The architecture and pressure-temperature conditions reached by a Cretaceous block-in-matrix serpentinite mélange exposed in the Zagros suture resemble those imaged in the active Mariana subduction zone. There, large magnitude-earthquakes (M${}_{\mathrm{w}}>9$) have never been recorded but smaller events – of poorly-constrained physical origin – in the range M${}_{\mathrm{w}}\sim$3-6 are widespread. Field and petro-structural constraints led to a first report of blueschist-facies seismic fault-related rocks in the Zagros serpentinite melange, including breccias, foliated cataclasites and ultracataclasites; all observed within a foliated mafic metatuffaceous block embedded in serpentinite schists. Fine-scale petrological characterization of ultrafine-grained, fluidized cataclastic material reveals the presence of newly-formed glaucophane, lawsonite, phengite, albite and pumpellyite, an assemblage inferred (based on thermodynamic modelling) to have crystallized in the lower lawsonite-blueschist facies at ∼0.6-1.0 GPa and 230-300 °C. Extensional veins containing similar mineral assemblages are observed crosscutting the aforementioned rocks but are also identified as comminuted fragments in all fault-related lithologies. Crosscutting relationships among the multiple generations of fluidized ultracataclasites and brecciated blueschists suggest that episodic faulting and hydrofracturing were contemporaneous processes at ∼20-35 km depth, i.e., at similar conditions as reported for metabasalts expelled by Mariana serpentinite mud volcanoes. Mechanical modelling confirms that the studied fault-related features can only have formed under nearly lithostatic pore fluid pressure conditions, maintaining the system in a critically unstable regime that promoted recurrent seismic faulting, as monitored in the Mariana seismogenic zone. These fluids are likely associated with externally and deeply-generated fluid pulses that may have reached the seismogenic window, imprinting a Ta-Th-Nb-HREEs-enriched trace element signature. This new faulted blueschist occurrence highlights the physical nature and the mechanical processes operating within fluid-saturated fault zones in the serpentinized subduction channel.

暴露在 Zagros 缝合线中的白垩纪块状蛇纹岩混杂岩所达到的结构和压力-温度条件类似于活跃的马里亚纳俯冲带中成像的那些条件。在那里，大地震（M${}_{\mathrm{瓦}}>9$) 从未被记录过，但较小的事件——物理起源较差——在 M 范围内${}_{\mathrm{瓦}}～$3-6 很普遍。现场和岩石结构的限制导致了 Zagros 蛇纹岩混杂岩中蓝片岩相地震断层相关岩石的首次报告，包括角砾岩、叶状碎裂岩和超碎裂岩；所有这些都在嵌入蛇纹岩片岩中的叶状镁铁质变凝灰质块中观察到。超细粒流化碎裂材料的精细岩石学特征揭示了新形成的蓝闪石、硬柱石、菱镁矿、钠长石和抽水镁石的存在，推测（基于热力学模型）在下层硬柱石-蓝片岩相中结晶的组合∼0.6-1.0 GPa 和 230-300 ℃。观察到包含类似矿物组合的伸展脉横切上述岩石，但在所有断层相关岩性中也被确定为粉碎的碎片。多代流化超碎裂岩和角砾化蓝片岩之间的交叉关系表明，幕式断层作用和水力压裂在约 20-35 公里深度是同时发生的过程，即与马里亚纳蛇纹岩泥火山喷出的变玄武岩报告的条件相似。力学模型证实，所研究的断层相关特征只能在近乎岩性孔隙流体压力条件下形成，使系统保持在极不稳定的状态，从而促进了反复发生的地震断层，如马里亚纳地震带所监测的那样。这些流体很可能与外部和深层产生的流体脉冲有关，这些脉冲可能已经到达了地震发生窗口，留下了富含 Ta-Th-Nb-HREE 的微量元素特征。这个新的断层蓝片岩事件突出了在蛇纹石化俯冲通道中流体饱和断层带内运行的物理性质和机械过程。