SM-ND ISOTOPIC EVIDENCE FOR CRUSTAL CONTAMINATION IN THE CA.1750 MA-WANAPITEI COMPLEX, WESTERN GRENVILLE PROVINCE, ONTARIO

The Wanapitei Complex consists of a variably metamorphosed gabbronorite lying immediatelt adjacent to the Grenville Front Boundary Fault. U-Pb zircon geochronology indicates a crystallization age of 1747(-5)(+6) Ma for a noritic component, with both Grenville-aged (ca. 1000 Ma) metamorphism and minor older inheritance indicated. Geochemical evidence is consistent with plagioclase-pyroxene fractionation, but indecates additional open-system behaviour. epsilon(Nd(1.75)(1)) data indicate contamination of a depleted mantle by light rare earth element-enriched material during the Penokean. This was followed during emplacement by extensive contamination of the then isoptopically near-chondritic magma with variable amounts of evolved archean crustal material, on the order of 40% in exteme cases, generating epsilon(Nd(1.75)) values between 0 and -7.5.