Radial mosaic internal structure of rounded diamond crystals from alluvial placers of Siberian platform
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- 作者：A. L. Ragozin ; D. A. Zedgenizov ; K. E. Kuper ; V. S. Shatsky
- 关键词：Diamond ; Internal structure ; Splitting ; Radial mosaic pattern ; Diffraction of backscattered electrons ; X ; ray topography
- 刊名：Mineralogy and Petrology
- 出版年：2016
- 出版时间：December 2016
- 年：2016
- 卷：110
- 期：6
- 页码：861-875
- 全文大小：6,401 KB
- 刊物类别：Earth and Environmental Science
- 刊物主题：Earth sciences
Mineralogy
Geochemistry - 出版者：Springer Wien
- ISSN：1438-1168
- 卷排序：110
文摘
The specific gray to almost black diamonds of rounded morphology are especially typical in alluvial placers of the northeastern part of the Siberian platform. The results of study of internal structure of these diamonds are presented. X-ray topography and birefringence patterns of polished plates of studied diamonds show their radial mosaic structure. Diamonds consists of slightly misorientated (up to 20′) subindividuals which are combined to mosaic wedge-shaped sectors. Electron back-scatter diffraction technique has demonstrated that subindividuals are often combined in the single large blocks (subgrains). The whole crystals commonly consist of several large subgrains misoriented up to 5° to one another. The total nitrogen content of these diamonds vary in the range 900–3300 ppm and nitrogen aggregation state (NB/(NB + NA)*100) from 25 to 64 %. Rounded diamond crystals of variety V are suggested to have been formed at the high growth rate caused by the high oversaturation of carbon in the crystallization medium. It may result in the splitting of growing crystal and their radial mosaic structure as a sequence. High content of structural nitrogen defects and the great number of mechanical impurities – various mineral and fluid inclusions may also favor to generation of this structure.