Highly saline lithium-rich hydrothermal fluids (measured chloride concentration up to 44 g kg−1, lithium concentration up to 162 mg kg−1) occur in the deep calcareous Muschelkalk aquifer beneath the northern Alpine foreland (Molasse) basin. We have combined geologic, hydraulic, hydrochemical, and stress field data of the Triassic Muschelkalk aquifer beneath younger sediments of Triassic–Jurassic successions and the Cenozoic Molasse basin of SW-Germany for a synthesis to constrain the origin and development of these brines. In contrast to the regional southeast plunge of Jurassic and Cenozoic strata, low-gradient groundwater flow in the Upper Muschelkalk aquifer is to the north, induced by regional recharge from west, south, and east. The investigated area is seismically active and north trending maximum horizontal stress likely fosters development of necessary fracture permeability for northward flow in the competent carbonates of the Upper Muschelkalk aquifer. The highest lithium concentrations and total dissolved solids (TDS) can be found in the southern parts of the Muschelkalk aquifer. Here, the Muschelkalk Group overlays directly a crystalline basement swell separating two ENE-trending Permocarboniferous troughs. We argue that the highly saline lithium-rich fluids originate from fluid–rock interaction of meteoric water with Variscan crystalline basement rocks and entered the Muschelkalk aquifer on top of the basement swell by permeable faults and fractures. The marginal calcareous sand-rich facies of the Muschelkalk enables the inflow of brines from crystalline basement faults and fractures into the aquifer. We thus argue for an external origin of these brines into the aquifer and further intra-reservoir development by dilution with meteoric water.

中文翻译：

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德国西南部莫拉斯盆地的 Muschelkalk 含水层：对钙质热液储层中高盐度富锂卤水的起源和发育的影响

高盐度富锂热液（测得氯化物浓度高达 44 g kg−1，锂浓度高达 162 mg kg−1）存在于北部高山前陆（莫拉塞）盆地下方的深层钙质 Muschelkalk 含水层中。我们结合了三叠纪-侏罗纪系列较年轻沉积物下方的三叠纪 Muschelkalk 含水层和德国西南部新生代莫拉斯盆地的地质、水力、水化学和应力场数据，进行综合，以限制这些卤水的起源和发育。与侏罗系和新生代地层的区域性东南倾降相反，上Muschelkalk含水层的低梯度地下水流向北流动，这是由西、南、东区域补给引起的。调查区域地震活跃，北向最大水平应力可能促进上 Muschelkalk 含水层有效碳酸盐岩向北流动所需的裂缝渗透性的发展。Muschelkalk 含水层的南部地区锂浓度和总溶解固体 (TDS) 最高。在这里，Muschelkalk 群直接覆盖在结晶基底隆起之上，该隆起将两个 ENE 走向的二叠石炭系海槽分开。我们认为，高盐度富锂流体源自大气水与瓦里斯结晶基底岩石的流体-岩石相互作用，并通过渗透性断层和裂缝进入基底膨胀顶部的 Muschelkalk 含水层。Muschelkalk 的边缘富含钙质砂岩相使盐水能够从结晶基底断层和裂缝流入含水层。因此，我们认为这些盐水是从外部进入含水层的，并通过大气水稀释进一步在储层内开发。