Reduced, fluorine-enriched mantle preconditions giant tin mineralization

Mantle redox conditions and halogen budgets influence crustal ore formation, yet mantle domains beneath intraplate magmatic provinces remain poorly understood. Here we combine zircon oxybarometry and apatite halogen data from 1,515 zircon and 309 apatite grains in Mesozoic mafic rocks across South China to investigate the underlying mantle. We identify a previously unrecognized domain that produced reduced, fluorine-enriched mafic magmas. This domain lies distal to the Paleo-Pacific subduction front and coincides with the world-class South China tin province, contrasting with the more oxidized, less fluorine-enriched magmas of the continental-margin arc. We attribute this signature to metasomatic enrichment involving phlogopite-bearing assemblages. Such a mantle reservoir may precondition tin-fertile transcrustal magmatic systems by stabilizing divalent tin, suppressing tetravalent tin incorporation into early titanium-bearing minerals, and promoting tin enrichment in highly differentiated, fluorine-rich melts. These findings highlight the redox and halogen architecture of the mantle as a key deep-seated control on continental-scale tin metallogeny. Reduced, fluorine-rich mantle conditions beneath South China may have preconditioned the crustal magmatic system for tin enrichment, providing a key deep-seated control on the formation of its world-class tin deposits, according to analysis of zircon and apatite data from Mesozoic mafic rocks across South China.