Abstract Continental flood basalts are currently considered as unconventional CO2 storage reservoirs given several knowledge gaps remain. This study addresses the question whether subvertical fractures and joints in the storage complex and its overburden may lead to long-term CO2 leakage or whether commencement of self-sealing can be expected at an early stage of geochemical reactions. The latter occurs when mineral precipitation outcompetes mineral dissolution. The nature of secondary mineral precipitation and the change of ion concentrations over time were studied in a batch reactor experiment where basalt wafers with a low surface area were exposed to CO2-saturated formation water at a pressure of 80 bars and 60 °C. Primarily stilbite (a zeolite) and montmorillionite (a smectite) were observed in suspension and kaolinite, Fe-oxide and Na-nontronite were additionally identified as authigenic minerals on the surface of the basalt wafers at the end of the incubation. These observations are in agreement with the state of mineral saturation based on the water composition throughout the incubation. Carbonate minerals were undersaturated throughout the incubation suggesting limited carbon mineral trapping capacity under the given conditions. A mineral nucleation phase (day 1 to 6) dominated by cation release due to dissolution and a mineral growth phase (day 8 to 44) dominated by cation uptake due to precipitation were identified. The latter resulted in the formation of considerable mineral mass, which was deposited almost completely on the wafer surface.

中文翻译：

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矿物溶解和沉淀反应及其受矿物表面积控制的净平衡：大陆溢流玄武岩与 CO2 饱和水在 80 bar 和 60 °C 之间相互作用的实验研究

摘要 大陆溢流玄武岩目前被认为是非常规 CO2 储存库，因为仍然存在一些知识空白。这项研究解决了储存综合体及其覆盖层中的近垂直裂缝和接头是否会导致长期 CO2 泄漏或是否可以预期在地球化学反应的早期阶段开始自密封的问题。后者发生在矿物沉淀胜过矿物溶解时。在间歇反应器实验中研究了次生矿物沉淀的性质和离子浓度随时间的变化，其中具有低表面积的玄武岩晶片在 80 巴和 60 °C 的压力下暴露于 CO2 饱和的地层水中。主要在悬浮液和高岭石中观察到辉沸石（一种沸石）和蒙脱石（一种蒙脱石），Fe-氧化物和 Na-nontronite 在孵化结束时被另外鉴定为玄武岩晶片表面上的自生矿物。这些观察结果与基于整个孵化过程中的水组成的矿物质饱和状态一致。在整个孵化过程中碳酸盐矿物不饱和，表明在给定条件下碳矿物的捕获能力有限。确定了矿物成核阶段（第 1 天至第 6 天）由溶解引起的阳离子释放主导，矿物生长阶段（第 8 天至第 44 天）由沉淀引起的阳离子吸收主导。后者导致形成相当多的矿物质，其几乎完全沉积在晶片表面上。