Lithium isotopes constrain the role of fluid in Ta-Nb-Li-Sn enrichment in the Limu granite, South China

The distinctive roles of fluid activities in the rare-metal enrichment in granite have garnered considerable attention, yet ongoing debate persists. Lithium isotope systematics (δ⁷Li) of the Limu granite from South China provide unambiguous evidence for solving such an issue. The varied δ⁷Li values in Yucai-1 (-0.2 to +0.9 ‰), Yucai-2 (-0.4 to -0.3 ‰), and Shuiximiao (0 to +1.7 ‰) granites indicate three types of fluid activities, i.e., fluid exsolution and the separated alterations induced by Yucai and Shuiximiao fluid. The published H-O isotope data and the absence of external ⁷Li-enriched reservoirs confirm the magmatic origin of both Yucai and Shuiximiao fluids, excluding interference from external fluids. The Yucai fluid contained abundant Sn and Li but lacked Nb and Ta, whereas the Shuiximiao fluid was enriched in Ta, Nb, Li, and partially in Sn, explaining the metallogenic selectivity of different granite bodies. Our findings shed further light on the crucial role of fluid in rare-metal enrichment in granite.