Stylolites’ Morphological Characteristics And Genesis Study Of Yangshan Gold Deposit In Gansu Province

Yangshan gold mine zone is suited in Wen County, south of Gansu Province. It is located in West Qinling mountains region structurally. It lies in the fault of Anchanghe-Guanyinba, north of Mianlue-Maqu structural zone. Within the fault zone, geological structures are more developed, which grew a large number of stylolite structures in the bottom of Triassic limestone of mining area in particular. Basing on the study of the formation mechanism and morphology of stylolites, it is found that the stylolites turn out to have self-affine fractal roughness with a well characterized crossover length scale separating two self-affine regimes, and the morphology is mainly affected by two self-stabilization systems: the long range elastic redistribution of local stress fluctuations, which roughen the surface, and surface tension forces along the interface, which smooth it. We considered stylolites as the combination of complex waveform, defined the characterized crossover length scale as L, found the value of stress is directly proportional to the value of L. From that we can estimate the value of stress when stylolites form by pressure solution of blocks of rocks into each other.This paper took stylolites structures in the drill cores as a main line, aimed to searching the relationship between stylolites and mineralization, made a quantitative and qualitative analysis by observing the characteristics of stylolites, calculated the stress and depth, speculated the age of formation, and contrasted with other evidence, e.g. the age of quartz vein. Main research of this paper is as follows:The stylolites structures in the bottom of Triassic limestone of mining area were selected as samples in this paper. By analyzing the morphologies of samples, the value of stress is around 77 MPa. From that, the depth of stylolites Z is around 2.9km. Combining the data of previous studies, the age of sample is around in the Cretaceous period, which corresponding to a mineralization of Late Jurassic to Early Cretaceous. But the clear and explicit relationship between stylolites and mineralization is thought yet to further validated.