Precise discrimination on the mineralization processes of the Jinding Pb-Zn deposit, Lanping Basin, western Yunnan, China: Evidence from in situ trace elements and S-Pb isotopes of sulfides

The Jinding Pb-Zn deposit is located in the Meso-Cenozoic Lanping Basin, SW China, which is the second largest Pb-Zn deposits in Asia. It has been studied by many researchers because of its huge reserves and complex geological metallogenic history, however, there are still highly controversial aspects regarding its ore genesis and precise mineralization processes. In this study, we carried out a detailed field geological investigation combined with LA-(MC) ICP-MS trace element and S-Pb isotope microanalysis. The ore-bearing strata of Jinding deposit are sandstones of Jingxing Formation, and sandy-breccias and limestone breccias of Yunlong Formation. The mineralization of the deposit can be divided into two main stages: the stage I and stage II. The stage I can be further subdivided into the early stage I which mainly includes disseminated pyrite, marcasite, sphalerite, and galena; and the late stage I mainly including lumpy sulfide and minor celestite; while the stage II mainly include sphalerite, galena, pyrite, celestite, barite, calcite, and gypsum. These mineralization stages are characterized by different mineral assemblages and structural characteristics from early to late. Furthermore, the in situ trace elements and S-Pb isotopes of sulfide minerals showed regular evolutionary characteristics during the mineralization. According to the correlation of different trace elements in the sphalerite, the important coupled substitutions are discovered: 4Zn(2+) reversible arrow 2Fe(2+) + Ge4+, 2Zn(2+) reversible arrow Fe2+ + Mn2+, 3Zn(2+) reversible arrow In3+ + Sn3+ and other complex substitution relationships. Based on the evolution of trace elements and isotopes, we conclude that the ore-forming fluids of the Jinding Pb-Zn deposit is related to the basin brine rich in metals and the H2S-rich fluids in the early stage, and the mixing of meteoric water in the late stage, which extracted the red-bed clastic rocks rich in Fe, Mn and Tl, thus leading to the increase in the content of Fe, Mn, Tl and other elements. In addition, sphalerite also shows a wider range of trace element characteristics and a narrower range of Pb-208/Pb-204, Pb-207/Pb-204 and, delta(34) S values. The metal is mainly derived from the sedimentary strata of Lanping Basin. The giant Jinding Pb-Zn deposit is formed by the superposition of multiple sources of fluids. Bacterial sulfate reduction (BSR) plays an important role in the sulphate reduction, and there may also be a small contribution from thermochemical sulfate reduction (TSR) to sulphur reduction in the western ore block. Finally, we discussed the precise mineralization processes and ore genesis of the Jinding Pb-Zn deposit, and concluded that it is a MVT Pb-Zn deposit of metagenetic clastic rock bearing ore type enriched in dispersed trace elements such as Cd and Ge, whose mineralization was controlled by interlayer structures.

Automated summary

In this study, the mineralization processes of the Jinding Pb-Zn deposit in Yunnan, China were investigated through field geological investigation and LA-(MC) ICP-MS trace element and S-Pb isotope microanalysis. The mineralization of the deposit can be divided into two main stages, with different mineral assemblages and structural characteristics. The ore-forming fluids are believed to be related to the basin brine and H2S-rich fluids in the early stage, as well as the mixing of meteoric water in the late stage. The sedimentary strata of the basin also contribute to the metal content of the deposit.