New scientific analyses reveal mixing of copper sources in the early Iron Age metal production at Ili, western China.

The crucial role that Xinjiang played in cultural communication across the Eurasian steppe in prehistory is evidenced by the large number of copper-based objects that represent the early metallurgical technologies found across this region. Our research adds new chemical and isotopic analyses of 44 copper-based objects dated to the early Iron Age of Ili in Xinjiang, western China. As noted in a number of publications, tin bronze and arsenic copper/bronze were the dominant alloying types across Xinjiang during the second and first millennium BC, whereas some specific types of objects such as cauldrons are often made from pure copper. The western Tianshan Mountain, including the well-known mining site Nulasai, is the most likely copper source for the Ili metalworking. Meanwhile, a combination of lead isotopes, lead concentrations and trace elemental data reveals new evidence for the mixing and recycling of different sources of copper.