An outcrop in the layered gabbro section from the Wadi Wariyah of the Oman ophiolite has been investigated to provide new insights into the hydrothermal activities that cover a large temperature range in the lower crust at fast-spreading mid-ocean ridges. Our observations reveal a complex veining system composed of gabbroic dikes, hydrous mineral (amphibole, epidote, and prehnite) veins and associated alteration, which strongly overprinted the layered gabbros shortly after the solidification of the gabbroic cumulates. The general strike of the veins is roughly perpendicular to the magmatic foliation of the layered gabbro. Mineral-based geothermometry indicates a wide temperature range (ca. 1,000−250°C) of hydrothermal activities, spanning from hydrous suprasolidus stage (VHT) through amphibolite facies (HT) and epidote-amphibolite facies (MT) down to the prehnite-pumpellyite facies (LT), which induced significant differences in selective element depletion and enrichment as well as in exchange of Sr and O isotopes. A key observation is the omnipresence of relics from a previous temperature stage in a given hydrothermal paragenesis formed at lower temperatures, implying that the same pathways were used for hydrothermal veining in a broad temperature interval spanning about 750°C. Our observations support a model that focused fluid circulations, in the form of combined microcracking (grain boundary spacing) and macrocracking (veining), developed shortly subsequent to the complete solidification of the layered gabbros, which may have facilitated effective cooling for magma crystallization in the lower crust.

中文翻译：

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阿曼蛇绿岩层状辉长岩中的多级热液脉：对下大洋地壳集中流体循环的影响

对阿曼蛇绿岩 Wadi Wariyah 层状辉长岩剖面的露头进行了调查，以提供对覆盖快速扩张的大洋中脊下地壳大温度范围的热液活动的新见解。我们的观察揭示了一个由辉长岩脉、含水矿物（角闪石、绿帘石和孕长岩）脉和相关蚀变组成的复杂脉络系统，在辉长岩堆积物凝固后不久强烈叠印了层状辉长岩。脉的总体走向大致垂直于层状辉长岩的岩浆叶理。基于矿物的地温测量表明热液活动的温度范围很广（约 1,000-250°C），从含水上固体阶段 (VHT) 到角闪岩相 (HT) 和绿帘石-角闪岩相 (MT) 再到早长岩-菱镁岩相 (LT)，这导致了选择性元素消耗和富集以及 Sr 交换的显着差异和 O 同位素。一个关键的观察结果是，在较低温度下形成的给定热液共生作用中，前一温度阶段的遗迹无处不在，这意味着相同的途径用于在大约 750°C 的宽温度区间内进行热液脉络。我们的观察结果支持了一个模型，该模型以组合微裂纹（晶界间距）和宏观裂纹（脉纹）的形式集中流体循环，在层状辉长岩完全凝固后不久发展起来，