Determination and Analysis of Rb/Sr Ratio in Yixing Purple Sand Using Energy Dispersive X-Ray Fluorescence Spectrometry
XU Wei-xuan1, CHEN Wen-bin2*, SHAN Ai-xian3
1. School of Arts, Tiangong University, Tianjin 300387, China
2. Shenzhen EDXRF of IoT Technology Ltd., Shenzhen 518017, China
3. School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
Abstract：The natural isotope87Rb, a trace element rubidium in geology, is radioactive and can be used to determine geological age. The ratio of rubidium to strontium (Rb/Sr) and the strontium isotope ratio (87Sr/86Sr) are commonly used scientific methods for studying the provenance characteristics of ancient ceramic raw materials. 87Sr is primarily formed through the radioactive decay of 87Rb. The rate of rubidium decaying into strontium is related to the chemical weathering history and geological age. Since the Ming Dynasty, Huanglong Mountain in northwest Dingshu Town, Yixing, has served as the primary source of purple clay raw materials due to its abundant mineral deposits. This experiment aims to perform a non-destructive determination of Rb, Sr, and the Rb/Sr ratio using energy-dispersive X-ray fluorescence spectrometry on a select number of samples from historical Yixing purple sand works of different periods. The Rb/Sr ratio in the ore materials is related to the depth of the ore layer, influenced by factors such as chemical weathering history and leaching of surface water and rainwater. The deeper the geological layer corresponding to the raw materials, the lower the Rb/Sr ratio; shallow surface ore materials experience greater leaching of Sr, resulting in a higher Rb/Sr ratio.The experimental results show that during the Ming and Qing dynasties, when traditional hand tools were used for mining, the Rb/Sr ratio of the samples was relatively close. From the late Qing dynasty to the 1960s, due to modern mining operations (projects of Wells No. 1 to No. 3) based on the foundations of the Ming and Qing quarries, the Rb/Sr ratio of the samples was slightly lower than during the Ming and Qing periods, though the difference was not significant. From the 1970s to the 1980s, the primary source of ore materials was mechanized deep-well mining at Well No. 4, which had a digging depth of -80 meters, significantly exceeding the previous depths of -20 to -50 meters, resulting in a notable decrease in the Rb/Sr ratio of the samples. In recent decades, most of the ore materials from Huanglong Mountain have been sourced from surface layers or manually excavated materials, resulting in Rb/Sr ratios in the samples that are generally higher than those of historical samples from earlier periods. According to the experimental data, the Rb/Sr ratios of purple clay samples from different periods are related to the depth of the ore layers. They are consistent with the documented depths of mined layers corresponding to each era. Quantitative analysis performed using EDXRF, facilitated by calibration curves, endows this method with high operability. The method is simple to operate and provides rapid analysis, facilitating a quick comparison between a large number of reference data and test samples. This has certain application prospects for tracing the provenance of Yixing Huanglongshan purple sand ore materials and identifying the age of their products.
Key words：Yixing purple sand; Rb/Sr; EDXRF; Ancient ceramics; Nondestructive testing
徐伟轩，陈文彬，单艾娴. 能量色散X射线荧光光谱法用于宜兴紫砂Rb/Sr比值的测定与分析[J]. 光谱学与光谱分析, 2025, 45(09): 2550-2556.
XU Wei-xuan, CHEN Wen-bin, SHAN Ai-xian. Determination and Analysis of Rb/Sr Ratio in Yixing Purple Sand Using Energy Dispersive X-Ray Fluorescence Spectrometry. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2025, 45(09): 2550-2556.
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