Numerical Modeling of Deformation at the Baiyun Gold Deposit, Northeastern China: Insights into the Structural Controls on Mineralization

The Qingchengzi ore field is an important gold-polymetallic center of the North China Craton. It has been recognized that the gold deposits in Qingchengzi were controlled by structures like lithological interfaces and fractures along mechanically weak bedding and foliation planes, but it still remains poorly understood how the structures affected the localization of the gold deposits. Finite element based numerical modeling was used to reproduce the deformation process of the Baiyun gold deposit during the mineralization period. Paleoproterozoic schist and marble are widely exposed in Qingchengzi, and a large part of the Baiyun gold ores occurs along the interfaces between the schist and the marble. The modeling results suggest that the mechanical contrast between the schist and the marble may be a major reason why the stress was localized along their lithological interfaces under a compressional stress regime. Two parts of their lithological interfaces were identified to be easily stress-localized and first fractured: the interface between the schist and its underlying marble at shallower levels and the one between the schist and its overlying marble at deeper levels. Stress concentration in these two parts is independent on the dipping angle and direction of the interfaces. Therefore, mineralizing fluids may have been concentrated into these two parts. The first one is consistent with the present ore bodies of the Baiyun gold deposit, and the second one could be considered for deep prospecting. These findings also provide implications for the structural controls of lithological interfaces on the mineralization in other gold deposits of this region.