Dziadkowiec Joanna, Zareeipolgardani Bahareh, Dysthe Dag Kristian, Røyne Anja
The NJORD Centre, Physics of Geological Processes (PGP), Department of Physics, University of Oslo, Oslo, 0371, Norway.
Institut Lumière Matière, Université de Lyon, Université Claude Bernard Lyon 1, CNRS UMR 5586, Campus de la Doua, F-69622, Villeurbanne, cedex, France.
Sci Rep. 2019 Jun 20;9(1):8948. doi: 10.1038/s41598-019-45163-6.
Fluid-induced alteration of rocks and mineral-based materials often starts at confined mineral interfaces where nm-thick water films can persist even at high overburden pressures and at low vapor pressures. These films enable transport of reactants and affect forces acting between mineral surfaces. However, the feedback between the surface forces and reactivity of confined solids is not fully understood. We used the surface forces apparatus (SFA) to follow surface reactivity in confinement and measure nm-range forces between two rough calcite surfaces in NaCl, CaCl, or MgCl solutions with ionic strength of 0.01, 0.1 or 1 M. We observed long-range repulsion that could not be explained by changes in calcite surface roughness, surface damage, or by electrostatic or hydration repulsion, but was correlated with precipitation events which started at µm-thick separations. We observed a submicron-sized precipitate that formed in the confined solution. This liquid-like viscous precipitate did not undergo any spontaneous ripening into larger crystals, which suggested that confinement prevented its dehydration. Nucleation was significantly postponed in the presence of Mg. The long-range repulsion generated by nucleation between confined mineral surfaces can have a crucial influence on evolution of the microstructure and therefore the macroscopic strength of rocks and materials.
流体引起的岩石和矿物基材料的变化通常始于受限的矿物界面，在这些界面处，即使在高覆盖压力和低蒸气压下，纳米厚的水膜也能持续存在。这些水膜促进反应物的传输，并影响矿物表面之间作用的力。然而，受限固体的表面力与反应性之间的反馈尚未完全理解。我们使用表面力仪（SFA）来跟踪受限环境中的表面反应性，并测量在离子强度为0.01、0.1或1 M的NaCl、CaCl或MgCl溶液中两个粗糙方解石表面之间的纳米级力。我们观察到一种长程排斥力，这种排斥力无法用方解石表面粗糙度、表面损伤的变化，或静电或水化排斥来解释，但与始于微米级间距的沉淀事件相关。我们观察到在受限溶液中形成了亚微米级的沉淀物。这种类似液体的粘性沉淀物没有自发地熟化成更大的晶体，这表明受限环境阻止了它的脱水。在镁存在的情况下，成核明显延迟。受限矿物表面之间成核产生的长程排斥力可能对微观结构的演化以及岩石和材料的宏观强度产生至关重要的影响。
