Reproduction of melting behavior for vitrified hillforts based on amphibolite, granite, and basalt lithologies

European Bronze and Iron Age vitrified hillforts have been known since the 1700s, but archaeological interpretations regarding their function and use are still debated. We carried out a series of experiments to constrain conditions that led to the vitrification of the inner wall rocks in the hillfor...

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Bibliographic Details
Published in:Scientific reports 2021-01, Vol.11 (1), p.1272-1272, Article 1272
Main Authors: McCloy, John S., Marcial, José, Clarke, Jack S., Ahmadzadeh, Mostafa, Wolff, John A., Vicenzi, Edward P., Bollinger, David L., Ogenhall, Erik, Englund, Mia, Pearce, Carolyn I., Sjöblom, Rolf, Kruger, Albert A.
Format: Article
Language:English
Subjects:
639/301
704/2151
704/2151/330
Archaeology
Avfallsteknik
Basalt
Cooling
Crystallization
Debates
ENGINEERING
Experiments
Forensic science
Heat
Heating
Humanities and Social Sciences
Laboratories
Melting
Microscopy
Mineralogy
Minerals
multidisciplinary
Quartz
Rocks
Science
Science (multidisciplinary)
Spectrum analysis
Vitrification
Waste Science and Technology
X-ray diffraction
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Summary:European Bronze and Iron Age vitrified hillforts have been known since the 1700s, but archaeological interpretations regarding their function and use are still debated. We carried out a series of experiments to constrain conditions that led to the vitrification of the inner wall rocks in the hillfort at Broborg, Sweden. Potential source rocks were collected locally and heat treated in the laboratory, varying maximum temperature, cooling rate, and starting particle size. Crystalline and amorphous phases were quantified using X-ray diffraction both in situ, during heating and cooling, and ex situ, after heating and quenching. Textures, phases, and glass compositions obtained were compared with those for rock samples from the vitrified part of the wall, as well as with equilibrium crystallization calculations. ‘Dark glass’ and its associated minerals formed from amphibolite or dolerite rocks melted at 1000–1200 °C under reducing atmosphere then slow cooled. ‘Clear glass’ formed from non-equilibrium partial melting of feldspar in granitoid rocks. This study aids archaeological forensic investigation of vitrified hillforts and interpretation of source rock material by mapping mineralogical changes and glass production under various heating conditions.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-020-80485-w