Study on Hosting State between Calcite and Matrix in Root Amber from Myanmar
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摘要:
本研究聚焦缅甸根珀中普遍存在的白色脉状矿物的赋存状态及其与琥珀基体的相互关系。通过常规宝石学测试结合红外光谱分析，确定了根珀样品中黄色-棕褐色区域符合典型缅甸琥珀的产地特征；拉曼光谱显示根珀样品中白色脉状矿物为方解石，黑色颗粒状矿物为黄铁矿；光学显微镜和扫描电子显微镜详细表征了白色脉状方解石与琥珀基体的空间伴生状态，方解石呈现侵入式形态穿插于根珀基体内部结构，即大量微米级的方解石脉存在于根珀黄色-棕色基体中，它们之间的界限未见明显的成分过渡现象。值得注意的是，方解石脉与琥珀基体交界处存在大量破损碎块，这可能是导致根珀透明度较低的一个潜在因素。方解石作为一种稳定的碳源，与有机物琥珀和黄铁矿共存的现象揭示了该品种琥珀埋藏时期的古环境特征，这不仅有助于厘清根珀的形成过程，还能进一步反映古环境的变迁历史。
Abstract:This study aims to explore occurrence state of prevalent white vein-like minerals in root amber from Myanmar and their interrelationship with amber matrix. The results of the conventional gemmological tests and Fourier transform infrared spectroscopy (FTIR) confirmed that the yellow-brown matrix of the root amber samples exhibit the typical provenance characteristics of amber from Myanmar. Raman spectroscopic test results identified the white vein-like minerals as calcite and the black granular minerals as pyrite. Optical microscopic and scanning electron microscopic tests provide detailed characterization of the spatial coexistence of the white vein-like calcite and amber matrix. The calcite exhibits an intrusive morphology, interspersed within the internal structure of the root amber matrix, indicating the presence of numerous micron level calcite veins inside the yellow-brown matrix of amber. There is no compositional transition at boundaries between calcite veins and amber matrix. Additionally, the presence of large amounts of broken fragments are observed at the junction between the calcite veins and amber, which could be a potential factor contributing to low transparency of the root amber. The coexistence of calcite as a stable carbon source, with organic amber and pyrite insights into the paleoenvironmental conditions during burial period of root amber.This not only clarifies the formation process of root amber, but also further reflects the historical changes in paleoenvironment.
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Keywords:
- root amber /
- gemmological characteristic /
- associated calcite /
- occurrence state /
- Myanmar
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图 1 含白色脉状方解石的缅甸根珀样品：(a)样品FR-1A和FR-1B；(b)样品FR-1A平行双面抛光片；(c)样品FR-1B平行双面抛光片；(d)样品YR-3平行双面薄片；(e)样品LM-4平行双面薄片；(f)样品LM-5平行双面薄片
Figure 1. Root amber samples from Myanmar with white vein-like calcite inclusions: (a) samples FR-1A and FR-1B; (b) parallel double-sided polished slice of sample FR-1A; (c) parallel double-sided polished slice of sample FR-1B; (d) parallel double-sided polished thin slice of sample YR-3; (e)parallel double-sided polished thin slice of sample LM-4; (f) parallel double-sided polished thin slice of sample LM-5
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图 2 根珀样品FR-1B在自然光下(a)和长波紫外光下(b)的照片
Figure 2. Photos of root amber sample FR-1B under natural light(a) and long-wave ultraviolet light(b)
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图 3 根珀样品黄色基体区域的红外光谱
Figure 3. Infrared spectrum of the yellow matrix areas in the root amber
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图 4 根珀样品FR-1B中白色矿脉区域(a)及其与方解石参考红外光谱(b)
Figure 4. White vein-like region of root amber sample FR-1B (a) and its infrared spectrum and reference infrared spectrum of calcite (b)
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图 5 根珀样品FR-1B中白色方解石的拉曼光谱
Figure 5. Raman spectrum of the white vein-like calcite in root amber sample FR-1B
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图 6 根珀样品中黄铁矿颗粒的拉曼光谱
Figure 6. Raman spectrum of the pyrite prticles in the root amber sample
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图 7 根珀样品FR-1A的显微特征：(a)薄片样品FR-1A；(b)基体区域；(c) 方解石区域；(d) 黄铁矿区域
Figure 7. Microscopic characteristics of root amber sample FR-1A: (a) thin section of sample FR-1A; (b) matrix region; (c) calcite region; (d) pyrite region
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图 8 根珀样品表面的显微特征(a，40×)及扫描电子显微镜下背散射图像(b，400×)
Figure 8. Micrograph of sample surface (a, 40×) and backscatter image of sample under SEM (b, 400×)
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图 9 根珀样品能谱面扫描图：(a)方解石脉二次电子成像图, 6 500×；(b-d)为能谱扫描结果
Figure 9. Energy spectral face scans of the root amber sample: (a)the secondary electron image of the calcite vein, 6 500×; (b-d) the results of the energy spectral scans
表 1 缅甸根珀样品的基本特征
Table 1 Basic gemmological characteristics of root amber samples from Myanmar
样品编号 RI(点测) 相对密度 荧光特征 FR-1A 1.54 1.22 LW：强蓝白色；SW：中等蓝白色 FR-1B 1.54 1.31 LW：强蓝白色；SW：惰性 YR-3 1.54 1.14 LW：强蓝白色；SW：惰性 LM-4 1.54 1.09 LW：强蓝白色；SW：弱蓝白色 LM-5 1.54 1.20 LW：强蓝白色；SW：弱蓝白色 
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