Multistage genesis of the carbonate-hosted Tuokesai Pb–Zn deposit, West Tianshan, NW China: Synsedimentary strata-bound mineralization and hydrothermal remobilization

Abstract

The Tuokesai Pb–Zn deposit is located in the eastern section of the West Tianshan Orogen within Precambrian carbonate rocks. However, the genesis of the ore, including sedimentary exhalative and sedimentary-metamorphic types, remains controversial owing to varying interpretations of strata-bound and vein-type mineralization. In this study, we aimed to construct an innovative genesis model, focusing on two mineralization types, by analyzing fluid evolution, material sources, and trace element distributions. Three mineralization stages were identified, each with specific pyrite generation. Stage I pyrite–sphalerite–galena bands (Py-1 and Py-2) represent strata-bound mineralization. Stage II sphalerite–pyrite–quartz veins (Py-3) and Stage III pyrite–quartz–calcite veins (Py-4) represent vein-type mineralization. Fluid inclusion microthermometric and H–O isotopic analyses revealed that Stage I fluids are characterized by low temperatures (132–171 °C) and moderate salinities (11.8–17.3 wt% NaCl eqv.), and are derived from modified seawater. Conversely, fluids in Stages II–III are associated with moderate temperatures (165–267 °C) and variable salinities (2.1–35.3 wt% NaCl eqv.), being derived from a mixture of magmatic and meteoric water. The in situ S isotopic composition suggests that Py-1 and Py-2 (δ³⁴S = 9.46–12.20 ‰) originated from the thermochemical reduction of marine sulfate, whereas Py-3 and Py-4 (δ³⁴S = 0.85–3.85 ‰) originated from magmatic components. LA–ICP–MS analysis of trace elements in pyrite, combined with machine learning classification methods, indicated that Py-1 and Py-2 have a synsedimentary origin whereas Py-3 and Py-4 have a magmatic-hydrothermal origin. Overall, our findings support a novel multistage genesis model for the Tuokesai Pb–Zn deposit, suggesting that Neoproterozoic syngenetic strata-bound mineralization was overprinted by Late Paleozoic vein-type hydrothermal remobilization. This model highlights the importance of incorporating diverse geological events into our understanding of the ore-forming process to facilitate the exploration of carbonate-hosted Pb–Zn deposits within the West Tianshan Orogen.