Abstract. Phyllosilicates are generally regarded to have a reinforcing effect on chemical compaction by dissolution-precipitation creep (DPC) and thereby influence the evolution of hydraulic rock properties relevant to groundwater resources, geological repositories as well as fossil fuel reservoirs. We conducted oedometric compaction experiments on layered NaCl-biotite samples to test this assumption. In particular, we aim to analyse slow chemical compaction processes in the presence of biotite on the grain scale and determine the effects of chemical and mechanical feedbacks. We used time-resolved (4D) microtomographic data to capture the dynamic evolution of the transport properties in layered NaCl-NaCl/biotite samples over 1619 and1932 hours of compaction. Percolation analysis in combination with advanced digital volume correlation techniques showed that biotite grains influence the dynamic evolution of porosity in the sample by promoting a reduction of porosity in their vicinity. However, the lack of preferential strain localisation around phyllosilicates and a homogeneous distribution of axial shortening across the sample suggests that the porosity reduction is not achieved by pore collapse but by the precipitation of NaCl sourced from outside the NaCl/biotite layer. Our observations invite a renewed discussion of the effect of phyllosilicates on DPC, with a particular emphasis on the length scales of the processes involved. We propose that, in our experiments, the diffusive transport processes invoked in classical theoretical models of DPC are superseded by chemo-mechanical feedbacks that arise on longer length scales. These feedbacks drive NaCl diffusion from the marginal pure NaCl layers into the central NaCl-biotite mixture over distances of several hundredμm and several grain diameters. Such a mechanism was first postulated by Merino et al. (1983)

中文翻译：

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黑云母支持岩盐溶解-沉淀蠕变中的长程扩散传输

摘要。通常认为层状硅酸盐通过溶解-沉淀蠕变 (DPC) 对化学压实具有增强作用，从而影响与地下水资源、地质储层和化石燃料储层相关的水力岩性质的演变。我们对分层的 NaCl 黑云母样品进行了 oedometric 压实实验以测试这一假设。特别是，我们的目标是在颗粒尺度上分析存在黑云母的缓慢化学压实过程，并确定化学和机械反馈的影响。我们使用时间分辨 (4D) 显微断层扫描数据来捕获层状 NaCl-NaCl/黑云母样品在 1619 和 1932 小时的压实过程中传输特性的动态演变。渗流分析结合先进的数字体积相关技术表明，黑云母颗粒通过促进其附近孔隙度的降低来影响样品中孔隙度的动态演化。然而，在页硅酸盐周围缺乏优先应变定位以及整个样品的轴向缩短的均匀分布表明孔隙率的降低不是通过孔隙坍塌而是通过来自 NaCl/黑云母层外部的 NaCl 沉淀来实现的。我们的观察引发了对页硅酸盐对 DPC 影响的重新讨论，特别强调了所涉及过程的长度尺度。我们建议，在我们的实验中，在 DPC 的经典理论模型中调用的扩散传输过程被在更长的长度尺度上出现的化学机械反馈所取代。这些反馈驱动 NaCl 从边缘纯 NaCl 层扩散到中央 NaCl-黑云母混合物中，距离为数百微米和几个晶粒直径。Merino 等人首先假设了这种机制。(1983)