Igneous rocks of the Early Precambrian greenstone-granite complex of northeastern Minnesota consist of four major groups: (1) metavolcanic tholeiitic basalt and basaltic andesite;(2) metavolcanic trondhjemite gneiss, intrusive tonalite, extrusive and hypabyssal dacite and rhyodacite; (3) intrusive quartz monzonite and; (4) post-kinematic intrusive syenodiorite and syenite. Major and rare earth elements, Rb, Sr and Ba were precisely determined for rocks of each group. Quantitative trace-element modeling is combined with isotopic and experimentalpetrologio evidence to delimit the origin of the individual rock types: (1) basalt by shallow melting of mantle peridotite followed by fractional crystallization to produce basaltic andesite; (2) trondhjemite, tonalite and dacite by partial melting of eclogite at mantle depths; (3) quartz monzonite by partial melting of short-lived graywacke at crustal depths; and (4) syenodiorite and syenite by partial melting of a mixed peridotite-eclogite source at mantle depths. Initial Sr 87/Sr 88 ratios of previously determined isochrons for all rock types are less than 0.701, and preclude magma origin by remelting of older granitic crust. The tectonothermal event 2700-2750 m.y. ago in northeastern Minnesota and adjacent Ontario represents addition of new erustal material from the mantle.