Origin of the Yinshan Pb-Zn-Ag Deposit in the Edong District Section of the Middle–Lower Yangtze River Metallogenic Belt: Insights from In-Situ Sulfur Isotopes

Abstract

The investigation into the enigmatic origin of Pb-Zn mineralization within the Middle-Lower Yangtze River Metallogenic Belt has long been marred by a paucity of prior studies. Seeking to alleviate this dearth of knowledge, our study meticulously scrutinizes the Yinshan Pb-Zn-Ag deposit nestled within the Edong district of the belt, endeavoring to cast an illuminating spotlight upon its enigmatic genesis. We identify two distinct epochs: (1) the pre-mineralization pyrite epoch (Epoch I) mainly characterized by colloform and massive pyrite, and (2) the hydrothermal mineralization epoch (Epoch II) which can be further divided into three stages: pyrite-arsenopyrite (stage 1), galena-sphalerite (stage 2), and vein pyrite (stage 3). We conduct in-situ sulfur isotope analyses on sulfide minerals from both epochs, revealing δ34S values ranging from −0.5 to 4.8‰ for Epoch I and varying from 2.2–4.9‰ (stage 1), 1.1–3.0‰, 4.2–7.1‰ (stage 2), and 2.1–3.8‰ (stage 3) for Epoch II. Integrating our sulfur isotope data with the geological characteristics of the deposit, we infer that Pb-Zn mineralization was related to a granite of ~130 Ma age. Additionally, our study suggests the possibility of coexisting Mo mineralization beneath the Pb-Zn mineralization. Our findings contribute to a better understanding of the origin of Pb-Zn mineralization in the Middle-Lower Yangtze River Metallogenic Belt.