The role of an oxidized lithospheric mantle in gold mobilization.

Phanerozoic orogenic gold mineralization at craton margins is related to the metasomatism of the lithospheric mantle by crustal material. Slab subduction transfers Au from the crust to the metasomatized mantle and oxidizes the latter to facilitate the mobilization of Au into mantle melts. The role of volatiles in the mobilization of Au in the mantle is unclear because of the absence of direct geochemical evidence relating the mantle source of Au to Au mineralization in the overlying crust. This study uses lithium isotopes from a large suite of lamprophyres to characterize the mantle beneath the eastern North China Craton, which hosts giant Mesozoic gold deposits. Our results indicate a strong genetic link between carbonate metasomatism in the mantle and Au mineralization in the overlying crust. Although pre-enrichment of Au in the mantle is critical for forming giant Au provinces, the oxidation of the lithospheric mantle controls the mobilization of Au.