Late Archean high-Mg granitoids (sanukitoids) in the southern Karelian domain, eastern Finland: Pb and Nd isotopic constraints on crust−mantle interactions

The geochemical and isotopic data suggest that the Nilsiä and Lieksa granitoids originated at ca. 2.73 Ga from a mantle-wedge source enriched in LILE, U, Th and Pb by recycling of continental material in subduction-related slab dehydration processes shortly (up to 200 Ma) before melting. A considerably large amount of crustal lead was contributed from subducting sediments into the overlying mantle wedge. Consequently, the isotopic composition of mantle-wedge lead was overprinted by crustal lead isotope signatures. It is suggested that crustal recycling through subduction zone processes played an important role for the enrichment of the mantle wedge and generation of mantle-derived high-μ granitoids in the Archean.