Computational simulation of the ore-forming processes associated with the Sanshandao-Haiyu gold belt, Jiaodong Peninsula, eastern China: implications for the duration of ore formation

Abstract

The Sanshandao-Haiyu gold belt, Jiaodong Peninsula, Eastern China accounts for more than 1,400 t gold resources, which is always recognized as a coupled result of structural deformation, pore-fluid flow, and hydrothermal alteration-mineralization processes. However, the ore-forming processes associated with this gold belt has not been fully understood by the coupled perspective. In this paper, we use computational modeling to study the spatial distribution of dilation (positive volumetric strain) and the mineralization rate, which can predict the mineralization patterns from a chemical perspective, so as to solve the fully coupled problem during ore-forming processes. The model was loaded on the FLAC3D platform to test four scenarios: 1) Syn-compression in the NW-SE direction; 2) syn-compression in the WNW-ESE direction; 3) syn-compression in the NNW-SSE direction, and 4) syn-extension in the NW-SE direction. The simulation results show that only the syn-compressional scenario can produce wide dilation zones with a distribution pattern similar to the known orebodies. The higher dilation zones with the volumetric strain (>0.1%) and the highest pore-fluid flux are closely associated with the fault geometry, particularly for the gentle segments near the steep-flat transition areas. Besides, the dilation zones also occur with very high absolute values of pore-fluid pressure gradient and temperature gradient, indicating significantly perturbed physical-chemical conditions. The receiver operating characteristic (ROC) curves of the mineralization rate show that the area under the curve (AUC = 0.862) of the NW-SE syn-compression model is the highest among these four scenarios, indicating a major paleo compression stress direction of NW-SE during ore-forming period. Furthermore, based on the mineralization rate, we estimated that the mineralization duration of the Sanshandao-Haiyu gold belt would be less than 100,000 years. These simulation results can not only enhance our understanding of the ore-forming processes in the Sanshandao-Haiyu gold belt and Jiaodong Peninsula but also demonstrate that these can be used directly or indirectly for deep mineral exploration.

Fractal evolution characteristics of fracture meso-damage in uniaxial compression rock masses using bonded block model

“…As the mining depth further increases, it is anticipated that the maximum horizontal principal stress will exceed 50 MPa 29 . Situated as a coastal mine with ore bodies extending below sea level, the Sanshandao gold mine faces a complex water-rich environment due to intricate fault structures and developed joints and fractures in the rock mass 30 . The fault activity results in a heatgathering effect, causing deep high-temperature heat flow upward, thereby subjecting underground mining activities to a high-stress corrosive environment.…”

Three-Dimensional Mineral Prospectivity Modeling with the Integration of Ore-Forming Computational Simulation in the Xiadian Gold Deposit, Eastern China

“…Here we manually refined the Xiadian fault surface model constructed above to avoid the post-ore cutoff or deformation. A conceptual model (Figure 6), including the Xiadian fault zone, hanging wall (Jiaodong Group Precambrian metamorphic rocks), footwall (Linglong granite), and erosion cover, is necessary for ore-forming numerical modeling [47,49,84]. In this study, the dimensions of the overall model spanned 7 km horizontally and 10 km vertically.…”

“…The specific mechanical, hydraulic and thermodynamic parameters of rocks are given in Table 2. These values are based on rock mechanical experiment data or related hand book and numerical simulation experiments in Jiaodong [49,84,90].…”

“…The initial temperature of the top surface was 25 • C and kept fixed, and the temperature gradient was 20 • C/km. The initial temperature of the top of the fault zone was set to 180 • C, a temperature range consistent with the gold mineralization [49,84,90].…”

“…Additionally, numerical modeling can also simulate temporalspatial metal precipitation or rock stress geodynamics to delineate the fluid pathways and traps to locate potential mineralization. For example, Liu et al [13], Hu et al [48], and Shan et al [49] used the dilation space, mineralization rate, and/or geochemical interaction as ore proxies to find the favorable metal deposition location at depth. Ford et al [50] and Wilson et al [51] discussed the fault geometry controls on the rock deformation and fluid flow regular pattern and determined the mineralization exploration strategies in strike-slip fault fluid systems.…”