Archaeological research on trade and exchange systems in Melanesia was studied by chemical analysis of artifacts and their raw materials. By proton-induced x-ray (PIXE) and y-ray (PIGME) analysis in an automated system, more than 2000 obsidian specimens were analyzed for 21 or less elements. The data analysis has shown that discrimination is possible between source subunits within a related volcanic suite of sources. The source groups, and the artifacts belonging to them, were sorted by multivariate clustering and allocation procedures. Apparently obsidian was carried from sources to sites more than 400 kilometers away, across a sea barrier, around 6000 years ago and more than 3000 kilometers from the Bismark Archipelago to Vanuatu (New Hebrides) 3000-4000 years ago. -- AATA