OSL chronology of traditional zinc smelting activity in Yunnan province, southwest China

Abstract

The production of zinc has played an important role in both the technological and the economic history of ancient china. However, the lack of studies on zinc smelting remains with convincing chronology limits our understanding on the history of zinc production.

Our recent field survey in Yunnan province, southwest china, has discovered zinc-smelting sites in Qiaojia County. The location is in the Jinsha River Valley, which has abundant lead, zinc, copper and mineral coals. Large numbers of crucible and slags were excavated, which indicates a large scale of zinc production in the region. A profile of 10 layers containing slag pellets altered with fluvial sediments presents clear evidence of a series of zinc smelting events. The ages of both the fluvial sediment and slag layers have been obtained using luminescence dating. Detailed chronology indicates that large scale of zinc production in this area can be traced back to late Qing Dynasty (AD 1854).

Introduction

Zinc (Boiling temperature: 907 °C) was a difficult and enigmatic metal in the antique world. It immediately volatilizes and reoxidizes when people attempt to reduce the zinc ore in an open furnace. The earliest use of zinc is to make brass, an alloy of zinc and copper. Brass was manufactured by heating zinc-bearing copper ore and charcoal to 1000 °C in a sealed crucible to directly dissolve zinc vapor into the copper (Craddock, 1978). Regular production of unalloyed zinc occurred relatively late in metallurgical history. In China, smelting of zinc was achieved based on the principle of distillation by ascending vapors (Hu and Han, 1984, Mei, 1990, Zhou, 1996). Recent studies suggest that regular zinc production in China is known to have begun in the16th Century AD in the Chongqing region (Zhou, 2007, Zhou et al., 2012). Zinc was mainly used for making brass coins and copper-bearing artefacts in the late Ming (AD 1368–1644) and Qing (AD 1644–1911) Dynasties (Zhou, 2012). The Chinese mining and smelting of zinc have a significant impact not only on the domestic economy, but also on European industrial production via exporting (Craddock and Hook, 1997).

Early studies by historians of metallurgy, mainly based on historical records and analyses of brass coins, provide us a time outline since the late Ming Dynasty (Zhang, 1925, Zhao, 1984, Zhou and Fan, 1993, Zhou, 2001). A recent case study of ancient zinc smelting sites in Chongqing analyzed production remains directly relates to older zinc smelting with an established chronology (Zhou et al., 2012). A brief outline of general temporal and regional distribution of zinc production is provided. Geological surveys focusing on traditional zinc production since the early 20th century have identified several zinc smelting sites in Hezhang, Guizhou, in 1954 (Xu, 1986); in Huize, Yunnan, in 1939; in Weining, Guizhou, in 1940; and in Huili, Sichuan, in 1941 (summarized in Mei, 1990). The sites documented by historians and geologists are mostly located in the Chuan-Dian-Qian region, a triangle-shaped area surrounded by Sichuan, Yunnan and Guizhou Provinces. The region is known to have an abundance of zinc and lead ores, coal, and other resources for zinc production (Zhou, 1997). However, lack of studies on zinc smelting sites with convincing chronology limit our understanding on the history of zinc production in this region. This paper presents the results of our recent survey to explore the history of traditional zinc smelting in this area.