In the Bushveld Complex, South Africa, open pit mines are faced with a challenge of rock slope stability due to geological structures (fractures, faults and dykes) that compartmentalize the rock mass. Geophysical surveys (seismics, magnetics and electrical methods) were conducted in a 0.2 km² area at Tharisa mine, with the goal to delineate fractures that may be potential conduits for water migration into the pit. Special processing techniques were applied to the dataset to obtain good quality seismic, magnetic and resistivity models. The P-wave velocity models show distinct low velocities in the centre of the seismic profile, indicating the presence of weak zones associated with faulting or fracturing. Seismic reflection method was used to image the deeper discontinuities and mineralization contacts. Near surface reflections are observed throughout the profiles and are correlated with the contact between the chromitite and host rock. Ground magnetic surveys were conducted to delineate dykes and fractures. De-trending and de-culturing techniques were applied on the magnetic data for correcting regional and temporal variations. The low magnetic regions indicate the presence of fracture systems in the subsurface, whereas the high magnetic region is correlated with the dolerite dyke that crosscuts the pit. The electrical resistivity tomography exhibits linear low resistivity contrast zones that differentiate between the fractured and undisturbed hard rock at an estimated depth of 4–10 m. Resistivity shows discontinuities that suggests the presence of fracturing and dyke-host rock contacts. Correlation among magnetics, P-wave velocity models, resistivity section and seismic data is evident when overlaying the different datasets, implying that the low magnetic regions are highly weathered and prone to fracturing. The integration of geophysical data is encouraging, because it was able to image the depth to the bedrock, fractures within the host rock and dyke in a complex mining environment.

中文翻译：

---

用于描述南非布什维尔德综合体西部露天矿裂缝特征的多种地球物理方法

在南非布什维尔德综合体，由于地质结构（裂缝、断层和岩脉）分隔岩体，露天矿面临着岩坡稳定性的挑战。^{在 Tharisa 矿区 0.2 km 2 的}区域内进行了地球物理调查（地震、磁学和电学方法），目的是描绘可能是水迁移到矿坑中的潜在通道的裂缝。对数据集应用了特殊的处理技术，以获得高质量的地震、磁力和电阻率模型。P 波速度模型显示地震剖面中心存在明显的低速，表明存在与断层或压裂相关的薄弱区域。地震反射法用于对更深的不连续面和矿化接触面进行成像。在整个剖面中观察到近地表反射，并且与铬铁矿和主岩之间的接触相关。进行地面磁力勘测来描绘堤坝和裂缝。对磁数据应用去趋势和去文化技术，以纠正区域和时间变化。低磁性区域表明地下存在断裂系统，而高磁性区域则与横切矿坑的辉绿岩脉有关。电阻率断层扫描显示出线性低电阻率对比区域，可区分估计深度为 4-10 m 的裂隙和未受干扰的硬岩。电阻率显示出不连续性，表明存在断裂和岩脉-主岩接触。当叠加不同的数据集时，磁学、纵波速度模型、电阻率剖面和地震数据之间的相关性很明显，这意味着低磁区域风化程度高且容易发生破裂。地球物理数据的整合令人鼓舞，因为它能够对复杂采矿环境中的基岩深度、主岩和岩脉内的裂缝进行成像。