新疆两处遗址出土绿松石文物的成分分析和产源判别

绿松石是一种产地有限,却在世界范围内被广泛使用的珍稀宝石资源,研究绿松石文物的矿料来源可为了解古代不同地区间珍稀资源的获取与交流模式、文化传播途径、早期贸易网络等学术问题提供帮助。新疆绿松石文物的矿料来源是近年来科技考古关注的热点问题之一,目前存在中原说、波斯说、新疆说和多元说等观点。研究新疆绿松石文物的产源,其难点在于既要保证文物的安全,又要确保分析数据的准确性,同时要避免样品表面污染对数据结果带来的干扰。鉴于此,采用等离子体原子发射光谱LA-ICP-AES对新疆加依、西沟两处墓地出土的绿松石进行化学成分分析,并结合秦岭东部五处产地的绿松石成分数据,经主成分分析绘制散点图——建立产地区分模型。主成分分析结果显示加依墓地样品中有五枚是罕见的锌绿松石,其余同西沟墓地绿松石的成分相近,均含有相对较高比例的Fe和Sr。结合中原地区的绿松石成分数据对比分析,发现新疆两遗址绿松石的微量元素特征相近,以高B2O低BaO为特征区别于中原地区的绿松石样品。在产地区分模型中,代表加依墓地和西沟墓地出土绿松石的散点聚集成团,且明显区分于白河、郧县、洛南、竹山、淅川五地的散点分布区域。综上结果表明新疆东部两处遗址的绿松石制品与中原东秦岭五处绿松石矿区所产矿料的成分差异较大,鉴于近年来新疆哈密发现与两处遗址同时代的绿松石采矿遗址,推测加依墓地、西沟墓地的绿松石制品其矿料来自中原地区的可能性较小。

Study on Chemical Composition and Provenience Differentiation of Turquoises Excavated from Two Sites in Xinjing

Study on geological provenience of turquoise can reveal a lot about ancient trade, organization of resources and cultural exchanges, thus the origin of turquoise artifacts excavated from Xinjiang has been a hot issue in archaeometry in recent years. At present, there are three major academic hypotheses on the provenience of turquoise objects found in Xinjiang: Central Plains, Xinjiang or Persia. In order to determine the provenience of turquoise excavated from Jiayi and Xigou sites, two cemeteries in the eastern part of Xinjiang have been chosen, and we examined the turquoise samples using LA-ICP-AES to analyze the chemical composition and PCA to compare the results with samples from five regions in the eastern Qinling Mountains(Central Plains). The results of the composition analysis of the objects from these two sites have shown that five of the Jiayi site samples are rare zinc turquoise, while the other samples are similar to those turquoise samples of the Xigou site and contain relatively high level of Fe and Sr. Based on the comparative analysis of the turquoise composition data between these two sites and samples from the Qinling Mountains, it was suggested that the trace elements of turquoise artifacts from Jiayi and Xigou sites are not similar to the turquoise samples in the Central Plains, different in view of higher level of B2O(Wt%) and lower level of BaO(wt%). According to the provenience differentiation model, the samples from these two sites have formed a cluster and are clearly distinguished from the distribution areas of Qinling Mountains. Hence, it can be concluded that the composition of the turquoise artifacts excavated from Jiayi and Xigou sites is different from the minerals of Qinling, Mountains in Central Plains. Based on the discovery of the ancient turquoise mining site in Hami, Xinjiang, the turquoise artifacts found in Jiayi and Xigou sites are barely likely to be from Central Plains.