First report of composite pseudotachylyte-ultracataclasite veins at the Main Central Thrust (central Nepal): formation conditions, fabrics, and fabric forming process

Research on the internal fabric of the pseudotachylyte has been less. No reports of the pseudotachylyte and ultracataclasite composite veins from the thrust sheet, Nepal Himalaya. The presence of pseudotachylyte-ultracataclasite vein at the vicinity of the MCT reveals repeated processes of fragmentation, fluidization, injection, flow, and solidification. Pseudotachylyte-ultracataclasite formed at high pressure low temperature probably during the Late Miocene to Early Pliocene, younger than 7.5 Ma针对假熔岩（pseudotachylyte）内部组构的研究仍较为匮乏。目前尚无尼泊尔喜马拉雅逆冲岩席（thrust sheet）中产出假熔岩与超碎裂岩（ultracataclasite）复合脉体的相关报道。主中央逆冲带（Main Central Thrust，MCT）附近产出的假熔岩-超碎裂岩脉体，揭示了碎裂、流液化、注入、流动及固结等多期重复的地质过程。假熔岩-超碎裂岩形成于高压低温环境，其形成时代大致为中新世晚期至上新世早期，年龄小于7.5 Ma。