Petrogenetic constraints for the genesis of Archaean sanukitoid suites: geochemistry and isotopic evidence from Karelia, Baltic Shield

We envisage a temporal evolution of the composition of the mantle in this region. This pattern of evolution controlled production of the sanukitoid melts and explains why the sanukitoids have such a restricted range of ages. Sanukitoid magma production must have followed from a major, global mantle enrichment event. These magmas could not have been produced earlier because the Archaean mantle had not become sufficiently enriched before 2.7 Ga. We suggest that their scarcity after the major period of sanukitoid magmatism may be due to the increased thickness of overlying crust, which can inhibit mantle enrichment.