Application of the multi-dimensional study of geochemical anomalies in deep metallogenic prediction of the Zhexiang gold deposit in southwestern Guizhou, China

Due to the lack of effective deep exploration techniques, it has become a key and difficult task to expand the scale of prospecting by obtaining the mineralization information in the deep and peripheral areas of the proven typical deposits of the Huijiabao anticline in southwestern Guizhou. To truly reflect the characteristics of deep geological anomalies, this study investigated the deep ore-bearing Longtan Formation of the Zhexiang gold deposit in the eastern Huijiabao anticline. The information on deep Au anomalies was extracted through geochemical exploration in boreholes of any azimuth according to the profiles, longitudinal profiles, and deep 3D planes of survey lines. Then this study summarized the distribution patterns of geochemical anomalies and evaluated the deep metallogenic potential of the Zhexiang gold deposit. The geochemical data obtained from deep boreholes were processed using the iterative histogram method and the sample length weighted average grade method, respectively. The results show that the Longtan Formation in the mining area had Au anomaly background values of (0.04~0.12)×10^-6 and an anomaly threshold of about 0.24×10^-6. As revealed by the anomaly contour maps generated from the processed data using the above two methods, the distribution characteristics of Au anomalies are in high agreement with those of deep ore bodies, and the distribution ranges of high Au anomalies in all profiles are highly consistent with the morphologies of the proved ore-bearing zones (bodies). Moreover, the large-scale and unclosed high Au anomalies follow the dip direction of fault F₂₀ in the first member of the Longtan Formation. The 3D distribution of Au anomalies shows that the nearly EW-directed high anomaly zone in the central mining area is consistent with the axial region of the Huijiapu anticline. As indicated by the analysis of the multi-dimensional geochemical anomalies and the geological characteristics of the study area, fault F₂₀ is the main ore transmitting and controlling fault in the mining area, and the northern and eastern deep parts around the mining area have great metallogenic and prospecting potential. In addition, two prospecting targets were delineated, needing further engineering verification. This study plays an important demonstration role in guiding the exploration of other mining areas in the Huijiabao anticline. The feasible study methods can be referenced for the study of geochemical anomalies in other mining areas.