Trace Element Characteristics of Calcite From the Bainiuchang Deposit, Southeastern Yunnan, China: Genesis and Exploration Indications Revealed by LA ‐ ICP ‐ MS Analysis

The Bainiuchang deposit, located in southeastern Yunnan Province, is one of the most important super‐large Pb–Zn–Ag deposits in China. This study focuses on calcite from this deposit. Based on systematic field geological surveys and sampling, combined with macroscopic morphological observations and microstructural analyses, LA‐ICP‐MS was employed to systematically investigate the petrographic characteristics, genetic mechanism, and formation process of calcite, as well as the constraints of fluid evolution on mineralisation. The results show that calcite can be classified into ore‐bearing and barren types, both occurring as veins and in dendritic‐network forms. Their morphological features indicate that structural control was the dominant factor governing vein formation and modification. The total Fe + Mn contents of ore‐bearing calcite (> 0.94%) are significantly higher than those of barren calcite (0.13%–0.22%). The ore‐bearing calcite displays a wide range of ΣREE (0.99–736.98 μg/g) and diverse REE distribution patterns, whereas barren calcite exhibits low ΣREE (0.34–18.83 μg/g), weak REE fractionation and LREE depletion. Ce anomalies are not pronounced in either type; however, Eu anomalies indicate a gradual transition of the ore‐forming fluid from reducing to oxidising conditions. The ore‐forming materials were derived predominantly from deep granitic magma. Rare earth elements were transported mainly as complexes in the fluid and their distribution characteristics were significantly influenced by the influx of meteoric water and interaction with wall rocks. Geochemical indicators such as Fe, Mn and REE can thus serve as key discriminators for distinguishing ore‐bearing from barren calcite. Integrating these results with previous studies, this study concludes that the Bainiuchang deposit is a typical magmatic‐hydrothermal deposit.