Browsing by Author "Plaza, Maria Teresa"

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    A new piece of the puzzle: slag and ore analysis to reconstruct the prehispanic smelting technology at the Atacama Desert, Chile
    (SPRINGER, 2023) Plaza, Maria Teresa; Garrido, Francisco; Larreina-García, David
    The Incas appropriated many local metallurgical technologies throughout the Andes, each of which had its unique peculiarities and was based on local ancestral knowledge. The widespread use of tin-bronze during the Inca expansion, the development of mining and smelting sites, as well as ethno-historical records evidence the Incas' interest in copper smelting, a key activity in the Andes since ca. 1400 BC. However, little is known about the technical parameters achieved by ancient metallurgists and the changes that occurred during the Inca expansion. In this paper, we address these changes through a case study of Copiapo valley, focusing on the Vina del Cerro site, one of the most famous Inca smelting centres of the southern Andes. Although this place was architectonically restructured by the Incas, its operations began long before the imperial expansion and used wind-powered furnaces. We analysed 19 slag and 11 copper ore samples using OM, SEM-EDS, WD-XRF, and XRD analyses. Results identified heterogeneous and viscous slags, rich in SiO2 (43 wt%) and poor in FeO (13 wt%). Copper retention was high (up to 60 wt%). Microstructural analyses indicate that slags were formed under unstable oxidising conditions, reaching temperatures that ranged between 1000 to 1100 & DEG;C. The copper produced was very pure. High-grade copper ores containing up to 69 wt% CuO were reduced at the site, combining carbonates (malachite, azurite), halides (buttgenbachite, clinoatacamite), and some sulphates (brochantite). We propose that even under the relatively unfavourable conditions for slag formation, the smelting conditions generated at Vina del Cerro were competent enough to extract metal, but not necessarily enough to form liquid slag. These conditions were facilitated by the local metallurgists' thorough knowledge of the wind flow and their ability to select the right ore. This new information contributes to understanding the efficiency of metallurgical technology and the knowledge, skills, and adaptability of the ancient metallurgists from Copiapo valley, a group that was integrated into the economic networks of the Inca Empire.
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    Obsidianas, turquesas y metales en El Sur De Chile. Perspectivas sociales a partir de su presencia y proveniencia en Isla Mocha (1.000-1.700 D.C.)
    (2018) Campbell Toro, Roberto Juan José; Carrión, Hugo; Figueroa, Valentina; Peñaloza, Ángela; Plaza, Maria Teresa; Stern, Charles
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    Technology, Use and Reuse of Gold during the Middle Period: The Case of Casa Parroquial, Atacama Desert, Chile
    (2021) Plaza, Maria Teresa; Martinon-Torres, Marcos
    The life-histories of gold artefacts can provide rich insight into technology and culture, but so far the potential of this research approach has not been exploited in the south central Andes. Here we present the analysis of 34 gold and silver objects from the Middle Period cemetery of Casa Parroquial (San Pedro de Atacama, northern Chile), using pXRF, SEM-EDS, PIXE and digital microscopy. Chemical analyses detected variable compositions (2.4-73.1 per cent Ag and 0.2-3.4 per cent Cu) suggesting that artisans used both native gold and artificial gold-silver-copper alloys. Based on their manufacturing techniques, quality and designs, we identify two working styles, one technically more 'careful' than the other. Given their elemental and technological variety, together with the lack of local production evidence, we propose that these artefacts were imported as finished objects from Tiwanaku or Cochabamba and northwest Argentina. However, we identify a series of objects that were modified or reshaped as they entered a new cultural context, revealing complex life-histories. Modifications used relatively simple mechanical means: punching, cutting and folding, most likely made in multi-craft contexts by non-metallurgists from San Pedro.