Unveiling hydrothermal center in the Xiayu Ag-Pb-Zn-Au Orefield, central China: Insights from geology evidence and ore grade characteristic

• Six mineralization stages are recognized in the Xiayu orefield. • The metal precipitation sequence can be generalized as: Zn → Au-Pb → Ag. • Metal ratios (Au/Ag, Zn/Ag, and Pb/Ag) increase toward the Haopinggou deposit. • Southwestern Haopinggou deposit represents a hydrothermal center in the Xiayu orefield. The Xiayu orefield, situated within the Xiong’ershan ore concentration area of the southern margin of the North China Craton, is an important polymetallic production region. Recent studies suggest that the steeply dipping Ag-Pb-Zn-Au veins belong to a magmatic-hydrothermal system related to unexposed intrusions. The hydrothermal center and associated metal zonings, however, remain unclear. Addressing these knowledge gaps is essential for elucidating ore-forming processes and refining regional exploration strategies. This study addresses these issues through a statistical analysis of 436,003 ore grades, integrated with field and petrographic investigations. Our results discovered clear patterns of metal zonings that show a hydrothermal center is located under the southwestern part of Haopinggou deposit in the Xiayu orefield. Samples from this orefield clearly exhibit six paragenetic stages, in which sphalerite precipitation was followed by gold and lead mineralization, which in turn preceded the formation of chalcopyrite and argentite, with native silver occurring in the final stage. Based on these stages, we employed characteristic metal ratios to provide evidence for elemental zonings: Au/Ag, Zn/Ag, and Pb/Ag ratios increase toward the southwestern Haopinggou deposit. These variations reflect the sequential deposition of ore minerals, which is jointly governed by mineralization stages, decreasing temperature gradients, and intensifying fluid-rock interaction distal to the hydrothermal center. The observation aligns with the geological features of the Xiayu orefield, specifically the presence and spatial configuration of breccia pipes. This interpretation is further substantiated by a synthesis of existing fluid inclusion information, hydrothermal alteration assemblages, and geochronological constraints. These findings demonstrate the utility of statistical analysis methodologies in mineral exploration, providing a robust framework for identifying hydrothermal centers and delineating exploration targets.