Preliminary geochemical and Nd isotopic investigations of Archean volcanic and volcaniclastic rocks of the Yathkyed greenstone belt, Kivalliq region, Northwest Territories

Geochemical and Nd isotopic data for nine mafic supracrustal rocks from the upper and lower tectonostratigraphic units of the Yathkyed greenstone belt are presented. All are tholeiitic except one calc-alkaline andesite from the upper unit. Incompatible-element plots demonstrate that seven samples have flat, parallel patterns comparable to modern MORB, but exhibit increased light-rare-earth-element enrichment and variable development of minor Nb and Ti troughs with decreasing Mg number. The remaining three rocks are light-rare-earth-element enriched and have variably developed Nb and Ti troughs. Two sedimentary rocks from the lower unit have flat rare-earth-element patterns similar to those of the basalts. Nd isotopic data indicate that most samples are isotopically juvenile, having eNd values ranging from +3.4 to +0.5, only slightly lower than depleted mantle. Two samples, one each from the upper and lower units, may have been contaminated by older crustal material.