Provenance study on metal materials of the bronze weapons foundry site (2019 field session) in the ancient capital of the Zhu State, Shandong, China

A large number of bronze-casting relics of the Warring States period were discovered for the first time at the ruins of Zhu State Ancient City, Shandong, Eastern China. The microstructure, composition, and lead isotope ratio of slags and bronzes were examined. The results reveal that the slags are smelting slags, and the bronzes predominantly consist of copper-tin–lead alloys. Three types of lead materials were employed in the casting of weapons by the Zhu State: the first type likely originated from Hunan, while the other unique types could be local mineral materials from Shandong. With the growing demand for casting weapons and the constraints on metal resource circulation among various countries, the Zhu State was compelled to exploit a new type of lead material produced in neighboring regions after the early Warring States period. There was a significant shift in the lead materials used in Shandong from the middle Warring States period, transitioning from external input to the combination of the lead materials from Chu and local sources. This study provides new evidence for exploring the source, circulation, and relationship with neighboring countries concerning the mineral materials used in the production of bronzes in the Shandong area during the Eastern Zhou period.