Geophysical modeling in gold deposit through DC Resistivity and Induced Polarization methods

Abstract Ore mining fundamentally depends on the definition of its tenor and volume, something extremely complex in disseminated mineralization, as in the case of certain types of deposits of gold and sulfites. This article proposes the use of electrical tomography for definition of a geophysical signature in terms of electrical resistivity and chargeability, in an outcrop of mineralized quartz lode at the end of an inactive gold mine. One of the targets was to analyze the continuity of the mineralized body, the occurrence of new outcrops and the applicability of the method as an auxiliary tool in mineral extraction. Three parallel lines of electrical tomography in a dipole-dipole arrangement, being orthogonal to the orientation of the gold lode, were installed in an area outside the mine. The results allowed the geophysical characterization of the mineralized zone by high resistivity (above 1000Ω.m) and high chargeability (above 30mV/V). The results of the 2D inversion models were interpolated in 3D visualization models, which allowed definition of the contour surfaces for the physical parameters measured, and the morphological pattern modeling of the mineralization. The data reveal the existence of a new lode in subsurface, localized 30m to the south of the lode outcrop. The versatility of the acquisition and data processing indicate the application potential of electrical tomography as a criterion for sampling and tenor definition in ore extraction activities, since it is objective and low cost.

摘要 矿石开采的核心前提是确定矿石的品位与体量，而在浸染状矿化场景中（如部分金矿床与硫化物矿床），这一工作往往极具挑战性。本文以某废弃金矿尽头的矿化石英矿脉露头为研究对象，提出采用电法层析成像（electrical tomography），基于电阻率与激电率（chargeability）参数确定目标区域的地球物理特征。本次研究的目标之一包括：分析矿化体的连续性、识别新露头的分布，以及评估该方法作为矿产开采辅助工具的适用性。研究团队在矿区外的区域布设了三条平行的电法层析成像测线，采用偶极-偶极装置，且测线方向与金矿脉走向正交。实测结果显示，矿化带具备高电阻率（大于1000Ω·m）与高激电率（大于30mV/V）的特征，据此可完成矿化带的地球物理表征。将二维反演模型的结果插值至三维可视化模型中，可生成实测物理参数的等值面，并完成矿化体的形态模式建模。数据结果表明，在该矿脉露头以南30米的地下区域，存在一条新的矿脉。由于该方法具备客观性强、成本低廉的优势，且其野外采集与数据处理流程兼具通用性，因此电法层析成像可作为矿石开采活动中采样与品位确定的辅助判据，具备良好的应用潜力。