title: Brown diamonds from an eclogite xenolith from Udachnaya kimberlite, Yakutia, Russia.
abstract: We have performed petrographic and spectroscopic studies of brown diamonds from an eclogite xenolith from the Udachnaya pipe (Yakutia, Russia). Brown diamonds are randomly intermixed with colorless ones in the rock and often located at the grain boundaries of clinopyroxene and garnet. Brown diamonds can be characterized by a set of defects (H4, N2D and a line at 490.7 nm) which are absent in colorless diamonds. This set of defects is typical for plastically deformed diamonds and indicates that diamonds were likely annealed for a relatively short period after deformation had occurred. Excitation of brown colored zones with a 632.8 nm He-Ne laser produced the typical diamond band plus two additional bands at 1730 cm(-1) and 3350 cm(-1). These spectral features are not genuine Raman bands, and can be attributed to photoluminescence at ∼710 nm (1.75 eV) and ∼802 nm (1.54 eV). No Raman peak corresponding to graphite was observed in regions of brown coloration. Comparison with previous reports of brown diamonds from eclogites showed our eclogitic sample to have a typical structure without signs of apparent deformation. Two mechanisms with regard to diamond deformation are proposed: deformation of eclogite by external forces followed by subsequent recrystallization of silicates or, alternatively, deformation by local stress arising due to decompression and expansion of silicates during ascent of the xenolith to surface conditions.
authors.affiliation: Research School of Earth Sciences, The Australian National University, Canberra, ACT, Australia. aleksandr.stepanov@anu.edu.au
authors.forename: Aleksandr S
authors.initials: AS
authors.lastname: Stepanov
authors.forename: Andrey V
authors.initials: AV
authors.lastname: Korsakov
authors.forename: Olga P
authors.initials: OP
authors.lastname: Yuryeva
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Nadolinniy
authors.forename: Maria
authors.initials: M
authors.lastname: Perraki
authors.forename: Kris
authors.initials: K
authors.lastname: De Gussem
authors.forename: Peter
authors.initials: P
authors.lastname: Vandenabeele
mesh_terms: D003116:Color; D018130:Diamond / Q000032:analysis*; D056448:Earth Sciences / Q000379:methods; D004578:Electron Spin Resonance Spectroscopy; D012426:Russia; D013059:Spectrum Analysis, Raman / Q000379:methods
chemical_list: D018130:Diamond