Controls on metal distributions of the Fengzishan Zn–Pb deposit at the giant Jinding ore field in western Yunnan Province, SW China: Insights from field mapping and 3D geological modeling

Abstract

The world class Jinding Zn–Pb ore field, located in the Meso–Cenozoic Lanping Basin in western Yunnan Province, SW China, contains significant deposits that are primarily controlled by stratigraphy and structure. However, the migration pathways and driving mechanisms of ore-forming fluids are poorly understood, which limit the minerals exploration. Based on typical orebodies in the Fengzishan Zn–Pb deposit, this study used field mapping and three-dimensional (3D) geological modeling to depict the metal distribution and identify key ore-controlling structures. The results show that lead, zinc, and other base metals are concentrated in the hosting sandstones and breccia limestones of the Upper Triassic Sanhedong Formation. These rocks are located beneath the unconformity with the Miocene Jinding Group and within the hanging walls of NS-trending thrust faults and EW-trending tear faults. Oxidized metal-rich brines from the Jinding Group and reduced H₂S-rich fluids from the Sanhedong Formation migrate along the thrust and tear faults. Elevated Pb, Zn, Cd, and Ag concentrations and low Zn/Pb ratios were observed, suggesting multiple ore-forming fluid recharge events. We propose the following key suggestions: the spatial distributions of metals are controlled by the Jinding Group, the Sanhedong Formation, the unconformity between them, and the thrust and tear faults; the two-source fluids exhibit lateral and vertical flow through fault zones; and this migration is primarily driven by regional EW-trending compressive stresses. Based on regional geological data, the depths and adjacent areas of the Fengzishan and Nanchang deposits were identified as potential exploration targets for mineralization. These insights provide valuable perspectives for understanding the ore-forming processes of Jinding Zn–Pb ore field and similar regions.