The seismic potential of faults depends on the local mineralogy and can change upon mineral reactions. We conducted friction experiments on serpentinite, carbonate and carbonated serpentinite fault gouges at temperatures from 400°C to 630°C, under 100 MPa effective normal stress and fluid saturated conditions. Pure serpentinite fault gouges exhibited unstable slip with significant strain-hardening. Carbonate-bearing serpentinite fault gouges showed stable sliding at temperatures <500°C, but displayed unstable stick-slip behavior and strong strain weakening at temperatures ≥500°C. Microstructural analyses revealed localization and the formation of olivine and pyroxene from devolatilization reactions at temperatures ≥500°C. The degree of devolatilization increased near major slip planes and was enhanced by higher temperature and carbonate content, as shown by three-dimensional micro-computer tomography analyses. Nano-scale transmission electron microscopy analyses revealed the absence of hydrous and carbonate phases along major slip planes. We attribute the strong weakening and unstable slip behavior in carbonated serpentinite fault gouges to the formation of nano-sized anhydrous phases of olivine and pyroxene along the slip plane. Our results indicate that serpentinized fault zones may experience seismic event nucleation at temperatures approaching the thermodynamic stability limit of serpentine. This suggests that the absence of seismic events cannot exclusively be attributed to serpentinization. The formation of carbonates, through replacive and additive carbonation, can explain aseismic deformation in transform faults, but at elevated temperatures, devolatilization reactions in carbonated serpentinites cause strong localization and strain weakening, accompanied by laboratory seismicity.

中文翻译：

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反应诱导的（碳酸盐）蛇纹石断层凿子弱化的实验证据


断层的地震潜力取决于当地的矿物学，并可能随着矿物反应而改变。我们在 400°C 至 630°C 的温度下，在 100 MPa 的有效法向应力和流体饱和条件下，对蛇纹岩、碳酸盐岩和碳酸盐蛇纹岩断层凿孔进行了摩擦实验。纯蛇纹岩断层凿槽表现出不稳定的滑移，伴有明显的应变硬化。含碳酸盐的蛇纹岩断层凿槽在 <500°C 的温度下表现出稳定的滑动，但在 ≥500°C 的温度下表现出不稳定的粘滑行为和强烈的应变减弱。 微观结构分析揭示了在 ≥500°C 温度下脱挥反应的定位以及橄榄石和辉石的形成。 如三维微计算机断层扫描分析所示，在主要滑移面附近脱挥程度增加，并且随着温度和碳酸盐含量的增加而增强。纳米级透射电子显微镜分析显示，沿主要滑移面不存在含水相和碳酸盐相。我们将碳酸盐蛇纹岩断层凿孔中的强弱化和不稳定滑移行为归因于沿滑移面形成纳米级橄榄石和辉石无水相。我们的结果表明，蛇纹岩断层带在接近蛇纹岩热力学稳定性极限的温度下可能会经历地震事件成核。这表明地震事件的缺失不能完全归因于蛇纹石化。 碳酸盐岩通过替换和加性碳化形成可以解释转换断层中的地震变形，但在高温下，碳酸盐蛇纹岩中的脱挥反应会导致强烈的局部化和应变减弱，并伴有室内地震活动。