The measured profile of the Lower Permian Qu Di Formation in the chlorite sericite mother rock of Gerville-sandy siderite.

3. 1.5- 1 residual sand-microscale metamorphic structure, plate structure. Debris: timely 18%, cuttings 15%, plagioclase 2%, muscovite 1%, and a small amount of potash feldspar and tourmaline. Metamorphic minerals: sericite 28%, chlorite 25%, siderite 8%, carbonaceous 2%. 2×, single polarization (left) and orthogonal polarization (right)

3. 1.5-2 detritus has poor sorting property, and the particle size range is 0.03- 1mm..4x, with single polarization (left) and orthogonal polarization (right).

3. 1.5-3 Left: The debris is timely, sub-circular-sub-angular, with fine particles, mostly flat and slender, with a long diameter of 0.03 ~1mm.. 10×, orthogonal polarization. Right: plagioclase, sub-angular-sub-circular, with obvious sericitization, particle size of 0.07 ~ 0.4mm 10×, and orthogonal polarization.

3. 1.5-4 detritus: compressed and elongated, with long diameter orientation, with a diameter of 0.05 1.4mm, and it is sericite mica. If well preserved, there are intermediate-acid porphyry, sericite phyllite, granite and dolomite fragments. 2×, single polarization (left) and orthogonal polarization (right)

3. 1.5-5 metamorphic minerals: sericite and chlorite are in the form of microscopic scales, which are obviously arranged in a directional way, making the rocks in a plate-like structure. Iron has been precipitated from siderite with a particle size of 0.0 1 ~ 0.02 mm, and the carbon distribution is uneven. 10×, single polarization (left) and orthogonal polarization (right)