Singularity mapping and spatially weighted principal component analysis to identify geochemical anomalies associated with Ag and Pb-Zn polymetallic mineralization in Northwest Zhejiang, China

In recent years, several moderate to large Ag and Pb-Zn polymetallic deposits have been discovered in northwestern Zhejiang Province, China. They are part of an important polymetallic mineralization belt in southeastern China. A hybrid approach combining singularity mapping and spatially weighted principal component analysis (SWPCA) is used to delineate anomalies for Ag, As, Pb and Zn, in stream sediment samples. On basis of a specific spatial weighting factor associated with NE–SW faults systems, singularity index values estimated for each of the four elements are combined into the first principal component (PC1) using SWPCA to obtain a single integrated anomaly that is spatially correlated with the known Ag and Pb-Zn deposits. Anomalies without known mineralization are considered to be target areas with potential for finding similar undiscovered polymetallic deposits. By means of weights-of-evidence modeling it is shown that the integrated anomalies show strong spatial correlation with the known Ag and Pb-Zn polymetallic deposits and with folds and faults that probably are genetically related to the Ag and Pb-Zn mineralization. There exist some high anomaly target areas without or with extremely minor known Ag and Pb-Zn polymetallic deposits. It is concluded that: (1) the hybrid method provides a useful tool to identify mineralization associated anomalies; and (2) there is probably a high potential to find undiscovered Ag and Pb-Zn polymetallic deposits on the newly identified anomalies without known significant mineralization in the study area.

► A hybrid approach is proposed to identify mineralization associated geochemical anomalies. ► The approach combines singularity mapping technique and spatially weighted principal component analysis method. ► It provides a convincing case-history study for using the hybrid approach. ► The method is demonstrated to be powerful.