提供了沿海洋岩石圈底部岩浆聚焦效率的新估计。模拟的聚焦效率随地幔渗透率和抗压性而变化。要产生5-7 km的洋壳，其中均匀的次脊地幔熔化约20%，则需要超过70%的聚焦效率。反过来，这表明基质渗透率和体积粘度处于先前估计值的高端。
Magma genesis and transport link mantle convection with surface volcanism and hence with the long-term chemical and morphological evolution of the Earth's; crust. Modeling the dynamics of magma-mantle interaction in tectonic settings remains a challenge, however, because of the complexity of multi-component thermodynamics and melt segregation in a permeable, compactible, and actively deforming mantle matrix. Here I describe a flexible approach to formulating the thermochemistry of such models based on the Enthalpy Method, a technique commonly used in simulations of alloy solidification. This approach allows for melting and freezing based on a familiar binary phase diagram, consistent with conservation of energy and two-phase compaction and flow. I present an extension of the Enthalpy Method to more than two thermodynamic components. Simulation of a one-dimensional upwelling and melting column provides a benchmark for the method. Two-dimensional simulations of the melting region that feeds magma to a rapidly spreading mid-ocean ridge demonstrate the utility of the Enthalpy Method. These calculations provide a new estimate of the efficiency of magmatic focusing along the base of the oceanic lithosphere. Modeled focusing efficiency varies with mantle permeability and resistance to compaction. To yield 5-7 km of oceanic crust with ∼20% melting of a homogeneous, sub-ridge mantle, a focusing efficiency of greater than 70% is required. This, in turn, suggests that matrix permeability and bulk viscosity are at the high end of previously estimated values.