Li mineralization processes in the Gaoaobei W-Li deposit, Nanling, South China: Evidence from chemical compositions of mica and cassiterite U-Pb dating

Abstract

Tungsten (W), lithium (Li), and other rare metals are essential components in various industries. The coexistence of tungsten and lithium deposits represents a deposit type with great economic potential. However, the process of W-Li co-mineralization remains poorly understood, presenting challenges in elucidating the mechanisms governing their concurrent presence. This study focuses on the Gaoaobei tungsten (W) deposit, notable for its substantial lithium (Li) content, classifying it as a greisen-type W-Li deposit. Specifically, what is the process of Li enrichment and mineralization within tungsten deposits, and which factors play a critical role in controlling the occurrence of Li mineralization events in tungsten deposits. The monazite U-Pb dating indicates that the medium-coarse-grained biotite monzogranite in the Gaoaobei deposit formed at 226.3 ± 1.9 Ma, while the medium-grained muscovite granite was dated at 160.0 ± 1.4 Ma. The cassiterite U-Pb ages of results for the medium-coarse-grained biotite granite (wall rock), medium-grained muscovite granite (metallogenic granite), and aplite indicate that the hydrothermal stage Li mineralization in the Gaoaobei W-Li deposit ranges from approximately 159.0 ± 4.6 Ma to 155.3 ± 4.5 Ma. The Gaoaobei W-Li deposit is characterized by early-stage alterations, including biotitization, albitization, and muscovitization, followed by late-stage silicification and sericitization. The study reveals that the mica types in the Gaoaobei W-Li deposit are predominant Zinnwaldite, Protolithionite, and Lepidolite, characterized by high Al and Fe contents and low Ti, Ca contents, among other features. The mineral compositions of various mica types demonstrate an evolutionary trend from early to late stages, showing an increase in Li, Rb, Ta, and Zn contents, and a decrease in W, Sn, and Nb contents. The magmatic muscovite exhibits Nb/Ta ratios mostly exceeding 4 and Li/Rb ratios mostly below 1.5. In contrast, hydrothermal muscovite displays lower Nb/Ta ratios (mostly below 4) but higher Li/Rb ratios (mostly above 1.5). Re-equilibrated muscovite falls within the intermediate range of these two categories (Nb/Ta = 0 to 4; Li/Rb = 0.1 to 2), highlighting that a Li/Rb ratio greater than 1.5 can serve as a criterion for evaluating the potential for Li mineralization. The majority of Zr/Hf ratios of muscovite in the Gaoaobei deposit are below 10, suggesting promising prospects for W, Sn, Mo, and other deposits. This study establishes the initial determination of the granite-forming ages for the Yanshanian period granite in the Gaoaobei mining area and links the hydrothermal stage Li mineralization age of the Gaoaobei deposit to the Late Jurassic large-scale W-Sn mineralization event in the Nanling Range. These findings provide valuable insights for the exploration of rare metal deposits such as Li in W mines in the Nanling Range and similar deposits worldwide.