Multistage magmatic-hydrothermal processes formed world-class granite-related lithium mineralization at Yifeng-Fengxin, South China: Evidence from zircon mineralogy

Abstract Interpreting the origin and magmatic-hydrothermal processes of highly fractionated granites can provide important information about crustal evolution and lithium (Li) mineralization. Our study focuses on the Yifeng-Fengxin deposit of South China, a newly discovered world-class Li deposit with >11 Mt of Li2O resources. We present zircon ages from different granite phases hosting the deposit and define three types of zircons characterizing the main stages of magmatic-hydrothermal activity, which spanned 153 Ma to 102 Ma. Dating of paragenetically well-constrained zircons shows that Li mineralization mainly occurred during three periods: 144–139 Ma, 133–131 Ma, and 105–102 Ma. Based on the analysis of Nd-Hf isotopic compositions from multiphase granites, the ore-related Ganfang granitic complex in the Yifeng-Fengxin district derived from the Proterozoic crust and juvenile crustal materials with the input of minor mantle-derived magmas. The formation of these granites could have resulted from multiple episodes of high-temperature (>600 °C) magma recharge from a deep reservoir. The enrichment of siderophile elements (Sc and Ti) in zircons may have resulted from the recharge of mantle-derived magmas and remelting of mafic–ultramafic rocks. The residual magmas evolved to low states of oxygen fugacity (ΔFMQ < 1). Trace element distributions, especially rare earth element (REE) + Y with P, and electron probe microanalysis (EPMA) mapping, indicate that zircon grains in the highly fractionated magmatic system have complex charge balances. The charge balances may be provided by Li, U, Ca, Sc, P, Y, and REEs from Li-rich melts. These data support an Li preenrichment process in early granitic melts, and hydrothermal overprinting and redistribution in the late stage. We propose that hydrothermal remobilization plays a crucial role in the formation of economic Li deposits. Zircon can be used as a microfingerprint to reveal the magmatic-hydrothermal evolution of highly fractionated granites and associated rare metal deposits.