Internal Structure of the Median Tectonic Line fault zone revealed by analysis of continuous borehole core

一个钻孔穿过473.9m深的中构造线(MTL)，这是Ryoke花岗岩和Sanbagawa变质岩之间的分界线。岩心样品揭示了深部断裂带的内部结构，并在450℃至地表的不同温度条件下经历了一系列断裂事件的演化。根据应力反演分析，断裂带的演化历史可分为四个阶段，在演化的第一阶段，断裂带经历了脆塑性转变。显微组织分析揭示了脆塑性过渡区附近的应力状态。蚀变矿物分析揭示了演化过程中断裂带内的热液活动。碳质的拉曼光谱揭示了脆性断裂过程中沿MTL断裂带的摩擦加热。

A drill hole penetrates the Median Tectonic Line (MTL) at 473.9m depth which is the boundary between the Ryoke granitic rocks and the Sanbagawa metamorphic rocks. The internal structure of MTL fault zone was revealed by the drillcore samples, and has evolved through a series of faulting events under various temperature conditions from 450℃ to the surface. The evolution history of the fault zone can be divided into four stages based on the stress inversion analysis, and the fault zone experienced the brittle-plastic transition at the first stage during their evolution. A microstructure analysis revealed the stress state around the brittle-plastic transition zone. Analyses of altered minerals revealed the hydrothermal activities within the fault zone during the evolution. Raman spectroscopy of carbonaceous matter revealed the frictional heating along the MTL fault zone during the brittle faulting.