| China is the earliest country in the world to mine and use jade. A majority of ancient jade unearthed within the territory of China in past dynasties since the Neolithic Age have used Hetian Jade (nephrite) as the raw material. Secondly, nephrites of the same quality but different origins have different values, so it is an urgent need to study the origin characteristics of Hetian Jade. Finally, as a major ancient jade material in China, nephrite has never been discontinued. Therefore, it is of great historical and cultural significance to study characteristics of various nephrite origins in China, set up a signature system of various nephrite origins and analyze from the characteristics of ancient jade for judging the source of ancient jade and further identifying the exchange scope of prehistoric culture. Based on nephrites from four typical origins in China (Ruoqiang in Xinjiang, Sanchahe in Qinghai, Xiuyan in Liaoning and Liyang in Jiangsu) as the research object, the present study carries out field geological investigation and sampling in these areas, coupled with indoor experiment, identification, comprehensive analysis and microscopic observations and conducts a gem mineralogical survey, using electron probe micro-analyzer (EPMA), X-ray powder diffraction (XRD), infrared spectroscopy (IR), Raman spectroscopy (Raman) and X-ray photoelectron spectroscopy (XPS), etc. For the first time, the present study has explored into chemical components of nephrites from 10 mining areas in 4 places, i.e., Xinjiang, Qinghai, Liaoning and Jiangsu comprehensively, using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Meanwhile, combined with measurements of ancient jade unearthed from Liangzhu Culture Zhuangqiaofen Ruins at the Neolithic Age (LA-ICP-MS), it makes an analysis from two aspects, i.e., characteristics of nephrites from all typical origins and source of the ancient jade.Microscopic observations showed that the main component of nephrites from all typical origins (Ruoqiang in Xinjiang, Sanchahe in Qinghai, Xiuyan in Liaoning and Liyang in Jiangsu) was tremolite, whose content was generally higher than 95%, mostly above 98%. The nephrite structure in all typical origins represented a typical microscopic felt-like structure of tremolite. Nephrites from Ruoqiang, Xinjiang contained a small amount of dolomite, zoisite, diopside, forsterite, serpentine and quartz. Nephrites from Sanchahe, Qinghai contained a small amount of diopside, calcite, serpentine, apatite, zoisite and quartz. Nephrites from Xiuyan, Liaoning contained a small amount of apatite, epidote, serpentine, chlorite, talc, graphite, pyrite, magnetite and limonite. Nephrites from Liyang, Jiangsu contained a small amount of biotite, calcite and opaque black metallic minerals. Along with the size of crystal grain, nephrites from Ruoqiang in Xinjiang, Sanchahe in Qinghai and Liyang in Jiangsu displayed cryptocrystalline-crystalline-coarse crystalline structural characteristics.Through EPMA analysis, major chemical components of nephrites from all typical origins were SiO2, MgO, CaO and a little FeO+Fe2O3. Besides, w(SiO2), w(MgO) and w(CaO) were relatively stable. The variation was not large. They were basically the same as the ideal chemical components of tremolite. By calculating chemical formula of minerals, the author obtained the occupation of B-site ions and judged that all the nephrites from all typical origins belonged to the calcium hornblende family. Major chemical components of nephrites from all typical origins did not vast greatly.XRD results showed that nephrite samples from all typical origins basically had the same diffraction peak combinations. Generally, they showed the highest peak around 3.13 A. The peaks were generally strong around 8.54 A,3.28 A and 2.71 A, too. They had basically the same diffraction characteristics as tremolite in the JCPDS-International Centre for Diffraction Data. All of the cell parameters were close to theoretical values of tremolite, too. The main difference was that characteristic peak intensities of nephrite samples from different origins were slightly different: the powder diffraction peak of nephrite sample from Liyang Jiangsu was low around 4.54 A, slightly different from the other four origins. The powder diffraction peak of nephrite sample from Ruoqiang, Xinjiang was