New textural evidence on the origin of carbonado diamond
- Autor(en)
- R.A. Ketcham, C. Koeberl
- Abstrakt
Three-dimensional textural observations of inclusion and porosity patterns in a 23- carat carbonado diamond using high-resolution X-ray computed tomography reveal new information bearing on the nature and origin of this enigmatic material. A prominent patinaed surface is texturally linked to a banding and grading of inclusions and pore space beneath, extending several millimeters into the specimen. In situ observation demonstrates that almost all inclusions are polymineralic and show replacement textures, corroborating previous work indicating that the pore network is fully three-dimensionally (3-D) connected, and that virtually all macroinclusions are secondary. Large metal inclusions are only found immediately adjacent to the margin of the specimen, and are thus also likely to be secondary or even tertiary. However, we also report pseudomorphs after a phase forming pristinely euhedral rhombic dodecahedra, individually and in clusters from 0.3 to 1 mm in diameter; although we could find no evidence of this phase persisting, it nevertheless represents the first "true" macro-inclusion reported in carbonado, which almost certainly formed syngenetically with the diamond material. The pore system is essentially trimodal, consisting of single and clustered pseudomorphs, oblate pores 0.1-0.3 mm in length with a clear preferred orientation, and 20 μm to
- Organisation(en)
- Department für Lithosphärenforschung
- Externe Organisation(en)
- University of Texas, Austin, Naturhistorisches Museum Wien (NHM)
- Journal
- Geosphere
- Band
- 9
- Seiten
- 1336-1347
- Anzahl der Seiten
- 12
- DOI
- https://doi.org/10.1130/GES00908.1
- Publikationsdatum
- 01-2013
- Peer-reviewed
- Ja
- ÖFOS 2012
- 105116 Mineralogie
- Link zum Portal
- https://ucrisportal.univie.ac.at/de/publications/23f343df-7378-4bc5-8c11-ec294f8b1f1d