Serpentinization of ultramafic rocks in the sea and on land leads to the generation of alkaline fluids rich in molecular hydrogen (H2) and methane (CH4) that favour the formation of carbonate mineralization, such as veins in the sub-seafloor, seafloor carbonate chimneys and terrestrial hyperalkaline spring deposits. Examples of this type of seawater–rock interaction and the formation of serpentinization-derived carbonates in a shallow-marine environment are scarce, and almost entirely lacking in the geological record. Here we present evidence for serpentinization-induced fluid seepage in shallow-marine sedimentary rocks from the Upper Cretaceous (upper Campanian to lower Maastrichtian) Qahlah Formation at Jebel Huwayyah, United Arab Emirates. The research object is a metre-scale structure (the Jebel Huwayyah Mound) formed of calcite-cemented sand grains, which formed a positive seafloor feature. The Jebel Huwayyah Mound contains numerous vertically orientated fluid conduits containing two main phases of calcite cement. We use C and O stable isotopes and elemental composition to reconstruct the fluids from which these cements precipitated and infer that the fluids consisted of variable mixtures of seawater and fluids derived from serpentinization of the underlying Semail Ophiolite. Based on their negative δ13C values, hardgrounds in the same section as the Jebel Huwayyah Mound may also have had a similar origin. The Jebel Huwayyah Mound shows that serpentinization of the Semail Ophiolite by seawater occurred very soon after obduction and marine transgression, a process that continued through to the Miocene, and, with interaction of meteoric water, up to the present day.

中文翻译：

---

阿拉伯联合酋长国上白垩统 Qahlah 组浅海蛇纹石化衍生流体渗流

海洋和陆地超镁铁质岩石的蛇纹石化导致产生富含分子氢的碱性流体（H2) 和甲烷 (CH4) 有利于碳酸盐矿化的形成，例如海底矿脉、海底碳酸盐烟囱和陆地高碱泉沉积物。这种海水-岩石相互作用和在浅海环境中形成蛇纹石化碳酸盐的例子很少，而且几乎完全缺乏地质记录。在这里，我们提出了在阿拉伯联合酋长国 Jebel Huwayyah 的上白垩统（上坎帕阶到下马斯特里赫特）Qahlah 组的浅海沉积岩中蛇纹石化引起的流体渗漏的证据。研究对象是由方解石胶结砂粒形成的米级结构（Jebel Huwayyah Mound），形成了正面的海底特征。Jebel Huwayyah Mound 包含许多垂直定向的流体管道，其中包含两种主要的方解石水泥相。我们使用 C 和 O 稳定同位素和元素组成来重建这些胶结物从中沉淀出来的流体，并推断这些流体由海水和来自下面的 Semail 蛇纹岩蛇纹石化的流体的可变混合物组成。基于它们的负 δ13C 值，与 Jebel Huwayyah Mound 位于同一区域的硬地也可能有相似的起源。Jebel Huwayyah Mound 表明，海水对 Semail 蛇绿岩的蛇纹石化发生在俯冲和海侵后不久，这一过程一直持续到中新世，并且与大气水的相互作用一直持续到今天。