The evolution of hyperextended rift systems is linked to complex tectonic processes in which fluid activity is much more important than previously thought. This study sheds light on the fluid-sediment interactions within the distalmost parts of the Mauléon-Arzacq hyperextended basin (Western Pyrenees) focusing on the post-depositional modifications of pre- to syn-hyperextension sediments due to hydrothermal fluids. Strong field- and petrography-based evidence demonstrates the presence of fluid-related products affecting the Jurassic to Cretaceous sediments exposed in the Chaînons Béarnais (easternmost Mauléon basin). These are supported by new U–Pb dating of carbonates and microthermometry of fluid inclusions showing temperatures of up to 250 °C and highly depleted δ¹⁸O and strongly enriched ⁸⁷Sr/⁸⁶Sr values. Two main stages of fluid activity can be defined: (i) a carbonate-rich stage leading to fabric-destructive replacement dolomitization of the pre-rift carbonates, widespread hydro-fracturation giving rise to different types of hydraulic breccias cemented by multi-phase dolomite and calcite dated at ~ 96 Ma; and (ii) a Na-SiO₂-rich stage associated with authigenic albite and quartz, mainly affecting syn-rift deposits. Finally, the occurrence of dolomitic marbles and mylonites provide evidence for strong recrystallization and ductile shearing affecting the sediments during the latest stages of hyperextension at ~ 94 Ma. The Chaînons Béarnais represent a primary target to investigate fluid-rock interactions linked to extensional tectonics that can be used as an analogue to compare to other fossil rift systems (e.g. Adriatic paleo-rifted margin) or present-day magma-poor, hyperextended rifted margins (e.g. Iberia-Newfoundland).

超伸展裂谷系统的演化与复杂的构造过程有关，在该过程中流体活动比以前认为的重要得多。这项研究揭示了Mauléon-Arzacq超伸展盆地（西比利牛斯）最远端区域内的流体-沉积物相互作用，重点研究了由于热液引起的沉积物到超伸展前沉积物的沉积后变质。基于野外和岩相学的有力证据表明，与流体有关的产物的存在影响了ChaînonsBéarnais（最东端的莫伦盆地）暴露于侏罗纪至白垩纪的沉积物。这些是由碳酸盐和流体夹杂物示出高达250℃的温度的测温的新U-Pb定支承和高度耗尽δ ¹⁸ O和强烈富集⁸⁷Sr / ⁸⁶ Sr值。可以定义流体活动的两个主要阶段：（i）富含碳酸盐的阶段导致对织物的破坏性置换，使前裂谷碳酸盐白云石化，广泛的水力压裂产生了由多相白云石胶结的不同类型的水力角砾岩。方解石的日期约为〜96 Ma；（ii）Na-SiO ₂自生钠长石和石英相关的富集阶段，主要影响同裂谷沉积。最后，白云岩大理石和mylonite的存在提供了证据，表明在〜94 Ma的超伸最新阶段中，强烈的重结晶和韧性剪切作用会影响沉积物。ChaînonsBéarnais是研究与伸展构造相关的流体-岩石相互作用的主要目标，伸展构造可以用作与其他化石裂谷系统（例如亚得里亚古裂谷边缘）或当今岩浆贫瘠，超扩展裂谷边缘的比较（例如伊比利亚-纽芬兰）。