higher around 2.71 A than around 4.54 A. In the other four origins, however, characteristic peaks were higher around 8.54 A than around 2.71 A.IR results showed that the infrared absorption frequency of nephrites from all typical origins mostly appeared in 3700～3600 cm-1 and 1200～800 cm-1 in high-frequency range, and 800～600 cm-1 and 600～400 cm-1 in low-frequency range. Infrared spectra of nephrites from all typical origins were similar at room temperature and resembled the standard IR spectrum of tremolite, suggesting that nephrites from all typical origins was composed of pure tremolite. The content of impurities was very small. Only nephrites from Liyang showed a 3691 cm-1 absorption peak related to Na and K, which hadn’t been reported in previous studies. This feature can be used as an important indicator to distinguish nephrite in Liyang, Jiangsu from other origins.Raman test results showed that characteristic peaks in Raman spectrum of nephrites from all typical origins had a certain degree of consistency. Major characteristic peaks include 124 cm-1,178 cm-1,224 cm-1,371 cm-1,395 cm-1,527 cm-1, 675 cm-1,932 cm-1,1029 cm-1,1061 cm-1 and 3674 cm-1. All of them were consistent with the standard Raman spectrum peak of tremolite. The OH vibration bands of emerald jade, cyan jade and pale green jade from different origins were split into three bands at 3500-3800 cm-1 and the intensity showed a trend of gradually decreasing.XPS test results showed that Fe2+ and Fe3+existed in tremolite. Typically, Fe2+ appeared in any of M1, M2, M3 and M4 electrodes, while Fe3+ often occupied M1, M2 and M3 electrodes.The change rule of trace elements showed that metallogenic materials in materials came from protolith and had a good inheritance. All trace elements across nephrites from all typical origins, except nephrites from Sanchahe, Qinghai (Ba enrichment and Rb depletion in trace elements), showed Ba and Nb depletion and Rb and U enrichment. With respect to the partitioning behavior of rare earth elements, nephrites from Liyang, Jiangsu showed a rightward curve with light rare earth enrichment. The light rare earth section was flat, while the heavy rare earth section was steep, with evident negative anomaly of Eu, and belonged to intermediate-acidic metasomatism. Nephrites from Xinjiang differentiated between light and heavy rare earth. The negative anomaly of Eu was evident. Ce didn’t’ have obvious abnormal characteristics, suggesting that nephrites from Xinjiang were formed by contact-metasomatism between intermediate-acidic magmas and Cambrian magnesian carbonate. The partitioning curve of rare earth elements in Sanchahe, Qinghai tended to be flat. The differentiation degree between light and heavy rare earth was not evident. Rare earth elements in Xiaozaohuo, Qinghai, however, presented a significant leftward curve of heavy rare earth enrichment. The former was contact-metasomatic between basic intrusive rocks and magnesian carbonate, while the latter was between intermediate-acidic intrusive rocks and magnesian carbonate. Most of nephrites from Xiuyan, Liaoning displayed a flat cure with insignificant differentiation between light and heavy rare earth. There existed a flat rightward curve with little light rare earth enrichment and heavy rare earth depletion. Most of nephrites from Xiuyan showed negative anomaly of Eu. Only a few showed positive anomaly, indicating that nephrites from Xiuyan had a complex metallogenic fluid.Finally, by comparing the ancient jade unearthed from Liangzhu Culture Zhuangqiaofen Ruins to modern nephrites from all typical sources in terms of color, gloss, transparency, refractive index, relative density, main components and trace elements, etc, the author found that the partitioning behavior of rare earth in the ancient jade unearthed from Zhuangqiaofen present a leftward curve with negative anomaly of Eu. Predecessors’studies have reported that the partitioning behavior of rare earth in Xiaomeiling Jade Mine in Liyang, Jiangsu (the source of Liangzhu Culture jade materials) presented a rightward curve with negative anomaly of Eu. Therefore, it is believed that the source of the ancient jade unearthed from Liangzhu Culture Zhuangqiaofen Ruins is not Liyang, Jiangsu, but mostly like nephrite from Xinjiang. |
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