Genesis of the Xinling vein-type Ag-Pb-Zn deposit, Liaodong Peninsula, China: Evidence from texture, composition and in situ S-Pb isotopes

Abstract

Abstract The Qingchengzi ore filed in the Liaodong Peninsula is a polymetallic ore field, including 15 Pb-Zn deposits, 3 Ag deposits, and 17 Au deposits. The mineralization is closely related to the Mesozoic magmatism. Among those deposits, two styles of vein mineralization, namely, Pb-Zn and Ag mineralization are developed in the ore field which has reserves of 1.5 Mt of Pb + Zn, 2000 t of silver, respectively. It is still unclear whether the two styles of mineralization are related, while the knowledge carries fundamental importance to understand the mineralization events at a regional scale. To address this, we selected the Xinling Ag-Pb-Zn deposit as a case study, which demonstrates excellent two independent Pb-Zn and Ag mineralization events, but at a single deposit scale. Detailed mineralogy characterization was carried out, along with in situ geochemical and S-Pb isotope analysis of the sulfides from the two styles of mineralization. The Pb-Zn mineralization comprises 0.5–4.5 m wide veins of sphalerite-galena-pyrite which extend along strike for 20–100 m, whereas the Ag mineralization consists of 1.0–4.0 m wide veins of quartz-Ag bearing tennantite series -hessite (minor sphalerite, galena, chalcocite) which extend along strike for 30–110 m. The mineral assemblages and trace elements of sulfides indicate a Pb, Zn, and Fe-rich ore-forming fluid and a Cu, Sb, As, Ag, and Te-rich fluid. LA-ICP-MS mapping and data processing by a software package XMaptools highlight trace element remobilization of primary sphalerite as a result of the overprinting event. Sphalerite geothermometer indicates that Pb-Zn veins formed at medium temperatures (251–273 °C), whereas the Ag mineralization precipitated at low temperatures (185–246 °C). Sulfides from the Pb-Zn and Ag ore bodies have δ34S values ranging from 4.94 to 6.35‰ and 4.99 to 6.36‰, respectively, indicating that the sulfur may be derived from magmatic fluids. In situ Pb isotope analysis of sulfides reveals very different Pb isotopic ratios in Pb-Zn mineralization (lying on the Pb evolution curve of crust: μ = 9.74) when compared to the Ag mineralization (lying on the lower curve with μ = 9.5), suggesting they may form from distinct magmatic-hydrothermal systems. The observation and dataset suggest that the Pb-Zn maybe medium temperature carbonate-replacement mineralization and was overprinted by later epithermal Ag mineralization.