How the metal supply for mintage shifts in the transforming monetary system of the Han Empire: Archaeometallurgical study of the Wuzhu coins from the Guanghuacun cemetery, Chengdu, Southwest China

The monetary system and the metal supply for mintage are both important for state governance. The relationship between these two issues in the Han Empire, China, still need to be verified. In this paper, 23 Wuzhu coins of the three Shanglin offices ( , SLSG) of the Western Han dynasty (202BCE-8CE, WHD) and the Eastern Han dynasty (25-220 CE, EHD), excavated from Guanghuacun cemetery, Chengdu city, were studied by SEM-EDS, ICP-AES and MC-ICP-MS, etc. The results show Cu-Sn-Pb, Cu-Sn, and Cu-Sb-Sn-Pb alloys, and identify one of the coins with the highest content of tin in ancient China. The lead isotopes and trace elements reflect the changes in the provenances of metal materials for mintage from concentrated to scattered between the SLSG and EHD periods. The lead isotopes infer that the lead of SLSG coins was mainly derived from the Xiaoqinling region, and the sources of lead for EHD coins should include the Xiaoqinling, the Sichuan-Yunnan-Guizhou Rhombic Block , the Qinling , and the lower Yangtze regions. These findings on the shift in metal supply for mintage in the transforming monetary system provide a new insight into the issues of political and economic policy of the Han Empire.