The heterogeneous mineralogical compositions of fault gouges, formed during fault evolution, influence frictional properties and slip behaviour. While the influence of individual mineral phases on friction has been extensively studied, the impact of varying systematically mineral phases in gouge mixtures on macroscopic frictional behaviour remains unclear. Thus, we performed 34 frictional experiments on fault gouges composed of three representative mineral phases: muscovite (platy phyllosilicate), quartz (granular silicate) and calcite (granular carbonate), known for their markedly distinct frictional properties. Using a biaxial rock deformation apparatus (BRAVA), we performed tests on fault gouges with grain sizes <125 μm under normal stresses of 50–100 MPa, at room temperature and water-saturated conditions. Our data indicate that the mineralogical composition of fault gouges significantly affects frictional strength, healing, and stability with a non-trivial pattern. Increasing the muscovite content leads to a decrease in frictional strength, from 0.62 for pure calcite and 0.56 for pure quartz to 0.33 of pure muscovite, along with reduced frictional healing and a velocity-strengthening behaviour. This weakening is promoted by a transition from localized deformation along discrete shear planes in granular-rich fault gouges to distributed deformation within the entire gouge layer with increasing muscovite content. At fixed muscovite content, frictional properties depend on the dominant granular phase. Calcite-dominated mixtures exhibit more marked frictional weakening rather than quartz-dominated ones, suggesting a non-linear mixing law between friction coefficient and muscovite content. This different trend is likely due to favourable conditions for fluid-assisted pressure-solution of calcite and foliation development, unlike quartz. When only the granular phases are mixed, we observe complex behaviour with the indentation of quartz into calcite, resulting in higher values of healing rates than those of pure end-member mixtures.

中文翻译：

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非均质矿物学组成和断层行为：三元断层岩石成分的系统研究


断层凿孔在断层演化过程中形成的异质矿物学成分会影响摩擦特性和滑移行为。虽然已经广泛研究了单个矿物相对摩擦的影响，但气刨混合物中系统性变化的矿物相对宏观摩擦行为的影响仍不清楚。因此，我们对由三种代表性矿物相组成的断层凿孔进行了 34 次摩擦实验：白云母（片状层状硅酸盐）、石英（颗粒硅酸盐）和方解石（颗粒碳酸盐），它们以其明显不同的摩擦特性而闻名。使用双轴岩石变形仪 （BRAVA），我们在 50-100 MPa 的法向应力下，在室温和水饱和条件下对晶粒尺寸为 <125 μm 的断层凿槽进行了测试。我们的数据表明，断层凿孔的矿物学成分会显著影响摩擦强度、愈合和稳定性，并具有非平凡的模式。增加白云母含量会导致摩擦强度降低，从纯方解石的 0.62 和纯石英的 0.56 降低到纯白云母的 0.33，同时减少摩擦愈合和速度增强行为。这种弱化是通过从富含颗粒的断层凿槽中沿离散剪切平面的局部变形转变为随着白云母含量的增加而在整个凿孔层内的分布式变形而促进的。在固定的白云母含量下，摩擦特性取决于主要颗粒相。与以石英为主的混合物相比，以方解石为主的混合物表现出更明显的摩擦减弱，这表明摩擦系数和白云母含量之间存在非线性混合定律。 与石英不同，这种不同的趋势可能是由于方解石的流体辅助压力固溶和叶状发展的有利条件。当仅混合颗粒相时，我们观察到石英压痕到方解石中的复杂行为，导致愈合速率值高于纯端元混合物。