High geothermal gradients facilitating lithium mineralization: Insights from the Ke’eryin–Taiyanghe plutons, central China

Understanding the critical processes that lead to lithium (Li) enrichment is essential for the exploration and development of Li resources—a key component of “low-carbon” energy. The Ke’eryin-Taiyanghe plutons in central China provide a unique opportunity to investigate Li mineralization. The Ke’eryin pluton, a potential parental magma for spodumene-bearing pegmatites, consists of porphyritic biotite granite (KBG) and two-mica granite (KTMG), which crystallized at ∼209 Ma and ∼202 Ma, respectively. Sr–Nd–Hf–O isotopic compositions suggest that metasedimentary rocks and basaltic basement rocks were the major sources of the Ke’eryin pluton. A positive correlation between Li content in zircons and their δ¹⁸O values suggests that assimilation of metasedimentary rocks played a significant role in Li enrichment. The KBG is composed primarily of cumulate phases, whereas the KTMG represents the residual melt that underwent Li-rich melt extraction. Consequently, the Ke’eryin pluton cannot represent the parental magma composition of spodumene-bearing pegmatites. The Taiyanghe pluton consists of diorite (TD) and granodiorite (TG), which crystallized at ∼210–212 Ma. The TD originated from partial melting of an enriched lithospheric mantle, as indicated by its enriched isotopic signatures. The TG was derived from partial melting of tholeiitic basaltic rocks and metasedimentary rocks. Pressure-temperature estimates indicate the existence of a high geothermal gradient during the Late Triassic, which facilitated crustal assimilation and prolonged magmatic fractionation. We propose that high geothermal gradients are an essential factor in promoting Li-enrichment in magmas. A global compilation of major Li-pegmatite deposits and high-temperature/pressure metamorphic events reveals a close spatiotemporal correlation.