Maw-Sit-Sit Jade from Burma: A Particular Jade Formed by Dynamic Metamorphism and Metasomatism
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摘要: 以缅甸莫西西玉为研究对象, 采用镜下分析、X射线粉晶衍射、电子探针、拉曼光谱、红外吸收光谱等分析测试方法, 重点对该玉石的成分、玉相和振动光谱特征进行了研究。研究表明, 莫西西玉主要由一组分布不均的富铬矿物组成, 即铬硬玉[x(Kch) 为15%~18%]、富铬氟镁钠闪石[w(Cr2O3)为4%左右]、钠长石、含铬钠长石[w(Cr2O3) 为1%左右]、钠铬辉石[x((Kch) 为62%~65%]及铬铁矿。玉石具典型的糜棱、交代网脉状及交代假象结构。在300~580cm-1拉曼位移范围内, 钠铬辉石和铬硬玉中由Cr—O和Al—O弯曲振动致拉曼谱峰, 其峰形、峰位、半高宽及振动频率均存在较明显的差异。研究结果初步证实, 莫西西玉属一种典型的由不同期次动力变质与低温热液交代作用形成的玉石。Abstract: Mineralogical composition, texture and vibrational spectrum and origin of Maw-sit-sit jade from Burma are studied. The testing methods of optical microscope, EPMA, X-ray powder diffraction analysis, infrared absorption spectrum and Raman spectrum are employed in the research. The results show that mineralogical composition of Maw-sit-sit jade mainly consists of chrome-jadeite[x(Kch) =15%~18%], chromian eckermannite[w(Cr2O3) =4% or so], albite, chromiferous-albite[w(Cr2O3) 1% or so], kosmochlor[w(Kch) =62%~65%], chromite, etc. The jade is formed by the dynamic metamorphism and metasomatism characterized by mylonitic, metasomatic network and metasomatic pseudomorphous textures. The shape, the location and the semi-height breadth of Raman spectra of the chrome-jadeite and kosmochlor in the range 300~580 cm-1 are closely associated with the Cr3+ concentration, and at the same time are restrained by the bend vibration of Cr-O and Al-O. The research indicates that Maw-sit-sit jade are formed by the superimposition and reformation of multistage dynamic metamorphism and low-temperature hydrothermal metasomatism.
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Keywords:
- Maw-sit-sit jade /
- texture /
- vibrational spectrum /
- Burma
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