Abstract At mid-ocean ridges, oceanic crust is emplaced in a narrow neovolcanic region on the seafloor, whereas basaltic melt that forms this oceanic crust is generated in a wide region beneath as suggested by a few geophysical surveys. The combined observations suggest that melt generated in a wide region at depths has to be transported horizontally to a small region at the surface. We present results from a suite of two-phase models applied to the mid-ocean ridges, varying half-spreading rate and intrinsic mantle permeability using new openly available models, with the goal of understanding melt focusing beneath mid-ocean ridges and its relevance to the lithosphere-asthenosphere boundary (LAB). Three distinct melt focusing mechanisms are recognized in these models: 1) melting pressure focusing, 2) decompaction layers and 3) ridge suction, of which the first two play dominant roles in focusing melt. All three of these mechanisms exist in the fundamental two phase flow formulation but the manifestation depends largely on the choice of rheological model. The models also show that regardless of spreading rates, the amount of melt and melt transport patterns are sensitive to changes in intrinsic permeability, K0. In these models, the LAB is delineated by the melt-rich decompaction layers, which are essentially defined by the temperature dependent rheological and freezing boundaries. Geophysical observations place the LAB at a steeper incline as compared to the gentler profile suggested by most of our models. The models suggest that one way to reconcile this discrepancy is to have stronger melting pressure focusing mechanism as it is the only mechanism in these models that can focus melt before reaching the typical model thermal LAB. The apparent lack of observable decompaction layers in the geophysical observations hints at the possibility that melting pressure focusing could be significant. These models help improve our understanding of melt focusing beneath mid-ocean ridges and could provide new constraints for mantle rheology and permeability.

中文翻译：

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扩散速率和渗透率对大洋中脊下熔体聚集的影响

摘要 在大洋中脊，洋壳位于海底狭窄的新火山区，而形成洋壳的玄武岩熔体则产生于下面的广阔区域，一些地球物理调查表明。综合观察表明，在深处的广阔区域产生的熔体必须水平输送到地表的一个小区域。我们使用新的公开可用模型展示了应用于大洋中脊的一套两相模型的结果，不同的半扩张率和内在地幔渗透率，目的是了解大洋中脊下的熔体集中及其与海洋中脊的相关性。岩石圈-软流圈边界（LAB）。在这些模型中识别出三种不同的熔体聚焦机制：1) 熔体压力聚焦，2) 分解层和 3) 脊吸力，其中前两者在聚焦熔体中起主导作用。所有这三种机制都存在于基本的两相流公式中，但其表现在很大程度上取决于流变模型的选择。模型还表明，无论铺展速度如何，熔体量和熔体传输模式对固有渗透率 K0 的变化都很敏感。在这些模型中，LAB 由富含熔体的分解层描绘，这些分解层基本上由温度相关的流变和冻结边界定义。与我们的大多数模型建议的更平缓的轮廓相比，地球物理观测将 LAB 置于更陡峭的倾斜位置。这些模型表明，解决这种差异的一种方法是拥有更强的熔化压力聚焦机制，因为这是这些模型中唯一可以在达到典型模型热 LAB 之前聚焦熔体的机制。地球物理观测中明显缺乏可观察的解压层，这暗示着熔融压力聚焦的可能性很大。这些模型有助于提高我们对大洋中脊下方熔体聚集的理解，并可以为地幔流变学和渗透率提供新的约束。