Copper production in late prehispanic northern Chile

The spatial organization, scale, and technology of copper production were greatly altered by the Inka incorporation of the Tarapacá Valley of northern Chile during the 15th and 16th centuries. Using survey data, we first document the valley's local pre-Inka copper production tradition, based on the use of wind-driven smelting furnaces known as huayras or huayrachinas. We then trace the transformations in copper production attendant upon imperial incorporation, including the spatial organization and scale of smelting. Based on materials excavated at the site of Tarapacá Viejo, we discuss the evidence for specific stages in the copper production process, such as ore processing, secondary refining, alloying, casting, and the production of finished artifacts. Through this analysis, we shed light on how the Inka reorganized and concentrated copper production at Tarapacá Viejo, and document the adoption of several new techniques, such as lining casting molds with bone ash. This and other lines of evidence indicate linkages between copper production technologies and techniques at Tarapacá Viejo and other Inka installations in Chile and northwestern Argentina. While connections between the Copiapó Valley and Argentina have long been known, such robust evidence has not been previously documented for the Tarapacá Valley.