Spatial Simulation and Characterization of Three-Dimensional Fractures in Gejiu tin District, Southwest China, Using GEOFRAC

Fracture is an important factor controlling mineralization and ore distribution in metallic deposits. Fracture also affects mechanical stability of drifts. A plausible three-dimensional discrete fracture network (DFN) was constructed using GEOFRAC, a geostatistical method of conditioning directions (strikes and dips) and locations of sample fractures. The northern part of the Gejiu tin district, southwest China, was selected, using 10,212 fractures sampled on drift roofs at five different levels and along a 5463 m length. Key parameters of this DFN are fracture density, direction, and the connective condition of disks that form a fracture plane. The simulated fractures were verified by good correspondence of their directions with those of the sample fractures; furthermore, continuous fractures longer than 1 km matched the faults observed in outcrops. The most notable result was clarification of fracture control by the orebody shape: Simulated gentle fractures (30° dips or less) formed layered orebodies and created boundaries between each layer, while steep fractures (60° dips or more) displaced the layers by acting as faults. Such fault-type fractures and the densely fractured portions require caution with respect to mining safety. It was concluded that GEOFRAC is useful for three-dimensional DFN modeling in underground mines.