Constraints on the Geochemical Provenance of Refined Copper and Brass Artifacts from the Gaspereau Lake Area, King’s County, Nova Scotia: Insights into the Metallurgical and Trace Element Systematics of European Contact-era Trade Alloys

English Abstract:

During the 16^th and 17^th centuries, copper and copper alloys were key trade materials with considerable spiritual and functional significance to indigenous peoples. A collection of 9 copper-based archaeological artifacts from the Gaspereau Lake area of Kings County, Nova Scotia were analyzed by a variety of microanalytical methods in order to constrain the European origin of the contained metals, providing insight into the timing and nature of trade activities between the indigenous peoples of the Atlantic Northeast and European explorers/settlers, and geographic constraints on ore sources for the production of the metal alloys.

The artifacts range in composition from pure (refined) copper to gilding metal, bronze, and a variety of brass alloys. Refined copper coinage of known European provenance (Sweden, Spanish Netherlands, England, Hungary) and age (spanning a ~300 year period) were characterized by SEM-EDS to provide a reference provenance data set for the range of bulk and “speiss” inclusions (contaminant inclusions formed during smelting) expected in refined copper from the period bracketing European exploration of North America. The majority of speiss compositions ranged from single element (Pb) to complex alloy compositions (Pb-As-Sb-Fe-Sn-Ni-Ag). Similarities in speiss composition exist between Swedish and Spanish coinage (containing Cu sourced from Sweden) minted from 1560 to 1680 and three of the artifacts. Preliminary LA-ICPMS data indicate that Sb/As ratios in the artifacts may be used to differentiate Swedish from central European sources of Cu, owing to the presence or absence of specific sulfosalt minerals in the original mined ores. Preliminary Pb isotope data from the Pb-bearing speiss inclusions (by SIMS) shows that whereas ~pure Cu artifacts with minimal speiss contamination sit closer to compositional fields for the primary Swedish site of Cu production (Falun deposit, Great Copper Mountain), artifacts composed of brass alloys or heavily contaminated with Pb-rich speiss have Pb isotope compositions overlapping with the Central European sources in Poland and Germany, suggesting a non-Swedish source for Cu or Zn required for brass production, and/or Pb-bearing flux used during Cu smelting. The Pb isotope heterogeneity of the Falun deposit is also being evaluated.