Disseminated sulfide mineralization at the Babbitt Cu-Ti-Ni- PGE deposit of the Duluth Complex is found within iron-and titanium-rich gabbroic rocks that occur near the contact with metasedimentary rocks of the underlying Virginia Formation. In order to evaluate possible metal sources Re- Os and Pb isotopic studies are planned. These two isotopic systems will provide direct evidence as to the relative importance of crustal or mantle sources of metals Mechanisms of metal-enrichment will be evaluated by tracing chemical variations that accompany fractional crystallization, crustal assimilation, magma recharge, and magma mixing. The addition of crustal sulfur at Duluth is thought to be a prime reason for the differences in what may be a continuum between sulfide-rich and sulfide-poor, oxide- apatite rocks. Because of the chemical similarities a comparative study with Fe-Ti-P-rich rocks from the St. Urbain and Labrieville anorthosite complexes in Quebec is planned. Results will aid our understanding of similarities and differences between mineralization in layered intrusions, subvolcanic intrusives, and massif-type anorthosites and related rocks.
