河南卢氏县拐峪采矿遗址出产绿松石的Sr、Pb同位素产地特征探析

Origin characteristics of Sr and Pb isotopes of turquoise from Guaiyu mining site in Lushi County, Henan Province

河南卢氏县拐峪绿松石采矿遗址位于伊洛盆地西缘,该遗址的发现为研究中原早期绿松石的来源提供了重要的考古学信息。为判定该古矿产出绿松石的流向,尝试利用热电离质谱仪(TIMS)检测了拐峪古矿绿松石样品的Sr、Pb同位素组成,并结合秦岭5个主要绿松石矿的相关同位素数据,尝试寻找其产地特征。分析结果显示,拐峪绿松石^(87)Sr/^(86)Sr值相对较高,整体大于0.719 0,高于其他产地,可视为其产地特征之一;采用^(208)Pb/^(204)Pb-^(207)Pb/^(208)Pb联合示踪可得到较好的结果,在相关图解中拐峪绿松石具有独立的数据聚集区,可作为判断其产地证据之一;采用^(208)Pb/^(204)Pb-^(87)Sr/^(86)Sr和^(207)Pb/^(208)Pb-^(87)Sr/^(86)Sr联合示踪,也得到了较好的判别效果,拐峪绿松石与其他产地界线清晰,无明显重叠,表明Sr、Pb同位素组成是判断拐峪绿松石产地的重要证据。

The Guaiyu turquoise mining site in Lushi, Henan Province is located in the western margin of the Yiluo Basin. The discovery of the mining site provides important archaeological information for the study of the provenience of turquoise in the early Central Plains. In order to determine the direction of the turquoise from the ancient mine, the Sr and Pb isotopic compositions of Guaiyu turquoise were detected by thermoelectric ionization mass spectrometer(TIMS). Combined with the isotopic data of five major turquoise deposits in Qinling Mountains, the provenience characteristics of turquoise from Guaiyu ancient mining site were explored. The results show that the^(87)Sr/^(86)Sr ratio of Guaiyu turquoise is relatively high, which is greater than 0.719 0 on the whole, and higher than that of other turquoise deposit, which can be regarded as one of the characteristics of the Guaiyu turquoise. There is a high degree of overlap among Pb isotopic compositions, however, the^(208)Pb/^(204)Pb-^(207)Pb/^(208)Pb diagram shows some independent data gathering areas,which can be used to judge the origin of the Guaiyu turquoise. In addition,combination of^(208)Pb/^(204)Pb-^(87)Sr/^(86)Sr and^(207)Pb/^(208)Pb-^(87)Sr/^(86)Sr also obtained a good discrimination result, and the boundary with other regions is clear without obvious overlap. The Sr and Pb isotope composition is an important evidence to judge the origin of the Guaiyu turquoise.