A glimpse into the monetary supply network of the Tang empire in the seventh century CE: archaeometallurgical study of Kaiyuan Tongbao coins from Lafu Queke cemetery, Xinjiang, Northwest China

Abstract

The supply of coins and their metal materials is important for state governance. Many details about the monetary supply network in ancient China still need to be verified. In this paper, 15 early Tang dynasty Kaiyuan Tongbao 開元通寶 coins excavated from the Lafu Queke 拉甫却克 cemetery, Hami 哈密 city, were studied by combining scientific analyses (PXRF and MC-ICP-MS etc.) with the archaeological context and historical texts. The results show that all of these coins are made of Cu-Sn–Pb ternary alloy. The lead isotopes match with the isotopic signatures of some southwest China lead mines consistent with historical records, 14 coins are located in the range of Southern China geochemical province, and the lead of 5 coins could be considered as highly radiogenic lead (HRL). Combining these results with the archaeological context and historical texts, it can be inferred that the coins minted in southwest China were made from locally exploited raw metal, and supplied to the northwest borderland of the Tang dynasty in the seventh century CE.