The mechanisms of fluid penetration through the gabbroic lower crust are important for the hydration of oceanic lithosphere. In the Oman ophiolite, which preserves an entire sequence of oceanic lithosphere formed at a fast‐spreading ridge, the layered gabbros and dunites are extensively serpentinized. In this paper, we describe the characteristic textures of serpentinized troctolite and olivine gabbros recovered from the CM1A site of the Oman Drilling Project. In the troctolite, an olivine mesh texture is pervasively developed and is characterized by two types of veins: early lizardite + brucite + magnetite and late Al‐rich lizardite + magnetite. These veins suggest the initiation of serpentinization at <350°C and a supply of Si and Al from plagioclase during the later stages of serpentinization. Plagioclase surrounding serpentinized olivine grains commonly shows radial fracturing. Numerical simulations using the discrete element method applied to coupled fluid flow, reaction, and fracturing reveal that volume expansion of olivine grains during serpentinization results in the simultaneous fracturing of olivine and surrounding plagioclase, and that the thermal stress during cooling of oceanic lithosphere might also cause preferential olivine fracturing prior to serpentinization. The simulations also predict a self‐organizing fracture network that connects the olivine grains and passes through both olivine‐rich and olivine‐poor layers, resulting in permeability enhancement during serpentinization. Our results suggest that reaction‐induced fracturing plays an essential role in the infiltration of seawater through the lower crust and into the mantle within oceanic lithosphere.

中文翻译：

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反应引起的压裂响应流体通过大洋下地壳渗透：蛇纹化斜方晶石和数值模型的见解

流体穿过辉长岩下地壳的渗透机制对于海洋岩石圈的水合作用很重要。在阿曼蛇绿岩中，它保留了在快速扩张的山脊上形成的整个海洋岩石圈序列，层状辉长岩和杜尼岩广泛蛇纹石化。在本文中，我们描述了从阿曼钻探项目CM1A站点中回收的蛇纹石化的滑石和橄榄石的特征纹理。在斜方岩中，橄榄石网状结构普遍形成，其特征在于两种类型的脉：早蜥蜴石+水镁石+磁铁矿和晚富铝蜥蜴石+磁铁矿。这些静脉表明，在蛇纹石化的后期，温度<350°C时开始蛇纹石化，并从斜长石中供应硅和铝。蛇纹石化的橄榄石晶粒周围的斜长石通常显示出放射状裂缝。使用离散元方法对流体流动，反应和破裂进行耦合的数值模拟显示，蛇纹石化过程中橄榄石颗粒的体积膨胀导致橄榄石和周围斜长石同时破裂，并且在海洋岩石圈冷却期间的热应力也可能导致蛇纹石化之前优先进行橄榄石压裂。模拟还预测了连接橄榄石颗粒并穿过富橄榄石层和贫橄榄石层的自组织裂缝网络，从而在蛇纹石化过程中增强了渗透性。