Tracing the source of iron bloom slags and iron ores excavated from archaeological sites in Chungju area, South Korea

Abstract

Iron ores and iron bloom slags from two iron archaeological sites (Chilgeumdong: 300–600 AD, Wanori: ∼20th century) as well as iron ores from six iron deposits in Chungju, South Korea, were examined to assess the provenance of the raw iron ores. Different ore mineralogy proves to be a useful tool in interpreting the ore provenance of samples from the iron archaeological sites, although limited by the simplicity of the assemblage. The application of Ca + Al + Mn vs. Ti + V diagram for classifying the genetic type of magnetite suggests that the iron ores of the iron archaeological sites may have originated from multiple deposits. Comparing the chondrite-normalized REE patterns and the correlation between La_n and Ce_n in iron ores and iron bloom slags aids in determining the provenance of samples from the iron archaeological sites. Despite notable deviations, the use of Pb-Sr isotope ratios as a means of identifying the origin of unprocessed iron ores proves to be a meaningful approach. Based on our findings, it appears that the iron ores discovered at archaeological sites were typically sourced from nearby iron deposits like Changdong, Yeonsudong, Daekyo, and possibly Manjeong. This preference for local sources as opposed to more distant ones, such as Obok and Yusang, seems to have remained a constant throughout various historical epochs, spanning from the Baekjae to the Joseon period. Overall, this study demonstrates the effectiveness of integrated interpretation of various complementary approaches, including ore petrography, trace and rare earth element geochemistry, and Pb-Sr isotope analysis, in determining the provenance of raw iron ores excavated from iron archaeological sites.