Revealing mineralization process of the Lehong carbonate-hosted Zn-Pb deposit: Insights from in-situ LA-ICP-MS analysis and fluid inclusion study of dolomite

Abstract

Carbonate-hosted Zn-Pb deposits account for approximately 20% of global Zn-Pb resources. Understanding the fluid evolution and the source of metallogenic materials in these deposits is crucial for advancing exploration and the development of Pb and Zn resources. As a common gangue mineral in carbonate-hosted Zn-Pb deposits, dolomite is ideal for tracing the detailed evolution of ore-forming processes. While previous studies on fluid evolution in Zn-Pb deposits on carbonate minerals has been limited. The Lehong Zn-Pb deposit, a typical large-scale deposit in the Sichuan-Yunnan-Guizhou metallogenic belt, is characterized by a close association between dolomite and sulfides during the mineralization period, with distinct growth zoning under cathodoluminescence. Therefore, we selected the Lehong deposit as the focus of this study. This research employed in-situ LA-ICP-MS trace element analysis, fluid inclusion studies to investigate dolomite from different mineralization stages.

The paragenetic sequence of the Lehong deposit was divided into Pre-Ore, Ore, and Post-Ore stages, with an additional Cu mineralization event identified. Dolomite exhibited complex zoning patterns that reflect fluid-rock interactions, meteoric water input, replenishment of ore-forming fluid, and sulfide crystallization. Spatial analysis revealed a decreasing influence of ore-forming fluid and an increasing impact of meteoric water with distance from the massive ore zones. Temporally, the waning of ore-forming fluid and the increasing influx of meteoric water led to the development of low-temperature, low-salinity fluid (166.5 °C, 5.32 wt% NaCl equivalent) during the post-ore stage. Trace element data indicated that sulfide minerals deplete corresponding metals in dolomite, while Cu and Zn-Pb associated dolomite exhibit higher metal concentrations compared to barren ones. Additionally, we propose a mineralization process model for the Lehong deposit, which enhances the understanding of both its geology and mineralization processes. Overall, this study highlights the potential of using dolomite as a geochemical tracer to reconstruct fluid evolution and ore-forming processes in carbonate-hosted deposits, providing valuable insights for mineral exploration strategies.