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The acquisition of large-scale copper-based alloys was premised on large-scale mining and mineral smelting, which also implied the enhancement of social organizational capacity and the emergence of a new social order. Moreover, the lead in these ancient unalloyed copper wares is supposed to be an impurity in the copper ore, reflecting the source of the copper ore.Īs the main raw material for manufacturing copper alloys, copper minerals have an important relationship with the Bronze Age civilization. Therefore, in order to eliminate the influence of additional tin and lead on the lead isotopic studies for copper, this paper focuses on unalloyed copper artifacts with very low lead and tin content. put forward that several artifacts with low lead contents (<1 wt%) and malachite samples from various sites also showed similar lead isotope ratios, suggesting that the source of highly radiogenic lead in alloys is indeed copper ores with variable lead content. However, Qin proposed that it is difficult for lead in cassiterite or tin ingot to have an effect, as the copper content in Chinese bronze ware products is much higher than the tin content. There is much evidence that the lead in cassiterite and tin ingot is highly radiogenic. In addition, it has been suggested that lead isotopes reflect the origin of tin minerals even for low-lead copper ware in Southern Africa.
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When the content is below a certain level, e.g., 1 wt% is a relatively low value among all proposals, lead isotope should be considered to reflect the source characteristics of other ores. Archaeologists hold different views on the threshold for excluding interference from lead impurities in other ores. Therefore, the lead content needs to be used as a criterion to determine whether lead material was intentionally added to the metal artifact. It is generally believed that if a copper-based artifact has a low lead concentration, its lead isotope data should reflect the source of copper ore. In addition, several artifacts, turquoises, and smelting slags with low lead contents from other regions such as Sichuan and Jiangxi have similar isotopic features. Some unalloyed copper sickle-shaped objects and Zhang sceptres, which are recognized as characteristic products of the Hanzhong community, hold a highly radiogenic lead composition. For example, the copper sickle unearthed from the Haimenkou site in Yunnan Province contain evident abnormal lead. However, among the highly radiogenic copper-based artifacts from China, there are not only many high-lead bronzes but also a number of unalloyed copper wares. thereupon refuted this conclusion from the result of lead content in the Central Plains bronzes, which was much higher than that in African tin ingots, that there was no archaeological evidence to prove the connection between the Central Plains and Africa in the Shang Dynasty. compared the lead isotope data of Shang bronzes with tin ingots, tin grains, and bronze products in Africa, and argued that the lead materials for the bronzes of Yinxu originated in Africa. The recently published papers have gained wide attention in China and internationally. For example, the Qinling Mountains, the middle and lower reaches of the Yangtze River, and other places are possible sources of radiogenic lead ores. Since the application of lead isotope analysis to trace the raw materials of Shang bronzes in the 1980s, Jin has first put forward the famous view that the highly radiogenic lead was originated from the northeast Yunnan, whereas some scholars have proposed different viewpoints. As a result, the controversy over highly radiogenic lead, especially around lead-rich bronzes, has been raging in Chinese archaeology. In the Chinese Bronze Age, the casting of bronzes with high lead content was a common practice. During a few decades, the bronzes containing highly radiogenic lead were subsequently identified in many places of China, such as Henan, Sichuan, Jiangxi, Shanxi and Shaanxi. In this case, the isotopic composition of lead directly reflects the geochemical information of the lead ore raw materials (represented by galena) used for the metalwork. It is generally believed that when the content of lead in copper-based artifacts is high (more than 2 wt%), it is artificially added. Ancient bronze products were always made from a mixture of some raw materials in a certain proportion, and lead is a widely distributed element in various minerals and ores.