The alteration of adjacent rocks within the deposits is relatively simple, and the alteration processes (Figure 7) mainly include dolomitization, calcitization, and pyritization, with silification and argillation also occurring over a smaller distribution range.
(d) Argillation, with the clay substances occurring as cryptocrystalline microflakes with grain sizes smaller than 0.02 mm and gaps interspersed between opaque minerals, (-) 10 x 2.
Changes in microstructure eventually lead to reduced density, development of the pore system, and increased degree of argillation
. As reported in literature [2,11, 20, 27-30], it can be inferred that the changes in microstructure maybe an important reason for rock softening and deterioration.