Data pertinent to pore-water composition in Opalinus Clay in the Mont Terri and Mont Russelin anticlines have been collected over the last 20 years from long-term in situ pore-water sampling in dedicated boreholes, from laboratory analyses on drillcores and from the geochemical characteristics of vein infills. Together with independent knowledge on regional geology, an attempt is made here to constrain the geochemical evolution of the pore-waters. Following basin inversion and the establishement of continental conditions in the late Cretaceous, the Malm limestones acted as a fresh-water upper boundary leading to progressive out-diffusion of salinity from the originally marine pore-waters of the Jurassic low-permeability sequence. Model calculations suggest that at the end of the Palaeogene, pore-water salinity in Opalinus Clay was about half the original value. In the Chattian/Aquitanian, partial evaporation of sea-water occurred. It is postulated that brines diffused into the underlying sequence over a period of several Myr, resulting in an increase of salinity in Opalinus Clay to levels observed today. This hypothesis is further supported by the isotopic signatures of SO4 2− and 87Sr/86Sr in current pore-waters. These are not simple binary mixtures of sea and meteoric water, but their Cl− and stable water-isotope signatures can be potentially explained by a component of partially evaporated sea-water. After the re-establishment of fresh-water conditions on the surface and the formation of the Jura Fold and Thrust Belt, erosion caused the activation of aquifers embedding the low-permeability sequence, leading to the curved profiles of various pore-water tracers that are observed today. Fluid flow triggered by deformation events during thrusting and folding of the anticlines occurred and is documented by infrequent vein infills in major fault structures. However, this flow was spatially focussed and of limited duration and so did not markedly affect the bulk pore-water.

中文翻译：

---

Mont Terri和Mont Russelin（瑞士汝拉州）Opalinus粘土中的孔隙水演化和溶质运移机制

在过去20年中，通过长期在专用钻孔中进行原位孔隙水采样，对钻芯的实验室分析以及地球化学特征，收集了与Mont Terri和Mont Russelin背斜的Opalinus粘土中的孔隙水成分有关的数据静脉填充物。结合对区域地质的独立知识，这里试图限制孔隙水的地球化学演化。在盆地倒置和白垩纪晚期大陆条件的确立之后，马尔姆石灰石作为淡水的上边界，导致盐度从侏罗纪低渗透率序列的原始海洋孔隙水中逐渐向外扩散。模型计算表明，在古近纪末，Opalinus粘土的孔隙水盐度约为原始值的一半。在查蒂安/阿基坦群岛，发生了部分海水蒸发。据推测，盐水会在数个Myr的时间内扩散到下面的序列中，从而导致Opalinus粘土的盐度增加到今天观察到的水平。当前孔隙水中SO4 2-和87Sr / 86Sr的同位素特征进一步支持了这一假设。这些不是海水和陨石的简单二元混合物，但是它们的Cl-和稳定的水同位素特征可以用部分蒸发的海水的成分来解释。在表层重新建立淡水条件并形成侏罗褶皱和逆冲带之后，侵蚀导致嵌入低渗透序列的含水层被激活，导致今天观察到的各种孔隙水示踪剂的弯曲轮廓。在对角线的推动和折叠过程中，变形事件触发了流体流动，并通过主要断层结构中不频繁的静脉填充来证明。但是，这种流动在空间上是集中的，持续时间有限，因此并未显着影响整体孔隙水。