Geology, mineralization and model of the giant Maoping carbonate-hosted Pb-Zn deposit (5 Mt), South China

Abstract

The giant Upper Yangtze Pb-Zn metallogenic province, also known as the Sichuan-Yunnan-Guizhou (SYG) Pb-Zn province hosting >500 carbonate-hosted epigenetic Pb-Zn deposits that contain >20 Mt Pb + Zn base metal reserves. The giant Maoping Pb-Zn deposit is the second largest deposit in this province and owns >5 Mt Pb + Zn metal reserves with ore grades of 12 wt.%-30 wt.% Pb + Zn. Such large tonnages and high grades make it among the top 100 similar mineral deposits in the world. The ore bodies are predominantly located within the strata of the Upper Devonian (Zaige Formation) and Lower (Baizuo Formation)-Upper (Weining Formation) Carboniferous. The principal ore minerals consist of galena (Gn), sphalerite (Sp), and pyrite (Py), while the primary gangue minerals include dolomite (Dol), calcite (Cal), and quartz (Qtz). Three mineralization stages of carbonate minerals have been identified: (1) pre-sulfide stage 1, (2) syn-sulfide stage 2, and (3) post-sulfide stage 3. Trace elements and C-O-Sr isotopes of three stages’ carbonate minerals, together with S-Pb isotopes of sulfides, revealing that the metamorphic basement rocks played the role of the metal source during the early stage of Pb-Zn mineralization, whereas the metal contribution of the sedimentary wall rocks found to be more prominent during the late stage of Pb-Zn mineralization. In addition, the dissolution of marine carbonate rocks and CO₂ degassing may have also played an important role in the formation of the Maoping deposit. Furthermore, syn-sulfide stage 2 calcite has a U-Pb age of 214 ± 20 Ma obtained by LA-ICPMS in-situ analyses, suggesting that the hydrothermal mineralization occurred during the Triassic. Our study proposes a new coupled metallogenic model of fluid-structure-lithology assemblage and provides new insights about the formation and evolution of the Maoping deposit with significant implication for understanding and exploration of similar Pb-Zn deposits worldwide.