The Pingqiao deposit, a newly discovered large-scale fluorite-cookeite deposit in Guizhou, Southwest China, represents a new and unusual type of lithium (Li) mineralization. Recent exploration has identified over 90 kt of Li2O reserves. Using in situ laser ablation−inductively coupled plasma−mass spectrometry to analyze the primary Li-bearing mineral, cookeite, and associated minerals, as well as major and trace elements and Li isotopes of the ore-hosted strata, this study investigated the spatial distribution, occurrence, and enrichment mechanisms of Li. The study yielded new geological and geochemical evidence to improve our understanding of Li mineralization.
The results indicate that two generations of cookeite (Ckt-I and Ckt-II) and fluorite formed during the same hydrothermal stage, with crystallization temperatures of between 95 °C and 270 °C. Ckt-I is enriched in light rare earth elements and exhibits a negative Eu anomaly (average of 0.55), which decreases in Ckt-II (average of 0.88). This indicates gradual cooling of the ore-forming fluids, accompanied by the tetrad effect caused by fluorine (F) in the fluid. Nanoscale secondary ion mass spectrometry mapping of pyrite and cookeite suggests a shared Li and F source from the same mineralization event. The ore’s Li isotope composition (−4.06‰ to +3.15‰, average of −1.24‰) is slightly negative, with variations implying upward fluid migration from deep Li-rich basement rocks, possibly mixed with basinal fluids. The U-Pb dating results of calcite associated with cookeite (134 ± 4.5 Ma) and fluorite (Sm-Nd isochron age: 148 ± 8 Ma) aligning with the regional ages links the mineralization event to medium- to low-temperature basinal fluids of the Yanshanian movement. Based on the research described in the previous paragraph and comparison with other types of Li deposits, a metallogenic model for the Pingqiao deposit is proposed, which offers new insights into this unusual type of Li mineralization.
