Available data show that the anorthositic rocks of the Nain Plutonic Suite carry Sr and Nd isotopic enrichments, which are due either to crustal assimilation or to derivation of parent magmas from enriched mantle sources. These conflicting hypotheses can be tested by rare-earth element (REE) and Sr, Nd and Pb isotopic studies of available samples from country rocks and contact zones of the plutonic suite, as well as better characterization of the interiors of plutons. Combined with new Pb isotopic data from the Kiglapait Intrusion, the studies will furnish a definitive test of contamination versus source enrichment. Tectonic and thermal history of the region before, during, and after the anorthosite episode will also be illuminated by comprehensive study of mineral closure ages by the argon-argon method.
