Tizapa 鉱山における変質インデックスとクラスタ解析を用いた探鉱ポテンシャル評価

抄録

The Tizapa Mine, an underground operation located in the State of Mexico, Mexico, has sustained its production for over 30 years through continuous exploration since its opening．This report re-evaluates exploration guidelines for the deep and peripheral extensions of the deposit̶the focus of recent efforts̶by integrating geochemical indicators and statistical analysis．First, the Alteration Index (Ishikawa et al., 1976), which was previously validated in shallow zones, was reexamined using recent drilling data．The results confirmed that elevated index values persist in the footwall of the deep and peripheral zones．Furthermore, while some barren drill holes penetrated areas with low alteration indices, a systematic review of this data clarified the exploration potential of ore body extensions and proved effective for refining target areas．Subsequently, a correlation matrix was generated for the assay grades and intersection lengths of the mineralized composites, and partial correlation coefficients were examined to clarify the intrinsic relationships among the elements within the mineralized zones．Furthermore, to objectively characterize the mineralization, a cluster analysis using a Gaussian Mixture Model was applied to the drill hole data．This revealed that the massive sulfide cluster is localized almost exclusively within the main Tizapa ore body．By integrating the Alteration Index with cluster analysis, a genetic hypothesis linking mineralized occurrences within the concession to the main Tizapa ore body was developed, leading to the successful identification of new highpotential exploration zones．The combination of these two methods is expected to serve as a robust indicator for both nearmine extension exploration and the evaluation of new mineralized prospects.