重庆地区出土青铜器铅同位素比值研究

Isotope ratio study of lead contained in bronzes excavated from the Chongqing area

青铜器矿料来源和产地研究,是青铜时代至关重要的考古问题,也是考古的重点和难点之一。通过比较青铜器样品和矿床的Pb同位素分析数据,可以进行青铜金属原料来源的产地研究。为此,本工作利用MAT262固态离子源型质谱仪对重庆地区云阳李家坝遗址,涪陵小田溪墓群,万州大坪墓群,开县余家坝遗址东周时期巴地青铜器的铅同位素进行了测定和比值研究。结果显示其中合金中铅都为普通铅,而非放射性成因铅。实验数据反映出206Pb/204Pb比值分布在17.4630~18.6960,207Pb/204Pb比值分布在15.5573~15.8490,208Pb/204Pb比值分布在36.7828~39.3869,除了两个数据外,大部分器物铅同位素比值分布范围几乎重叠,显示了稳定铅源的存在。此外,这批数据与滇川黔铅锌多金属成矿区的底苏和大梁子矿床数据分布范围相近,局部重合,表明其铅料来源与这一地区有着一定的关系。实验结果反映了重庆地区东周青铜器群在铅料来源上具有同一性和连续性,说明了巴人在春秋时期就已经建立了独立的青铜冶铸业,一直延续到战国时期。

The origin of ore is a key issue in bronze age archaeology. It has also been one of the most difficult stud- ies. By comparing isotope ratios of lead found in ore beds and those from bronze, the researcher can sometimes i- dentify the source and origin the bronzes. This study used the MAT - 262 thermal ionization mass spectrometry （TIMS） to detect the isotope ratios of lead contained in bronzes from the Lijiaba, Xiaotianxi, Daping and Yujiaba sites in the Chongqing area. The results indicate that Pb in the bronze alloys is common lead, and that the ratios of 2~6pb/2~4pb, 2~Tpb/2~4pb and 2~spb/Z^4Pb are 17.46 - 18.67, 15.56 - 15.85 and 36.78 ~ 39.39, respectively. Except for two data sets, all results have good overlap and fall within a narrow range, indicating the same origin of the lead material. Furthermore, the isotope ratios of lead contained in bronzes from the Chongqing area match those of Pb - Zn deposits in the Sichuan - Yunnan - Guizhou Pb - Zn mineralization district, with the results being espe- cially close to those isotope ratios of Disu and Daliangzi Pb - Zn deposits. The results suggest that lead ore used for bronze in Chongqing during the East Zhou period came continuously from the same location. The results also sug- gest that the bronze smelting site of the Ba people is independent from that used from the early Spring and Autumn Period to the Warring Period.