Numerous mud volcanoes (MVs) are scattered through the Gulf of Cadiz (GoC), most of which are situated close to the WNW-ESE trending fault system in this region. In this study we have investigated six MVs in locations adjacent to major tectonic lineaments with the purpose of defining fluid and solid mobilization depth and ascent through the accretionary prism. Three of them, R2, D2 and Funky Monkey MVs, were discovered during RV Meteor cruise M149 in 2018. Their morphologies were characterized by multibeam bathymetry and vary from flat-topped to cone-shaped, reflecting different nature of the emitted products and variable degrees of activity. Mud breccias and pore fluids were sampled at the summits of all MVs to determine their physical properties and composition of the solid and liquid fractions. The physical properties and lithological changes demonstrate recent activity of Yuma, Ginsburg, Meknes and Funky Monkey MVs. At these sites, we traced back the origin of venting fluids to clay mineral dehydration through major and minor elements geochemistry, high content of illite in the mud breccia matrix and calculated reaction temperatures of 60–100 °C using the Mg–Li geothermometer. Differences in fluid composition imply a dominant clay dehydration signal in the shallow MVs and a stronger crustal input in the deeper MV (Funky Monkey). In contrast, R2 and D2 MVs are textbook inactive mud domes, showing no venting and a chemical composition/reaction temperature similar to seawater. If crustal input in MVs fluids will be confirmed by subsequent studies (e.g., through Sr isotopes), this could lead to a rethinking of fluid migration in the GoC, where transform faults (and MVs located close to them) focus the crustal signal from depth. Based on the MVs active state and the geochemistry of the fluids, we can distinguish which structure would be more suitable for further analyses (B isotopes, illite crystallinity) in order to identify possible sources of hydrocarbon-rich fluids channeled through MVs.

许多泥火山 (MV) 散布在加的斯湾 (GoC) 中，其中大部分位于该地区的 WNW-ESE 走向断层系统附近。在这项研究中，我们调查了与主要构造线相邻位置的六个 MV，目的是定义流体和固体的流动深度以及通过增生棱柱的上升。其中三个，R2，D2和Funky Monkey MVs，是在2018年RV Meteor Cruise M149期间发现的。它们的形态以多波束测深为特征，从平顶到锥形不等，反映了发射产物的不同性质和不同程度的活动。在所有 MV 的顶部对泥角砾岩和孔隙流体进行采样，以确定它们的物理性质和固体和液体部分的组成。物理性质和岩性变化表明 Yuma、Ginsburg、Meknes 和 Funky Monkey MV 的近期活动。在这些地点，我们通过主要和次要元素地球化学、泥角砾岩基质中伊利石的高含量以及使用 Mg-Li 地温计计算的 60-100 °C 反应温度，将排放流体的起源追溯到粘土矿物脱水。流体成分的差异意味着浅层 MV 中主要的粘土脱水信号和较深 MV（Funky Monkey）中更强的地壳输入。相比之下，R2 和 D2 MV 是教科书式的非活性泥浆穹顶，没有排气，化学成分/反应温度与海水相似。如果 MVs 流体中的地壳输入将被后续研究证实（例如，通过 Sr 同位素），这可能会导致重新思考 GoC 中的流体迁移，其中变换断层（和位于它们附近的 MV）从深处聚焦地壳信号。根据 MV 的活动状态和流体的地球化学，我们可以区分哪种结构更适合进一步分析（B 同位素、伊利石结晶度），以确定通过 MV 引导的富烃流体的可能来源。