TY - JOUR

T1 - Radial mosaic internal structure of rounded diamond crystals from alluvial placers of Siberian platform

AU - Ragozin, A. L.

AU - Zedgenizov, D. A.

AU - Kuper, K. E.

AU - Shatsky, V. S.

PY - 2016/12/1

Y1 - 2016/12/1

N2 - 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.

AB - 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.

KW - Diamond

KW - Diffraction of backscattered electrons

KW - Internal structure

KW - Radial mosaic pattern

KW - Splitting

KW - X-ray topography

UR - http://www.scopus.com/inward/record.url?scp=84979561651&partnerID=8YFLogxK

U2 - 10.1007/s00710-016-0456-0

DO - 10.1007/s00710-016-0456-0

M3 - Article

AN - SCOPUS:84979561651

VL - 110

SP - 861

EP - 875

JO - Mineralogy and Petrology

JF - Mineralogy and Petrology

SN - 0930-0708

IS - 6

ER -