Chogani Alireza, King Helen E, Tutolo Benjamin, Živković Aleksandar, Plümper Oliver
Department of Earth Sciences, Utrecht University, Utrecht, the Netherlands.
Department of Earth, Energy, and Environment, University of Calgary, Calgary, Alberta Canada.
Nat Geosci. 2025;18(2):191-196. doi: 10.1038/s41561-024-01629-5. Epub 2025 Feb 10.
Water is a principal component of Earth's fluids, and its interaction with rocks governs lithospheric geochemical and geodynamic processes. Water-rock interactions are crucial in societally relevant resource management, including subsurface extraction and storage of energy, the deep carbon cycle and generating critical metal deposits. The prevailing view is that fluids navigate through the lithosphere without being influenced by the distinct properties that arise from matter confined at the nanoscale. Here we use electron microscopy and neutron scattering data to show that a diverse range of lithospheric rocks, including sandstones, peridotites and serpentinites, consistently show nanoporosity, predominantly with pore sizes < 100 nanometres. Using molecular dynamics simulations, we demonstrate that water's dielectric permittivity-a fundamental property that governs its geochemical behaviour-diverges in nanoconfinement from its bulk counterpart under conditions ranging from ambient to extremes of 700 °C and 5 GPa. Our geochemical simulations suggest that changes in water permittivity due to confinement will decrease mineral solubility, a process that is not currently considered in models of fluid-rock interactions. Given that permittivity is also intimately linked to ion speciation, pore-size-dependent properties should be expected to exert a primary influence on rock reactivity and the geochemical evolution of fluids during fluid-rock interactions.
水是地球流体的主要成分，它与岩石的相互作用控制着岩石圈的地球化学和地球动力学过程。水 - 岩相互作用在与社会相关的资源管理中至关重要，包括地下能源开采与储存、深部碳循环以及关键金属矿床的形成。普遍观点认为，流体在岩石圈中流动时不会受到纳米尺度物质所产生的独特性质的影响。在此，我们利用电子显微镜和中子散射数据表明，包括砂岩、橄榄岩和蛇纹岩在内的多种岩石圈岩石始终呈现纳米孔隙率，主要孔径小于100纳米。通过分子动力学模拟，我们证明，在从环境条件到700°C和5 GPa极端条件的范围内，水的介电常数（一种控制其地球化学行为的基本性质）在纳米限域中与其本体状态不同。我们的地球化学模拟表明，限域导致的水介电常数变化将降低矿物溶解度，这一过程目前在流体 - 岩相互作用模型中尚未被考虑。鉴于介电常数也与离子形态密切相关，预计孔径依赖性性质将对流体 - 岩相互作用期间的岩石反应性和流体地球化学演化产生主要影响。
