Infiltration triggered by selective dissolution of pyroxenes is a major mode of melt migration in the mantle. A common view, supported by experiments and numerical models, is that the geometry of the melt plumbing system is governed by the stress field induced by solid-state flow of the host peridotite. Yet, salient melt migration structures frozen at an early stage of development in the mantle section of the Trinity ophiolite reveal that lithological heterogeneities drastically impact melt trajectories. Where melts reach a pyroxenite layer, dissolution-induced permeability abruptly increases, initiating a feedback loop confining melt migration to that layer regardless of its orientation relative to the stress field. This process results in the development of a network of interweaved dunitic channels evolving to thick tabular dunites where the melt reacts with closely spaced pyroxenite layers. This reacting melt was rich in alkali elements and water, as evidenced by the minerals (mostly amphibole and micas) encapsulated in the Cr-spinel grains that crystallized during the reaction. This “pioneer melt” differs from the volumetrically dominant depleted andesite that fed the crustal section. In fact, the migration of andesite benefited from the enhanced permeability provided by the dunites formed by the pioneer melt. As a result, dunites are palimpsests, the compositions of which record successive percolation events. The geometry of the melt pathways is extremely challenging to model because the abundance, spacing, and orientation of lithological heterogeneities cannot be predicted, being inherited from a long geological history.

中文翻译：

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将地幔中的熔体轨迹与应力场和岩性非均质性联系起来的罗塞塔石碑（加利福尼亚州三一蛇绿岩）

由辉石的选择性溶解引发的渗透是地幔中熔体迁移的主要方式。实验和数值模型支持的一个普遍观点是，熔体管道系统的几何形状受主橄榄岩固态流动引起的应力场的支配。然而，在 Trinity 蛇绿岩地幔部分发育早期冻结的显着熔体迁移结构表明，岩性非均质性极大地影响了熔体轨迹。当熔体到达辉石岩层时，溶解引起的渗透率突然增加，启动了一个反馈回路，将熔体迁移到该层，而不管其相对于应力场的方向如何。这一过程导致交织的砂岩通道网络发展成厚板状砂岩，其中熔体与紧密间隔的辉石岩层发生反应。这种反应熔体富含碱金属元素和水，包裹在反应过程中结晶的 Cr-尖晶石晶粒中的矿物质（主要是闪石和云母）就证明了这一点。这种“先驱熔体”不同于供给地壳部分的体积占优势的枯竭安山岩。事实上，安山岩的迁移得益于先锋熔体形成的沙丘岩提供的增强渗透性。因此，沙丘是重印本，其组成记录了连续的渗透事件。熔体通道的几何形状对建模极具挑战性，因为丰度、间距、