Application of the fine-grained soil prospecting method in a loess-covered area of central China

Loess-covered landscapes occupy a large area of the globe and have substantially high potential for mineral exploration; however, as mineral information is obscured by loess cover, suitable prospecting techniques need to be applied. The fine-grained soil prospecting method—a deep-penetrating geochemical technology that can be used to identify concealed deposits—has been proven effective in some cases. In this study, we applied this method for mineral exploration in the loess-covered Luoning Basin in Central China. Our results revealed strong geochemical anomalies (e.g., Au, Ag, Pb, Zn, and Cu) over related and concealed ore deposits. Furthermore, a regional geochemical survey in the Luoning Basin revealed the spatial distribution and suites of elements that were consistent with the mineralization type. Moreover, higher geochemical anomalies of Au, Ag, Pb, and Zn were spatially related to an Au ore deposit and Ag–Pb–Zn polymetallic deposit, respectively. The results of a detailed geochemical survey in the Zhonghedi Ag–Pb–Zn polymetallic deposit further revealed that the distribution of surface element anomalies was associated with tectonic fractures throughout the exploration region, which are closely related to the distribution of orebodies. These results imply that the fine-grained soil prospecting method is suitable for anomaly delineation during detailed geochemical surveys as well as regional-scale surveys. Based on our results, we suggest that geochemical anomalies in the loess-covered surface in our study area are presumably the result of geogas dispersion processes; we provide a schematic model explaining how ore-forming and associated materials are brought to the surface by geogas flowing upwards along faults and fractures and, ultimately, accumulating in fine-grained loess soils. Overall, our research demonstrates that fine-grained soil prospecting can effectively aid the search for concealed mineral deposits in loess-covered landscapes. •Fine-grained soil prospecting can identify hidden orebodies.•Clay particles adsorbs metal particles migrating from underlying ore deposits.•Anomalous Au, Ag, Pb, & Zn were detected above concealed ore deposits.•Soil overlying buried orebodies in loess-covered areas contains geochemical markers.