When we dig a tunnel in sericite quartz-schist with dobby drills, regular bending of the boreholes appears, which affects drilling speed and the borehole quality.
The quartz-mica schist together with paragneiss constituted the old supracrustal series.
长石石英云母片岩与副片麻岩一起构成了古老的表壳结构。
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The Mengjiatun Formation complex is a suite of supracrustal rocks formed in the early Neoarchean, and its typical rocks include garnet quartzite, biotite-quartzschist and amphibolite.