Pseudotachylyte are solidified melts that form from frictional heating on a fault plane during earthquakes and play an important role in the mechanism of faulting. Pseudotachylytes interact with mineralizing fluids and their textures are altered over long periods of time; consequently, determining seismic parameters by characterizing pseudotachylytes in the field remains challenging. In this study, we performed heating experiments on faulted pseudotachylyte-bearing cataclasites recovered from the Wenchuan Earthquake Fault Scientific Drilling Project-2 (WFSD-2) to constrain the formation of temperatures and microstructural evolution of the pseudotachylytes. These experiments revealed that melting occurred at 1100 °C, while microlites formed at 1100 °C and disappeared at 1500 °C, and metallic iron spherulites formed at 1300 °C. Fractures and cracks occurred in the pseudotachylytes after rapid cooling, implying an increase in pore volume that allowed for fluid infiltration and subsequent alteration. Because natural pseudotachylyte of the WFSD-2 shows the lack of microlite and the presence of metallic iron spherulites, our results imply that its formation was at temperature of 1300–1500 °C under water-deficient conditions.

Pseudotachylyte 是凝固的熔体，由地震期间断层面上的摩擦加热形成，在断层作用机制中起着重要作用。Pseudotachylytes 与矿化流体相互作用，它们的质地会随着时间的推移而改变；因此，通过表征现场拟速溶物来确定地震参数仍然具有挑战性。在这项研究中，我们对从汶川地震断层科学钻探 2 号项目 (WFSD-2) 回收的含有断层拟速裂石的碎裂岩进行了加热实验，以限制拟速裂石的温度形成和微观结构演化。这些实验表明，熔化发生在 1100°C，而微晶在 1100°C 形成并在 1500°C 消失，金属铁球晶在 1300°C 形成。快速冷却后假速溶物中出现断裂和裂缝，这意味着孔隙体积增加，允许流体渗入和随后的改变。由于 WFSD-2 的天然假晶石显示缺乏微晶石和金属铁球晶的存在，我们的结果表明它的形成是在缺水条件下 1300-1500°C 的温度下形成的。