## 2 Materials and Methods  
### Samples  
In the Xichang segment of the Anning River fault zone, pseudotachylyte has been found in the pre-Avalonian granite genesis, representing coseismic deformation at the fault source depth during a geological historical period. This study collected a large number of pseudotachyltyte and related tectonic rock samples, which are the main research objects of this study (Figure 1).  
Samples AF19-43A, AF19-43D, AF19-43G, AF19-44A, AF19-44C, and AF21-4 (of which 43D, 43G, and 44C are rolled stone samples, and the rest are in situ samples, as shown in Figures 2 and 3) are mylonite and shattered rock containing pseudotachylyte. These were all collected from the west side of Lizhoushan, Minsheng Township, Changshitou Village, Xichang City, Sichuan Province, with the coordinates N28\({}^{\circ}\)05\({}^{\prime}\)27.94\({}^{\prime\prime}\) E102\({}^{\circ}\)02\({}^{\prime}\)55.71\({}^{\prime\prime}\) (Figures 2 and 3). The elevation is 1725 m.  
Figure 1: Simplified geological map of the sample collection area along the Anning River fault zone. (**A**) Schematic diagram of the Anning River fault zone [40]; (**B**) simplified geological map near Lizhou, where the red line represents the location of the Anning River fault zone and the blue line indicates the position of geological cross-section AB; and (**C**) geological cross-section AB.  
Figure 2: Sections of samples from the sample collection area. (**A**) Schematic diagram of the sampling profile on the south bank of the river at Changshitou Village (AF19-43A to AF21-1); (**B**) schematic diagram of the sampling profile on the south bank of the river at Changshitou Village (AF21-1 to AF21-4).  
The sampling site is located on the southern riverbed of a river channel trending nearly east-west, where the bedrock is composed of early Proterozoic granite genesis. Locally, mylonite or shattered rocks develop, with several branching pseudotachylyte veins along the mylonitrile foliation (Figure 3). The vein widths are approximately 1-2 cm, and they extend in east-west and southwest directions, with traceable widths of about 20-30 m. These veins cut each other, showing features of synchronous activity. The attitudes of the pseudotachylyte veins are \(246^{\circ}<53^{\circ}\), \(260^{\circ}<54^{\circ}\), and \(276^{\circ}<80^{\circ}\). The surrounding mylonitrile foliation in the host rock has an attitude of \(72^{\circ}<80^{\circ}\). A 20 cm wide pegmatie vein is also developed in the host rock (Figure 3), with an attitude of \(310^{\circ}<54^{\circ}\), and pseudotachylyte is observed along the vein, with an attitude of \(302^{\circ}<47^{\circ}\).  
In the riverbed, mylonite cobbles containing pseudotachylyte veins can be seen. These cobbles provide the three-dimensional spatial distribution characteristics of the pseudotachylyte veins. Some veins are filled in clear, straight fractures (Figure 3), while others are injected along the fractured network formed by the shattered rocks (Figure 3).  
Figure 3: Images of specimens. (**A**) AF19-43A granitic genesis containing pseudotachylyte; (**B**) AF19-44A gneiss containing pseudotachylyte; (**C**) AF21-4-2 and AF21-4-3 breccia containing pseudotachylyte; (**D**) AF19-43D breccia containing pseudotachylyte; (**E**) AF19-43G mylonite containing pseudotachylyte; and (**F**) AF19-44C breccia containing pseudotachylyte.